Peak performance?

It's not uncommon to find people wondering about the point and purpose of amateur observational astronomy and, as I've said before, it really comes down to what you personally make of it and take from it. Last night I had another nice little example of why I find it an exciting and rewarding interest.

Because the sky was reasonably clear (although a little misty with a threat of cloud moving in), but because the Moon was past 1st ¼, I decided to have another evening observing and getting to know the Moon using just a lunar map and a 10x50 binocular on a tripod.

Part way into the observing session I noticed what appeared to be two sunlit peaks inside the nighttime portion of the Moon, roughly south and west of the southern "headland" of Sinus Iridium. I had a good look at my lunar map and, as best as I could tell, the peaks I was seeing belonged to Mons Gruithuisen Gamma and Mons Gruithvisen Delta.

Later on, after the cloud had got the better of me and I finished the session, I decided to double check my decision using the Virtual Moon Atlas. From that Mons Gruithuisen Gamma and Mons Gruithvisen Delta did appear to be the features I'd seen. But then I read something in the information that had me doubting myself: the size of each dome is given as around 12 miles by 12 miles.

That seemed liked an awfully small feature for me to have seen with a 10x50 binocular.

This is where the fun and the reward comes in. Last night's session, rather than just being an exercise in passive observing, has now turned into a little journey driven by a desire to test my assumption that the features I'd identified are too small for me to have seen. At the moment I'm not fully sure how I'm going to answer the question but, one way or another, I'll seek out an answer.

And I'll have a lot of fun doing it.

And, if you've got an answer, please feel free to let me know. Learning from knowledgeable and experienced people is part of the fun.

File Under: Observational Astronomy, Lunar Observing.


Paul Sutherland said...

Was there a noticeable size to the peaks then? Just because they are small doesn't mean we can't see the light from them - otherwise we'd not be able to see the stars with their imperceptible angular sizes presumably. Or am I missing the point?


Dave Pearson said...

No, there was no noticeable size to speak of and, yeah, your point about actually seeing stars is one of the things I've been thinking about.

The more I think about it and look into it the more I'm sure that I did correctly identify what I saw.

It's nice to have this kind of doubt, it helps overcome silly assumptions and "gut reactions".

Ian Musgrave said...

If the shadows are long enough then you should be able to see them in 10x50 binoculars, a bright speck and along shadow ill give you an appreciable 3D effect. Have a look at this site on observing lunar crater rays for some ideas on picking up hard to see things.

Dave Pearson said...

Thanks for that Ian. As Paul pointed out too, given the contrast the peaks would have had against the black terrain it seems reasonable enough that I did correctly identify what I saw.

That's an interesting link by the way. Bookmarked.