Mouldy Mirror

[ambrishnat]

I bought an 8" GSO dob 2nd hand about a year ago, only to discover it had a little mould on the primary mirror. While I was at first disappointed, it has still proven to be a vast improvement over my 4.5" EQ2 skywatcher, and the mould hasn't seemed to affect the views much at all (as far as I can judge with no access to an equivalent non-moulded telescope).

Nevertheless, I decided to clean it, as I've heard that mould can develop further and damage coatings if left for too long. So two days ago I tried cleaning off the mould using the kitchen sink + detergent + hands method I found here. While much of the other grime lifted off readily, after nearing 2 hours of cleaning I still couldn't move the mould.

Is this something I should have another go at? Or am I being over-zealous? I really don't like having the mould there, but I don't want to be too enthusiastic about cleaning my mirror, and ruin the coatings. While the kitchen sink method seems to be acknowledged as a rather safe method for cleaning mirrors, I'm wary of wearing down the coatings with excessive cleaning. But I am wondering if I've been too gentle, as I've read about other cases of people successfully removing mould.

Has anyone else had any similar experiences? Am I being pedantic, or do I just need to spend more time cleaning? I've been wondering that maybe I should I just forget about it and enjoy my telescope as it is. I'll at least attach a packet of desiccant to the inside of my scope's dust cap to prevent further growth. The city I live in is very humid.

I've attached a few photos of said mould, post cleaning. Any ideas would be much appreciated.

On a more positive note, I found Neptune for the first time the other night. Wrinkles and all, I do love my scope.

[John]

Some of the GSO made dobs did not have good overcoatings on the mirrors and therefore need re-aluminising more quickly than other types. I suspect yours is one of those rather than the cause being mould.

If the scope is still delivering well for you then carry on using and enjoying it but it might be worth finding out about re-aluminising services available near you for future reference.

[ambrishnat]

Thanks, I'll definitely look into re-aluminising.