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I need advice on cleaning a corrector plate
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I've got an Meade LXD75 8" Schmidt-Newtonian. The corrector plate has some smears on it (someone tried to wipe off dew). Here's a picture:
I don't believe they are scratches - it looks like smearing to me when I look closely.
Does anyone have an recommendations on how to clean this without messing up the coatings? Should I even clean it at all? I haven't specifically noticed anything when viewing or imaging, but if it would make a difference and it's not too hard, I'd prefer to have it clean.
Any advice would be appreciated. Thanks so much.
Posted at 2:35PM, 26 January 2008 PDT
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If these are standard coatings, then simple isopropyl alcohol won't hurt them. I don't know what the composition of UHC coatings are, so I can't advise you if that's what you have here.
It's important to use enough liquid to float the debris off, rather than too little and having to wipe it off. However, it's also very important not to let any get down inside the scope. One way to prevent that is to clean it "upside down" ... that is, aim the tube down so the corrector plate is pointing straight down.
Apply a good soaking of isopropyl alcohol to either a handful of sterile cotton balls or a roll of gauze. Roll either of these soaked bundles across the surface of the corrector, taking care not to squeeze any liquid into the center or around the very edge -- where it might creep in under the seal.
Let dry, then look at it again to see how much improvement you've made. If it's better but still messy, repeat the exercise with a new wad of gauze or cotton balls. Remember to use a rolling ... not a rubbing ... motion and you should be fine.
Posted 5 months ago.
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Thanks for posting a photo. Before seeing this I thought the corrector on my 8" SNT looked bad! This really need to be cleaned.
You need to remove as much dust and debris as possible before wetting and wiping in order to prevent scratches. I use a "blow bulb" used to clean camera lenses, but a a bulb for removing rear wax will work also. For more stubborn bits use a new, very clean natural hair brush being very careful.
It is possible that some of the smears may be stubborn as well. You may want to look here
www.astro-physics.com/products/accessories/cleaningproduc...
for some alternative cleaning solutions. They are pricey though. I have found nice cotton squares at places like LensCrafters. As indicated by chipdatajeffb, isopropyl alcohol is a good place to start. You want to use fluids that evaporate without leaving any residue. Some folks use ethanol, methanol, or acetone, but care is warranted, especially with acetone. These need to be checked for compatibility with the optical coatings (not to mention the paint!). Once you know the solid bits of debris have been removed, the idea is to wet the edge of a cotton square and drag it across (around) the corrector. Use no force! Let the adhesion from the wetted edge supply all of the pressure. Once the cloth stops trailing some of the solvent, stop. Use the cloth only once (I flip mine over once and use it again, but I am careless).
Go slowly, take time and care. The cost of replacing the corrector is the same as buying a whole new telescope.
Originally posted 5 months ago.
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JMZawodny edited this topic 5 months ago.
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Thanks - I'm going to take a look at using the isopropyl alcohol with lens cotton. I've got a blow bulb so I'll gently get any bits off first. I've been searching elsewhere and that seems to be the general consensus. I'll go easy and post a picture of the results when I'm done.
Posted 5 months ago.
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Checkout this link
www.arksky.org/asoclean.htm
Posted 5 months ago.
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Thanks NC - that's a very, very thorough report. It jibes with the suggestions above and seems pretty credible.
Posted 5 months ago.
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I wound up using the arksky link above that NCStarGeezer recommended. I think it did a great job. Here's the result:
There's some dust I need to gently blow off, but otherwise it did a great job. I wound up having to clean the inside as well (not for the faint of heart!) because I believe the previous owner was a smoker. I was very gentle and the vast majority of the spots, blemishes and smears are now gone. There are some fine scratches, but I believe they were there before the cleaning.I reattached the corrector plate assembly (I did not remove the plate from it's casing since I've heard that's really, really dangerous because getting things aligned again can be very difficult) and collimated the scope succesfully.
Overall I'd highly recommend this process. Thanks so much for the advice! Now if I can just get rid of these clouds, I can see how well it worked.
Posted 5 months ago.
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