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Old 05-07-2018, 08:23 PM
Wavytone
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Saturnian moon challenge

With Saturn nicely positioned for the next month or so, here's a challenge - especially for those curious about their limiting magnitude - how many and which ones of Saturns brighter moons can you spot ?

They have a nice range of magnitudes:

8.8 Titan
10.0 Rhea
10.6 Tethys
10.8 Dione
11.4 Iapetus
12.2 Enceladus
13.2 Mimas
14.8 Hyperion
16.7 Phoebe

And Sky Safari shows there current positions nicely (as well as the background stars).


Now... where's Big Joe...
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Old 07-07-2018, 09:27 PM
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Zubenel (Wes)
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The Westerly front that’s dumped Snow on the alps has just arrived with 20k so the see was not great with only occasional glimpses of Cassini’s division . titan being at the bottom of the FOV with Dione and Rhea being seen at all magnifications from 36.6x to 285.5 x . To the right of Saturn in my FOV Tetys was seen at 127x and 142.5 ( 12mm and 9mm Nagler) only. No sign of Pheobe Enceladus or Mimas being within the glare zone of Saturn .Moving to the top side and opposite side to Titan the was no sign of Hyperion however Iapitus was seen with HD 314379 though both 12mm & 9mm Nagler including the 6mm Radian use my 10” F5. let see what tomorrow nigh brings 👍🏻
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Old 08-07-2018, 09:00 AM
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mental4astro (Alexander)
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Interesting proposition, Wavy.

Saturn's glare ramps up the challenge.

Three nights ago I managed to see Enceladus which was very close to the rings using n 8" f/4 dob from home here in Sydney. I thought I could just make out Mimas, but its even closer proximity to the rings and dodgy seeing I can't count it as seen. Image wasn't stable enough and the glare of the planet proved too much, so for now I'll just say Enceladus I'll keep pushing with different scopes and see what each has to say under different skies too.

Alex.
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Old 08-07-2018, 09:46 AM
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Tinderboxsky (Steve)
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Yes, I enjoy the challenge of observing these moons at Opposition. I am using a 140mm refractor with good optics but only the first 6 moons listed are within reach. Titan, Rhea, Tethys, Dione and Iapetus have been relatively straight forward. Enceladus is quite difficult at 140mm aperture given it’s close proximity to the rings and the glare from Saturn. I have observed it successfully during the previous couple of Oppositions by using an occulting bar.

A related challenge is to observe all moons within reach of your telescope on the same night. I have found this needs a night where the moons are well positioned combined with very good seeing and transparency and a dark sky.

I last achieved this on 29th June 2017 just after the last Opposition. To quote my notes at the time:

"Clear, sharp disc with multiple banding gradations. Strong 3d effect even though no shadow on rings. Rings wide open. Clear, sharp rings and Cassini Division. Multiple sharp gradation evident. 6 moons: Titan, Rhea, , Tethys, Dione, Iapetus and Enceladus (required Saturn behind occulting bar). Field star adjacent to Titan. Second observation 2 hours later showed the obvious movement of the planet and its moons in relation to the star.” - Seeing 5/5, transparency 7/7, Scope Vixen NA140SS with LVW5 giving 160X. Occulting bar in Baader 10mm Classic Ortho with 2X Televue barlow giving 160X.

.. next challenge; Mars and it’s two moons! I plan to borrow a larger scope for this challenge.

Last edited by Tinderboxsky; 08-07-2018 at 09:50 AM. Reason: Additional information
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Old 17-07-2018, 08:38 PM
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Tinderboxsky (Steve)
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I managed to complete my personal challenge this Opposition to see concurrently the six moons within reach of my 140mm refractor.
Titan, Rhea, Dione, Tethys and Iapetus were straight forward and nice sharp points of light. Enceladus was more difficult but was just visible and formed a triangle with Rhea and Dione.
The night certainly contributed to the success. Seeing was as good as it gets. Transparency was good but there was some moisture around.
Needless to say, Saturn itself was sharp and spectacular.
Scope Vixen NA140SS with LVW 5 giving 160X.
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Old 18-07-2018, 09:16 PM
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hotspur (Chris)
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an interesting read and some good information,I have enjoyed spotting these moons through my scope.
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Old 18-07-2018, 09:51 PM
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DeepSkyBagger (Patrick)
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I can report that from 53.5N, I managed to see Iapetus on 2/7/18. It was magnitude 11.2. Saturn was at its culmination altitude of 14 degrees. I used a 12" Newt.

Way down there in the dense atmosphere and thick LP, I have no hope of seeing Hyperion or Phoebe, but Mimas might be possible on the very best nights.
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Old 19-07-2018, 03:47 PM
Wavytone
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I can make Enceladus and Mimas... with Saturn at about 80 degrees elevation crossing the meridian, but this scope gives me an unfair advantage. I’m usually using 250-300X.

Hyperion requires a much bigger scope, 18” or more.
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Old 20-07-2018, 07:50 AM
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I spent time with Saturn's moons in May. I had the same list of 9 moons that are visually possible to observe. Seems the other 53 moons were discovered photographically by the large professional observatories or space craft.

I managed to see the 8 brightest ones in the 32". Mimas was the only challenge and I had to wait an hour for it to swing around into a more favourable position away from the rings. Phoebe was no where to be seen using Sky Safari 6 with the enhanced star catalogue showing stars to magnitude 17.

I've since discovered Sky Safari doesn't plot Phoebe nor the faint outer Jupiter moons in their correct position. A check of the Minor Planet Centre data saw accurate data for Phoebe which I plotted on the SS6 star field.

Come June I ran the observation again and quickly saw the 8 moons from the previous month. Then it was off to Phoebe. After some quick star orientation I saw the faint little moon where the MPC had plotted it. I followed it for an hour and saw it move west against the background star field. It was moderately faint at magnitude 16.6, but I was able to hold it with direct vision.

I've not yet heard from anyone else who has seen Phoebe. If you have a large enough scope it's a nice challenge and a buzz when you find the little moon.
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Old 05-09-2018, 07:52 AM
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mental4astro (Alexander)
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Star testing two scopes last night, and with seeing rather dodgy Saturn was the better target for comparison.

I had an exceptional C8 and a gold tube Skywatcher 7" Mak side by side for this shoot out.

In the C8, Enceladus was visible in those moments of clarity. In the Mak, Enceladus was also visible, but its apparition was more fleeting than in the C8 - that little bit more aperture maybe making the difference? The image quality was jawdropping of Saturn through both scopes. So many distinct bands in the disc, and the Cassini division was so sharp and clear. The C ring showed distinct shading variations. Outstanding. If seeing had only been more steady... <sigh>

Unlike with my last post here, there was no mistaking Enceladus this time. Seeing was the difference, being that little bit more stable.

Alex.
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