A Night of Near Ring-Plane Crossing and a Titan Transit

As we close out 2025, Saturn offered one last moment of subtle drama before it passes Eastern quadrature on its way to a springtime Solar conjunction. On the evening of November 22nd, Towson enjoyed a brief window of clear skies – just enough for me to take in a rare combination of events: a Titan transit that was already in progress as dusk fell, and Saturn’s rings appearing as thin as we would see them all year (in fact, as thin as we’ll see them for the next 15 years!). The true ring-plane crossing back in the spring was lost to solar conjunction, so this November evening became the next closest recreation of the event.

Visual Attempt with the 6-inch RV‑6

My goal was simple but ambitious: could I visually detect Titan’s silhouette against Saturn’s disk during the transit? I began the session with my trusty 6" RV‑6 reflector on the HEM27 mount. Unfortunately, the mount was having a rough go of it. About every ten seconds or so it would stutter, just enough to be annoying but not enough to prevent visual work. 

I tried a few eyepiece combinations and filters in search of the “sweet spot” for the observation. I began with the excellent 8mm TMB eyepiece with a light green filter, but the image seemed a tad small at 150x. I then swapped that out for the Celestron Ultima Edge 15mm with the 2.5× TeleVue Barlow, yielding a still crisp view at 200x.

The seeing would occasionally steady for a few brief moments as the planet drifted silently by with the tracking turned off, floating through the field as if using a Dob. The ring shadow was unmistakable and striking as a crisp, dark line slicing across the globe. With the rings nearly edge-on, they looked like a taut thread stretched across the planet. Subtle dusky shading flanked the ring plane in both hemispheres, though neither side stood out more strongly.

But Titan itself? After twenty minutes of careful, unstrained observing with me perched on a stool peering into the eyepiece, I had to concede defeat. Whether it was the limits of the 6-inch aperture, the low contrast of the event, or simply my older eyes, the moon’s silhouette never definitively popped into view.

Imaging Session

After wrapping up the visual attempt, I moved to the front driveway where the Cyrus 10" Newtonian had been cooling. By 8 p.m. I was capturing data through the Baader 685 nm deep red filter. The seeing was average at best, perhaps even slipping below that as the night went on, and transparency hovered around 6–7/10 with a haze creeping in by a little after 9 p.m.

Even so, Saturn was rewarding. The rings were astonishingly thin on the live feed displayed on the laptop, and both the north and south equatorial belts were faintly visible. At 8:21 p.m. I noticed Titan as a small dot hugging the planet’s limb, promising an interesting capture from the night’s effort. I also played with the settings a bit, increasing the gain and exposure to brighten the disk and improve the odds of recording Titan and maybe another of the smaller moons. Conditions continued to deteriorate as we headed towards 9 o’clock, and with haze thickening I decided not to stay out to try to include a Jupiter run in the evening’s efforts.

Final Images

The processed results from the 10-inch show Saturn in its late‑2025 austerity: a nearly ringless world with a bold shadow line and muted atmospheric bands that are far better defined using the deep red filter. The WL (white light) image required some work to bring out any coloration. The composed final image which blends the color shot with the IR as the luminance channel serves as a satisfying souvenir of the 2025 near ring crossing event.

Achieving a Bucket List Item

There are certain astronomical events that intersect our lives only episodically, and Titan shadow transits has been one of those elusive moments for me. Years ago, as a young amateur seeing Jupiter’s moons cast their shadows on the giant planet, I wondered why I did not see that with Saturn. Of course, I soon realized that Saturnian moons do not do this routinely due to the planet’s axial tilt of 27°, lifting (or dropping) their orbits so that they don’t cut in front of the planet when it is facing the Sun. Only when Saturn is around the time of its equinox (when its rings appear very thin) do the moons begin to intersect the Sun’s plane as they move in front of their host planet. We are roughly halfway through such a season with the ringed planet having reached autumnal equinox for its Northern hemisphere last May. I know that only a few months remain of this opportunity, my last realistic chance for years to come. The next similar alignment won’t take place until 2038, at which point I’ll be a much older observer, perhaps with a little more wisdom but a little less stamina for predawn adventures.

Given that Titan orbits the planet every 16 days these transits will take place only once or twice a month. And given that the orbit is almost exactly 16 days you have to be on the right side of Earth with Saturn in a reasonably dark sky. Thankfully the Western hemisphere is well position for the current series. The window opened as Saturn emerged from Solar conjunction this spring. My concerns of missing it have been slowly nagging me as I watched the May and June windows be clouded out and the July 2^nd opportunity unavailable as I was away.

July 18th was on my calendar as the next transit, but as it approached it came with iffy forecasts: some sources predicted hopelessly thick clouds, while others suggested there might just be enough breaks to make an attempt worthwhile. I set my alarm anyway and, with a quiet stubbornness familiar to many amateur astronomers, rose at 3:15 a.m. to scan the skies. It was quite overcast but there still were occasional breaks through which Saturn would pop out for a few minutes. I rolled out the Cyrus 10” f/6 Newtonian and performed a quick mirror collimation.

I decided to prioritize visual observation rather than seeing it on a laptop screen, wanting to witness this event with my own eyes. When a sizable break appeared a little after 4 a.m., I popped in my 8mm TMB eyepiece and Meade 2x Barlow and brought the planet into focus. Perched on the first rung of my step ladder, I saw the planet as a light tan orb with the rings as a spike through it. I continued studying the planet, waiting for those fleeting moments of steady seeing. My first micro-glimpse was uncertain – did I see something or was it a trick from my aging eyes? But after a couple of minutes the dark dot continued to pop in & out of view, clinching it as the shadow of Saturn’s largest moon.

All too soon the clouds reclaimed the view. I swapped out the eyepiece for camera in hopes they would relent for a few minutes so that I could grab an image of the event. But it was an hour of frustration as the planet never emerged for an encore. But while the imaging effort failed, it was a pure delight and sense of accomplishment to witness that shadow cast across another world.

Last week the forecast for early Thursday morning caught my attention with partly cloudy skies and predicted above average seeing – rare conditions for this spring and early summer of 2025. Unable to pass on the prospect, I set out the Cyrus scope around 10 p.m. and settled in for a short rest with the alarm set for 3 a.m. As usual I ended up naturally waking up ahead of the alarm – odd how your body will do that! 

As I stepped outside I was greeted by warm, muggy air; just the sort of atmospheric hush that can often presage very good seeing. The malingering clouds were punctuated by generous breaks, one of which framed Saturn. I started the usual pre-observing sequence: mirror collimation, finder alignment before commanding the scope slew to Saturn. I centered it on the laptop screen and honed the focus, using the high-contrast edge of the rings' black shadow on Saturn’s bright equator as my guide.

Imaging began in the deep red/infrared wavelength using a Baader 685 filter, firing off five 2-minute video runs. Next I changed camera filters to begin a run of color captures. I did a quick stack and sharpen of one of the early video captures and was happy that it revealed delicate banding and even a hint of the Cassini Division. Encouraged by seeing conditions nudging up to 8/10, I pressed on to take a total of nine videos. Then with the laptop battery flagging I invested in capturing a nearby star’s Airy disk as a sharpening reference, managing two short videos before the battery gave up a little after 5 a.m. Time to pack it in and get ready for work!

The next day’s processing brought a pleasant surprise with the best Saturn images I’ve had in months. The R/IR set showcased layered bands, with the NEB and SEB standing out sharply. I was especially intrigued by the dark SPR, perhaps a lingering effect from Saturn’s long winter. The rings, though dim, opened enough to reveal the Cassini Division at their tips, while the planet’s shadow starkly cut off the rings where they ducked behind the globe.

The true showpiece, though, was the color session. Saturn’s pastel hues—blue to tan—came through beautifully. Again, the NEB and SEB dominated, while the SPR, though less sharply defined, was the darkest and bluest region on the disk. What caught my eye most was a subtle bluish belt in the NTR region, around latitude +50°, visible in each of the nine runs, so surely not an artifact. I’ll be curious to see if it turns up again in my next imaging session.

Observing opportunities given the lousy weather seem to come at a premium these days, especially when a quick shower and heading out to work follows your pre-dawn session. But these two sessions this month made every lost minute of sleep worth it. And among the many milestones, I can now add the thrill of witnessing a Titan Transit shadow—a sight I’ll not soon forget. 

Transit Terminus

This past Veterans Day the tiny planet Mercury was scheduled to cross the face of the Sun in an event visible in its entirety from my vantage point in North America. Such alignments are infrequent yet not as rare as those when we get to see Venus interposed between us and the Sun; we get two of those within a decade and then the interlude is over a century before the next transit pair. For Mercury we get to witness roughly 13 such events in a century. Like any celestial phenomena that takes place in under 12 hours, not every point on the globe gets to see the transit - in some locales the entire event happens while the Sun is below the horizon (a.k.a. night time).

I've been fortunate enough to catch a couple of prior Mercury transits. My first was on Saturday May 9, 1970, just about two months following the amazing total Solar Eclipse for the east coast that took place on March 7th. My notes have long since been lost on that event but I do recall seeing the tiny dot of our smallest planet against the Sun using my RV-6 Newtonian using a solar filter by the same company. The next transit that I have a clear memory of (and some notes) was Monday May 9, 2016. It's not just coincidence that both are on May 9th - the orbital mechanics dictates that a transit of Mercury can only occur within a couple days of May 8th or November 10th when Mercury's orbit intersects Earth's plane. If Mercury happens to be undergoing inferior conjunction at that time we have ourselves a transit.

Looking at the predictions for Mercury transits beyond 2019 showed that while there was one set for 2032 and another in 2039 neither would be visible from my side of the planet. That makes the next candidate May 7, 2049 - putting me well into my nineties. So for me the reality was that the November 11th event would be my swan song for any planetary transits. In a year that brought several reminders of my own mortality here was the universe offering yet another commentary upon it.

I decided to try to make this last Mercury transit the best yet. The prediction for 1st contact was 7:35 a.m., which meant the Sun would be quite low in the sky. If I could find a suitable location I might be able to witness that 1st contact and maybe even the "black teardrop" effect. But a more realistic goal was to try to obtain some nice photographic captures of the tiny orb as it marched its way across old Sol. I planned to take the RV-6 on the Atlas mount with me and the Canon Rebel t6s camera and the DFK21AU042 planetary video camera. I gathered everything together the evening before and then fashioned a solar filter using some Baader solar film, sandwiching it between stiff cardboard. The weather forecast was iffy - most prognostications had high clouds moving in as the morning wore on. I set out the equipment so that when I got up it would be easier to load it into the Rogue and set off in search of a venue with good eastern horizon.

The pre-dawn was not encouraging. While portions of the sky were clear the eastern direction had a buildup of high altitude clouds - the Sun was clearly not going to penetrate it. Regardless I set off looking for a location. I toyed with the idea of heading to the parking lot at Leidos where I work. It would be pretty empty on Veterans Day (a government holiday) and the horizon is pretty good. But the commute could be 30 minutes or more meaning the transit would likely be underway by the time I made my own transit and got set up. In the end I set up on the western edge of the ball field by the BYKOTA senior center in Towson, trying to position myself to catch the Sun soon after it rose. I had used the spot before in 2004 to catch the Venus transit soon after sunrise.

Setup outside BYKOTA, waiting for clouds to disperse

The 1st and 2nd contacts came and went without my witnessing them, a combination of clouds and obstructing building. Finally by about 8 a.m. the clouds thinned just enough that I could target the Sun using the shadow technique. I popped in the 16mm Plossl and focused. It took a moment but then there it was - a tiny black silhouette of planet Mercury against a solar disk completely devoid of sunspots. Yay! I could at least say I had successfully witnessed my third transit of Mercury!

Fighting clouds & buildings at the start

My initial attempt to record the phenomena was with the DFK21AU042 video imager, but it proved a frustration. With the Sun over my shoulder making it hard to see the screen and focus at the same time I was not getting any worthwhile results. I switched to the 35mm camera adapter for eyepiece projection using the 16mm and the camera's live view mode,  working to bring the solar limb into sharp focus. Even though I finally got to what seemed to be a good sharpness it was challenging to see if the view contained the tiny dot of planet Mercury. Without any sunspots that could serve as landmarks to guide me to position the best I could do was approximate, My approach evolved into taking a shot, bringing it up for review and enlarging it on the tablet to see if I by chance had caught the messenger planet. If not I used the RA/Dec control pad to slew to another part of the Sun to take another shot. It took a little while but finally ended up with a pretty decent image of the transit.

Mercury Transit - ISO 400 at 1/15 sec using 6" f/8 with 16mm Plossl

As I worked to get some photos there was a gradual stream of dog walkers, joggers, and curious neighbors wondering what the heck was going on. I obliged most of them with a peek through the scope so that they could tell friends and family they had seen it. By a little before 9 a.m. I decided to pack up and head home to finish observing and capturing the transit. I was back in business on the driveway of 404 within about a half hour, setting up the Vixen 80mm as well so that I could take some whole disk shots of the Sun sporting Mercury. The clouds continued to threaten - in the short video below you can see them crossing the face of the Sun. There were a few times when the clouds won but surprisingly the bulk of the transit window the Sun was visible.

Around 10:30 a.m. I decided to start taking a set of bracketed shots of the whole disk every 15 minutes in the hopes of creating a final product that would document the tiny speck making its way towards 3rd contact. I got most of the shots but the 10:45 one was a bit out of focus. It was quite challenging to get a sharp focus on the Samsung tablet that was connected to the Canon due to the Sun making it hard to see the screen. I resorted to having a pillow case draped over my head every 15 minutes as I tried to recenter the Sun and check the focus.

Mercury marches across the Sun on Nov. 11, 2019 (times EST)

As we slid past noon the tablet was running low on battery, signaling that photography would soon be over. I took a few more looks at the tiny, silhouetted dot to appreciate the scale of things in our solar system. As the clouds began to thicken yet again I decided to conclude observations and began to breakdown the setup. I may have missed the ingress and egress but overall it was a fine and memorable event to mark my last planetary transit!

Mercury Transit - 2016

When I noticed earlier this year that the US east coast was in a good position for the May 9th transit of Mercury I made sure to put some placeholders into the work schedule - before work and around lunch time. One of the best perks of having a WFH ability is to take advantage of stepping away for an hour to run some errands - or catch a transit of the Solar System's innermost planet. A couple weeks prior I had purchased a filter for the Vixen (which has the added bonus of being yet another piece of paraphernalia in the tool chest for the August 2017 eclipse). However, we were in quite the rainy/overcast mode for weeks before so it seemed as though it'd be a missed opportunity.

The forecast indicated that the prospects would be best in the morning and then likely steadily deteriorate. The transit was due to start at about 7:10 a.m. with the Sun only about 10 degrees above the horizon. That would be challenging given the horizon.

I set up the Vixen and got the camera ready a little before 7. The sky had some clear sections but it looked like it was going to gradually worsen with high, thin clouds moving in. At first it seemed that a position just outside the front door would work, but the window of opportunity between trees proved to be inadequate. Finally the sunlight breaking at the end of the driveway guided me to a spot where I had a reasonable chance to observe for 20-30 minutes.

By the time I got the Sun targeted the transit was underway. And what a blank looking disk Sol exhibited - just one unimpressive sunspot formation to be seen. And there, at about the 11 o'clock position, was that unmistakeable circular pinprick of a shadow. I ran off multiple shots at a range of exposures, then spent a little time inspecting the minute ball using the 20mm eyepiece.

During the time I had multiple neighbors ask what I was up to, and the clouds carried out their threat to occlude the event so that by 8:30 I was back at my home office desk and ready to start the day. This is one of those events that is hardly spectacular yet for an astronomy wonk something you want to catch, highlighting the scale of our Sun compared to one of the smallest planets.

Mercury - tiny dot at about 11 o'clock