Hey Mike, thanks!
Yes, acquired using Brad’s scope. Remote imaging – got to love it. It opens up many possibilities. Just compile the imaging plan, upload it, and then get some sleep. Planning and image processing is the fun part. IMO, acquiring the data is rather mundane/routine.
Indeed, there is always a trade off between highlighting the spiral structure and not burning out the core. DDP does a reasonable job, but I usually don't stretch to final levels using DDP. I’ll only stretch to say 60%, and then finish off with curves in photoshop. This makes it easier to manage the colours in a phased approach. I typically go with a core size similar to that of the largest star in the frame for aesthetics; however there are some exceptions with this if the galaxy core is quite diffused.
I got tired of imaging cleaning. I really could have chased them further to remove more speckles. Brad has recently redone the calibration frames which I’ve noticed a significant improvement, but still not perfect. Plenty of hot/dead pixels present making for some heavy work. RC Console cleaned quite a few with a 20% threshold, may have cleaned it better with a different value. I left ACP dithering as default – didn’t tweak it further in fear of losing the guide star on the tiny ST237 chip. I’m getting use to ACP’s style of imaging as I’m also using it for remote operation in my own observatory. A couple of sub frames weren’t guided correctly, but I included them in the combine routine. After blinking the images straight after registration, the error appeared random so the combine routine removed the outlier pixels.
Not entirely sure about the gradient source. The RC12.5 of Brad’s doesn’t have the “shorty” light shroud around the primary (this may have changed). I’m also not aware of local light pollution sources at the remote observatory site (in SA) – Fred will know. Could be a combination of things.
Interesting to hear about the dark current leaks. This would have a detrimental effect. Regardless of the scope/camera combination, I always dither – even if using a class 1 chip. I don’t know of a more effective way to remove a dead column unless of course you want to build a pixel map of the chip. The downside of using a map is its static and may not represent the current pixel correctness. i.e. some pixels die over time. I'm open to suggestions.
Thanks for your comments.
EDIT: I should also add, that one night, the weather was quite warm at the remote location and the chip couldn't be cooled to the set point of -15. This did not help the situation in controlling noise! Perhaps, need to persuade Brad to get an FLI.
