I caught a little light on M45 a couple of years back at the end of a long night of collecting M33 subs. It really didn't do justice to the nebulosity and I wanted to get out and give it a real run. Wednesday night (coldest of the season so far) was that chance.
It was an auspicious start as after I placed the tripod in its marks, installed all the gear and wired up, then went to drift align, I found I was within two arc-minutes of the pole. I took that as a good omen and moved along. It was the first time I haven't had to make any tweaks to the alignment when setting up.
Next was focusing. Because it was still too early for Aldebaran or Capella to be high enough in my sky. I slewed to Caph and started there. I haven't quite gotten the knack of using the Bahtinov mask tool in
APT, so I have been using the
FWHM/HFD measurement to fine tune the focus. That went OK and I was able to slew over to my target for framing.
One thing I have noticed in earlier images is that the
coma correction hasn't been quite what I expected. After reading through Toms thread, I spent some time earlier this week validating that the back focus spacing was actually 55mm (44 for the Canon and 11 for the t-ring). I also decided to remove the stop-ring from the back of the CC to allow the front face of the t-ring to sit flush with the top of the focuser tube. As I tightened the locking nuts on the focuser I applied even pressure to the back of the camera to keep everything as flush as possible while securing the
DSLR/CC into the drawtube. I like the results better than any I have seen thus far.
By 1915 I started collecting 180 second subs and ran until about 0100 Thursday morning when the clouds started to move in. During that time I got 84 subs and
APT did an automatic
meridian flip - I love the tool for that capability. I wound up tossing 6 subs because they were somewhat invaded by clouds and had a lighter background than the rest. I calibrated with 81 flats and 81 dark flats. I like this combination better than flats and a master bias, it seems to produce better results for me. I also passed on adding any darks as I had nothing nearly cold enough in the library and as the temps had dropped to 17F I didn't want to spend more time collecting them. Frost was forming on the
OTA and camera and I didn't want to keep them out in the air either. I find that dithering between each image does a decent job of reducing noise when I get this many subs.
Data was calibrated and stacked with
DSS and post-processed using
StarTools 1.6.382. I tried first with 1.7.447 but I still don't have the hang of the new modules and terminology yet. I will go back and try again. The 1.7 version did keep more faint nebulosity, but felt a bit "unkempt" to me. I used a pretty standard process for me - Autodev, Bin, Crop, Wipe, Autodev w/ROI selected, Deconvolution, HDR, Sharpen, Color, and de-noise classic. Went over to PhotoShop, but just to save the upload jpg file - no adjustments done there.
Comments and suggestions are encouraged.
Bob
Hardware: Celestron C6-N w/ Advanced GTmount, Baader MK iii CC, Orion ST-80, Canon 60D (unmodded), Nikon D5300 (modded), Orion SSAG
Software: BYE, APT, PHD2, DSS, PhotoShop CC 2020, StarTools, Cartes du Ciel, AstroTortilla