Quote:
Originally Posted by Cimitar
Thanks mate 
I'd imagine your f/5 scope will throw up some different challenges than what you've been used to. The sky glow will certainly become an issue more quickly.
Can a single 16sec exposure show much detail in a nebula? If you use that approach will you need to take hundreds of images and stack? 
Have you considered guiding your f/10 scope? If your mount allows it, you could get longer exposures by guiding. |
Hi Evan,
No doubt the sky glow is an issue but it always has been. You're correct that the refractor makes a monster of it quite quickly. The 16 seconds was purely part testing sequence. With the moon almost full, it's about as bad as it gets. I ran 350 subs on Helix at ISO 800 for 16 sec and I was surprised I could make it out at all. The main reason I choose Helix was the stars around it are very faint and the moon was only about 10degrees away. As I said, the absolute worst case scenario. Regarding the stacking, I'm pretty used to stacking upwards of 600 subs to only get 3 odd hours of intergation. Yes it is time consuming but it's the only way I could manage it with my mount which takes me to your last comment. Yes, I believe tracking on the mount is possible but there's very like information available. I guess it's because most people don't do what I am trying to with such a basic setup. The actual mount gets jitters as it moves around. It's driven by a plastic spur gearbox so it is never going to be smooth although I do have some modifications in mind. Time will tell if I actually do it. Regardless though, we come full circle and get back to sky glow. On the f/10 at ISO 3200, a 22sec sub ( being all the mount could reliably do cleanly ) was underexposed but I made it work so an extent. Often I would take longer shots to frame the object but anything above 40 seconds had too much sky glow anyway. With the f/5, that's theoretically only 10sec. Now iso3200 is noisey so maybe 20 sec at 1600 might work. I just have to find a new sweet spot. I'll get there, it all a part of the challenge. I must say that I'm enjoying the data collection and analysis and understanding why things work the way they do.