The secondary mirror on my GS 10 inch has scratches on it.
Dont ask me how that happened as I dont know
I can buy a replacement for $50 from Andrews which is the cheap option , but I was considering perhaps going to a smaller secondary of 2.14" to reduce the CO and hopefully get better contrast viewing planets.
Standard secondary = 63mm + 3mm extra thickness for holder = 66mm obstruction . 66/250 = 26.4% central obstruction.
I have run the numbers and a 2.14" secondary will give a 21.7% CO, whilst giving a 1.5 degree field at 75% illumination. Fully illuminated field is 0.25 degrees.
My conclusion is that the GS is designed for maximum FOV use, but a smaller secondary would give me a happy medium between fov and smaller CO for planetary use.
To go to a different size secondary will mean buying a new spider and holder. I'm considering going for a three vane, again for diffraction spike reasons.
I would appreciate any comments and recommendations including what and who to buy from.
Thanks