Macro Rubinar 8/500 secondary delamination

[bojan]

My Macro Rubinar 8/500 was pretty good (but not ideal) after main mirror relax (as per Dr. Strickling, https://www.strickling.net/russentonne.htm).

When trying to go a bit further and dicmantle the front group, I noticed what looks like de-lamination of the secondary mirror.. it is quite visible when looking at the angle.

Anyone had similar and tried to fix it?
Thanks in advance for any info and/or suggestion!

Cheers,
Bojan

[By.Jove (Jove)]

Usual cause of coating failure is water molecules getting in between the coating and the glass, slowly with time, and it’s quite common around the edges of mirrors - an irregular “black edge”.

You could disassemble and have it recoated, if it’s worth it. Similar occurred in an old Meade 2045 I had many years ago, was not worth recoating.

[bojan]

Jove, thanks for the reply.
Yes.. it seems it is coating peeling off.

Most likely this will not affect the image much if at all.. so I decided not to worry about it.

[JA]

Hi Bojan,

Yes I would agree with leaving it be. It's taken considerable time (I suppose) to get to where it is now so the rate of degradation is very small and the defect quite insignificant. Perhaps you could pamper it somewhat with as relaxed a life as possible in respect of the magnitude and frequency of thermal cycling and store it with plenty of desiccant, just in case.

Best
JA

[bojan]

Hi JA,

yes, it is pretty old, was bought ~15+ y ago (for a special project, as new, from rugift.com store)..
I did not use it very often since, my intention was to be part of SHG setup, and thinking it may be useful for TSE 2028, being a small and easy to carry around.