Imme
17-05-2018, 01:19 PM
OK guru's......gimme some love here people.
I've been chasing a tilt issue for months.
First up - the rig.
GSO F5 reflector
GSO coma corrector (at 78mm spacing which I believe is in the perfect window)
ASI 1600 OSC -15C
EQ6 guided
ZWO tilt adjuster installed (but moving it anything from flat cause more issues...remove it completely and the issue remains....so take it out the equation)
What I know -
Guiding is good
Regardless of sub length I get elongated stars so not a guiding issue
Colimation is as good as I can get it using a laser collimation tool which was then followed up with a star test with artificial star at approx. 50m distance.
Tilt across the image is the same
Appears to me that the image is in the same focus across the image so sensor tilt out?
I doubt it is a scope issue as my old reflector (at F4) did the same thing....although it was a little worse on that scope (longer trailing)
Don't think it's the camera either......my old camera did the same
Coma corrector.....nope, don't think so.....I've tried some shots with it not in the image train and I still had trailing
The second pic is a 1600x zoom of a star.....notice the chromatic spectrum displayed Red, Orange, Yellow, Green , Blue, Indigo, Violet......same order as a rainbow.........to me that says it is some form of optical/focus/splayed spectrum type issue that causes the spectrum to stretch. I could work with this if I was using a refractor, they have lens that do strange things.......but this is a reflector!
So.........throw me some ideas please everyone.
What do you think I should be checking next to try and fix this?
The images below are from a 1 hour stack....but it doesn't matter, a single image would basically be the same...at 1 second or 5 minutes exposure length!
I've been chasing a tilt issue for months.
First up - the rig.
GSO F5 reflector
GSO coma corrector (at 78mm spacing which I believe is in the perfect window)
ASI 1600 OSC -15C
EQ6 guided
ZWO tilt adjuster installed (but moving it anything from flat cause more issues...remove it completely and the issue remains....so take it out the equation)
What I know -
Guiding is good
Regardless of sub length I get elongated stars so not a guiding issue
Colimation is as good as I can get it using a laser collimation tool which was then followed up with a star test with artificial star at approx. 50m distance.
Tilt across the image is the same
Appears to me that the image is in the same focus across the image so sensor tilt out?
I doubt it is a scope issue as my old reflector (at F4) did the same thing....although it was a little worse on that scope (longer trailing)
Don't think it's the camera either......my old camera did the same
Coma corrector.....nope, don't think so.....I've tried some shots with it not in the image train and I still had trailing
The second pic is a 1600x zoom of a star.....notice the chromatic spectrum displayed Red, Orange, Yellow, Green , Blue, Indigo, Violet......same order as a rainbow.........to me that says it is some form of optical/focus/splayed spectrum type issue that causes the spectrum to stretch. I could work with this if I was using a refractor, they have lens that do strange things.......but this is a reflector!
So.........throw me some ideas please everyone.
What do you think I should be checking next to try and fix this?
The images below are from a 1 hour stack....but it doesn't matter, a single image would basically be the same...at 1 second or 5 minutes exposure length!