[Matthieu (Matt)]

Hi all,

I believe that my 16" dob mirror is in dire need of a recoat as per the attached picture. Note that this was taken at dusk in the garage with open door, mirror pointing East after sunset without any artificial light.

I haven't pulled the trigger as I'm not quite able to determine whether it would make a small or huge difference.

I find that on globulars and galaxies the brightness compared to the human eye doesn't really seem to align with the numbers as I expected the following light gathering ability:
- x165 for my Megrez 90FD
- x329 for my C5 (2x the Megrez)
- x3331 for my 16" (10x the C5)

Whereas to my eye, the jump from the 90mm to the C5 is very similar to the jump from the C5 to the 16". I can see the difference, it counts as an upgrade, but it doesn't feel like a massive upgrade.

Is my experience due to the failed coating or is it a case of brightness perception not scaling linearly?

PS: I had planned to join the Gippsland Star Party to compare to other scopes but the weather didn't play ball