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An observation of the Cauchy domes


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Last night the conditions were perfect for observing the area around Cauchy. Rupes Cauchy is the fault line south and Rima Cauchy is the rille north of the crater Cauchy. Of the two the Rima is harder to see well unless the solar illumination is just right which was the case yesterday around 10pm:

 

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I was using my Svbony 102 ED refractor with a StellaLyra 5mm EP giving a near optimal x143 magnification. Rima Cauchy was the best I've ever seen which is probably due to the good illumnation and relatively good seeing. I knew that there are some lunar domes nearby but had not seen them until yesterday. They were very prominent especially omega and tau (marked on the map obove). Afterwards I checked the LAC Apollo era maps which are very good for subtle low contrast features and identified the three domes that manged to see. The third one closest to Rupes Cauchy was very subtle.

 

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I did not spot the vent on top of the omega dome, with a 100mm instrument I was not really expecting it. I wonder has anybody seen it visually and what aperture was needed?

Clear skies!

Nik

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I have tried to spot the vents in domes with a 4" Refractor and failed. The Cauchy domes, and those around Milichius and Hortensius, as described in "Discover The Moon" by Jean Lacroux and Christian Legrand. They say the vents should be visible with 'a powerful telescope'. I'm not sure what that constitutes! I intend to give them a go with my Mewlon, if the clouds ever disappear!

Malcolm 

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On 13/05/2024 at 11:48, lunator said:

I will have to track these down I will add them to my Lunar target list.

Me too! After many years of ignoring the Moon I now find myself fascinated. Challenges like this have rekindled my interest in the hobby. Thanks for posting @Nik271

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On 13/05/2024 at 08:19, Nik271 said:

I did not spot the vent on top of the omega dome, with a 100mm instrument I was not really expecting it. I wonder has anybody seen it visually and what aperture was needed?

According to "Discover The Moon" Gruithuisen Gamma is a circular dome, 20km across, with a 2 km diameter vent. They say it should be visible in a 150mm scope. I'm going to try tonight with the Mewlon if the seeing is any good.

Malcolm 

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Posted (edited)
1 hour ago, MalcolmM said:

According to "Discover The Moon" Gruithuisen Gamma is a circular dome, 20km across, with a 2 km diameter vent. They say it should be visible in a 150mm scope. I'm going to try tonight with the Mewlon if the seeing is any good.

Malcolm 

There was a thread about this last year:

Mons Gruithuisen Gamma summit craterlet - Observing - Lunar - Stargazers Lounge

The Gruithuisen domes are well placed tonight. So far, my ED120, while showing the domes sharply at up to 300x, has not revealed the summit crater on the top of dome Gamma. 

It's fun trying though 🙂

Edited by John
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Seeing here was mediocre last night, I could not use more than x140. No sight of the vent. Some nice views of Aristarchus though.

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9 hours ago, John said:

There was a thread about this last yea

I thought I got it last night, a small dark spot, not well defined, on the top end of it. However, on reading the linked post above (thanks @John ), I suspect it was just an albedo marking.

Seeing was just ok, the moon was wobbling. I was using M180, Maxbrights with 1.25 GPC and Tak Abbe 18mm. Calculations would suggest this gives x150, but I'm never really sure when binoviewers and GPC are in the optical path!

Malcolm 

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Yep, conditions not ideal last night. Lots of shimmering, but some OK views of Gassendi and Aristarchus. I was also using an M180 and Maxbrights, but with 20mm TV Plössls and a 1.7 GPC, which gives about 1.5x. I estimate this to be about 170x. It is difficult to calculate the magnification because shifting the focus in the M180 changes the focal length. I think with no GPC it is about 2380mm and with the 1.7 GPC is about 3450mm. 

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