Tuesday, 28 April 2009

A Whale?

At last I've processed my folder full of pictures I called 'galaxy madness'. There's a whole lot of galaxies you can see and a whole lot more you can photograph with a 20" telescope on a good night in spring. Here's a funny one I found in the funny sounding constellation Canes Venatici. I detrailed and stacked 22 x 30second images of it (f/4.8, f.l=2400mm) so the exposure was 11 minutes on my Canon EOS 350D. It's an amazing likeness, n'est-ce pas?

Monday, 6 April 2009

20" vs 8"

This is the same subject as in the last photo, the Owl nebula, M97, in Ursa Major. I popped over to the observatory and took about 80 x 15s shots of the nebula through the 20" newtonian, which I could barely see through the camera after focusing on Merak. The telescope was descending from the zenith to the west. Most of the images were trailed because of poor consistency of the motor tracking and a good few were slightly spoiled because of car headlights on main beam shining right into the dome. Who's fault is this? The ridiculous number of cars on a tiny road at midnight or the observatory siting? We could do with a big sign to block the lights out. The bright moon made the background light subtraction most difficult, as it gave a subtle gradient across the picture that when processed becomes more severe. I whacked all 80 RAW picture files into Deep Sky Stacker and after about half an hour while I watched the Sky at Night, it had stacked them into one image with 8 minutes' worth of exposure (32 pics). Just look at the difference from my windswept 8" f/6.3 Schmidt-Cassegrain image on the post below. I couldn't track for as long, but the f/4.8 (fast) optics, good focus and massive aperture really helped bring out the triangle of 15th mag (ish) stars in the nebula. You can even see a couple of galaxies if you look carefully to the left and upper left of the nebula and the reddish outer edge of the nebula is just perceptible. (image repeated for comparison with below)