I'm getting ready to pull out the main mirror and secondary mirror and clean them.
I'll take some pictures as I go and post them here.
Talking of the main mirror:
Back in 2015 TS -Teleskop Service in Germany
- were offering certificates for their ONTC mirrors.
I'm not sure if they do now?
Here is my certificate from 2015 for my 10" f4 ONTC mirror completed by the famous Wolfgang Rohr.
You can see that the Strehl ratio is 0.922.
Peak to valley 1/6.8 waves.
RMS 1/22.1 waves.
here:
https://i.ibb.co/G5TSG9S/10-inch-f4-...t-complete.jpg
using Google translate on the German text it says:
TS Mirror – TSHS250f4
D=258mm
Mirrored surface=254mm
SN=A_TSHS250f4- 04/09/2015
Slight overcorrection (about 1/6 lambda) in the middle.
However, this area is covered by the secondary mirror, so that the mirror is significantly better in practical operation than 1/6.8 wave.
cheers
Allan