Marius rille

[davidc135]

I'm chuffed that I was able to see around half of the Marius rille last night using my 8.5'' f/7.5 Dob at x215. What has been your experience and what scopes have you succeeded with? A good figure and a 20% co helpd my Newt resolve the first 120km but I wonder if smaller apos or other scopes have shown this tricky feature.

David

[Nik271]

I don't remember seeing this visually in my Maks (with 120 and 180mm aperture) but I've never looked for it. I checked some old images taken with the 180mm Mak last year of the Marius area and the rille shows clearly. So I seems that 180mm should resolve it at least part of the way:

 

[davidc135]

Nice photo. Showing a little more detail than I could see visually in the 214mm Newt. For instance, whilst the two craterlets between Marius C and B were easy in the moments of best seeing the smaller (2.5km? craterlet) to the west of Marius B was difficult. I was able to follow the rille some way to the SW of this feature and then lost it. The terminator was  to the east of Marius P so close to the rille but I don't know how much that matters.

Whilst the first curved part nearest to Marius C wasn't too hard the rest of it was only barely seen or impossible. Comparable in trickiness to the craterlets in Plato?

David

Edited March 20, 2022 by davidc135

[Nik271]

I will give it a try visually with the Mak next time the seeing and Moon phase allows. It's a nice challenge! 

Edited March 21, 2022 by Nik271

[mikeDnight]

Hi David,

As for smaller apertures, I've seen it many times in a 100mm refractor, and although I can't recall observing it in a smaller aperture, I'd imagine it would be entirely possible in an 80mm given steady seeing and when the Moon is high. I think catching it during the right illumination and under good seeing helps. 

[davidc135]

Hi Mike,

So a reasonable challenge for many scopes but not as tricky as resolving the Plato craterlets? I posed this because I know of one experienced observer who's failed to catch it with a 6'' apo. at a number of attempts. Maybe his scope has a problem or he's been unlucky with conditions.

David

Edited March 30, 2022 by davidc135

[kirkster501]

I'll have a go at this with the 300P too.  

[Stu]

Thanks for the post @davidc135. It’s not a target I’ve been aware of so will have a look for it in future.

From the date of your post, I assume an around 11 or 12 day old Moon is the most favourable illumination?

[davidc135]

4km Marius P towards the end of the rille was still just in shade so a bit earlier in the cycle than in nik271's image.  I don't know how key that is.

The first 15km was fairly easy after which I was able to follow most of it during moments of good seeing around and beyond a small crater to the west of Marius B, finally losing it some way before it reached a dome.

David

 

[Nyctimene]

Tried to spot the rille this evening with the Heritage 130 P Flextube under moderate to good seeing conditions (Hesiodus A concentricity visible for 50% of observing time). At 187x mag (Seben Zoom 8 mmf + Baader 2.25x Barlow), I was able to make out the two craterlets between B and C (mentioned above) repeatedly in moments of good seeing, but not the rille itself, during 30 mins observing time. As a compensation, the Marius Hills field (300 volcanic domes; Lunar 100 No. 42) were optimally illuminated, as was the sharp line of the Agricola mountain range near the Aristarchus plateau. - Will give the rille another try with the 8", as I felt, it must have been just a tiny bit beyond the limit of vision. With good seeing and mags of 200+, it should be visible.

Stephan

[Nik271]

I had a look last evening (12.5 days old Moon) under so-so seeing with my 180mm Mak. I used x200 magnification and could easily see the first 50km of the south end of the rille, up to where it makes a bend around  a craterlet. I think illumination and seeing is key, the southern end certainly looks doable in smaller scopes under good conditions.

[mikeDnight]

5 hours ago, Nik271 said:

I had a look last evening (12.5 days old Moon) under so-so seeing with my 180mm Mak. I used x200 magnification and could easily see the first 50km of the south end of the rille, up to where it makes a bend around  a craterlet. I think illumination and seeing is key, the southern end certainly looks doable in smaller scopes under good conditions.

Same here but using the 6" refractor at X171 so perhaps not a great challenge, but i know where to look. The seeing improved later in the evening as the moon got higher. May be now this feature has been brought to our attention, more observers will see it, which wouldn't be surprising.  William Herschel noted " When our particular attention is once drawn to an object, we see things at first sight that would otherwise have escaped our notice."

[MalcolmM]

3 hours ago, mikeDnight said:

May be now this feature has been brought to our attention, more observers will see it, w

Guilty! I'll be looking for it now

Malcolm

[davidc135]

Seeing OK last night but not as good as a month ago and I could see the Rille only between Marius C and B fleetingly in the 81/2'' Newt. Magnification x 280.

The terminator was well to the West which may be relevant and so I tried for Rima Sharp but without success. I think that challenge is another step up.  David

Edited April 14, 2022 by davidc135