Observation report 15/2/2011

After almost a full day of pouring rain, the skies cleared in the late evening and the seeing was excellent. The moon was bright enough to cast crisp shadows and to illuminate the smoke from one of our chimneys as it rose straight upwards.

Given the brightness of the moon there seemed little point spending time attempting to view anything else so I decided to attempt a few features on the Lunar 100 list. First up was the Copernicus crater, easily found but perhaps would have been better a couple of days early when the illumination was more oblique. It wasn’t as bad as some of the features towards the eastern limb though, where most detail was lost in the brightness. A short hop north-west took me to another crater, Aristarchus, and then back over to the east to see the impact rays across Mare Crisium from Proclus.

At 50x magnification the fractured floor of the Gassendi crater was just about visible, but needed observing for some time for the details to resolve. Sinus Iriuum with its missing south-eastern rim was easy to see.

I spent some time trying to find the straight wall running south from about 18°S 8°W, but couldn’t see it at all, again probably due to the angle of lighting and whilst I could see the Petavius crater, it’s floor features weren’t visible to me for the same reason.

I upped the magnification to around 80x and was rewarded with a fantastic view of Schroter’s Valley and of the different surface textures in Mare Serenitatis after which I went looking for the Alpine Valley leading up to Mare Frigoris. It took some time to pick that out and then once I’d seen it I couldn’t believe it had been so difficult to find. It’s described as a “graben”; I had to look up what that means. The best description I can come up with is something like a rift valley.

Posidonius and Fracastorius were very clear as was the Aristarchus Plateau, but after some searching I was unable to identify Pico to my satisfaction. It also took me some time to find the Hyginus Rille before I realised I’d been staring right at it for several minutes.

With time getting on I decided I couldn’t stay out much longer, so finished by finding the Archimedes crater and the oblique impact features at Messier, Messier A and Schiller. Just on the bright side of the terminator and still partially in shadow, Schiller stood out strongly, looking very impressive.

By this time Saturn was about 25° above the horizon and I couldn’t really call it a night without a quick viewing. It was time well-spent as the image was far sharper than a few nights previously. I tried pushing the magnification up to 250x using a barlow, but couldn’t achieve focus. It’s probably asking too much of the ST102 anyhow and the barlow is only the cheap and nasty one that was supplied with my ST80, so I wasn’t expecting much. I do have a much better one arriving shortly, so I’ll try again at around 170x next time the seeing is good.

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