When Smaller Is Better

Venus is a notorious tease. Her brilliance in the deepening twilight sky is a lure to any beginning astronomer, yet nearly all come away disappointed after centering the planet in the eyepiece. No details are to be had (at least none to an untrained eye without the aid of a filter) other than the changing phase of a featureless cue ball. 

The exception is when we view Venus in UV light. Thanks to an as yet unknown compound in the Venusian atmosphere that absorbs ultraviolet light the planet shows structure in its omnipresent cloud deck. As we know, UV is not something our eyes can discern. The best we can do visually is to apply a violet filter such as a Wratten #47 that reduces the glare a teases out a tiny bit of that structure as low contrast shadings. Most common of these (and with a scientific rationale for their existence) are the "cusp caps" seen at either or both poles.

All is not lost, however. The amateur who has outfitted his rig for planetary imaging can take advantage of the fact that the camera's sensor can record in UV. Some cameras are better than others in terms of their sensitivity in the UV portion of the spectrum, but even if you do not happen to have one of the more UV friendly models the odds are good that with the addition of an ultraviolet filter you can capture some details. A little over a year ago I purchased an Astrodon UVenus filter to pair with my ZWO ASI178MC (color) camera to see if I could capture the cloud patterns, and was delighted to have success earlier this year.

In researching the best approach to obtaining a good image of Venus in UV one of the tips that I ran across was to avoid lenses in the optical path. The anti-reflection coatings on them can apparently cut down on the UV transmission, making the image dimmer (and consequently requiring a lower frames-per-second rate that introduces atmospheric smearing). It has also been noted that the corrector plate on an SCT is not designed to provide correction in the UV range, so that design may be a bit handicapped when attempting UV capture.¹

Another factor I have noticed is that while you can detect cloud markings when Venus has become a large but slender crescent on either side of an inferior conjunction, the results seem far more interesting when the phase is somewhere greater than 35%. Enough of the disk is presented to allow one to often capture cups caps/collars as well as streaks in the middle of the planet that a crescent won't show.

My recent session a couple weeks ago was under average seeing with only fair transparency. Our sister planet was sporting a 70% phase and a diameter of only 16" as the planet continues to pull away from us following last August's inferior conjunction. Having to forego the 2.5x Barlow means it is a small image that one gets to work with, but it was clear even on the laptop screen during capture that the cusp caps were visible. Post processing can afford some help in enlarging the image (such as adding drizzle in AutoStakkert3!, leveraging the resizing functionality in Registax, or even using a custom resizing application like Topaz's GigaPixel product).

Since I had the time I decided to do a second capture, but this time with the Tele Vue 2.5x Powermate Barlow in the imaging train. I could immediately see the impact in terms of a dimer image, dropping my fps from 32 down to 9. This of course allows more time for atmospheric blurring to occur, reducing the number of frames of steady seeing that can be harvested. 

So while the image was certainly larger, the attenuation of UV light by the Barlow gave an image with far less clarity. Yes, the cusp caps are there, but the details in the smaller image, even after undergoing enlargement, were far superior. The verdict was clear - leave the Barlow in the box and work with whatever size we have to get the best UV image of the elusive Venusian cloud details.

¹ https://www.thefreelibrary.com/Imaging+Venus+in+the+ultraviolet%3a+a+new+development.-a0357147028 

Heavenly Symmetry

A first impression the prospect of traveling halfway across the country to catch an annular eclipse seemed extravagant to me. After all, we do not get to see the ghostly corona and fiery prominences during that period where Moon occults Sun. The stars do not come out and nature reacts far less confused when the Sun, even a small amount of it, remains exposed. You might be tempted to equate it with seeing a 99% partial eclipse of the Sun. 

However, the facts were that witnessing an Annular Solar Eclipse was an unchecked item on my astronomy bucket list, and the one this October was (given my age and location) very likely my last opportunity to catch such an event. What the heck - YOLO, right?

The first step in the journey was selecting a location. Studying the path and the weather prospects I decided to target New Mexico for a long weekend. The path crossed two interesting cities - Albuquerque and Roswell. Given the almost legendary dark skies of the southwest I felt that spending a couple evenings at an Airbnb outside Roswell might offer the additional perks of checking out the UFO/Alien scene in Roswell by day and then enjoying a star-studded sky in the evenings. By the end of March I had my flight, rental car, and accommodations all set. 

Practice Run Capturing Clouds & Sun

Discussing my plans over Labor Day weekend with my son Dave I was delighted that he took me up on my offer to come along. We edited the itinerary a bit so that we'd be at the Albuquerque Balloon Festival to witness the eclipse rather than Roswell. With the venue change I pondered whether I might get a unique photo opportunity since there were plans to launch balloons during the eclipse. I spent the next several weeks researching how to filter the Sun sufficiently while still getting some of the background in the picture, something I've seen before that make annular/partial solar eclipse photos interesting. In the end a set of neutral density filters (one of them variable) and an IR/UV blocking filter seemed to offer the promise that if a balloon floated by the eclipsed Sun I could hopefully capture that bit of serendipity.

Travel day - Friday the 13th - started off with a curveball. Southwest texted me at 6 a.m. that they had cancelled the first leg our flight and rebooked us to a direct flight that was departing a half hour earlier. We hustled along to get to the airport to allow enough time to check bags and clear security (I was happy that my long rectangular box holding my tripod was not any issue getting checked in). Several hours later we were in Albuquerque and scouting out online reviews for a good Tex-Mex lunch.

The next morning as we stepped out from the room we could see a host of colorful hot-air balloons hanging off in the distance. The weather, despite forecasts for 80% clouds at the start of the week, looked promising with some scattered, high cirrus hanging around. We Ubered to the Balloon Festival field with camera, tripod, folding chair, and filtered binoculars in tow by 8:15. It was packed, but fortunately the field was quite large and accommodated the tons of people who had assembled for a good time. We found our plot of land and set up our little camp.

The first 45 minutes we enjoyed seeing some of the colorful and fanciful balloons taking off. A pretty steady breeze out of the north was making it a chilly fall morning, and unfortunately it soon caused the event planners to put a hold on launching any more balloons. The field MC was providing a running commentary of what was going on interspersed with some music.

8:38 a.m. MDT

I strap on the mylar solar filters to my 7x50 binoculars and check out the Sun. No major sunspots are present but a couple can be made out when I steady my hand. I fire off a couple of shots to refine the exposure settings and await for the action to begin. 

9:15 a.m. MDT

The announcer tells the crowd that the eclipse has begun, and a bit of a cheer goes up as everyone sees the tiny, initial bite taken out of the top of the Sun using our solar safety glasses that were being passed out upon entering the field. Which makes me wonder - how disappointed were the vendors that were trying to sell them? 😏

Moon marching across the Solar disk, ready to cover AR3465

The field MC provides updates on the eclipse's progress between the songs being played, and in a moment of bad science around quarter after 10 he mentions that people with good eyesight might see that the edge of the Moon has crept up upon the sunspot and will be covering it soon. While AR3465 is clearly the largest sunspot on the face of ol' Sol today and easily seen in my binoculars, it would be impossible for us to see it naked eye.

With about 20 minutes before 2nd contact we're also told that there won't be any balloon launches as we approach maximum. It's a disappointment but understandable as the winds have been constant since our arrival and would likely make it too dangerous. They still hope to do a "balloon glow" on the field during the time of greatest eclipse where the balloon is inflated but tethered to the ground.

10:20 a.m. MDT

I stop for a moment to look for Venus, and it takes very little time for me to pick it out high above us in the deep blue desert sky (even without my "distance" glasses). Once I point to it Dave can also quickly see it, although at first is not sure whether it's a plane at high altitude catching the glint of sunlight. The binoculars quickly resolve the question as I can see a disk exhibiting a phase to it. I try to grab a picture of it but the camera cannot do it, yielding only an overexposed sky, yet again demonstrating the amazing ability of our eyes to take in a logarithmic range of brightness that a CMOS sensor cannot.

By 10:25 the field has taken on that odd late-in-the-afternoon light that seems surreal for the hour of the day. There is not any wildlife in the area to observe, but given how my human instinct tells me the Sun should be close to setting I strongly suspect that our fellow animals are likely reacting to the change in light, albeit not as profoundly as in a total eclipse. 

This is the first eclipse I have experienced without any of the "pinhole projector" effects. Normally there are some deciduous trees around and they provide the multiple crescent images at this point, but in a wide, empty field suited for hot-air balloons there are none. The field announcer mentions that if you have a Saltine cracker, the dozen or so holes that perforate it will serve nicely as a makeshift projector. Perhaps that should have been part of the handout along with the solar eclipse glasses? 😄

With less than 10 minutes to go we are told that even the balloon glow cannot take place due to the winds, and instead the best that can be done is a "candlestick", where the propane burner is fired to create a tower of flame sans balloon. 

And finally we are at the moment we've waited for!

10:34:41 MDT

Second contact is announced and the crowd cheers as people begin to make out the off-center unbroken ring of light encircling the Moon.

10:37:12 MDT

We've reached the climax of maximum eclipse. To the unfiltered eye the Sun is still glaring and without hint of being 90% covered, but with eclipse glasses, and especially in the binoculars, there is this amazing alignment to behold. A perfect glowing circle of bright light that seems like it is a Hollywood special effect made for Lord of the Rings stands before us. Lots of cheers and the roar of the hot-air balloon burners lighting up the field makes the entire experience unique and unforgettable. This is what I came for - that incredible, visceral connection that an eclipse can provide during those brief seconds of totality/annularity. While I wondered if the annular version would come close in that impact, the stunning symmetry in the sky does not disappoint!  

Facebook Livestream:

10:39:35 MDT

All too soon Luna has crept to the eastern solar rim and prepares to exit. Dave is using the binoculars as we head to 3rd contact and - without any foreknowledge of the Baily's Beads effect - mentions to me that he sees the brief sparkling of the sunlight along the Moon's limb as it exits. My constant firing off shots allows me to also capture the phenomenon digitally.  

As the Moon begins to retreat from the face of the Sun, many of the folks assembled on the field begin to head out as well. It really has become noticeably cooler, and judging from the comments I overhear I am not the only one wishing I had brought a heavier jacket. While it is a bit anti-climatic it seems that it would be almost rude for me to break down the modest equipment and hail our Uber. Dave takes the time to explore the long line of vendors' tents in search of some souvenirs for us to remember the day while I continue to document the egress towards 4th contact. 

By noon we collapse the tripod and camp chair and place the request for our ride. With only a few more minutes left I take my final shots of the Moon departing the Sun in hand-held fashion as we make our way out. While not the epic traffic jam that I encountered following the 2017 total eclipse, the wait and fees for the Uber tell us that a lot of people have participated in this annular eclipse. While a bit tired I am joyful at what God granted me in witnessing this eclipse with my son and checking off another of my astronomical bucket-list items!

Not Feeling Lucky

"Diligence is the mother of good luck." - Ben Franklin

I guess it's been the better part of a decade since I first encountered the term "lucky imaging" that is used in amateur astronomy to characterize the technique of stacking and enhancing video frames to produce the stunning planetary, lunar, and solar images that we see so often today. The moniker derives from the fact that we are able to extract those brief, "lucky" moments when the seeing has steadied for a split second to create a photo that reveals details the eye could never behold. Indeed, not just our eyes, but those of us old enough to have tried capture using film greatly appreciate the superior results (and in many ways the simplicity) of using this digital video approach.

While the term has a rational basis for its origin, I have to confess it has never sat quite right with me. Using it connotates that I pointed my telescope at my target, yelled "action!" and hoped for the best. If the imaging gods smiled on me then I was rewarded with a detailed image of  Mars revealing Olympus Mons or kilometer-sized craters on the floor Plato. If they did not I was left with a fuzzy outcome that no amount of post-processing could salvage. Better luck next time kid! 

Of course, any serious solar system imager knows that aside from decent seeing, luck is a rather small component of creating a nice capture of your target. There is the research into what equipment to use and the financial investment in acquiring it. That equipment then often needs a knowledgeable and skilled hand for optical alignment (collimation) to wring every last sub-arcsecond detail from our quarry. Once that is checked one needs to engage in a successful polar alignment to enable tracking of the object at high magnification. If an Atmospheric Distortion Corrector (ADC) in your imaging train then that, too, must be adjusted throughout the imaging session to combat the subtle smearing that occurs when light travels through our home planet's blanket of air. 

One of the biggest challenges is achieving a sharp focus. "Lucky" imagers do not get the benefit of a Bahtinov mask to provide the assurance that they have a crisp image. The user must study the image on the screen to identify a high-contrast feature to zero in on and then twiddle the knob incrementally back and forth while evaluating the outcome after each minute adjustment. If being done by hand that means waiting a few moments after each tweak for the target to stop dancing around the field. (Those of us who have outfitted our scope with an electronic focuser would never part with it!) 

Once collimated, polar aligned, and focused it's on to setting up the gain and exposure in the software's capture interface. Having the fastest possible shutter speed while holding the graininess of the capture at bay is another balancing act that the imager has to perform. Finally, we're ready to capture some video!

With gigabytes of data safely stored on the hard drive you're halfway home. Next comes the post-processing effort where we transform those thousands of frames into a single thing of beauty. But between those two points lies a bevy of software products to perform that magical massage, and the time to learn how to use them. One of the most critical stages, the wavelet sharpening, is part science but very heavy on art. Here the observer must use their skills to sharpen the stacked outcome in such a way as to provide the clearest view that does not introduce artifacts into the final product. Only after all this effort based upon investment in equipment, study, and experience does the reward of a detailed photograph of a member of the solar system emerge. 

Lucky? Really? 

I may be tilting at windmills here, but I am launching a campaign to retire the "lucky imaging" description for a more appropriate acronym. I asked the question on the Cloudy Nights forum and got some interesting (and humorous!) suggestions along with pretty universal support to call our technique something else. Some of them contained the word "planetary" in the acronym, which would describe most of my personal effort but snub the amazing work done by Solar and Lunar imagers. After collecting descriptive terms and jockeying them around I think I finally have the replacement acronym:

Solar, Planetary, and Lunar Imaging Capture & Enhancement (SPLICE)

Not only does it cover the targets for which we most often apply the technique, the "splice" has a slight double entendre in that in many ways that is at the heart of what we do - gather the best parts of our movie and then splice them together for our finished product. 

Coming up with a suitable acronym is certainly the easier part of this effort. The real challenge will be to get our favorite print publications (and other influencers such as podcasters and YouTube creators) to adopt it. It's up to us to ask them to remove "lucky imaging" from the amateur astronomy lexicon!

An Autumn Grab Bag

Overall the past 4+ months have not been kind to amateur astronomers in my area. There seemed to be an above average number of cloudy evenings, and those that were clear often had a haze triggered by smoke drifting down from Canadian wildfires. So to say that the return of some cooler, crisp fall evenings was most welcome is probably an understatement. 

Jupiter and Saturn took some of my attention, but I also made time to check in on some targets among the Astronomical League's Urban List in my ongoing assessment of how easily they can be spotted from suburban skies that suffer from significant light pollution.

August 19, 2023 
Sky: Mostly clear, temps ~65° F, light winds
Transparency: 7/10    
Seeing: 5/10
Limiting Magnitude: 3.2

NGC 6818 
Planetary Nebula in Sagittarius
10” f/6 Newt   15mm Plossl  CGX-L Mount  

It took a 4-star alignment process to get the mount's GoTo working accurately enough to ensure that it was landing on targets with good accuracy, but that was a prerequisite given the light pollution in the southeast where my chosen target lies. But it was worth it, as once I peered into the 25mm eyepiece it was apparent as a small, uniformly round orb with perhaps a slight blue tint to it amid a handful of field stars. Popping in the 15mm enhanced the view of the planetary. There was no structure such as an annulus that I could discern, and it sported an even distribution of light. While a little faint, it bore direct vision well, even without a UHC filter. Alternating between direct and indirect vision yielded no evidence of the central star.

NGC 6934
Globular Cluster in Delphinus
10” f/6 Newt   15mm Plossl  CGX-L Mount  

I know that I have seen this DSO before with my 6” RV-6, but that observation is lost among the many that have gone by the wayside. I wish I had been better about archiving them for later access.

When inspecting the field with the 42mm once the scope completed its slew there was no sign of the globular. I did not tarry long before switching to the 25mm eyepiece with the Baader Moon & Skyglow filter, which revealed it immediately. I followed up with the 15mm which gave a good view of this globular. The field has stars that form roughly an “arrow” asterism pointing to the east. And the globular lies along the shaft of the arrow on the side closest to its apex. It is perhaps 4-5’ in size and can take direct vision but is improved with averted. No resolution of the member stars was noted. The globular is circular and has surprisingly even illumination – no sign of a brighter core discerned in the observation this evening.

September 3, 2023 
Sky: Thin haze, temps ~85° F, calm
Transparency: 7/10    
Seeing: 7/10
Limiting Magnitude: 3.2

IC 4756
Open Cluster in Ophiuchus
6” f/8 Newt  TV 25mm Plossl  HEM27 Mount

Once I verified the HEM27 was working well I decided to target this open cluster. I slewed to Rasalhague and then did a center operation to ensure the hop over to the cluster would be on target. And indeed, as soon as I peered in the eyepiece with the 42mm I could see a loose, large cluster of stars.

Bumping the magnification up to the 25mm came close to filling the field, implying the cluster size at about ¾ degree. There is one bright anchor star, perhaps 7^th or 6^th magnitude, in the south of the cluster – no color noted in it or any of the other members of this cluster. The other members range in brightness from about 8^th magnitude down to limit of visibility. All told about 40 stars are seen, but there is no nebulosity hinting at any mass of unresolved members. Very nice cluster and would be worth checking again under darker skies.

NGC 6709
Open Cluster in Aquila
6” f/8 Newt  8mm TMB  HEM27 Mount

Once the scope finished its slew I checked the area with the 25mm TeleVue Plossl, and my attention was drawn quickly to an eye-catching triple set of stars. West of it seemed to have a slightly above average number of stars, but nothing that screamed “I’m a cluster”!

Dropping in the 8mm TMB I see a few more stars and a dim fourth sun joins that pretty trio. I do a quick online check to verify that I am on the cluster, easily confirmed by the trio-plus-one showpiece of the field. As my night vision adapts, I see perhaps about 15 stars that may be cluster members in what is a coarse and not very rich offering. No hints of any nebulosity, and none of the stars depart from the standard white color. It is small, perhaps 10-15’ in size. While it may be really nice in darker skies, I'd be inclined to drop this one from the Urban List. 

Perseids 2023

It's been too long since I've packed up the scope and headed out to a dark sky venue. With 2023 coming together as a very favorable Perseid Meteor Shower event (little moonlight, shower maximum predicted for early morning Eastern time, and a weekend to boot) I head out to an AirBnB in Monterey, VA under Bortle 2 skies.

The forecast for Saturday evening has been dismal, but as I step outside at 9:30pm it's actually clear. I place the HEM27 mount outside and wait to see if conditions will hold. By 10pm it is beautiful, so I attach the 80mm Vixen and power up the iPolar in hopes of doing some pre-midnight non-meteor photography. But as I'm getting my polar alignment down I become increasingly aware of flashes over the northwestern horizon - what some might call "heat lightning". Pulling up the radar shows a line of slow-moving storms to the north. It's hard to determine if they might skirt my spot and only deliver a sprinkle, allowing me to leave the setup covered and ready to go after the storm, or instead bring a downpour. Not wanting to risk it I reluctantly put everything back in the house by 11pm. I set the alarm for 3am in hopes that there still may be a chance of glimpsing the Perseids.

I turn over and check the clock. It's 2:30am (amazing how often that seems to happen with one's internal alarm clock) so I lumber to the front door and step outside. I am greeted by amazingly clear, dark skies. The northeastern horizon in the distance lights up periodically as the thunderheads slowly continue their push eastward. My goal of coming away with a keeper shot of a Perseid blazing through the late summer night sky might yet be fulfilled! I quickly align the camera tracker on Polaris and get the camera focused. I decide to frame a region of Andromeda and Pegasus anchored with brilliant Jupiter in the corner and kick off the program for a series of 1-minute exposures. Come on Perseids, do your thing!

I keep an ongoing tally in my head as they sporadically streak across the heavens here and there, but they always skirt the trap I have so carefully laid. About 15 minutes in I begin to notice that I am losing stars near the zenith. Clouds are creeping in from the south, slowing reclaiming the sky, and in a few minutes even Jove is a feeble remnant of his original beacon. As if to tease me, the areas of the northern sky remain transparent with vain Queen Cassiopeia seemingly taunting me for not having chosen her at the outset of my quest.

I stubbornly persist a few minutes, trying to give these pokey clouds a chance to move on rather than repointing the camera. But finally my patience is exhausted and I give in. I pause the program and swing the camera around to the southwest where the sea-goat has begun his plunge below the horizon. It always delights me how in a Bortle 3 venue I can readily see the outline of so many constellations that, from Towson, are represented by only a handful of stars bright enough to punch through the light pollution. The intervalometer program engages again and the click of the shutter tells me I'm back in business. 

Another quarter hour passes and I notice a new enemy has attacked - my laptop screen is now glistening with dew that has formed on it. I could kick myself for not bringing along a few hand warmers that could be laid alongside the camera lens as a defense. I pause the program again to clear the dew and look for a bright object to check my focus. Ahh, the Moon has joined the party as she crests the mountain range to my east. While so often an unwelcome guest to a star party, this morning her thin crescent with sublime Earthshine is a fine target to help me ensure my focus is spot on. 

Assessing the heavens I opt to shift the frame to the Queen and her husband in hopes that a meteor will course through their celestial thrones. My meteor count continues to tick up with some that appear enticingly close to the region I've framed. Perhaps I have bagged a cool Perseid meteor shot?! 

All too soon the final enemy of my endeavor - dawn - is closing in as she begins to reveal the silhouette of the eastern mountains with her glow. Overhead is still reasonably dark so I continue to let the camera run, hoping for that one brilliant streak of light to flash through the frame. Finally I yield and close up shop, bringing the damp tools inside to be cleaned up and dried off. In the couple of hours I've seen about 60 Perseids and 4 strays. One was a beautiful fireball that dropped from Cassiopeia into Lyra sporting a green tint and momentary train. Visually, it has been a nice year for the Perseids and far more than I expected 24-hours earlier given the gloomy forecast.

I'm tired, but it's like Christmas morning and I am too impatient to wait to see what's on that SD card. Swipe right, swipe right, swipe right - sigh, yet another year where the Perseids have proven more recluse than Howard Hughes when it comes to having their photo taken. I have spent a couple hours fishing in the celestial sucker holes and come away empty despite what looked like promising nibbles. And yet like fishing, it was not really so much whether I landed that fireball on film, it was the rejuvenation of spirit found under a stary sky that sent shooting stars in all directions. And in that, the night and this trip have been a complete success.

Registax Heir

 A critical part of the planetary computer assisted video imaging (CAVI) - aka "lucky imaging" - is the sharpening of the stacked and aligned image with wavelets. It can seem like a black art as you push and pull levers to apply various wavelet changes to the image to make it clearer. There is also a huge amount of art here, where one balances between a heavily processed and artificial looking output vs. one that has left details on the table that should be brought out.

Registax has been the de facto freeware for the application of wavelet sharpening for quite some time. However, the last release was in 2010 - a virtual lifetime when it comes to a software product. As a result there have been alternatives emerging that the amateur imager may want to evaluate.

One of the new kids is waveSharp, and part of the attraction is that this is an open source project by Cor Berrevoets, one of the primary forces in the development of Registax. As stated in his announcement on CloudyNights of the availability of waveSharp at the end of last January,  

(Registax) was developed in 2011 only for windows 32bit computers, waveSharp is developed for 64bit computers and multiple operating systems (WIN64, LINUX, MACOS). Therefore this application is only meant to sharpen/enhance images that have been created using other software (alignment/stacking).

You can download the compiled executable for placement on your computer at the project's GitHub repository.

The interface is pretty clean, allowing you to open your image and then use sliders to apply the strength of your wavelets. Unlike Registax we have only 3 sliders, with the first one affecting the small-level detail, the third increasing the contrast on larger scale features. The "Denoise" (smoothing) sliders are not activated by default but must have their checkbox selected. 

The user also can select one of three filters to apply. Gaussian appears to be very similar to Registax, with the changes slow and gradual to create a sharpened image. ZeroGauss is quite strong, with minor adjustments having significant effects. The third choice, Bilateral, is supposed to help avoid the "rind" effect that we often see in planets like Venus and Mars with bright limbs. 

I've been using waveSharp for about two months now and have been very impressed with it. The changes are applied quickly (possibly a reflection of its 64-bit architecture) and the various filters are a nice touch. You can also save your settings and recall them for application to new images. The one thing that is probably not as easy as Registax is correcting RGB alignment (atmospheric distortion) to your image - it appears to be more automated in Registax. 

Change is inevitable but not always positive. While waveSharp is still in its early development it seems to be a suitable heir to the venerable Registax - give it a try!

Hanging Out in the Crib

Amateur astronomy has a bit of a reputation for needing significant and sophisticated equipment to enjoy. And if you are looking to target faint objects, or dive into photography, well then there is certainly some truth to that. But the universe has so much to offer, and some of those items really do not need much more than a nice venue and a pair of binoculars (or your eyes) to touch your soul.

One such type of event is an appulse¹, "an approach between two celestial bodies." As the Moon makes its monthly trek along the ecliptic it will often pair with one of the brighter planets. Due to the various inclinations of their orbits to the ecliptic sometimes we have wide space between the two, or on rarer occasion the Moon will cover up (occult) the object for a period of time. There are also four 1^st magnitude stars that lie sufficiently close to the ecliptic that they can sometimes be visited in the sky by one of the denizens of our solar system. I'll leave it as a research project for those interested in identifying them if you're not familiar with that quartet.

A little more subtle (unless, perhaps, you are in very dark skies) are the three open clusters that lie close enough to the ecliptic to also host one of the planets. Interestingly, these all lie in the Winter Zodiac. The Pleaides is the brightest and most spectacular of the trio. It also lies the farthest off the ecliptic at 4° and so will have infrequent visitors. Every 8 years Venus drops by for a visit to the Seven Sisters, making for a beautiful alignment. 

Venus Amid Pleaides

While M35 in Gemini does not have a catchy moniker, it does own the inside post position to the ecliptic, lying only 52 arc-minutes away. As a result it is more common to see interlopers jog by it, especially Jupiter which has a low inclination to the ecliptic and so unable to stray far from it. It is also noteworthy that M35 comes very close to the point in the heavens where the Sun reaches its greatest northern culmination (i.e., the Summer Solstice) - a conjunction that we can never observe unless there were a Total Solar Eclipse in progress. Talk about your rare event!

The Sumer Solstice - June 21, 2023 11am EDT

Finally we have M44, the "Beehive" cluster in Cancer. A little more than a degree off the ecliptic it also is in position to allow the occasional planetary orb to join its aviary for a night or two. While not as dense or showy as the other two clusters, it is still easily visible to the naked eye from dark skies and was known in antiquity as Praesepe (the "crib"). Sailors used it as a barometer since if it was hidden from view by a veil of thin cirrus clouds then overcast skies and possibly rain was in store for the next day.

All spring there has been a celestial chase between the Goddess of Love and the God of War unfolding in the evening twilight. Venus has been gaining on the Red planet, pursuing him through Taurus, Gemini, and now Cancer. In early June Mars attempted to hide himself among the stars of M44 for a couple of days while Venus drew near to Castor and Pollux to seemingly inquire as to his whereabouts. The dual appulses were beautiful and could be appreciated by one's eyes or simple binoculars. I happened to be at South Bethany in Delaware visiting my sister those evenings, and sitting out back along the canal watching the scene emerge as darkness fell was simple & sublime. 

While I couldn't take my scope, my Canon camera and a tripod were easy to bring and allowed me to create my own postcard souvenir of the trip. Taking a series of 10-sec shots at 18mm captured all the players on stage, and then as darkness fell a set of 3-sec shots at 55mm allowed Mars to have the spotlight as a ruby set amid the glittering bees. Simple processing in freeware such as Deep Sky Stacker and Sequator produced wonderful results with additional enhancement in Photoshop.

Appulses and other simple pleasures of the night sky are encountered multiple times a year. Don't overlook the opportunity they provide to sit back and drink in the profound majesty of the heavens in an uncomplicated way.

¹ This is basically another term for a conjunction

Ultra Venus

Perhaps no other object has such a wide gulf between its naked eye impression compared to its appearance in a telescope than Venus. In our twilight sky Venus demands attention, shining like a brilliant diamond. Whenever the crescent Moon stops by for a visit, I am always up for grabbing a few shots (even though I already have many prior encounters documented). And when our sister planet pairs with another planet (as it did earlier this year with Jupiter) or the Pleiades, amateur astronomers turn into paparazzi and flood the online galleries with their glamor shots.

Venus & Jupiter Feb 28, 2023

But few of those amateur astronomers will tarry very long with Venus in the eyepiece. The view is that of a dazzling, featureless cue ball emulating one of the Moon’s phases. Nothing stands out so it’s a quick check-in and on to something of greater interest.

With patience and some filtering there is more to see. A deep violet Wratten #47 filter not only knocks down the glare but provides subtle boost to the very low contrast features in the Venusian clouds. While at times one might make out a dusky region on the planet, the most common feature that appears is a brighter region at one (or both) of the poles. Know as a “cusp cap” it is an actual feature and not just an artifact manufactured by our brain. Large Hadley cells rise high into the atmosphere from the hot equatorial regions and then sink back down in the high temperate latitudes, forming a slightly darker “cusp collar” bordering the cooler cusp cap.

Planetary imagers also find themselves stymied by Venus’ reluctance to share features. Like most others, my prior attempts to record details on the 2^nd rock from the Sun using “lucky imaging” techniques produced crisp but bland captures of the globe.

Our professional brethren have also struggled with Venus until about a century ago when astronomer Frank Elmore Ross targeted it using Mount Wilson's 60- & 100-inch reflectors. His gig before that was a decade at Eastman Kodak studying photographic emulsions and filters, which led him to make photographs in IR and the newly released UV filter. While the IR failed to penetrate the cloud layer to show details as he had hoped, the UV unexpectedly did. Curiously, there was not much follow up to his discovery until images acquired by French amateur Charles Boyer nailed down a rotation period of about 4 days. His results were published in 1960 in Icarus (and rejected by none other than Carl Sagan). While radar data eventually established a retrograde rotation of 243 days for the planet, Boyer’s observations of a 4-day “super-rotation” of the Venusian atmosphere were eventually confirmed by Mariner 10. Thus we end up having two longitudinal “systems” for tracking central meridian on Venus: CM I for the surface, and CM II for the upper atmosphere clouds.

Over the last ten years amateur planetary imagers have gradually been targeting Venus using a UV filter and getting some nice results. UV filters are pricey (north of $200) and sometimes backordered for months. I finally budgeted for the Atrodon UVenus filter which was heralded as having some of the best UV transmission. Renowned imager Damien Peach put together a video on his patreon channel that provided further tips on obtaining a successful UV image such as combining it with an infrared blocking filter since many UV filters leak IR which can smear the image.

Sample transmission for UV filters

With Venus approaching its greatest eastern elongation (distance in our sky) from the Sun, it was time to try again to capture cloud details on our neighboring planet. Starting at sundown I worked on centering the planet with good focus to begin acquiring my UV videos. Reasonably calm seeing is really important for achieving that focus and often not present when dealing with an object like Venus that is never more than about 40° high, but I finally got that on my May 15^th session. I confess that I was pretty ecstatic being able to make out what seemed to be a southern cusp cap on the image shown on the laptop during acquisition, implying I would have something worthwhile to work with. And the next day when putting the video through my processing workflow I ended up with a nice result, clearly showing north and south cusp caps with some of the darker collar. The center of the planet shows segments of lighter and darker clouds.

Venus May 15, 2023 in UV

In my researching about capturing Venus in ultraviolet I came across a few sources that argued that introducing any sort of lens element in the imaging train (e.g., a Barlow lens, an SCT corrector plate) was to be avoided if possible since these can cut down on the amount of UV light considerably. The ideal situation is a mirror telescope such as my 10” Newtonian. For the heck of it I did a capture at the end of the session using the Barlow. While the seeing may have deteriorated by that point, my results certainly seemed to confirm that the benefit of a larger image was far offset by the decline in sharpness of the low contrast cloud features.

So, what do the darker regions represent? In classic Venus fashion the planet will not give up that information yet. Some scientists believe that it is a photochemical reaction in the atmosphere that results in UV absorbing material. However, there are even some who argue it could be cloud based microbial life generating these regions and liken it to algae blooms that we see here on Earth. With a bevy of spacecraft heading Venus' way later this decade we may eventually get an answer to this question.

As usual I submitted the final results to ALPO. A few hours later I heard back from Julius Benton, the Venus section coordinator. “Thanks. Your UV image looks very good!” was great feedback to receive, and confirmation that the multi-year journey to acquire the equipment and knowledge on how to make Venus finally give up some details was satisfying indeed.

Something to Crow About

There is real joy when the pleasant spring weather sets in, providing evenings of cool temperatures that I can tolerate with only a light jacket but the bugs cannot. Our garden spotlight softly illuminates the beautiful azalea newly flush with coral colored blossoms and the nearby deep purple irises. The distinctive clink of an aluminum bat connecting with a pitch let's me know that nearby Towson University is having a game this evening. Well, that and their stadium lights lighting up the tippy top of the trees in the field behind my house is also a dead giveaway. 

After setting up the scope I minimize what light pollution that I can by turning off the yard lights. This evening I'm hunting Crow - some celestial highlights of Corvus as he wings his way towards a midnight rendezvous with the meridian. As my night vision slowly improves I struggle a bit to discern the outline, a geometric pattern of half a dozen 2nd-4th magnitude stars. 

The first stop is an eye-catching asterism known as the Stargate. Lying roughly a degree southwest of M104, there is a good chance you may have already stumbled upon it when looking for the Sombrero galaxy. One could probably sweep it up in a star hop by extending a line from k Virginis and Spica westward about 12°, but I take the easy way out and key in the coordinates. At times with a computerized mount you feel like Picard on the Enterprise, barking out the location and issuing a "make it so!" pronouncement. 

At low power in the 10" Newtonian it is delightful - a triangle of stars within a triangle, each having one of the triad much fainter than the other two. Not really seeing any color here but the arrangement is very cool. A little higher power makes it easier to see the fainter members of each of the dual triangles. So what the heck is a "stargate"? Well, near as I can tell, this is a reference to the spaceship portal used in the 80's sci-fi series Buck Rogers in the 25th Century. Hey - if the Greeks can fashion a crow from a trapezoid on a stilt then a "stargate" ain't half bad!

From an easy asterism I go in search of my next objective - planetary nebula NGC 4361, an entry in the Herschel 400 list. If you can see the top of Corvus' trapezoid it would likely be fairly easy to target this with a Telrad. However, the scope is well-aligned so I succumb to the GoTo siren and ask it to do the work for me. I inspect the field at 25mm without any filter, but there's no sign of anything unusual in the eyepiece. Adding the Lumicon UHC and studying the area once more leads me to believe that there is a faint dab of light when using averted vision. Taking the magnification up to 95x with the 16mm + UHC filter darkens the background a bit more and makes me far more certain that I’ve got this 11th magnitude planetary. I use my makeshift drape/balaclava to block out extraneous light in hopes of getting a better look and maybe even catch the central star which is an incredibly hot Wolf-Rayet star, checking in at 270,000° Kelvin (compared to our Sun at about 5,700° K). While I can see the glowing orb a little better it fails to tease out the nebula's progenitor. The nebula appears circular and fairly evenly illuminated, perhaps twice the size of Jupiter. While given the moniker of "The Water Sprinkler" based on images of it that show internal detail, in my scope I discern a faint, glowing orb best seen with averted vision and lacking any structure. The field it is set in is very sparse, made more so due to the use of the UHC filter.

Next in my Corvian exploration is S1604 (Struve catalog entry #1604), one of the targets listed in the AL's Double Star program. This double is not in a very friendly star-hopping  location with multiple other similar stars near it and no solid anchor point to start from. It isn't listed among the keypad’s roster of double stars, so I do a quick lookup of the RA and Dec and key the coordinates. Having expended the effort at the outset of the session to get a good alignment pays dividends as the scope dutifully moves to the spot. Looking over the field at 25mm there are a couple of candidate suns that may be the target, and I think I see one of them as a double. Bringing the magnification up to 156x and revisiting each one I quickly confirm the right one. S1604 reveals itself as a splendid triple system that closely replicates a right angle. The two comes are very close in magnitude with the brighter one making a N-S alignment (PA ~0°) and the other E-W (PA ~90°) with the primary. This is curious, as Burnham's Celestial Handbook lists the position angles as 91° and 73°, clearly at odds with what I am seeing (and what is listed in the AL Double Star program list). Why the difference - is it an errata in Burnham's? I find it hard to accept that the stars changed position that much (especially given one of them is believed to be an optical alignment rather than a true common pair). Not sure that I am picking up any color here, although the faintest of the trio might have a ruddier glow to it.

Saving the most challenging for last, I set off for the Antennae galaxies - NGC 4038 and 4039. This duo of roughly 10th magnitude interacting galaxies should be doable in a 10" telescope, but the challenge becomes plucking them out from the bad light pollution. While the GoTo had been doing very well, for this item I decided to use my star hopping skills to have certainty that I was over the target. Locating TY Crv lying west and midway between g and e Corvi, I nudge the scope northeast until I encounter the 8½ and 9½ magnitude pair of SAO 157047 157046. From there it’s almost due north to HD 104496 and SAO 157048 where the galaxies should be found more or less midway between these two stars. I navigate the route with a high degree of confidence, reaching the endpoint and earnestly scanning the eyepiece field. Alas, there is nothing there to greet me. I check carefully with the 16mm and then the 9.7mm eyepiece, and then repeat the process using the Baader Moon & Skyglow filter. I even grab the balaclava once more to shield my eyes from extraneous light, but there is simply nothing to be had. Perhaps another, clearer evening, or waiting to try in early morning hours next winter, would bear fruit. Sadly the light pollution wins this round.

Star hopping to the Antennae

It's been a very satisfying evening under the stars with my feathered friend. While I'm tempted to continue looking for other spring objects in the area I decide to pack things up since I'll need to be at work in the morning. And that is part of the beauty of our hobby, the heavens (usually) will offer you another opportunity to explore its wonders, even amid suburban skies.

Under the Influence

The Howard Astronomical League lost one of their luminaries last month with the passing of Bob Prokop. The club never had a more ardent supporter than Bob, serving in the leadership role as a club president and supporting many of the club's outreach activities. He loved our hobby and it showed in many ways.

While I never had the opportunity to develop a personal relationship with Bob, I was certainly under his influence. He had the ability to advocate for the spectacular above us as well as the sublime. Was Mercury having a favorable apparition? Bob would be posting about it in the email group. Was the Moon's libration tilting a far-flung crater into a better position for us to grab a look at it? Our lunar expert knew the when, where, and how of the circumstances. On more than one occasion his exhortations found their mark and nudged me outside to hunt down what Bob was showcasing.

Bob was indefatigably upbeat about any clear night. Do NOT complain to him that the full Moon was ruining the evening lest you be embarrassed by Bob's retort as to the lunar features, asterisms, or other bright destinations that would not be suppressed by a glorious full Moon. And everyone in the club knew that he wasn't Googling that information, it simply flowed effortlessly from his years gazing up at the heavens. I still recall a passing comment that I made - something along the lines of "only a mediocre double star" - to which I was called to account in a most affable manner.

One thing that Bob and I were resolutely in lock step on was the value of star-hopping. We both cut our astronomical teeth by using instruments that required you locate your object rather than simply dialing it in. To quote Bob, "Of course, I am also the nut who has my telescope on an unmotorized alt/az mount with no finder scope... and can still find that 9th magnitude star faster than anyone with their fancy go-to software!" No brag, just fact.

I understood his lament that "today's kids" miss the anticipation and preparation involved when stalking a faint object, not to mention the thrill and sense of accomplishment when it finally appears in your eyepiece. Plus, who knows what stary vistas and uncharted beauty you may encounter along the path to your objective? While I have succumbed to the GoTo siren with my latest mount, I still do put the keypad down at times and drive myself to my destination. 

While my interactions with Bob were virtual, they were valued nonetheless. He was a welcome inspiration and source of knowledge for me and many of my club peers. He was one of those special people I've had the good fortune to come across who's love of the night sky was palpable and contagious. 

Getting Started

It's a question that I (and most amateur astronomers) get from friends from time to time: "I want to look at stuff in the sky - what sort of telescope should I get?" It is a tough question to answer because there are a multitude of variables (like how dark your sky is), a wide variety of celestial objects for which each has a "best" instrument, and the prospective user's existing familiarity with the night sky. 

It is understandable why folks get the urge to grab a scope and go out into the night. The images sent back from our spacecraft are stunning to say the least. And while most people grasp that their telescope is going to fall short of a billion dollar scientific instrument, they likely also have acquaintances posting to Facebook or Instagram with some pretty cool stuff. That's part of the problem with social media - it makes stuff look easy since we only display our victories, not the flubs we made getting there.

OK, so rather than totally dodging the question with a "it depends..." answer, let's consider the following scenario. We have a newbie who really knows very little about finding things in the night sky and who lives in suburbia (where their sky is not going to be bleached out by a ton of lights). They'd love to see a galaxy, some beautiful star clusters, and maybe a nebula (gas cloud) or two. They'd like to see Saturn's rings and Jupiter's Great Red Spot.

Those two sets of objectives (Deep Space Objects [DSO] and Solar System Objects) are somewhat mutually exclusive for our beginner. DSO present the challenge of being faint and potentially very difficult to find for a new telescope user. Of course you can buy a scope with computer assisted GoTo that will point the telescope to the object if you can align it properly (not to mention that you'll be jumping into the hobby for a much bigger financial bang). 

Planets, being brighter, are much easier to find with your telescope. However, features like the polar ice caps of Mars and the belts of Jupiter are more subtle than you might imagine to pick out with your eye. It's almost like playing an instrument with planetary observing - you need practice before you can detect some of the cool things your telescope can show you.
So - how can you break into this hobby without breaking the bank? The answer lies in a nice set of binoculars. Most people don't even consider them because they believe they are not powerful enough. The truth is that their wide field and additional light gathering power will indeed open up a lot of celestial DSO for you. They have the added benefit of being user friendly - no need to align anything, just pick them up and step outside to begin exploring. And - they pack easily for that trip to the beach or the mountains where the skies are much darker than at home.

There are a lot of sites with binocular recommendations. One thing to know up front is that the first number in the binocular description is the magnification (or power), the second is the diameter of the front lens (larger diameter = ability to see fainter objects). I personally own two pairs: a 7x50 by Celestron and a 15x70 by Oberwerk. The former are reasonably light and easy to use, the latter are a bit heavier but give wonderful views. I'd recommend a 7x50 or 8x56 for someone starting off - something you should be able to do for under $150 easily.

Binoculars - ready to go & user friendly!

"Sky Safari" App

Equipment is only half the battle. The really important thing is to begin to learn your way around the sky so that you can find things to look at. You don't need the binoculars to start this, your eyes and a star chart (or, even better, an app on your smart phone that can simulate the sky where you point the phone) are all you need. Start learning to identify the bright stars, then trace out the other stars in the constellation that has the bright star. From there see if you can locate stars in some of the dimmer constellations between the bright stars. As you do this you'll also become familiar with how astronomers quantify the brightness of an object (its "magnitude"). Once you've made friends with the stars overhead you can use them as markers to find the more interesting stuff.

Like what? Well, on a crisp February night you could swing by the Orion Nebula, a hydrogen gas cloud birthing new stars. Or high up in the sky catch the Seven Sisters (Pleaides), a beautiful collection of diamonds in the sky. For something more subtle you can track down the oval smudge of light that is the Andromeda galaxy lying some 2 million light-years from Earth. And since Jupiter is out in the evening sky take a moment to check it out - you may not see the Great Red Spot but you'll likely get to see some of its moons very close by as little stars. For other ideas I'd suggest picking up a book such as Touring the Universe Through Binoculars and let it guide you to a lot of fascinating destinations.

The tiny cloud represents the Orion Nebula
(It looks much better from dark skies)

An important lesson that you'll quickly learn is that when it come to the night sky a camera is much better equipped to show color and detail than our eyes. The camera opens its lens and collects light for many seconds, our eyes take an instantaneous reading of the photons. As such you'll not see the pinkish tinge in the Orion Nebula nor the spiral arms of Andromeda. But, you still do get to see them first hand, and that can be rewarding and exciting as well.

Orion Nebula - 2 sec Exposure

If you are still at it with your binoculars some 6 months later and you want to take the next step, then I'd say invest in a telescope. A great idea would be to go to a local club's star party and look through a variety of telescopes. But even if you can't, you cannot really go wrong getting an uncomplicated Dobsonian telescope in the 6-10" mirror size range. The additional light gathering power and magnification will open up a much larger range of DSO that you can hunt down from your yard.

Of course if it turns out that the thrill of seeing faint fuzzies in the sky does not give you the satisfaction you were hoping for the binoculars can always be used for checking the wildlife in your backyard - or getting an up close look at the horse you're betting on in the fourth race at Pimlico. 😏