M57 – the Great Ring Nebula. That dim, barely discernible deep sky object is the first that I spied in my 4 1/2″ Newtonian – and what propelled me towards upgrading to my 8″ CPC-800.
The photos I’ve taken periodically haven’t amounted to much. M57 is a small object to capture with my 40D DSLR camera – not filling all that many of it’s 5.7 µm pixels (a higher resolution camera would help here). And it’s pretty dim. But M57 has always fascinated me. Here’s a shot taken on September 29. It’s a 4 minute exposure, one that benefited from my iAstrohub autoguiding setup:
| Canon 40D | Parameter | Notes |
|---|---|---|
| Lens | CPC-800 telescope | F10 – No focal reducer |
| ISO | 800 | |
| Exposure | 240s | Auto-guiding to a few arc-seconds accuracy. |
| Exposures | 1 |
The single four-minute exposure looked good on the LCD of my camera. Actually – it looked quite good, and on images like this it almost seems like post processing is more trouble than it’s worth. Post processing, as is usually required – can be tedious. So this time, I just took the image directly from the camera’s raw file output – quickly edited it in GraphicsConverter (a Mac Photoshop wannabe) to remove the obviously spurious hot pixels generated during the long exposure – cropped it – and exported it as TIFF and JPEG files. That’s it!
I also took an 8 minute exposure, which had some slight but noticeable star trails. That Saturday night I had some guests, and perhaps I didn’t do a very careful polar alignment as we spent more time visually observing. I’ll chock the trailing up to that – seems like a good excuse to me! Of course, the more obvious answer is that my setup just isn’t tracking well enough yet.
One night soon if we get some breaks in the cloud cover, I plan to try for this object again while using a PowerMate 2.5x expander to fill more of those pixels. Spreading the light over more pixels will require multiple exposures and stacking/processing. But I’ll get it right eventually. For now, this single exposure is an improvement over my past attempts.
Still the neophyte astronomer!
The Neophyte Astronomer 