Last night we briefly had some clear dark skies before a waning gibbous moon and increasing cloud interfered with the view. I haven't used my Celestron NexStar SLT102 for about four years and I was keen to get it going again. I had a rechargeable Sky-Watcher Power Tank for many years, but this has now finally failed and so I have switched to a Powseed 45W variable power adapter which can supply the necessary 12v and it worked very well. The Celestron is computer driven alt-az 4inch f/6.5 refractor. I did a two-star set up on Sirius in Canis Major and Dubhe in Ursa Major.
I spent all the time I had observing M81 and M82 - two galaxies in Ursa Major. They fall into the same field of view in this telescope using a 25mm eyepiece and I was glad that when I requested the telescope to acquire these objects the pointing was spot on first time. However, using a DSLR on this telescope at prime focus can cause the telescope field to move (due to the weight of the camera) and screw up the tracking for a few minutes. When I had reacquired the galaxies it was fortuitous that I also had NGC3077 (another galaxy) in the field of view too.
The picture above is the result of 24x30s images (12 minutes) taken at ISO 3200 using a Nikon D90 at prime focus. The images were combined in DeepSkyStacker and the final image (binned x2) processed in Photoshop. M81 at the top of the image is a mag. 6.9 spiral (Sb) galaxy. To the left is M82 (mag. 8.4) which is at a similar distance to M81 (3 Mpc) and which looks anomalous due to a probable recent encounter with M81 which has caused a burst of star formation. To the lower right in NGC3077 and this is a small elliptical galaxy that is also local to M81/M82. It too has evidence of disruption to its structure caused by inter-galaxy interaction (though this image is not detailed enough to show this).
All text and images © Duncan Hale-Sutton 2021
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