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.