Yes all fair points Greg, lots of factors involved and my aging equipment doesn't help
Quote:
Originally Posted by gregbradley
What LRGB filters did you use for mono filtered imaging? Not all filters are parfocal and not all filters are 1:1:1 combine ratio. This is one main reason I use Astrodon. If you focus on the luminance you will find your other RGB filters and even narrowband are also in focus. There may be some tiny difference but its negligible.
|
I use parfocal Astronomik Type II (not typeIIc) so they are aging and I would love a set of 1:1:1 astrodons, my astronomik's are FAR from 1:1:1. This would simplify things a lot for me probably.
Quote:
Originally Posted by gregbradley
What camera are you using?
|
ST8-XME. The NABG KAF sensor probably doesn't help things by being NABG becaus any blooming makes the problem all that much harder to deal with.
Quote:
Originally Posted by gregbradley
Secondly what software do you use to callibrate and combine your images? Some combine methods work better than others.
|
MaximDL for calibration.
Quote:
Originally Posted by gregbradley
Another point is what angles do you image at? I tend to image objects that are near the zenith or slightly to the east and then image them down to maybe 45 degrees. Below that most subs start to deteriorate in quality.
|
Same as you - eastern hemisphere, Zenith down to about 45 degrees.
Quote:
Originally Posted by gregbradley
What scope is it? Does it have a corrector? Is there mirror shift? chromatic aberration?
|
Major problem #1 is probably the scope. Aging 12" SCT Meade. Stars are mushy. But, work with what I have.
Quote:
Originally Posted by gregbradley
How do you autoguide? Is there differential flexure which may get worse at certain angles?
|
Typically don't autoguide, exposures 300s or shorter on my PME don't typically exhibit trailing.
Quote:
Originally Posted by gregbradley
How often do you refocus and how sensitive is your scope to temperature shifts. How much does your environment shift in temperature?
|
Refocus every hour, but as I say, the exact accuracy of the focus varies and this is a problem. At 0.84"/pixel on the 12" I don't think I can get around this, there is always going to be some slight variance. Having said that, I should set FocusMax back to doing 3-5 image samples averaged, it might be on 1 image samples.
Quote:
Originally Posted by gregbradley
Are you imaging at a dark site or under light pollution? Is your seeing very variable or tends to be reasonably stable?
|
Seeing is very variable, and this would feed in to the variability of the focus accuracy throughout any given night.
So, in summary, I'm aware of the source of much of the error, but the question was around how much of a problem this is for other people and if it is how they mitigate it, as it's rare for me to see the problem in other people's images. Seems deconvolution might go a long way towards helping me. I then wonder how much work this is, so will be interesting to try it and see how it goes. Of course the comparison is drawn because it's simply not a problem for the OSC.
Thanks,
Roger.