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Need advice, should I clean my SCT corrector plate?


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A grubby corrector plate will have far more effect on the performance than a few spots on the primary mirror.  :smiley:

ahhh.. I've so been wanting someone to come in and say that. I really hope so. Guess I'll find out next time I try it out after the corrector clean. Many thanks Peter!

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I would certainly clean the corrector based on your photos. A layer of dust and grot will attract dew more readily. I would ignore the primary mirror for now, the benefit of cleaning is outweighed by

Hi Guys, I keep my scope in the shed - which is nearly at the outside temp - not sure if you want to bring a cold SCT into a warmer environment, as this would only create even more temp imbalance, cre

Hi, I've just had a quick read and the coatings seem to not be over coated for protection so be very careful - might be worth you holding off a little - wait to see if anyone has cleaned an SCT mirror

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I cleaned the corrector plate of my 14", it had to come out to remove some webs inside the tube (the guy I brought it of had taken a screw out and a spider moved in) Windex isn't available in the UK and what is, is vinegar based but a small amount of house ammonia (half teaspoon) in the cleaning mix is ok (spoke to Doc on the subject) I also have some photographic wetting solution .... in fact quite a lot if you decide to to use doc clay's formula, give me a shout. Be wary of cotton wool, only use the medical stuff and the  same as the kleenex tissue.

The Corrector plate came up great without marking/watermarks ... being a 14" it just took me some time. 

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Thanks Lardy, think to start off with I'm going to try baader wonder fluid applied with micro fibre cloth. Its all available through amazon so hopefully by this time next week I'll have a sparkly clean corrector plate. And a blotchy fungus ridden primary ;)

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Watching this thread with great interest just in case mine happens to have it when it arrives but there is no way in hell I'm taking mine apart.

Lol, i doubt many of us would. It takes a real daredevil to attempt that if you ask me. You can only imagine the insane collimation that would be needed afterwards! Give me a week or so and I'll post back with the clean corrector plate pictures.

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Cleaning the corrector plate is relatively straightforward, just make sure it goes back in the same orientation as it came out. You really do need to clean it separate from the main tube. Do not try to clean the secondary or primary mirror surfaces nless you have experience in doing it - too easy to sleak the surface and ruin it. You don't want to be practicing on your pride and joy. On re-assembly do not over-tighten the screws for the retaining either ring as this will pinch/distort the optics (ask me how I know...). If you try to clean the plate with it in-situ you will get fluid into the joint with the retaining ring and it's a nightmare to clean off. Always remove the plate for cleaning.

Setting up near trees that exude sap is the biggest issue, those little drops of resinous fluid are a right PITA to get off and demand use of a fluid solvent of some sort.

ChrisH

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Funny really, I got no problem doing a job on a car I've never done before but when it comes to my scope, squeaky bum time.

I've got Astronomania just up the road from me so if it bothers me that much, I will ask them for a quote on a clean and a service.

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Steve, Colin - thanks.  As said the corrector will be easy, 

http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/6151907/Main/6130442

Here's a thread off Cloudy nights - I think (me included) we spend too much time LOOKING THROUGH THE WRONG END OF THE SCOPE !!!!!!! (yes, me included) the actual image off the mirror is well away from focus - its just cleaning the mirror - so long as you take care and use the correct fluids/cleansers and being cautious of the coating - everything should be ok.

I was in exactly the same situation (as with probably thousands of us) when taking the corrector out to clean, once done, I was quite pleased with myself (as probably thousands of us were) with no long term issues - surely the mirror would be the same, as said, with caution - your just cleaning a mirror.

Steve those images are really nice on your page - very nice, if no one posts regarding mirror cleaning, you could start one, just to see the outcome.  it would be expensive and risky "posting" your scope back and forward over the country, in - house would be far more easier on the nerves than in transit - thanks again.   Paul.

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Paul, i totally agree about home cleaning it. Im not ruling out a primary clean yet. Thanks for the kind words about my images as well. I really need to clean the corrector, collimate then get a good lunar or jupiter session under my belt before i decide what to do with the mirror. Funnily enough, the scope has been in my much drier conservatory since yesterday evening and those mirror splodges dont look anywhere near as bad. When i took that photo there was still condensation on the primary which make them look very white. I actually had trouble spotting them when i looked at it this evening.

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Oh - as well as the fluid and microfiber cloth you need to get a hand air blower and ideally a soft camel hair brush as well - blow all dirt/grit well away, then very softly using camel hair brush give it a dusting, and then blow again, then dust again - you don't want to be wiping grit around your corrector plate!  I cleaned mine in situ without removing - just be very careful

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Paul, i totally agree about home cleaning it. Im not ruling out a primary clean yet. Thanks for the kind words about my images as well. I really need to clean the corrector, collimate then get a good lunar or jupiter session under my belt before i decide what to do with the mirror. Funnily enough, the scope has been in my much drier conservatory since yesterday evening and those mirror splodges dont look anywhere near as bad. When i took that photo there was still condensation on the primary which make them look very white. I actually had trouble spotting them when i looked at it this evening.

See, its just got a lot better Steve!! when I look down the wrong end of the scope, I get differing intensities of dew, looking against a blue sky - nothing, pointing the tube down against a dark wall they "pop" into view, so long as its just water streaks (like an out of focus spiders web) you should be fine.  Paul.

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Slightly off topic but relevant... I clean mirrors on office equipment all the time, most of my colleagues use different methods, tissue / glass cleaner/ chamois / water/ fairy liquid / isopropyl alchol... These mirrors are cheap mass productions.

I've never seen one cause a problem or become damaged and they get cleaned probably once every two months.

has anyone actually damaged their scope mirror?

I just find it hard to believe they can be that different

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I don't think you should discount the fact that at least some of the problem may be that the seeing has often been pretty rubbish recently.

I'd have no issue with cleaning the outside of the corrector.  I do mine relatively regularly because they often get dew on and then collect dust quite rapidly.

Personally I'd quite happily clean the mirror too, if I thought it really needed it.  I've had my Mak completely stripped down before now and when you know how it all goes together it's really no big deal.  Patience and care are the main requirements.  There aren't that many parts and they're not held together in any particularly complicated way.

The downside of stripping an SCT or Mak is recollimating after reassembly.  That really is a bit of a fag.  It helps to have a long garden (or a long house) and an artificial star.  If you're not happy with the idea of doing the collimation, I'd really recommend against taking it apart.

James

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I don't think you should discount the fact that at least some of the problem may be that the seeing has often been pretty rubbish recently.

I'd have no issue with cleaning the outside of the corrector. I do mine relatively regularly because they often get dew on and then collect dust quite rapidly.

Personally I'd quite happily clean the mirror too, if I thought it really needed it. I've had my Mak completely stripped down before now and when you know how it all goes together it's really no big deal. Patience and care are the main requirements. There aren't that many parts and they're not held together in any particularly complicated way.

The downside of stripping an SCT or Mak is recollimating after reassembly. That really is a bit of a fag. It helps to have a long garden (or a long house) and an artificial star. If you're not happy with the idea of doing the collimation, I'd really recommend against taking it apart.

James

And of course theres a big reason there to clean a corrector, the more gunge it collects the faster it dews up on a night outside and hence the more gunge it collects. Its almost an argument for regular cleaning. And yeah, you're right, the seeing has been worse than atrocious for a good couple of months now. This time last year we were getting far more clear and steadier nights, though also it was a lot colder, which probably had something to do with it, but hey, at least we had a nice summer eh! :/

And i really dont get on well with collimating so im definitely not taking mine apart, but i'll be cleaning the plate by gently stroking a microfibre cloth with a bit of cleaning fluid on across it so there shouldnt be any excess fluid getting into the seal around it. There won't be much fluid on the cloth even.

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I think you should spray it on and leave it to work. Dissolving is a non aggressive process......

+1 for Olly's no-contact cleaning recommendation. Even if you do decide to wipe in the end, try no-contact spraying first - it can be surprisingly effective. Someone told me about this method years ago and I've used it ever since with my 10" LX200

The method I use is to buy two cheap plant spray bottles, clean them thoroughly and fill one with distilled water and the other with a small quantity of pure isopropyl alcohol. (Keep the spray bottles in a sealed plastic bag when not in use.) Tilt the OTA just beyond horizontal so the corrector surface is just past vertical so any run-off will not pool at the edge of the corrector. Put a generous wad of kitchen paper or similar on the lower lip of the OTA, ready to absorb run-off. Spray the lower half of the corrector surface with IPA; leave it for a short time, letting it run down to the paper towel. Before it evaporates and leaves marks, spray the same area with distilled water; let the excess run off and then clear the surface by blowing with canned air from centre towards the edge, changing the paper towel as required to absorb run-off. Flip the scope over 180 degrees in Dec and treat the other half of the corrector the same way, again washing and blowing from the centre of the corrector to the lower edge.

I usually find that two cycles of the above wash and dry routine clears most of the grime on the corrector without any swabbing. Even if you do swab, doing a no-contact clean first will remove a lot of potentially harmful abrasive muck and make subsequent swabbing safer. As a precaution, after cleaning I place a desiccant plug in the drawtube for 24 hours in case any moisture got past the corrector plate gasket.

Adrian

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