Lunar challenge for tonight. 21st April.

[mikeDnight]

I'm currently observing the moon through my 100mm refractor, and thought I'd take a moment out in the hope of encouraging some of you to check out the ultra fine, white central rille running along the Alpine Valley. It's a challenge but its visible with critical focus. The rille appears to be closer to the southern wall than the northern, and may appear broken. See how you go, but persevere! ☺

[John]

4 minutes ago, mikeDnight said:

I'm currently observing the moon through my 100mm refractor, and thought I'd take a moment out in the hope of encouraging some of you to check out the ultra fine, white central rille running along the Alpine Valley. It's a challenge but its visible with critical focus. The rille appears to be closer to the southern wall than the northern, and may appear broken. See how you go, but persevere! ☺

Yes I can see it Mike. But I am using my 12 inch dob

 

[mikeDnight]

It still counts John.☺  In my 100mm this evening and using only 128X, the rille was visible with patience, but certainly not obvious. I have seen it looking much more obvious in the 100mm, but I suppose lighting plays a major part in just how obvious it can be.

[laudropb]

Had a go at this Mike with a 80 mm achromatic, but even at 144x could not see it. Have viewed it before with  a 120 ED and 8 inch Dob. Even with these larger apertures it took a fair bit of patience to see it as you said.

[Stu]

Not much luck here Mike. The seeing is not as good as last night. I had the Tak and Heritage 150p out initially, and though perhaps I could suspect something in the Tak. Then I got the 8” out, but similarly nothing really concrete, I’ve seen it quite clearly a couple of times in the Tak, but most of the time I fail.

[John]

32 minutes ago, mikeDnight said:

.... lighting plays a major part in just how obvious it can be.

I think that is very true, especially with these very fine details. Even the change in illumination over a few hours can make a difference. I believe that this rille is only 1km wide at maximum, less for most of it's length, and only 240m deep at the deepest point.

 

[paulastro]

2 hours ago, mikeDnight said:

I'm currently observing the moon through my 100mm refractor, and thought I'd take a moment out in the hope of encouraging some of you to check out the ultra fine, white central rille running along the Alpine Valley. It's a challenge but its visible with critical focus. The rille appears to be closer to the southern wall than the northern, and may appear broken. See how you go, but persevere! ☺

Easy, I could see it in my 30mm finder Mike 😄.

[Dark Vader]

I'm sure I caught several brief glimpses of it when the seeing settled and the wind dropped. 8" Dob, Hyperion IV zoom at 8mm, & 2.25x Barlow.

[Littleguy80]

Great challenge, Mike. I gave it my all but was found wanting on this occasion. I could blame it on the seeing, tired eyes or even the European Super League. Whatever the cause of my failure, I enjoyed the trying. My “quick 10 mins on the Moon” turned into 45 mins and that tells it’s own story. Lots of fun!

[AstroTim]

I didn’t manage to see the rille tonight either. I was using an 8” SCT, although I was having to view between the gaps of some high branches. It did seem as though there was a noticeable drop in contrast whenever even a couple of small branches entered into the FOV. 

Thanks for the heads up though as it has given me something to look out for on future nights, as I often stop for a brief look at the Alpine Valley area when viewing the moon.

[Pixies]

Nope - not here. The seeing was good, but not great. In my 8" dob, the most relaxing view was with the 8mm Vixen LVW: it's my widest view at that magnification, so not too much nudging. However, I couldn't make out the rille. The shadows of the southern edge of the valley were pin-sharp, though.

I thought the 4mm ortho might do it, but  that failed too. It involved so much nudging that I could not get relaxed.

[John]

If it's any consolation to those who didn't manage to see this rille, my seeing conditions here were excellent but even so it was a very challenging thing to see even with my 12 inch dob which has very good optics and is well collimated. It was not visible consistently by any means and even when it was, I just got glimpses of a few sections of the rille. Plus I've seen it before with this scope, and that helps a lot !

I've not seen the rille with any of my smaller aperture scopes which include some pretty good refractors to 130mm in aperture.

As well as the really excellent scope and, obviously tonight, seeing conditions, mikeDnight possesses visual acuity well beyond mine I'm sure to get this with 100mm of aperture

Great observing Mike

 

Edited April 22, 2021 by John

[mikeDnight]

Perhaps during the next lunation it may be more successfully sought. The Valley last night was well illuminated, so may be the rille was a bit washed out. It helps once you've seen it because then you know what to look for. Even at its best its the finest spider thread against an already bright background, and nothing like the images we often see. Different lunations give different lighting and more opportunities, so success will come eventually I'm certain.☺

Edited April 22, 2021 by mikeDnight

[Saganite]

Thanks for pointing out this challenge Mike. 

I spent almost 90 minutes last night ( 22/4 ) on this with my f15 and bino at a mag of circa 200x, and felt almost 'cross eyed' by the time I packed in just before 1.0 am.

I didn't get it.  The line of small craters along the rille were very strong with evident shadow but your point about illumination of the valley floor is the key I think. In moments of sharpest seeing I felt I may have got a brief glimpse of it where it is sharpest and deepest across the small basin, but certainly not enough to prove resolution, so I will keep trying as the opportunities arise. I noted five craterlets in Plato and the seeing was pretty good.

 

Edited April 23, 2021 by Saganite

[Stu]

I gave this a good go last night with FC100DC and Heritage 150p. We also had @Captain Magenta’s LZOS 105mm and  @GavStar’s AP 130mm GTX, so plenty of firepower!

Initially I thought I could see it in the Tak, and kept thinking I could. However, none of the others could, and in the end I couldn’t convince myself that I did see it, seeing just not quite good enough to be able to clarify exactly what I was seeing. Good fun trying anyway.

[John]

I did see traces of the rille again last night (the central section where the valley floor and the rille are their widest. But that was using a 12 inch scope again

I found the seeing more variable last night than the previous evening. Tantalising glmpses of really fine detail rather than longer looks.

I did spot St George crater again next to the Hadley Rille (which was still well defined despite the change in illumination.

Another target that the larger aperture helps with is resolving the tiny craters that form the Davy Crater Chain. The larger 3/4 are resolvable with smaller apertures and the others as a sort of pale line but during steady moments the 12 in scope resolves the smaller ones as well in this long, gently curving chain.

I didn't realise that they all had names !: