A Regal Conjunction

On September 19, 2025, a rare celestial event unfolded in the pre-dawn skies over Maryland: the conjunction of the Moon, Venus, and Regulus. I had high anticipation for this conjunction for several reasons. First, the tight grouping of the three celestial bodies was remarkable. Venus, the waning crescent Moon, and Regulus (Leo the Lion’s lucida) were packed within a 1-degree field of view. This meant that they were close enough to fit under a fingertip held at arm’s length, or easily with my telephoto lens racked out to 300mm.

So often the word “rare” is thrown about with abandon in regard to astronomical events. But this one does merit the appellation. A similarly tight grouping won’t occur again until September 22, 2041, when the trio will fit within a 7.2° circle. My research could not find any evidence of another triple conjunction from Maryland that will fit within a 1.0° field of view for at least the next 50 years.

Preparation

A few days out, the weather forecast looked very favorable for the morning of September 19^th, so I set about planning for it. I jumped on the Heavens-Above website and used their interactive sky chart and twilight times to get a preview. Those tools let me know that the event would be low on my eastern horizon, which was a problem due to the trees and houses that blocked my eastern view from home.

I needed a better venue and thought that somewhere along the nearby Loch Raven Reservoir might offer a clearer eastern horizon. I ruled out any trails as it could be risky navigating an unfamiliar path in the dark while carrying my camera equipment. Exploring virtually with Google maps, I noticed several small “observation decks” along the eastern side of the Dulaney Valley road bridge that crosses the reservoir. By midweek I had a game plan: park my car off on the shoulder near the bridge and walk a quarter mile to the platform.

The day before the conjunction, I weighed doing a reconnaissance of the bridge, anticipating that I would swing by right after work around 3:30 p.m. However, fate had other plans. Around 10 a.m., I received news that I was being laid off as part of budget cuts and had to hand in my laptop by 2 p.m. Given that 2026 was going to be my last year of part-time work as an OCR software developer, the layoff was not a significant impact, although there was the emotional aspect of no longer being employed after over half a century of work. The immediate upside was that it gave me an early departure time to head out to the reservoir. My drive out to the bridge validated my plans to park the car just before the bridge and walk out to the first fishing platform.

The Conjunction

I set my alarm for 4:30 a.m. Thursday evening, but I was up before the alarm went off. I dressed quickly and hustled out the door with my camera. I was at the pull-off area south of the bridge within a few minutes, parking the car and gathering my equipment. As I used my cell phone’s torch to light the path out to the platform, I pushed away the slight anxiety that creeps in, that sense of caution mixed with danger when doing something like this.

As I rounded the corner and stepped onto the bridge I saw my prize: an ocher-colored Moon rising, with Venus hanging just below it, both attenuated by the atmosphere. Regulus was not visible at that point, either hiding behind the trees or extinguished by the horizon haze. I was a bit surprised to see the Moon was in front of me rather than to my right over the water. As I advanced towards the bridge, the tree line slowly loomed taller and taller. By the time I was at the platform, the Moon and Venus were just skirting the treetops on the opposite shore. While not the imagined view of Moon rising over the waters of the reservoir, the setting was certainly beautiful.

The Crescent Moon & Venus

I set up the camera and bracketed a few shots of the slender orange crescent juxtaposed with a cream-colored Venus dangling below it. Time passed quickly, and as the duo climbed out of the haze, I could soon see Regulus hanging below Venus, forming a remarkable straight line. The earthshine was now evident, adding to the sublime nature of the appulse. For the next 45 minutes, I captured images at various focal lengths and exposures. Even at the full 300mm of the telephoto lens, all three members of the conjunction were in the frame due to the tightness of the conjunction. I knew the more challenging aspect in replicating with the camera what my eyes were witnessing would be the brightness contrast of these three. Venus outshone Regulus by about 100 times, while the Moon was just 5–6% illuminated, creating a dramatic visual contrast that our logarithmic eyes can handle well but pixels struggle to faithfully reproduce. Some things are just seemingly made for naked eye observation.

Moon, Venus, Regulus (and earthshine)

I had to contend with the southbound traffic coming from Jarrettsville Pike, timing my shots to miss their oncoming headlights intruding into my frame, even with the lens hood attached. I also noted that at times when some vehicles passed by on the bridge, there was some vibration, which likely ruined some shots. After about an hour and with dawn beginning to lighten the horizon, I packed up the camera and began the trip back home.

Conjunction reflected in the water below

As I pulled up in front of my house around 6:20 a.m., I assessed where the Moon was. It was still hidden behind trees, so I walked around to the backyard, camera and tripod in hand. It was not until I moved to the farthest southwest corner of the yard that the trio of conjunction companions cleared the rooftops. I fired off a couple of shots as the eastern sky gradually grew brighter, concluding my engagement with this magnificent conjunction by about 6:30 a.m.

The conjunction from my backyard

Witnessing this triple conjunction of the Moon, Venus, and Regulus was absolutely an unforgettable experience. The planning, the anticipation, and the sheer beauty of the event made it a night to remember, and the images will serve as a wonderful reminder of that September morning out at Loch Raven as the heavens aligned.

Chasing Planets: January's Observations and Challenges

The media has been hawking the auspicious "planetary parade" that allows an observer to see 6 planets during frosty January evenings. Of course two of those (Uranus and Neptune) are not naked eye objects. I do not mind articles that generate interest in our hobby, but my fear is always the "over promising and under deliver" risk.

However, January was indeed a fun month for us planet observers. Mars was occulted by the nearly Full Moon on the evening of the 13^th, and then two days later came to opposition for this apparition. Jupiter was positioned well and decided to throw a major eruption amid its North Tropical Zone southern jet stream on January 10^th, garnering a lot of attention. Venus also ascended the Zodiac after lying close to the southwestern horizon most of its current evening apparition, reaching greatest elongation on the 10^th heading for its highest altitude in the western sky on February 2^nd. The only downside has been the weather with classic winter turbulent seeing amid very cold temps.

Mars Occultation

The skies were clear but quite cold for the occultation of Mars. I set up the 10" Cyrus telescope and verified its collimation. The Moon served as a convenient focus target as I set up about 20 minutes before the scheduled disappearance. I knew that the difference in brightness would be a challenge and thought I'd have time to fiddle with the gain setting right before the occultation, but it happened so fast that I really did not get a great capture with the Moon very overexposed. Still, it was a very cool event to watch the Moon relentlessly approach the red orb and cover it up with about 30 seconds.

The Moon ready to cover Mars

January 17th Session

The evening of the 17th was predicted to have average seeing and temperature right around the freezing mark, which is fairly good for this region in winter. I again set the Cyrus scope out early to cool and verified its collimation. As Venus emerged from encroaching twilight I set to work on capturing our sister planet. 

Starting with the Deep Red filter (642+nm) and no Barlow, Venus provided a bright target upon which to focus. Doing a 5 minute capture resulted in a nice image, showing the planet past dichotomy and a common cue-ball appearance. I have yet to truly discern any cloud details in IR light.

Swapping out the Deep Red filter for an IR-block and UV set, I retargeted the planet and adjusted the settings to bring up the brightness in the fainter UV light. I could make out even on the on-screen image that there was uneven brightness in the sunlight reflecting off the Venusian cloud tops.

Processing produced a nice greyscale image with a some cloud structure. Interestingly, a well defined cusp cap was not really seen, although you might argue one was around the south pole region. This is somewhat in agreement with the UV Venus images I have been seeing submitted to the ALPO for the current evening apparition; cusp caps are not as prominent as I believe they were during the last apparition.

By now Saturn was visible in the deepening twilight, close and to the left of Venus. I figured why not give it one last capture since the upcoming mid-March solar conjunction and my obstructed western horizon meant it would soon be inaccessible. I added the Barlow back into the imaging path and returned to the Deep Red filter. Seeing was not very good, and the rings had closed up again compared to a few months ago. I had enough juice in the laptop for two 2-minute captures, resulting in a sub-par image where it is hard to even detect the globe's shadow being cast against the rings. Au revoir Saturn - until we meet again in the late spring!

Getting the AC adapter hooked up to the laptop I next swung over to Jupiter. My hopes were to get multiple captures into the evening if the weather held, recording not only the very recent North Tropical Zone southern jet stream eruption but also that continually expanding disturbance in the South Equatorial Belt that started back in November.

The seeing ended up being fairly good over the course of about 5 hours, allowing me to capture a lot of interesting features, including that NTrZ outbreak. As we began to close in on midnight the gods conspired to end my run as the cirrus clouds began to thicken and the tracking on the Celestron mount suddenly had a stall (it is always amazing how quickly the planet exits the frame when this happens). Rather than fight to recenter and continue amid the deteriorating seeing and transparency I decided to wrap things up on Jupiter.

In the middle of my Jupiter captures I had to take a break due to the location of the planet. When an object is high and near the meridian, the Cyrus telescope tube runs up against one of the tripod legs. The resolution would be to raise the tube up off the saddle, somewhat like extending with a pier. But that would be a lot of effort and so is not likely to happen in the near future (if at all). 

But rather than waste the time I opted to do a run on Mars which had just passed opposition a few days earlier. While at only about 13" in size the disk was large enough to take in some nice albedo features such as Syrtis Major setting and Sinus Sabaeus and Sinus Meridiani on the central meridian. The NPC was also a brilliant white and was a good feature to leverage in trying to get the best possible focus. Hopefully I will get in a few more sessions with Mars for this apparition, but it's going to shrink in size quickly now that it is past opposition.

While I did not achieve all my goals for the evening (I missed seeing the SEB disturbance on Jupiter), it was quite a good night for the middle of January. It reflects why planetary observing provides such a rich experience for the amateur astronomer.

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 

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.

A Filtered Experience

The topic for the HAL meeting this evening was "filters", which is a pretty big topic! After all, we have filters for visual use vs. imaging use, and then filters for specific targets from faint DSO to our brilliant Sun. Hopefully I provided a little insight at the session based on my personal experiences, especially as to planetary observing.

Back in '65 when I got my first scope, a classic 60mm refractor with .965" high-powered eyepiece, I knew one thing for sure that I really wanted to see was Jupiter's Great Red Spot. The scope showed the planet as a fuzzy disk with slight rainbow fringe, perhaps a stripe or two upon it, but no GRS in sight on the multiple occasions I target the giant planet. Somewhere - probably a library book that I had borrowed - I read how a blue filter would darken the GRS and therefore make it stand out better. Clearly that would make my target materialize in the eyepiece!

My dad was a local pharmacist and contracted with a camera shop down on Falls Road to provide film developing service for his customers. He was supportive of my hobby (so long as I didn't get the foolish idea that I could make a living looking at stars) and helped me to get a 2x2"Wratten 80A blue gelatin sheet and a mounting ring for the filter that was just a little smaller than the internal diameter of the refractor's dew shield. I carefully cut out my circle of blue, mounted it in the holder, dropped it into the front end of the scope and then waited for the next clear night. 

The view of Jupiter was quite pretty with its blue hue, but even after several attempts on different nights I still could see no GRS. (Of course, I am assuming that just by the odds I would have seen it on one of those evenings. I had not discovered Sky & Telescope with its listing of GRS transits yet, and online lookup would have been the glorious stuff of science fiction in the mid-60s). While filters lost a little of their charm from the experience, I felt that the principle was certainly sound. Reddish features would have their light blocked by a complementary blue filter, making them darker and easier to see. I began to suspect (correctly) that it was more an issue of small aperture than filter failure.

When I graduated to my 6" Newtonian I was finally able to catch sight of the Great Red Spot one evening without a filter. It had fairly good intensity back in the late 60's - similar to its appearance now. The availability of a glass filter that would screw into the bottom of the eyepiece was (as far as I knew) nonexistent. So no filters for visual inspection of my planetary quarry at that point in time.

But by now I was starting to play with using a second-hand Minolta range-finder camera to take pictures using the afocal method. Talk about a tedious hit or miss approach! You had to line up the camera over the eyepiece at where you think you are at focus, then hopefully get the planet in the field just based on the 6x30 finder scope, and finally snap the picture with a cable release while hopefully not jiggling the scope. Despite all that, I had occasional success with the technique. It also drove me to learn how to do my own B&W development rather than watch the photo lab assume nothing was on the roll of film and slice right through my field when trimming the negatives.

By this point I'm a HS freshman, networking with fellow amateurs at the Baltimore Astronomical Society and with enough pocket money from working at the pharmacy to buy some hobby stuff. I got another filter holder that would attach to the front of the Minolta and outfitted it with a Wratten blue gelatin. And then on a May evening in 1970 I did it - I actually captured the GRS photographically, a dark spot near the planet's central meridian. It was an OMG!! moment as I inspected that roll of film while hanging it up to dry. 

Jupiter - afocal method with 6" f/8 RV-6 at 140x
using Minolta camera with 80A filter

It was probably shortly after this that I began to find retailers of glass Wratten filters that we are so familiar with today. I started my collection with a #80A blue and it gradually expanded like a rainbow. Over the years I have found that, for visual planetary observing, they are not going the wow you like an O-III filter can do on an emission nebula. But they can be helpful if you approach their potential realistically, i.e., a tool that can improve the contrast of notoriously low-contrast planetary features. In addition, they do not cost an arm and a leg (at least not for the basic Wratten glass filters that almost any good astronomical supply house will carry).

Although I am given over more to imaging a planet rather than sketching it these days, I still do enjoy at the end of the session taking a few minutes to gaze upon my target before putting away the equipment. In doing so I'll almost always apply a filter in an effort to see the most that I can. Here are my common go-to filters using my 10" reflector (if you have a smaller scope then a corresponding filter with higher transmission rate may be a better fit):

The brilliance of our sister planet Venus means you have to knock down the glare significantly to be able to appreciate the disk. I often use a #47 Violet with only 13% transmission to accomplish that. The most I have been able to make out on Venus is some brightening at one or both polar regions ("cusp caps").

When Mars comes calling every other year it is a fun target and arguably one of the best for filter enhancement. The #80A medium blue is helpful in seeing the polar ice caps and lighter orthographic clouds that sometimes form. A light red #23A helps to darken the albedo features and boost their contrast. I have also found a deep yellow #15 to be a nice choice to reduce the planet's brightness and boost overall contrast.

Mars through my 6" f/8 RV-6 & Red #23A filter 10/7/2020

 

Jupiter is an absolute favorite for me given how dynamic it is. I have always found a yellow filter (#15 deep yellow or #11 yellow) as a good, all purpose aid to improving the contrast of the belts against the lighter zones. A pale blue (#82A) or medium blue (#80A) are helpful as well, especially with the Great Red Spot (the pale blue improves the contrast yet you can still pick out some of the red overtones to it).

While not as subtle as features among Venusian cloud tops, Saturn offers delicate features with its gradually darkening belts as you move from bright equatorial zone to dark polar hexagon. Again, a yellow filter seems to work well for improving the contrast a bit on the globe. 

Based on a very interesting "consumer reports" article on Cloudy Nights where author William A. Paolini compared multiple filters to find the ones that seemed to be the best for accentuating planetary detail, I have recently purchased a Baader Contrast-Booster filter. Now I just need to wait for this fall when we'll have Mars, Jupiter, and Saturn available for my own assessment of how well it does. 

If planetary observation is something you enjoy then you really should play around with some filters to see if they help you pick out some of the subtler details. Most retailers offer the Wratten color filters for under $20, and so long as you are not expecting miracles to happen, you'll likely find them an interesting and enjoyable accessory to have in your observing armamentarium. 

A Tangent on Venus

In last month's blog I chronicled my effort to see Venus as it skirted north of the Sun during its inferior conjunction. It was not a particularly easy task but certainly doable in clear skies. This month I'm doing a little armchair astronomy because that experience made me ponder when circumstances would be at their best to capture Venus as it moves between our home planet and the Sun.

Trigger warning - math is used in this blog post!

While you could spend time scouring the Internet to find the maximum distance that Venus can lie from the Sun during an inferior conjunction, where's the fun in that for anyone with geek tendencies? If we dust off our trigonometry and get some basic orbital elements we should be able to swag an answer to our question. 

It always helps to define some terms before solving the problem. The ecliptic is the plane in which the Earth orbits the Sun. In considering the orbits of other members of our Solar System we can speak of the inclination (tilt) of their orbit relative to Earth's orbit. Those two planes will intersect at two nodes (points). One node (the descending node ☋) would be when the neighboring planet is heading south when it crosses through our orbital plane, while the other (ascending node ☊) it is northbound. What is curious is that there does not seem to be a term for the point 90° farther along the orbit, where the planet would lie maximally above or below our ecliptic. For the sake of discussion, I'll call the point in the orbit where the planet lies at its greatest distance above (north) of the ecliptic as its cresting node and its southern counterpart as its sinking node.

Step 1: How far above the ecliptic does Venus lie when at its cresting (or sinking) node?  

We can readily find Venus' inclination to the ecliptic (3.4°) as well as its average distance from the Sun (a) and then calculate how far above the plane it lies (b) using basic trig:

b = a ÷ cot(θ)

Plugging in to the formula:

a (Venus-Sun distance) : 108 million km

cotangent of 3.4° = 16.8

b = 108/16.8 = 6.4 million km

Step 2: Knowing how high above the ecliptic plane Venus lies at cresting/sinking node and the distance between Earth and Venus at inferior conjunction, we can calculate the angle as seen from Earth for how far above the Sun Venus will appear in the sky: 

θ = tan^-1(b ÷ c)

b (height of Venus above ecliptic): 6.4 million km

c (Earth-Venus at Inferior Conjunction): 42 million km 

tangent ratio: 6.4 ÷ 42 = 0.1524

arctan(0.1524) = 8.67°

Wow - that is almost the length of the upper bowl of Big Dipper. My observation back in January had a distance of 4.8°, a little better than half the best it could be. So having determined the "what", let's turn our attention to "when" we would see one of these inferior conjunctions where Venus is at its cresting node.

This June will mark a decade since the last time Venus transited the Sun. As you may know, these events are quite rare, occurring as a set of transits 8 years apart. In the context of our ecliptic plane and Venus' plane, the inferior conjunction must occur while Venus is moving through its ascending or descending node in order for us to see a transit. And that is why they are confined to a few days around June 8th (as it reaches its descending node) or December 8th (ascending node). If our cresting node can reasonably be assumed to occur midway between June 8 and December 8, the approximate date for it would be on March 8th. As a result, for those of us in the northern hemisphere, an early springtime inferior conjunction will be our best opportunity to catch a glimpse of our sister planet directly above the Sun. 

From a listing of past and upcoming inferior conjunctions, we have the following ones that occur in March:

March Inferior Conjunctions
3/30/2001
3/29/2009
3/25/2017
3/23/2025
3/20/2033
3/18/2041
3/15/2049

Searching online for the inferior conjunction that happens March 23, 2025 we find the difference in Declination between Venus and the Sun will be + 7.5° - adhering pretty well to our predictions. With any luck I'll be around and have a clear day to set up the scope and try yet again to image the event.

A final observation before closing out this post. As discussed in April's 2020 blog when Venus traversed the Pleaides, our sister planet takes just shy of 8 years to return to nearly the same point in our sky. We see that 8 year interval again in the table above where each subsequent inferior conjunction arrives a couple days shy of 8 years. What if we look at the most recent inferior conjunction January 8th and project it out in an unscientific way to estimate its future conjunctions by simply adding 2,920 days repeatedly to it:

January Inferior Conjunctions

1/8/2022

1/6/2030

1/4/2038

1/2/2046

12/31/2053

12/29/2061

12/27/2069

12/25/2077

12/23/2085

12/21/2093

12/20/2101

12/18/2109

12/16/2117

Hmm - the next Transit of Venus is set to occur on December 11, 2117. We didn't land on it exactly because of our estimating shortcut, but there's no doubt that the most recent inferior conjunction is gradually walking the calendar backwards to become the next transit event, gradually losing a little of its northern clearance above the Sun's limb on each conjunction until it finally ends up crossing the orb.

If you have persevered to the end of this geeky blog entry - congratulations! It's probably due in some measure to the fact that, like me and the multitude of ancient astronomers that came before us, you find the patterns and rhythms of the heavens amazing and fascinating to explore.

Lunchtime Venus

Since late last spring Venus has been an evening star in our skies, shining brilliantly in the southwest. It was not the best of apparitions for those of us at mid-northern latitudes as it hung out in the basement of the zodiac when reaching its greatest distance from the Sun. I only managed a couple of casual observations and a single imaging attempt due to the planet often being obstructed by trees or buildings from my home observing venue.

Like all evening appearances of our sister planet, the transition from evening to morning star is defined by Venus reaching "inferior conjunction." This event, where the planet passes between Earth and the Sun, was set to occur on Saturday, January 8th around 7:40 p.m. our time. If the Earth-Venus-Sun orbital alignment were straight on we would witness Venus transiting the face of our home star at each one of these passages. But, just as we are not treated to a solar eclipse at every new Moon, Venus' orbital inclination of 3° to the ecliptic causes her to glide north or south of the Sun. Only roughly once a century do we get to witness a pair of transits, spaced eight years apart, with the most recent taking place in June of 2012.

This weekend's conjunction saw Venus skirting Sol's northern limb by about 4.5°, leading most websites such as In the Sky to state

At closest approach, Venus will appear at a separation of only 4°51' from the Sun, making it totally unobservable for several weeks while it is lost in the Sun's glare.

S&T Image Credit

In actuality, to describe it as totally unobservable is perhaps a bit of an exaggeration. It's one of those observing challenges that can be done, albeit with great care since even a brief exposure to the Sun's surface through any sort of optical aid can easily damage your retina. I've viewed Venus in the daytime before, both naked eye and with telescope, on numerous occasions, but had never attempted an Inferior Conjunction sighting. With the forecast for conjunction day looking quite good I decided to take up this challenge.

My hope was to actually get an image of the event, so I arose before dawn to mount the 6" reflector and perform an alignment. After battling some passing clouds I finally got the Celestron mount able to slew to a target with reasonable accuracy. I left the drive running and waited for my quarry to rise high enough in the eastern sky to view it. 

By 10:30 a.m. the winter Sun was well placed so I attached the camera and asked the mount to center Venus. I had placed a red filter in the optical path to help boost contrast against the bright blue sky, but the screen was still a bright, featureless canvas. I tried slowly sweeping the area a little bit to no avail. I finally removed the camera and substituted a 16mm eyepiece to see if I could make a visual sighting, but that, too, ended in failure. I reluctantly broke down the equipment and headed inside.

Not quite willing to accept defeat, while eating lunch I plotted my next attack. I considered that Venus should be positioned pretty much at the 12 o'clock position relative to the Sun's disk at this time. What if I positioned myself such that the apex of the neighbor's house blocked old Sol? Would that allow me catch Venus in the sky above the roofline with binoculars? I grabbed my trusty 7x50 Celestron binoculars and headed outside to find out. I swept the area until my arms grew tired with still no sign of the planet. As a last ditch effort I brought out the 15x70 Oberwerk binoculars to see if they might do the trick. After about five minutes - there!! A surprisingly bright, tiny crescent lying on its back was visible above the rooftop. It was a little surprising how clear one could distinguish the crescent shape and how white, like snow, the disk seemed in the blue sky. 

I hurried inside to grab the Canon and telephoto lens in hopes of capturing a shot using the same technique. When I emerged and used the Oberwerks to try to relocate Venus I struggled. Where the heck was it - I had just seen the darn thing. Then fate lent a hand when a jet billowing a contrail behind it crossed the field. Within a few seconds I had identified Venus again. Once the contrail had dissipated, it was again tough to pick out the tiny crescent. A few minutes later another jet deposited its white contrail in the vicinity, and again it became easier to pick up Venus in the field. Thinking about this I suspect that as the field jostled from my unsteady hand the planet moved with the contrail, thus becoming more apparent to my brain. Whatever the actual reason it was an undisputed truth that having the contrail in the field made picking up the planet easier.

In yet another testimony to our eyes' logarithmic response to light, the photos appear to have been a bust as well since exposures long enough to possibly pick up Venus were overexposed. The result is in a field containing a wide range of light intensities, our eyes will provide a good image whereas it is often impossible for the camera to capture it. And although I may have come away with no photographic proof of my success, the experience adds another page in my book of  amateur astronomy that I will have fond memories of.

A digital sketch of Venus & Contrail

 

The Venus Show

One thing is for certain - the disruption of our routines thanks to the COVID-19 virus outbreak has created a vacuum. Binge-watching has taken center stage for a lot of America, but if you step outside you'll find another show streaming through the evening twilight. Venus has been dazzling, high above the horizon like a super intense LED. Even the average person out for their stroll around the neighborhood notices this gem in the western sky.

Our sister planet returned to the evening twilight last fall. I recall catching sight of her in early November heading south on I-81 in Virginia on our way to NC, anchoring a wonderful Zodiacal alignment of Venus-Jupiter-Saturn. Slowly but steadily since then, like a diver ascending the ladder to the high dive platform, Venus has been gaining altitude from the Sun's glare.

Venus and crescent Moon Thanksgiving evening 2019

This evening apparition has been particularly auspicious, hitting a trifecta + one of favorable celestial mechanics. First, for us spring brings the angle of the ecliptic - that imaginary highway that the visible planets traverse - to its steepest angle with the horizon, reaching 73° on March 24th. This means that every degree that a planet lies from the Sun translates to maximum distance above our northern hemisphere horizon.

Next, that date of steepest ecliptic coincided with Venus reaching the point in its orbit where it forms a right angle alignment between itself, the Sun, and us - i.e., the greatest distance it can appear separated from our home star. The result of all this? Our brilliant neighbor began the evenings in late March a full 44° above the horizon, an inner-planet party animal that stayed up until close to midnight.

Another favorable aspect is that on March 20th the planet was at perihelion - the point in its orbit where it lies closest to the Sun. This contributes slightly to the planet's brightness so that when it hits that sweet spot between disk size and phase on April 28th it achieves an eye-catching maximum brilliance of -4.4 magnitude. While it may not be visually apparent that Venus is reaching an incremental notch above its normal brilliance it is as good as it gets (but don't tell the press less we start a "Super Venus!" meme). 

Perhaps the pièce de résistance of this apparition was Venus making a call upon the Pleiades, passing through their midst on April 3rd. While not rare (it happens every 8 years due to celestial mechanics returning Venus to roughly the same spot) it is one of the most lovely and photogenic conjunctions around. I have (somewhere) a shot of a similar alignment some 24 years ago taken on film. This time around I used the digital magic of taking 200+ shots with my 200mm lens and stacking them to produce a nice souvenir of the occasion (star spikes courtesy of Photoshop).

M45 and Venus on Apr 2, 2020

 

But wait - there's more! Like that diver perched high above on the platform our sister planet is preparing to swan dive into the glare of the Sun. Once we reach dichotomy (half phase) Venus becomes a more interesting target for amateur astronomers with even a modest scope. We enter a period where the size and apparent phase alter week by week and then day by day as we approach the June 3rd inferior conjunction date. If you have never tried to spot Venus in the daytime you'll have a great opportunity on April 26th using the Moon as your guide as it slides roughly 5° south of the planet. It also is a great time to see how soon you can pick out the phase using only binoculars or capture it using only your telephoto lens.

Remember, you don't have to practice social distancing with your old friends in the night sky - let them infect you with their beauty and mystery!

Fabulous But Frosty

Well January 2019 is just about in the record books - and it was both kind and cruel to my observation quests. The "big events" that I was interested in were the lunar eclipse on January 20th and the Venus-Jupiter-Luna alignment at month's end. It was kind in that the skies were indeed clear - but cruel in terms of the deep freeze one had to endure to witness them!

It seemed doubtful for a while that those of us in the mid-Atlantic would see the eclipse thanks to "Winter Storm Harper". (Seriously - we need names for these now? Apparently the NWS does not go along with the idea which is the brain child of the Weather Channel - you know, the folks who stand out there bringing you live coverage of catastrophic weather events, like this. But I digress with my disdain for hype). I happened to be a little NW of Baltimore at my son's in Waynesboro PA, and by the time Sunday rolled around it looked like it would be clear - but also bitterly cold and windy. It was too much to pack the scope but I figured the camera & tripod was worth a go.

I took a couple shots around 8pm through some high, thin clouds and then decided I'd just rest a bit after a busy day with my grandson. I startled awake at about 10:40 p.m. just in time to see the Earth's shadow having nibbled away at the Moon's edge. I could last about 5 minutes or so of taking shots before retreating into the home to warm up, leaving the camera outside tucked up against the house. Even with the tripod the wind ruined probably a third of my shots.

An overexposed eclipsed Moon with M44 to left

Just as totality began the battery on the camera signaled it was about done, further testimony to how cold it was. I brought it inside to change it out and as expected the lens immediately dewed over. I left it near a warm spot and popped on the wide field lens. It's definitely darker up in Waynesboro so I was fairly happy with the shots where I tried to include some of the fainter stars and the famous Beehive cluster. Then with the telephoto warmed up and ready for action again I swapped out lenses again and took some of the eclipsed Moon. I have not seen any official reports (or unofficial for that matter) but to me this was a fairly dark eclipse - perhaps a 2 on the Danjon scale as the deepest part of the shadow was grayer than the usual deep orange.

A rather dark eclipse?

By a little after 1 a.m. I abandoned any thoughts of eclipse egress photography - my grandson would be up in about 5 hours and I needed to be functional 😴

The second celestial highlight was the aforementioned appulse of Moon, Venus, and Jupiter. For several weeks I've admired the dance of Jupiter and Venus as old Jove slowly emerged from twilight to reach and then overtake the dazzling Venus. Those early morning January skies with the pair amid the stars of Scorpio were gorgeous - the combination of the winter transparency and the fewer lights made me literally stop and linger for a minute or two before climbing into the car to head off to work.

Venus & Jupiter mid-January

So with the waning crescent joining it was was time to grab the camera once more. But mother nature once again exacted a cold price with another Polar Vortex descending upon us (I'll let that piece of WC fluff slide...). Although technically colder than eclipse night the winds were not nearly as bad. That being said, it was a brief session admiring the alignment and grabbing a few quick shots before heading down the road.

So all in all January worked out just fine. After all, you can do something to fight off the cold, but with overcast skies you're just outta luck!

Venus - Moon - Jupiter January 31, 2019

Solar System Summer

Every so often it seems the planetary action clumps together. I recall many moons ago when my friend Herman Heyn was doing his sidewalk astronomy gig very routinely that he found a few winters to be challenging to pique citizen interest. Of course being in the heart of light polluted Baltimore made things like the Orion Nebula or Seven Sisters seem a little drab. Compared to Saturn and its rings or Jupiter and its moons, the wow factor just isn't there.

The Family Poses on August 6, 2018

We're approaching that alignment again as Jupiter gradually catches up to Saturn. Two years from now the two superstar ambassadors to amateur astronomy will be huddled together amid the stars of Sagittarius. They'll also be relatively low in the sky for us mid-latitude northern observers, but that won't keep their fans from trying to catch a glimpse of them.

As Labor Day is in our rear view mirror I have to admit that this summer we had a great Solar System family gathering in the evening skies. There was brilliant Venus in the western sky, moving from gibbous to crescent phase all the while maintaining her cloudy veil. Not the best of evening elongations as the western ecliptic lies close to the horizon this time of year, but always a dazzling jewel that is worth visiting and pondering this hellish world - like a scientific experiment gone bad.

Jupiter and GRS in 6" f/8 Reflector July 29, 2018

Next came king Jupiter. This is my favorite planet - not only due to its ample size but especially due to its changing nature. On any given night you might catch a shadow transit on the cloud tops, or the Great Red Spot (which has definitely shrunk but also become a bit ruddier in complexion) staring back at you. Cloud bands with delicate features also await the patient observer or videographer. One evening after having chased down down M104 in my 80mm scope I decided to end with Jupiter to see what the little refractor could do. Cranking up the power with an 8mm TMB Planetary eyepiece + 2x Meade Barlow I was delighted to clearly make out the GRS moving towards the preceding (setting) limb as well as a black pencil point on the clouds betraying Io's presence as it cut across the disk. Old Jove - always the showman.

A couple hours east was full-tilt Saturn, rings wide open as the northern hemisphere has its maximum solar exposure. As he ambles towards Pisces over the next 7 years the rings will gradually fold up until they are razor thin. But for this summer they were in their full glory like a preening peacock - Cassini's division obvious, shadow play on globe and rings creating that wonderful depth of field sensation, tiny moons gathered around the globe. And subtle but evident clouds gradually darkening towards the pole. What's not to love about this view?

Mars on Aug 23, 2018

And finally, bursting onto the stage beyond Saturn was Mars - back with a vengeance from its roughly two year hiatus, sporting a good size disk that we won't see again until (yikes!) 2035. Even with the poorly timed arrival of a global Martian dust storm it still was enticing to see the polar caps and fuzzy albedo markings on the red one. Mars takes magnification well due to its brightness, so you mainly need some patience and steady skies to begin to see some details. Playing around with filters is also enjoyable to see what additional features you might tease out in the different light. While the show's not quite over, for this orb the motto is definitely Carpe Noctum.