Trying for Rima Sharp

[Nik271]

Has anyone observed Rima Sharp with a modest aperture (e.g. 5 inches or less)?

I have tried a couple of times in what I thought is the right moon phase but the seeing was not cooperative.

I've heard it's not an easy one, certainly does not get many observing reports.

Tonight it should be right on the terminator, this is the simulation at 20:00 UT. It may be even more prominent a few hours later.

 

[Nik271]

I tried last night with Skymax 127 at about 9pm, the seeing was not the best but decent, I could see some faint details like Rima Prinz, but sadly no sign of Rima Sharp even when looking directly at the spot where its supposed to be.  Either its too small for 5 inches aperture or the sun angle was not right.

Aristarchus region looked very nice, with vallis Schroteri partially illiminated with deep shadows all round. 

I will try again this evening if the clouds cooperate. Sinus Roris will be fully in the sun and the elusive Rima Sharp may be easier to spot.

[davidc135]

I tried last night (Apr 14) in decent seeing with the terminator close by but saw nothing in the 81/2'' Newt. The seeing could have been better and the collimation was slightly off which didn't help but it seems a tough one.  David

[Nik271]

I also looked at the same night with no success. Surpising how hard it is considering it is showing big on most charts, even those from pre-satellite mapping era e.g:

I will keep trying around the 11-12 day of the Moon cycle.

Edited April 15, 2022 by Nik271

[davidc135]

My pocket version of Rukl only shows the northern 60 or 70 km but it's drawn much more emphatically than the truly difficult Alpine valley Rille.  David

[davidc135]

In spite of the breeze the seeing was helpful earlier tonight and I just spotted Rima Sharp fleetingly in the 8'5'' Dob. At least the lower two thirds of the Rille between the two headlands so I'm pleased with that. The terminator was well off to the West so an earlier moon might show it better.

Further East was the dome Gruithuisen gamma but I looked in vain for the summit craterlet.

David

[Nik271]

That's awesome! I was looking too around 10pm but the seeing was poor, on top of that I had only my 127mm Mak available, so I just kept to low power Moon views, which were very pleasing.

Edited May 14, 2022 by Nik271

[Nik271]

I finally got it last night with my trusty Skymax 127 🙂 The good seeing and the correct moon phase seem to be the key to success. Initially I had no high hopes since the 90% Moon was barely at 20 degrees elevation, but you never know; turned out the seeing was pretty good. I thought I could see something already at x130 and went for the 8mm Starguider giving about x185. This was the limit for the seeing and in moments of stability I could see a very thin hairline in the  'strait' separating the pair  Louville D and DA from the 'mainland' . This image from the LRO is pretty close to what I could see in the best moments. I've circled the portion of the rima that I could detect.

 

 

This little Mak continues to impress me. I know it is stopped down to about 120mm but it just shows that aperture is not everything! (at least not all the time) 

 

 

[davidc135]

Congrats, Nik271. That's good going in the Mak.

Similarly, I had the 8.5'' Dob out and was surprised at the seeing. As shown by your circle I managed the lower part of the Sharp rille from time to time. 

x215 mag worked well.   David

Edited June 12, 2022 by davidc135

[jonbosley]

I have it here, taken on 11 day moon. I was actually imaging Mairan Dome T nearby.  This is with my 18” Dob, Texas skies. 

[MalcolmM]

I've been trying to catch this one since reading this post. Finally got it at 06.00 this morning in steady seeing! 24 day old moon (~32%). The North section appeared as a very thin dark line between the two headlands. I could not see the southern section. Also, an interesting rille was visible as a dark line between Sharp and Sharp A. I cannot find a name for it, but it is mentioned in 'Craters of the Near Side of the Moon' under the description of Sharp.

Tak FC100DC plus Tak diagonal plus 3.3mm Tak TOE. It was also visible with a 4mm TOE. I may be wrong but I feel it should have just been visible in a 3" scope. 

Malcolm 

[Nik271]

Well done, Malcolm! Its one of these features where everything has to come together - correct illumination, good seeing, quality equipment and of course, a sharp-eyed observer 🙂

[MalcolmM]

2 hours ago, Nik271 said:

correct illumination, good seeing, quality equipment and of course, a sharp-eyed observer

Three out of four then 🙂

Malcolm (not so sharp) 🙂

[davidc135]

On 07/11/2023 at 09:26, MalcolmM said:

I've been trying to catch this one since reading this post. Finally got it at 06.00 this morning in steady seeing! 24 day old moon (~32%). The North section appeared as a very thin dark line between the two headlands. I could not see the southern section. Also, an interesting rille was visible as a dark line between Sharp and Sharp A. I cannot find a name for it, but it is mentioned in 'Craters of the Near Side of the Moon' under the description of Sharp.

Tak FC100DC plus Tak diagonal plus 3.3mm Tak TOE. It was also visible with a 4mm TOE. I may be wrong but I feel it should have just been visible in a 3" scope. 

Malcolm 

Great report, and testimony to the powers of a first class 4'' apo. I'll look up the little rille.  David