A Jovian Superfecta

Earlier this month I was hoping to get in another imaging session for the current Jupiter apparition, with the planet still standing relatively high as the May twilight deepened. I started in “White Light” (color) and quickly saw that the Great Red Spot (GRS) was rising and so I’d have it well positioned. The seeing however, was definitely sub-par, probably a 3 (maybe a 2?) out of 10.

Yet even under this mediocre seeing, it occurred to me that this was an opportunity to try for a wavelength superfecta, capturing the planet and its iconic storm in four different lights: WL, Infrared (IR), Methane (CH4) (UV), and Ultraviolet. It was a little challenging due to the low transmission I get in the CH4 and UV bands, causing the frames-per-second to drop dramatically. In such situations I leverage 2×2 binning, which groups four pixels into one. That makes the target effectively brighter, boosting the signal through this very dark filter. But it also reduces the image scale, so Jupiter appears slightly smaller and less detailed than in my unbinned captures.

The result was an interesting mosaic showcasing how Jupiter presents a different and scientifically valuable appearance in these varying bands of light. Each wavelength highlights a different altitude, particle size, or scattering process in the Jovian atmosphere. The GRS, being a deep, long‑lived anticyclone with complex vertical structure, becomes a perfect case study.

White Light

White light is the “baseline Jupiter”, the view closest to what the eye sees. It is a blend of scattering from cloud tops and deeper layers. The GRS’s color comes from chromophores (complex molecules produced by photochemistry) concentrated in its upper haze.

• The GRS appears as a salmon‑colored oval embedded in the South Equatorial Belt.
• Contrast is moderate because white light integrates photons from many atmospheric layers.

Ultraviolet (UV)

UV images emphasize high‑altitude hazes and aerosols. UV absorption is dominated by photochemical hazes. The GRS has a thick, vertically extended haze cap that blocks UV, making it stand out as a dark feature.

• The GRS typically appears dark in UV because its upper haze absorbs strongly at short wavelengths.
• Surrounding high-altitude haze regions appear bright.
• The UV view often looks “sharper” because it isolates the uppermost layers.

Infrared

Near‑IR wavelengths penetrate deeper into the cloud deck. IR brightness correlates with cloud-top altitude and temperature. The GRS’s anticyclonic upwelling lifts ammonia clouds to higher, colder levels, making it a strong IR reflector.

• The GRS often appears bright in IR because its cloud tops are higher and colder than surrounding regions.
• Belts and zones invert their contrast relative to visible light.
• Even though seeing is often steadier in IR, on this particular night it was not a huge help with poor conditions.

Methane Band

The methane absorption band is the most altitude‑selective of the four. Methane imaging isolates the highest cloud layers, with low-altitude features vanishing almost completely. The GRS’s brightness confirms its vertical extent and the strong upwelling at its center.

• Bright areas in CH₄ indicate very high-altitude clouds that reflect sunlight before it can be absorbed by methane.
• The GRS is usually bright in methane band because its cloud tops extend high into the upper troposphere.
• If you look closely you can also make out tiny NN-LRS-1 near the same longitude of the GRS but in the Northern Polar Region of the planet.

The GRS changes appearance because each wavelength samples a different combination of scattering, absorption, and cloud height. The storm’s vertical structure is complex: a tall central canopy, deep roots, and a surrounding turbulent wake. Multi‑wavelength imaging is one of the few ways amateurs can probe that structure directly.

If you’ve never tried imaging Jupiter beyond one-shot color, you may want to consider expanding your armamentarium to include some additional filters. I’d start off with an IR as it is the easiest and also has the advantage of being a mild antidote to poor seeing. Later on adding a simple UV or methane filter can expand your imaging opportunities of the planet and provide additional valuable scientific information. Jupiter rewards curiosity – and it rewards imagers who look at it in more than one light.

An All-Nighter with Jove

I always look forward to Jupiter oppositions in the winter zodiac. The current apparition has the giant planet hosted among the stars of Gemini, riding about as high as possible in the night sky for mid‑northern observers. The combination of it gliding above the worst of the turbulent atmospheric and long January nights (where in theory you might capture an entire rotation in a single session) are exciting prospects.

But winter is winter - especially in the Baltimore area. The cold is one thing to contend with, but even more of a spoiler are the clouds and unstable seeing. I’ve often felt that our region’s winter skies offer fewer usable nights than any other season, and it turns out that impression isn’t just grumbling. According to long‑term climatology, the region’s winter sky is overcast or mostly cloudy about half the time. And while I cannot find data on “seeing” I would bet we get most clear nights checking in at a 1-2 seeing level on the scale of 1-10.

Which is why the night of January 7–8, 2026 felt like such a small miracle.

The forecast from Astrospheric earlier that day told the usual winter story: cloud cover and seeing models leaning pessimistic, barely reaching “acceptable” levels. The kind of forecast that normally has me planning a short session – an hour, maybe ninety minutes – before the clouds roll in or the seeing collapses (or the cold gets the best of me). But heck, why not roll the dice? After all, Jupiter was a couple days from opposition, so prime time.

When I stepped outside around 8:30 PM, the first surprise was the temperature. It wasn’t bitterly cold, which meant I could stay chair‑side instead of retreating indoors between captures. I’d already set the scope out earlier to cool so I started my “pre-flight checklist”

• Confirm the spotting scope alignment
• Dial in a very solid collimation
• Check transparency (a respectable 7–8 by my estimate)
• Gauge the seeing (somewhere between 3 and 5, with brief moments of better steadiness)

With the QHY camera running through SharpCap, I was getting a very respectable 130+ fps in white light. I began a cadence of four‑run sequences every 15–20 minutes, each run a two‑minute capture. Europa was approaching the disk, with a transit predicted just after midnight – another incentive to keep going as long as the sky allowed.

And, surprisingly, the sky did cooperate. As I wrapped up each imaging run I was like a gambler pushing his luck, thinking “just one more capture before you call it quits”. Before I knew it, it was midnight and I had seen about half a Jupiter rotation at this point. Now my appetite was whetted for that elusive full rotation capture. I did some quick calculations in my head and figured I’d have to hang in there until close to 4 a.m. in order to see the GRS, which had started off setting, come back into view. I decided to go for it and did a meridian flip to ensure I could track the giant planet as it headed west in the sky.

I continued performing imaging captures but now roughly every 30-60 minutes, retreating inside between them not so much to warm up but to put my feet up and get a little rest. The days of staying up all night and at my scope may well be behind me!

By 3 a.m. I could see that some patchy clouds were finally working their way into my region, dropping the transparency a bit. About an hour later the Moon showed a bit of a halo around it, further evidence of deteriorating conditions. And while that sort of haze is not always a killer for seeing, in this instance I could see that it, too, was slipping as the early morning wore on. I took the final sequence at from 4:15–4:30 a.m. with the seeing slipping down to about a 3. But I had it – there was the GRS rising into view signaling I had seen the full planet’s cloud features pass in front of me.  

Despite the uneven seeing in the early morning hours, the dataset was strong enough to build a full cylindrical map in WinJUPOS. The region around the GRS is a little darker than ideal, but that’s simply the geometry of the night: I never caught it near the central meridian, so the limb‑darkened frames had to carry that section. Still, the map is a personal accomplishment that captures the character of Jupiter beautifully for that date, revealing many long-term features such as the GRS, Oval BA, the SSTB storms, and many others!

Yes, nights like that are rare in January. The forecasts don’t encourage you. The statistics don’t encourage you. And yet, every so often, the sky relents just enough to reward persistence. My reward on this night was a nearly full rotation, a Europa transit, some enjoyable visual observing of the planet between imaging runs, and a cool map documenting Jupiter as it came to opposition in 2026. Yep - if this is how my 2026 observing is going to go, I’ll take it!

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.

December Planet Parade

While it is nice to see a planet coming to opposition in the northern part of the zodiac given the much higher altitude it then attains in our skies. But while the planet heads north, our opportunities of good seeing go south. The heat of the day radiating into the atmosphere sets up turbulence and often results in poor seeing. It also seems that the winter months are more overcast. This year I went 51 days (late October to mid-December) between observations - not great! 

Uranus - December 18, 2024

At the start of the year one of the astronomy goals I had set was to image Uranus with its moons. I tried a couple of times earlier in the fall without success, but finally on the night of the 18th I got the SharpCap stacking working with Uranus as the target. I had to keep the region of interest (RoI) wide because otherwise the software complained of not having enough stars to align. I played with the exposure and gain to finally generate a nice stacked image that clearly showed some of the moons.

Using some post-processing tools to enhance the raw stack resulted in a fairly satisfying result. The Sky & Telescope online tool that shows where the moons are in relation to the planet was helpful in orienting the shot. I ended up capturing 4 of them (Titania, Oberon, Ariel, and Umbriel) - Miranda was probably lost in the glare of the planet. Maybe next time I'll try to include the Barlow in the imaging train to gain some more space between the planet and moon.

After that success I decided to focus on trying to capture the planet without overexposing it. For this run I did WL with an UV/IR cut filter. Uranus is very difficult to pull out details, and those usually require an IR wavelength and larger aperture. The ending result was perhaps a bit more blue than I expected, but overall definitely the best image of Uranus I have been able to produce.

Jupiter - December 23, 2024 

Just a couple days before Christmas the evening sky was clear but cold, but with predictions of average seeing so I thought I'd set up the scope. I was amazed to find that the seeing was actually above average as I dialed in Jupiter. I started off with a series of WL runs using the Cyrus 10" f/6 and a 2.5x Barlow. 

In between Christmas Eve activities the next day I found a little time to do some processing of the captures and was quite happy with the outcome. Oval BA was almost on the meridian, far easier to see than last year with a pale tan coloration. Out ahead of it was long enduring oval A8. The SEB had some spots of darker material, but my general impression is that the belt is weaker than it has been the last couple of years. The EZ had a lot of material swept into it from both NEB and SEB, presenting almost like latte foam art crafted by a talented barista. The NEB had a small, intense outbreak midway between the following limb and central meridian. 

I also ran a set of CH4 captures since the seeing was above average. As to be expected, BA was the most prominent object at that wavelength.

Mars - December 23, 2024  

By this time Mars had cleared the neighbor's tree and was an enticing target. I did several runs in WL with high hopes of getting a good capture. After four 2-minute runs I swapped out for the R+IR filter, but the laptop unfortunately cut off due to low power after only one capture.

Processing after Christmas showed a well-formed NPC with a "Lowell Band" around it comprised of Propontis II and Utopia. There definitely were some clouds around the south pole, and M. Cimmerium was well placed. In the center was the Elysium area which seemed to show as an elevated area more strongly than I recall previously. The single R+IR shot was also worthwhile, demonstrating how the longer wavelength can sometime bring out additional details, such as the subtle Gomer Sinus extension off of M. Cimmerium.

Overall, quite a nice way to wrap up 2024. It was another enjoyable year with lots of activity, from a Total Solar Eclipse to a pretty good comet. Hopefully 2025 will bring more clear nights and interesting features to enjoy!

Planetary Potpourri

August finally brought Jupiter and Mars above the tree line for me in the pre-dawn skies. The classic humid skies under a dome of high pressure that is typical of summer around here have the one advantage of often providing some steady skies. 

Saturn
Aug 1, 2024

The month kicked off with the final transit of Titan across the far southern Saturnian cloud-tops for the current apparition. From here on out the massive moon will skim across the south pole until our geometry brings it back across the planet again. Arising at 2 a.m., I was blessed with very fine seeing (9/10) and started with captures in WL with a UV/IR block, resulting in the color image shown above. The low albedo of Titan compared to the planet's clouds yielded a dusky silhouette of the moon just skimming across the SPR. On the planet there are multiple bands in the N. hemisphere while the S. hemisphere is a bit more homogeneous and bluer in appearance. The shadow of the rings on the globe is easily seen, as the globe reciprocates with its shadow on the rings. Some vague hints of Cassini's division are seen. While I did not discern it while doing the imaging run, upon processing I found that if you look closely, you can also make out the tiny shadow of Dione which was in transit at the same time, lying just preceding the CM and at the latitude of the southern edge of the SEB.

Switching to the R +IR filter yielded the greyscale image above as Titan started its egress from the planet's disk. Between the different wavelength and the limb darkening, Titan appears white rather than its dark silhouette earlier in WL when over the SPR. In this view the planet itself shows multiple bands and bright EZ. The banding striations in the Southern hemisphere are much easier to see in this wavelength compared to the WL, and while not obvious the Cassini division is also a tad easier to pick out. And as with the WL capture, you can catch Dione's shadow just past the CM and at the southern flank of the SEB.

Jupiter
Aug 23, 2024

Some above average seeing greeted me again on Friday morning the 23rd (seeing 8/10, transparency 7/10) for a Jupiter session. Started off with Great Red Spot near CM, followed by a very chaotic section of the SEB punctuated by a strong rift. Given that white clouds are higher in the atmosphere, it makes me speculate that perhaps this could be the beginning of an SEB fade? Time will tell. The images also allowed for a rough estimate of the GRS's size, which came out to roughly 13,100 km - a new low. For decades the boast has always been that you could fit 2-3 Earths inside the massive storm, but with our terrestrial diameter of 12,750 km it may soon come to pass that it won't be large enough for even a single Earth.

The South Temperate Belt, home to the long-enduring anti-cyclone "A" storms, was featuring 3 of them at this longitude. I believe from left to right we are looking at A4, A3, and A2. The North Temperate Belt also features a chronic storm, NN-WS-4, just trailing the GRS's latitude a bit.

The image also displayed some intense "hot spots" along the southern edge of the Northern Equatorial Belt, spawning blue festoons trailing down into the EZ. The NEB is now back to its dominant self, having extended northward to reclaim its girth. Along its northern edge we have some ovals. These appear to be the long enduring "White Spots" (such as WS-E, WS-Z) that have been surrounded by the expanding NEB, making them far more conspicuous than in recent years by the added contrast.

Mars
Aug 23, 2024

With power still remaining on the laptop after my Jove captures I swung over to Mars to see what was up. At just a little larger than 6", I am always amazed that the SPLICE process can pick up any features at all. Sinus Meridiani and a little of Sinus Sabaeus are seen as well as Margarifiter Sinus and M. Erythraeum. There is no sign of a South Polar Cap which has dissipated as winter retreats in the planet's Southern hemisphere. But the northern chill has begun as evidenced by a North Polar Hood beginning to form. Niliacus Lacus also can be seen extending out from under the hood. While this won't be a great apparition with Mars' size topping out at a little above 13" in January, it still promises to be fun imaging our mysterious neighbor.

With Saturn hitting opposition in a few days and Jupiter nearly at western quadrature, the 2025 planetary season is definitely upon us. Here's hoping for lots of opportunities to check in on them under clear and steady skies!

Jupiter's June

With the exception of Mercury at only 0.03°, all the planets have some tilt to their axis. As any fifth grader should be able to explain to you, Earth has an inclination of 23½° and that is what gives us our seasons as we orbit the Sun. As amateur astronomers we can sometimes notice the tilt when observing some of our planetary neighbors. Mars' axial tilt is about a degree larger than Earth's and can present one hemisphere more favorably than another. For example, our best views of Mars are when it comes to opposition right around the time of its perihelion. As it turns out Mars is always close to its Winter Solstice at that point in its orbit, so we see  southern hemisphere features like Hellas and Syrtis Major better because they are tilted towards us while northern albedo markings such as Mare Acidalium are tough to discern (map). 

Hubble captures Titan's Transit - Feb 24, 2009

Saturn, with an inclination of 26¾° is the easiest example of noticing the affect of axial tilt. At its spring and fall equinoxes the rings all but disappear as we view the planet's equator straight on. At its solstices we are treated to the full grandeur of the ring system during maximal display. Another aspect is that only when Saturn approaches its equinoxes will the orbital planes of its moons begin to intersect the globe of the planet from our vantage point. It is only at those points in its ~29-year orbit that we get to see Titan transit and cast its large shadow upon the clouds below. While not as rare as a Venus transit, seeing our Solar System's largest moon cut in front of its home planet is an infrequent event (and one that is on my bucket list for the upcoming equinox!)

And where does Jupiter lie on the axial tilt spectrum? It comes in at a mere 3°, barely tipping towards or away from our view. We never get a nice look at its polar regions as with Saturn, it is consistently featuring its full-on view. Despite Jove's stingy axial tilt, the observant amateur astronomer can still discern evidence of the inclination, even with a modest telescope, by studying the Galilean moons. 

Yesterday (January 20, 2024) on Jupiter the Druids assembled at their Stonehenge to celebrate their Northern Summer Solstice, the maximal tilt of the planet's north pole towards the Sun. About a week earlier I was out imaging Jupiter (under very poor seeing) with a serendipitous alignment three out of the four Galilean moons. Io was about to slip behind the planet, while Europa had just start its trek across the planet's face. Ganymede stood nearby just off the limb awaiting its turn to begin transiting the planet.

Jupiter on Jan 13, 2024 7:39 p.m. EST

Like most planetary moons, the Galilean quartet have their orbital planes roughly aligned to Jupiter's equatorial plane (i.e., if we could see those planes it'd be similar to seeing Saturn's rings). But in my capture we note that despite having orbits lying in that equatorial plane, none of them appear near the planet's equator as they approach Jupiter. We see that the two that are about to cut in front of the globe will do so across Southern hemisphere cloud tops, while the one that is about to duck behind the planet appears at a northern Jovian latitude. This let's us know that Jupiter's northern hemisphere, and by extension the orbital planes of these moons, is currently tilted towards us.

There's another piece of information to be gleaned from the image taken on the 13th. If we use WinJUPOS to apply a grid overlay on Jupiter, we can more easily see that the distance the moons lie from the equator varies. Io is closest to the equator at roughly 20°, Europa is about double at ~38°, while Ganymede is doing a more polar crossing at about 55°. If we consider the schematic below that approximates how a set of orbits lying in the planet's equatorial plane might appear with a north-leaning planet tilt, we can see the significance of this. Io must be orbiting closest to the planet since it is nearest the equator. Europa must lie (very roughly) twice as distant. and Ganymede is orbiting at a distance perhaps some 2½ times that of Io. When we check our hypothesis we see that our analysis was an acceptable swag: 

• Io: 422 km
• Europa: 671 km
• Ganymede: 1,070 km

But what about Callisto, the farthest out of the 4 Galilean moons at 1,883 km? If Callisto had been in the frame we would have seen it floating above or below Jupiter given the combination of the moon's more distant orbit and the planet's current maximum northerly tilt (much like the green orbit in our schematic above). 

Of course now that Jupiter has passed the Northern Summer Solstice in its orbit it will be moving towards an Autumnal Equinox roughly 3 years from now. As we head there you'll see the moons gradually fall back towards transiting the planet along its equator, and Callisto will once again join her siblings in crossing the Jovian cloud tops from as seen from our home planet. 

So often we set up the telescope and take a just a quick peek at our target, not tarrying to inspect the view in the eyepiece nor record what was seen. So here's a challenge for you to do something more. Observe Jupiter when a Galilean moon event is set to occur (S&T has a great online tool to predict when these occur, with three opportunities this coming week on the 22nd, 24th, and 29th). In a notebook sketch what you see (and you do not need a large scope to see these events). Continue to do this over the next three years and you'll have a cool record that shows the shifting tilt of the planet as evidenced by the changing appearance of the 4 brightest moons when near or in front of the planet. While you won't get an award for your effort, I bet you'll feel a reward for being able to demonstrate some of the mechanics of our Solar System through a patient recording of what you've seen first-hand.

The Pixel Sweet Spot

Earlier this week the forecast was for an evening of average to perhaps better than average seeing with cold (but not biting) temps. I rolled out the scope a little before sunset to begin cooling and got things ready - with Jupiter just past quadrature it is always going to be highest in the sky as soon as it becomes visible. 

I did the routine alignment, collimation check, and finder alignment before finally popping in the ZWO camera. Activating the camera I was greeted by a strange sight - an emerald green Jupiter. At first I thought maybe a Debayer setting was off in the capture interface but soon noticed that the histogram was not registering in blue or red, only green. I rebooted the laptop hoping maybe that would restore things, but no luck. I brought up a different capture application, but it, too, sported a green globe.

Rather than admit defeat I located my retired Imaging Source camera and popped it into the Barlow. The view and histogram confirmed that we were back to getting a color image, but I immediately was struck by how much smaller the image appeared to be. Hmm - what was that about?

It turns out that my older camera, a DFK21AU042, has a pixel size of 5.6µ whereas my ASI178MC has a size of less than half that, checking in at 2.4µ. The formula for calculating how much sky each pixel registers for your setup is as follows:

  (Pixel Size/Telescope Focal Length) * 206.265  

For my setup using a 2.5x Barlow that becomes:

DFK21AU042 = 0.31"

ASI178MC = 0.13"

The theoretical ideal for planetary imaging for under average seeing conditions is around 0.15" per pixel (Note that this is different than DSO imaging, where the average is about 1-2" per pixel). Clearly, my ZWO camera is a lot closer to the mark, and the better thing to have done would have been to stop and swap out my 2.5x Barlow for my 4x one to get a little lower arc-second/pixel value. But the window of calm seeing that we often get shortly after sundown wouldn't allow that, so I forged ahead.

Below are comparative images taken about a week apart of roughly the same Jovian longitude. It is pretty obvious from it that we lose resolution in the image acquired using the DFK21AU042 camera.

Is the image from the older camera terrible? No, hardly. We can still make out details like Oval BA and anti-cyclone storm A1 - something that was unheard of using film a few decades ago. But in astronomy, and in planetary imaging in particular, it is all about getting all the parameters as ideal as possible so that you can capture all the details available given the seeing conditions. Hopefully I get my ZWO camera fixed, but in the meantime I know from experience now to at least break out the 4x Barlow to try to get closer to that desired arc-second/pixel value.

More Than Meets the Eye

Sept 20-21, 2022  

While prepping for my HAL talk last month I stumbled across the fact that the Astronomical League has a Jupiter Observing program among its offerings. It's a program whose objectives I've certainly met over the years, but thought it would be fun to officially claim the prize. 

One task is to collect a series of observations on the 4 bright Galilean moons and interpret your data to characterize the moons and their orbits. You need a couple of sessions spanning over two hours, and this evening's clear skies (and an added bonus of a Ganymede transit) was a nice opportunity to meet some of the program's requirements. I decided to use the 80mm Vixen refractor since it is easier to set up and more than adequate for recording the bright moons.

By 10:30 I had Jupiter centered in the eyepiece. Ganymede's large and stark shadow is not hard at all to pick up on, even in this small aperture. While I could have simply sketch the moon positions, I opted for a set of video images at 30 minute intervals as a better approach. 

Galilean Moons, with Ganymede in Transit

When I finished the first capture I did a quick processing to see what I had. I was actually a little surprised at the detail on the planet using such a small aperture. It led me to wonder just how much detail could I get using the Vixen if I tried? 

Since I needed to wait a half hour to make my next capture I decided to explore the question. I popped in the Meade 2x short Barlow and brought the Region of Interest (ROI) as tight as I could. This smaller capture area allowed the frames-per-second rate to go from 96 to 286, increasing the chances of leveraging those microseconds of steady seeing into a nice photo.

Next day I set to work running the video capture through my workflow - PIPP, Autostakkert3!, and Registax6 to produce a final image. Although the details are puny compared to what the 10" Cyrus reflector produces, they are pretty amazing given the aperture. Not only do we get the major bands, but features such as festoons in the NEB, Ganymede's disk as it begins to egress, and even Oval BA can be clearly identified in the tiny image. 

Would one suggest an 80mm refractor as a good instrument for planetary exploration? Not really - but it clearly has a lot more to offer compared to what you'll see behind the eyepiece when you team it up with computer assisted planetary imaging. Visually it takes a little effort for me to discern Oval BA using the 10" with a suitable filter. Snaring it in a capture using a telescope with 3 inches of aperture is really quite a testimony to the high-contrast quality that refractors offer as well as the power of using the lucky imaging technique. If you use a similar scope as your main tool for exploring the night sky you might consider adding on a planetary video camera and discover for yourself the enjoyment of capturing features that you'll likely never see visually.

Cool Hot Spots

 July 16, 2022

It’s about 3:45 am when the alarm on my phone gradually intrudes upon my slumber, summoning me to an imaging rendezvous with Jupiter that I thought would be a good idea 6 hours earlier. I lay there for a moment and have the internal debate as to whether I really want to do this. A couple of minutes pass and I decide yes, I do want to keep the appointment – it’s worth the effort to see what interesting features might be on display. Donning more appropriate street attire and grabbing the laptop I head out to the driveway where Jupiter hangs like a brilliant beacon above my neighbor’s house. 

I wheel the scope out from the garage and pull off the covers. In my mind I tick down the checklist of tasks to perform before I can begin imaging. Validate mirror collimation, verify spotting scope alignment, adjust weight to achieve balance, power up mount & laptop, connect everything. After a few minutes I fire up the camera and go about getting Jupiter centered in the field.

As I sharpen the focus my attention is drawn to a very dark area along the North Equatorial Belt. Pretty weird – the intensity is almost reminiscent of a shadow transit, but it lacks the crisp, hole-punch appearance that I normally associate with such an event, seeming more distended. I continue my imaging run for about an hour and then break down the setup so that I will be ready for the next session.

Later in the day I turn my attention to processing the video capture into a sharpened image of the planet. As I twiddle with the wavelets I see that the dark area is a projection off the NEBs extending into the equatorial zone, and the color is a pronounced dark slate gray. That combination of information allows it to be classified as a beautiful example of a Jupiter “hot spot”.

Jupiter with "Hot Spot" 07/16/2022

As documented in John Rogers book The Giant Planet Jupiter, these blue-gray areas along the NEB’s southern perimeter have been observed over many decades. Research has found that most of the time there are perhaps a dozen of these features present, spaced roughly every 30⁰ around the planet. From what I have seen from other observers sending in their images to ALPO, these hot spots are far more prominent right now. Looking back over the 2021 images I can catch glimpses of these features in keeping with Roger’s statement, but they were more subtle.

What is a hot spot? Why is it such a different color than we normally see? Current theory holds that these are areas of high pressure (sinking air), and as the air warms in its descent the white ammonia crystals evaporate, allowing us to see deeper into the planet, possibly all the way down to the level where water clouds can form.

We actually have another reason to be curious about these features because on December 7, 1995, the Galileo atmospheric probe actually entered a hot spot and sent back data for almost an hour, finding less water and helium than expected. Understanding hot spots can help us interpret the data from the probe.

Another interplanetary voyager, Cassini, has also helped to unravel the mystery of these hot spots. Images taken by Cassini as it flew past the planet on its way to Saturn have been analyzed, leading to a hypothesis that a Rossby wave is producing them. Such a wave is undulating up and down in the atmosphere, generating a hot spot region as it plunges downward, displacing the colder air. There is a nice NASA video describing the research here. 

While it’s not clear if these hot spots will continue to be prominent for the remainder of this Jovian apparition it’s certainly possible. If you are an imager they should be fairly easy to pick up if you are using a scope in the 4-inch (refractor) to 6-inch (reflector) range. Visually a strong outbreak like this one from July 16^th should be doable in the same size instrument, especially if you boost the contrast by using a red filter. More subtle ones are likely going to need larger aperture, steady skies, and will also be aided by a red filter. If you do record one you might consider sending your observation to ALPO to document it.

Jupiter reaches opposition next month, a great opportunity to spend some time examining its features at a reasonable hour of the evening. Who knows – perhaps you’ll be able to say “Oh course I’ve seen the Great Red Spot, but have you seen a blue hot spot?”

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. 

Special Occasions

The science writers are at it again, hawking the "Grand Conjunction" of Saturn and Jupiter that will take place on December 21, 2020 as a bright Christmas Star for all to see. On that evening the two planets will be a scant 0.1° apart, close enough that they should both comfortably fit into most amateur telescopes at low to medium power. It is clearly a special occasion since the last time these two giants were visible this close together in the night sky was 1226 when St. Francis of Assisi was around. Of course there's also the fringe media that is having a ball with it, claiming this alignment at Winter solstice is a bad omen (just search for "grand conjunction 2020 predictions").

Hype aside, amateur astronomers are indeed excited to witness this alignment. Roughly every twenty years Jupiter catches up with Saturn, pairing up with it in the heavens. In 1980 and 2000 they got to within about 1¼° of each other, and will do so again in 2040. But the 2000 and 2040 alignments suffer from Sun glare, making the spectacle hard or impossible to appreciate. The spring of 2060 should deliver a mega hit to any conjunction junkie with Jupiter and Saturn getting within about 1 degree of each other amid Taurus while Venus threads her way through the Pleiades and a crescent Moon thrown in for good measure on the night of April 4th!

Grand Conjunction of 2060

So, looking at that Stellarium Online image of the conjunction on the night of April 4th in 2060, did you get excited? Did you think, "Wow, don't want to miss that!" (assuming you're under 40)? What is it about these gatherings of celestial orbs that makes the amateur astronomer circle the date on their calendar in expectation?

I think some of it relates to the yin-yang aspect of our hobby. On the one side we have the "passive" sense of the heavens. They are consistent, steady, predictable. There is something almost reassuring seeing Orion raise up from his side on a late October evening. We know that almost nothing of shallow or deep space has altered much since Galileo's first scope or Messier's compilation of faux comets. When I say "Albireo" your mind's eye brings forth a beautiful double star. Like travelers who've embarked on a country wide road trip to see the sights, we revel in comparing notes and swapping photos of the cool things we've visited. 

And then there's the "active" side of the night sky. Here we seek to catch ephemeral sights that may be constrained by location or good fortune. You venture out under cold, clear December skies on the 12th in hopes of catching a Geminid that is spectacular. We trek across country or even across continents in hopes of catching a few minutes of the solar corona. These two examples categorize the action; some of it is somewhat random (meteor showers, super novae, sunspots, aurora) while others are anticipated. 

Most of that predictable action centers around alignments. Conjunctions, eclipses, occultations, transits - all provide opportunities to experience something that ranges from uncommon to very rare. And while we have the sublime beauty of Saturn's rings or wispy tendril's of Orion's sword available to us on any clear night when they lie above the horizon, the beauty of a celestial alignment is often brief and may not be repeated in your lifetime. I doubt I shall ever see another Mercury transit but hope to work in another total eclipse.

Thankfully the universe is like a top chef at a 5 star restaurant, continually serving up one delightful alignment dish after another. In spring we had the octennial passage of Venus through the Pleiades, in fall we had a generational opposition of Mars. And now we get something even more uncommon, a "grand conjunction" of Jupiter and Saturn to close out a rather tedious year. So go out there and try to see it, photograph it, soak it in as yet another special occasion brought to you courtesy of the universe!

Jupiter & Saturn Drawing Together on Dec 8, 2020

New Tools

As I've noted before, the advances in technology have allowed amateur astronomers to obtain increasingly better planetary images. The ability to pluck several hundred images from a video containing thousands, align them into a composite, and then apply post-image processing to draw out the details is game changing. While I almost always spend a few minutes at the eyepiece soaking in the tiny planetary orb that I have chosen to examine for the session I am now invariably spending the bulk of time acquiring video of that member of our solar system. And yeah, the old eyes are not quite as sharp as they were when it comes to discerning surface features.

The enabling technology comes in two forms - hardware and software. Both can be expensive, but of the two there are times that software can be quite a bargain or even no cost (violating a variety of adages about getting something for nothing). As noted in a previous blog this summer I decided to give FireCapture, software that is used to record the video stream onto the laptop, a try.

One of the challenges with new software can be the user interface. Sometimes it is clean and intuitive, sometimes you need crib notes just to perform the basics until you get the routine down. FireCapture seems to fall somewhere in-between - lots of knobs and levers to play with but after a couple of YouTube videos you can be in the field using it, leaving the more advanced features aside while you handle the fundamentals. The fact that there is a "Dummy Cam" mode to allow us newbies to play around some was a great decision by the developer.

Overall this video capture software seems better than what I was using previously. The relevant settings are easy to access and adjust, and there is the ability to save these for each particular planet, allowing you to retrieve your last configuration with the click of a button. The zoom feature that allows you to get an enlarged image on your screen is also helpful, especially when trying to acquire a good focus. But the feature that really prompted me to switch over was the ability to bring up a crop box that allows you to capture just the planet and a bit of surrounding space, serving to reduce the file size. But wait - it gets better! The cropping zone actually adjusts to follow your target to compensate for your pole alignment inadequacies. Awesome!

The second piece of software that I began using was Planetary Imaging PreProcessor, or PIPP for short. This interface is far less intuitive - it has a bit of a geek feel to it where if you are not an insider you just don't get it. However, it is not so off-putting (like PixInsight) that you cannot be up and working with it in less than half an hour. The ability to save off and then load a configuration once you have adjusted the whistles and bells to your liking is a valuable feature.

PIPP comes into play after your session, and as the name implies is an intermediate step that allows you to tweak your video to stabilize the image, reject overexposed frames, perform a quality assessment of the frames, and a lot more. You can also generate a GIF animation from several still frames if you wish, allowing even me to create a "rotating Jupiter" sequence. I've certainly only scratched the surface here and have lots to learn, but again - awesome!

Jupiter animation taken 7/26/2019

Finally in my summer of experimentation I downloaded AutoStakkert! - another free piece of software that stacks the best of the planetary images into your final image ready for enhancement. This interface is not overly complex, was up and working with it fairly quickly. You load the video file, ask it to do some quality analysis, then select your alignment points. You can then define up to six outputs that represent the percentage of the best frames stacked into a final image. But the best part to me is that it will also give you a quick and dirty preview - an image that has some post-processing enhancement already applied to it. That is genius as it allows me to do a quick assessment of my video in the field within a minute, and quick feedback is so good to have when trying to do things such as assess your focus and exposure.

Saturn 7/26/2019

I have lots to learn in order to get the most out of these tools, but I already feel that this trio has allowed me to up my game a bit this summer. Alright Mars apparition 2020 - bring it on!