M82, M33 – AltAz Imaging at f/10!
The past few nights here in Woodinville have been really quite nice. And I’m not just saying that because our week of summer is going to end soon, but rather the air has been clean, calm, warm, and most important: dark. Very dark. Now, it’s really quite odd that some of the best times to do astronomy here you get the fewest number of hours to do it — it’s not “dark enough” until around 11pm, and there is an eerie brightness that begins to creep up to the east around 3.30am. But that’s still a few hours you can hit some nice targets.
The other day a co-worker came over and we hit up a lot of the usual “ooooh” targets, but then I remembered Epsilon Lyra. I’d only set up the CPC 1100, and this famous double double was easily resolved with an Ethos 21mm. Some separation was even visible with a 28mm meade cheapie. A few months ago I had some issues with secondaries, corrector plates, etc — so it was nice to see my optics are still working at least for 2.5 arc-second resolution. And here are some nice photos to prove it!
Both these images were done in full Alt-Az configuration with the Celestron CPC 1100. I used the Pyxis rotator to derotate the field so I could experiment with some longer exposures that usual — although of course tracking related issues still make themselves known in some of the subs. These are also taken at prime focus with no reducer and no corrector — full f/10 optics (probably more like f/11 with all the stuff hanging off the end of the scope.) For those curious, the imaging train goes as follows:
- CPC Back
- Televue SCT short back #1
- Pyxis camera field rotator (2″ nose adapter and SCT back adapter)
- Televue SCT short back #2
- Orion Skyglow imaging filter
- Orion StarShoot Pro V2.0 Color CCD
Normally one could insert a f/6.3 reducer in there as well if you really wanted but I wanted to really stress this system out a bit more. This first image is a stack of 24x (of 40 taken) 60 second exposures of M82 with 4 darks.
The second image here is pushing the limits even further of the ability of the CPC 1100 to track things in AltAz — full 2 minute exposures. This M33 image is a stack of 11 (of 19 taken) 2 minute exposures with 5 darks. Unfortunately it looks like my centering is a bit off — which seems to be a problem here since the image barely fits in the field of view. For comparison, I have a cropped version of M33 from the Televue NP101is. The image scale and detail here are pretty fun to compare side-by-side.