Catena Davy, Catena Timocharis & Rupes Recta.

[Doc]

6.12.2008

Meade lightbridge 16" Dob FL1829 F4.5

Moon illumiation 68.8%

In December's issue of Astronomy Now it lists the crater chain Catena Davy as a good object to find. Virtual moon atlas lists it as interesting formation needing at least 200mm of aperture to see it. Well I started by finding Crater Davy a large crater of about 22 miles in diameter that has steep sides but is relatively shallow.

It is cut through on it's South Eastern wall by Davy A a bowl crater of 9 miles in diameter. Emerging eastward out of the Davy Crater is Caterna Davy. A crater chain of about 30 miles in length which looks like a mountain range in my 6mm Orthoscopic at x304 mag. But by replacing this with the 4mm Orthoscopic giving me x457 I could definetly see this chain as cratlets. I counted at least 7 of them in a very straight line.

Also visible within the Davy basin is Davy C and Y. Both little craters off aproximately 2 miles across. These were only visible in the 4mm orthoscopic eyepiece.

Also in the Decembers issue of Astronomy Now it lists Catena Timocharis as a challenging object for the larger telescopes and according to the Virtual Moon Atlas this subject needs an aperture of at least 500mm. Thats a 20" scope so off course I had to try with my 16" just to see if I can capture it.

It is quite easy to find the Crater Timocharis it had only emerged from the terminator yesterday, it is a bowl shaped crater 23 miles in diameter. It stands isolated on the Mare Imbrium midway between Archimedes and Lambert. It dates from the Eratosthenian period of about 3.2 to 1.1 billion years ago.

I placed my 6mm Orthoscopic Telescope House eyepiece into the focuser this gives me a magnifcation of X304. I could see it's steep walls, rising about 7,000 feet above a very deep crater floor. No detail could be made out on the floor but the walls were bathed in reflected white light, it looked truly magnificent.

I then turned my eye to finding this elusive Catena Timocharis, unlike it's parent it only dates from the Copernician period of between 1.1 billion years to the present time. It was easy to find Timocharis B and just below this crater I could just make out what looked like a very small montain range, which I garthered was Catena Timocharis.

The 6mm Ortho could only just make out this rille like object. So I put my 4mm Orthoscopic in, this has a magnifcation off x457. A little to much for the scope as it was pretty hard to view between the dampening down issues I was having. But I definetly saw Catena Timocharis but could not distinguish between mountains are craters. So maybe you do need a 500mm aperture for this object after all, but I was very pleased to have seen this very elusive object.

Another object I wanted to track down was documented in Decembers Sky at Night magazine. Within the Mare Nubium area also called "The sea of clouds" is the formation known as Rupes Recta or "The Straight Wall". The length is about 110km and its height is between 240-300 metres, inspite of it´s appearance it is not a cliff, but a gentle slope, the width of the fault is 2.5km. The rille is dated from the Imbrian period of 3.8 to 3.2 billion years ago. This was easily spotted in my 6mm ortho at x304. I traveled the whole distance of 110 km and clearly saw the shadow caused by the sun. The area around the wall is peppered with small cratlets and I counted at least 10 with averted vision. The straight wall is disected towards its top by the Stags Horn Mountains. In my 4mm at x457 you can actually see the mountain slopes and the shadows of the mountains. To the west is Birt and Birt A. Birt is a wonderful bowl crater with very steep sides, it is cut through by Birt A on it's eastern flank.

I'm really pleased to have viewed these objects. Catena Timocharis is indeed a very difficult object to see, but I'm glad I took the effort to see it.

[solo]

Ace report,Doc. I too was looking at Catena Davy last night. Started with my 4" frac,just made out a 'presence' at x200 ( 10mm+2x barlow ) but no chance of seeing the craters.Switched to my 8" newt and nailed it straight away at x240. Also had a good cruise along the terminator and ended up concentrating on Clavius for a while before my head started thumping ( bad cold-lots of hassle from the missus for being out in -4 temperatures )then went in for a lemsip and a cuddle better

Cheers, John.

[Doc]

It's great to see someone else looking in the same region.

Your 4" wouldn't see this thats for sure. But how many of the little cratlets in the Davy chain did you see in your Dob?

Hope you get well soon.

[solo]

I definitely saw 4 last night but the air was a bit wobbly. I've seen 6 on a good night.I had my newt on its driven EQ5 last night which made things a bit easier. I find things a bit of a juggling act on the dob if i'm using high power on the moon.

Cheers, John.