OR: Titan shadow transit August 3 2025

[Dan Smiley]

I attempted to view Titan’s shadow transit from about 145-215am PDT without success. Seeing was horrendous using my 8" dob from my driveway in Mill Valley. Saturn was a constantly boiling image in some remarkably bad seeing. Rhea was visible but Titan itself (not its shadow) only intermittently appeared. I tried mags from 110x to 308x. Oh well on to August 18!

[Ted Hauter]

Sorry to hear. In moments of excellent seeing, remember these nights, longing for a clear, steady view.

Planets can be an hours and hours thing, when finally, a steady moment or two. Sometimes, right away knowing this is not going to sharpen up😂

On Sun, Aug 3, 2025, 6:48 AM 'Dan Smiley' via The Astronomy Connection (TAC) <sf-ba...@googlegroups.com> wrote:

I attempted to view Titan’s shadow transit from about 145-215am PDT without success. Seeing was horrendous using my 8" dob from my driveway in Mill Valley. Saturn was a constantly boiling image in some remarkably bad seeing. Rhea was visible but Titan itself (not its shadow) only intermittently appeared. I tried mags from 110x to 308x. Oh well on to August 18!

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[Mark Scrivener]

Sorry to hear Dan.

I went up Mt Hamilton to a friend's property near the summit. When we first swung the scope to Saturn (6" APO) it was a mess, you could barely tell it was Saturn, but at only 8deg I wasn't too worried. Conditions slowly improved as it rose, and by 2:20am when we packed it in we were getting long steady views at 400x. The image was still slightly soft (not as razor sharp as I saw earlier in the week), but not bad and Titan's shadow was easy to spot.

Interestingly the better seeing I experienced earlier in the week was from my backyard in San Jose, looking just a few degrees above my neighbors roof. Mt Hamilton typically has better seeing than the surrounding areas, so given it was just OK up there, I'm not surprised it was much worse down low. 

Fortunately we have a few more shots coming up (from SkyTools):

Aug 18 (shadow transit)

Sept 3 (shadow transit)

Sept 19 (both transit and shadow)

Oct 5 (transit)

Oct 21 (transit)

Nov 6 (transit)

Nov 21 (transit)

Dec 7 (transit)

Dec 23 (transit)

Jan 8 (transit)

Jan 24 (transit)

Mark

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[api...@pierceshearer.com]

https://gyazo.com/9133d796270f0d285cc4494d5d386700

 

 

From my street in Portola Valley with a C11 last night about 2 am

 

 

Andrew Pierce

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[api...@pierceshearer.com]

new and improved, this time with Titan to the upper right.

 

 

https://gyazo.com/b4b2a80c1f8a5adb0c5cdc072211836f

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[Jaimie Henderson]

Cool photo, Andrew!

Jaimie

[Arvind K]

+1 thanks for sharing the view!

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[Brad Templeton]

Another transit and shadow transit tonight, starting about 11:30 pm, sky looks clear

[Peter Natscher]

I observed a great Titan shadow transit from Fremont Peak last night, at mid-transit 1am.  I was observing with my 16" f/4.5 Dob at 380X. Seeing was super sharp with <1.0 arc-sec seeing, a condition FP is well known for. The shadow is the size of Titan itself, ~0.8 arc-sec.  It was a sharp, tiny and very black shadow against Saturn's subtle shaded equatorial belt.

[Brad Templeton]

Yes, seeing got good around mid-transit, even on the valley floor.   Could see Titan even in 4" refractor (which has better optics than my 8" SCT, though that could also see it.)

[Steve Gottlieb]

I had a similar view in my 24-inch around 1:30 from north of the bay area. Saturn was completely calm for several seconds at a time at 327x with nice colored shading in the equatorial region and the tiny jet black shadow from Titan quite prominent.  Before midnight with the planet low in the east, it was helpful to use an 8” off-axis mask. 

Earlier in the evening, I took another peek at comet C/2025 K1 (Atlas), which was slightly brighter than last month.

-- Steve

On Aug 19, 2025, at 11:14 AM, Brad Templeton <bra...@gmail.com> wrote:

Yes, seeing got good around mid-transit, even on the valley floor.   Could see Titan even in 4" refractor (which has better optics than my 8" SCT, though that could also see it.)

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[Dan Durkin]

I spied with my little eye - and a TEC140 at 200x - a little black spot on Saturn! I picked it up around 11:30 PM from the suburban backyard skies of Corte Madera, Marin, at essentially sea level. I also easily saw Titan (the Shadow Caster), Iapetus, Rhea, and Dione (trickier). Tethys is too close to the rings for me. By 12:30 AM, with Saturn higher and sharper, and the shadow spot farther into the disk, the spot was evident at even 140x. 

[marek.c...@gmail.com]

I was lucky that a fellow observer reminded me of the Titan shadow transit in an email earlier in the day. I saw Titan's shadow during moments of good seeing on the night of the 18th-19th. The seeing came and went, but it was good enough to see the shadow. I was using a 13" dob and 9mm and 5mm type 6 Naglers. I think there's another transit during Calstar, but I'm glad I caught this one, so there'll be less pressure to see the one in September.

I found myself pondering the concepts of the umbra and penumbra. When we see the shadow of a moon like Io, Ganymede, or Callisto on its parent planet's cloud tops, I wonder whether the "dark disk" we see corresponds very closely to the moon's umbra, or if it includes the inner part of the penumbra as well, and if so, how much? Of course, the greater distance from the Sun makes a shadow work a little differently from our Moon's shadow, since the Sun looks smaller out there.

If I had a really big scope in really good seeing, with a filar micrometer installed, it would be interesting to measure the visually-observed shadow and compare it to a calculation of the diameter of the umbra on the cloud tops. I'll bet someone has worked on this before. I can imagine someone like Barnard working on this with the 36" at Lick back in the day...

[Brad Templeton]

Two more transits of the Titan shadow left, one tonight from about 10:30pm to 1:30am, and another on the Friday of Calstar.  I plan to get to Calstar, but if somebody in the South Bay has something with lots of aperture I might like to do a test run of photographing with my cheap-ass ZWO planetary camera.   For this task I think you would like 16" or more, I know my 8" makes a fairly low quality image.    While you don't strictly need a tracking mount to do planetary photography, the FoV is so small that keeping the planet in the camera would be somewhat challenging in a fixed dob (which alas, is what most of the large objective scopes are.)  Otherwise I will try again with my 8" SCT from my back yard.       One obvious choice was the Foothill 16" SCT but they report it is out of col, and they plan to fix that for the next transit which will be during their usual Friday night public opening, with Saturn in opposition it would have been the target anyway...

In theory there is also a close asteroid pass but I think it has moved so far it will be below the horizon until dawn.

On Sunday, August 3, 2025 at 6:48:03 AM UTC-7 Dan Smiley wrote:

[Andrew Pierce]

I got a pretty good image last time with a “cheap ass ZWO planetary camera” and a C-11.  Unfortunately I am awaiting the return of my hand paddle from Astro-Physics and won’t have it tonight.

 

 

    Andrew Pierce   

    730 Polhemus Rd.,  # 101

    San Mateo, CA 94402
    Phone:  (650) 740-9742
    Email:  api...@pierceshearer.com

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[Peter Natscher]

There's one more shadow transit on October 5, 10pm. It's the last one.  Saturn will be 41° up in SE. 

[Richard Navarrete]

Which zwo do you have? All the planetary cameras are relatively cheap.

Richard

Sent from the all new AOL app for iOS

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[Mitchell Koerner]

I'm late coming back here, but I got lucky and had a nice view of this transit (my first ever Saturn shadow transit) from my porch in Sunnyvale.

I set up my telescope with a cooling fan about 2 hours before the expected transit. Then around 10:45, there were about 5 minutes of quite steady skies during the early transition from clear to cloudy. My wife and I viewed the shadow transit in my old XT10 and 8mm Delos through the thin layer of forming clouds. The moments when we could see the shadow also revealed Saturn's gas bands, another first for me. I stayed at the scope for another 1/2 hour, but the early views were the best views. The steadiness never quite returned to those initial moments. When I checked back an hour later, the clouds had completely covered the sky and I packed up.

Overall it was a really fun experience and I would have missed it if not for your reminder Brad — my thanks to you!

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