Possible cleaning of a school's Meade LX90 12" SCT

[Mark at Beaufort]

One of the local High Schools in Herefordshire were given a donation 2 years ago to purchase a Meade 12" SCT. They were also given a donation from a local company to purchase a Pulsar dome. The Meade has now been housed in the Dome for about 20 months. The location in the grounds of the school, dark site, is fairly close to a pond area where the school does other research. See attached photo.

Last night I was asked to talk to the pupils and was able to show them Mars. However, I was not that impressed with the quality of the image. I inspected the corrector plate and it was covered in dry fine dust but the main mirror was cloudy as if bad condensation had dried on its surface. Clearly if it was a Newt I would clean the mirror but the Meade is sealed so that is not possible.

Any thoughts on what to do? Leave the mirror alone just clean the corrector plate? Or send it back to Telescope House for a proper clean? Whatever the outcome the location near the pond area may not help so do you think the scope should also be covered inside the Pulsar dome?

Mark

[barkis]

If you decide to clean the optics Mark, it is best you do both I suggest. Of course it goes without saying really, but the removal of the corrector plate and the mirror, are tedious tasks, and great care has to be taken.

You may get some help here if you decide to DIY it.

My LX90 Is in an Obs, but I also keep it covered in an old Duvet cover, and a shower curtain on top of that. Keeps it perfectly clean.

If you contemplate Telescope House, get a quote first, I don't see it being a cheap job.

Ron.

http://jan.eaglecreekobservatory.org/

[Mark at Beaufort]

Thanks for that Ron. I was also thinking that when we have SGL5 there will be a number of you present who have greater knowledge than me on SCTs. I was going to persuade a few of you, during the daytime, to come over to the school to have a look - I would drive of course knowing the area - its only a few miles from Lucksall.

Regards

Mark

[brianb]

I don't see it being a cheap job.

The issue with cleaning SCTs internally is that disturbing the optics and throw the parts out of alignment radially which can really hit the optical performance. You have to be very careful that everything goes back together in the exact same orientation.

TH will do a good job &, in the absence of skilled local help, are probably the best option. If you could deliver & collect the scope yourself I'm sure that would save a fair chunk of money, as well as ensuring kinder treatment than couriers would be likely to inflict.

For storage, a dust cover will help, but a low power heater (15W bulb - fridge type) running continuously would help keep the condensation out.

[Space Bat]

If you feel confident cleaning a newt mirror and know the pitfalls of micro scratches...etc Then performing similar task on an SCT mirror is no different.

The Meade isn't sealed....remove the corrector and give that a good clean with a mixture of IPA and Distilled water as recommended.

If the mirror is not that dirty as it shouldn't be really and is only suffering from condensation spots then you should be able to clean the mirror in situ without breaking it down further.