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Help Finding Janus
#1
When I have Saturn up at 21:32:27 CDT August 22, and do a search for 14th magnitude Janus, I get a list of objects that does not include Janus. Is it because ST4 thinks it is too faint to see near the rings and therefore will not display? However, Mimus at mag 13 and Hyperion at 14.3 are shown.

Another app says that Janus is not a valid object. Several others have it displayed at RA 21h35m07s DEC 15°44'57".

Bug or just the way ST works?
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#2
Hi BMD,

When I do a Designation Search for Saturn then list the satellites, Janus isn't listed as an option. A search for Janus doesn't find it either. This looks like a Technoking question.

Phil S.
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#3
I did a tiny bit more research. The apps that show Janus appear to be taking Planetary Aberration into account and cannot turn it off. Both Janus and Daphnis (mag 24.6) are only 1.2" apart and are occulted by the rings if that is turned off. This might be why ST does not show Janus as it is behind the edge of the ring at the time specified with Planetary Aberration off. Did not find in help anything on Planetary Aberration.

Just taking a look at future good time to spot Janus, I see that in a few years, (March 26, 2039, ~2:20) it is at near max distance from the center of Jupiter and the rings are edge on.
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#4
Found a much better time much closer to current date. 2025 11/15 19:28CST. Up 52° in the SSE. Rings edge on. No bright satellites near. Janus just too faint to show in ST.
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#5
When I was last adding Saturn sats I had a look at Janus and determined that it was not observable in amateur instruments, even via imaging.
Clear skies,
Greg
Head Dude at Skyhound
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#6
Hi Greg,

Just curious what size instrument is required to observe Janus? Back in my active observing days I had access to the Perkins Observatory's 32" cassegrain telescope. I suppose that Janus is beyond the capabilities of that instrument too. The Richland Astronomical Society in Mansfield, Ohio also had a 31" f/7 Newtonian that was superb, but sadly that instrument has fallen on hard times.

Phil S.
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#7
Phil,

I am not aware that it has ever been observed visually. Its too close to the rings. I have not found any evidence of it ever being imaged by amateurs either. As far as I can tell the old ground based observations were sparse, required a large aperture refractor, excellent seeing, and some sort of chronograph. This isn't so much about aperture, but being technically difficult. Some sort of modern lucky imaging campaign might work.
Clear skies,
Greg
Head Dude at Skyhound
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#8
Thanks, Greg.
Phil S.
ST4 (4.0j, R22) Bundle
WIN 10 Pro, R9 3900X, 64 GB RAM, RTX 2070, 4k monitor
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#9
I've put it on my calendar to attempt on November 15, 2025 in the early evening in my 24". I've got a Televue 10.5 (315x) with a Tuttle Solar Skreen occulting half the FOV. Mars moon eyepiece. On that date and time, it will be off the rings which will be edge on. There will be no other "bright" satellites nearby. Might be an interesting time to attempt it. Unfortunately, our seeing in SE Texas is not very good in November, but with some more "Climate Change" who knows. LOL Thanks Greg for your input.

https://www.sciencedirect.com/science/ar...3581901500

This observation had similar circumstances but the observer admits most likely not seen as he may have had Mimas nearby. Unless his time of observation was close to 3:35CST when Janus would have been max from center of Saturn (25") and 4.3" from Mimas.
https://www.cloudynights.com/topic/20138...oon-janus/
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#10
Seeing Janus would be epic! Good luck!
Clear skies,
Greg
Head Dude at Skyhound
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