I own a 10" F5 GSO reflector (GS-830) and over the years have done upgrades to it but have never really been happy with the stars, they have always been footballs on one side. This is the list of mods I have done to it:
* Moonlite 2" Crayford focuser (2" travel)
* TS Optics carbon double spider
* aluminium inner brace to stiffen the inside of the tube around the focuser
* Black 3.0 paint to make it less reflective on the inside of the tube
I have a Howie Glatter with the Tublog for collimating the scope and I collimate as follows:
1) Put Howie Glatter collimator in the focuser with 1mm barlow'ed attachment, adjust secondary thumb screws to bring red laser dot onto center dot of primary mirror.
2) Remove collimator and 1mm barlow and place Howie Glatter into the Tublog and adjust the primary mirror knobs (release white locking knobs, adjust black knobs to bring black circle around the hole of the tublog.
I put the cheshire collimator in and give it a visual.. I can see all 3 primary mirror clips and the secondary is offset nicely on the stalk.. should all be good right?
I use a MPCC MKIII coma corrector and it had horrible stars so I purchased a Skywatcher 0.9x F5 corrector in the hope to fix it which is hasn't.. I've completely started my collimation from scratch and when I defocus my image, one side of the frame always has the donuts cut off My camera is an ASI 1600MM Pro.. the issue is only going to get worse when my ASI2600MM Pro eventually ships.. here's a preview of my donuts on the defocused image.. the Howie Glatter showed perfect collimation and I've even confirmed the laser is in collimation by putting it into a jig and spinning it, the red dot remained in the middle.
I thought I know enough about collimation but this is really doing my head in not being able to sort it out and one side always having horrible stars.. Is my secondary too far up/down the stalk?
Edited by weathermon, 13 April 2021 - 04:29 AM.