sc8 needs a bath

[wolfdogg]

I have a Celestron SC-8

im going to attempt to hand wash my primary and corrector in the months to follow. I have taken care of optics for almost 2 decades now, so i know how important care is. I have handled this scope for 20 years, and have had the corrector off once and cleaned it, and i tore apart the gear drives and reassembled to snug and lube everything up. So Im not afraid of the scope.

oh yeah, its dirty, yes. when you look at it on stray light, you can see a scum layer on it from either dew, or some other resi-due. I have seen that interior dewed up a few times over the years. Also, maybe its just the air that has entered into the chamber from the back end during eyepiece setup over the years that has slowly collected on the mirror. but its BAD. i can tell its degrading the image.

But, heres the question, does anybody see a good reason why i shouldn't clean my primary, and or the corrector?

I believe its aluminized, so i know i cant use any solutions. I was planning on luke warm distilled water, a few drops of pure dawn, and some sterile cotton, and maybe even a hair dryer, or air compressor if they are safe, which i think they arent for this, so maybe a can of compressed air, or just air dry.

I have never collimated a scope, and i will be doing the traditional method, not having a laser collimator on hand or access to one. im looking forward to see what traditionalists went through, ill tell you that much! It will make me feel official.

Can i have some input on this?

[nightfisher]

I ended up Having no choice but to do this with my old omc140 maksutov, as some orange juice got spilt over it, i cleaned it with utmost care but i dont think it was ever as good, also you might struggle with collimation after the job is done.

If you go ahead with this task ensure you have PROPER distilled water, not the rubbish sold at motor shops

note: if the optics are so old and so dirty consider recoating the primary and having the scope back to new condition all in one major stripdown

[dweller25]

Correct orientation of the primary, secondary and corrector plate is critical in an SCT. You must put registration marks on all three before you take the scope apart and then ensure all three go back with the same orientation on re-assembly.

Cleaning the corrector is no problem as they have very hard coatings - I don't know how hard the coatings on the primary will be.

Here is a guide on dis-assembly ......

Astromart Articles - Disassembly of an SCT: Child's Play

And here is a guide on lining up the optics .....

How do I align my Schmidt-Cassegrain telescope?s (SCT?s) corrector plate and secondary?

And here is a guide to collimation ......

http://skywatch.brainiac.com/collimation.pdf

And here are a lot of photo tutorials .....

http://www.cloudynights.com/item.php?item_id=2553

Hope that helps.

[Jarvo]

I cleaned the Meniscus lens on my Mak last year with a blower and a cleaning kit from Jessops. Used plenty of the fluid and it came up a treat -Your a brave man to take apart the primary though .....

Jarvo

[swamp thing]

Hi

Can't help with corrector cleaning. As I am a newt man, but.

No point in cleaning the primary in Distilled water with detergent in it, as this completely goes against the whole point of using Distilled water in the first place.

Best to rinse with tap water, then wash in tap water with your cleaner in, THEN rinse with Distilled water. This way you don't waste as much Distilled water.

You only need the Distilled water for the last rinse as this is what will be the last thing in contact with the surface, and this is where the purity of Distilled water counts.

Regards Steve

[wolfdogg]

from what i understand the 5 drops of detergent combined with a bowl of distilled doesn't really defeat the purpose, because that solution will still be dissolved solid free, short of phosphates from the soap i gather, but minus any hard minerals like i have in my tap, such as magnesium, calcium, etc..

I like the idea of running under luke warm tap water but i believe that wont get it perfectly clean where actually stroking the surface with the cotton would.

I was thinking of blowing it clean, then maybe running luke tap water over it (to your suggestion), long enough to get it as clean as possible, then dipping it into a solution of distilled as mentioned above with a few drops of non scented pure dawn liquid soap, then using large pieces torn from

the sterile cotton rolls dipped into the solution thoroughly then pulling across (OUCH) once only with no pressure, lightly drug across, then trashed, for each piece. then after that's complete another rinse, then doing it again in the solution, or a new batch, with a bit of pressure if anything is not clean.

Does that sound like suicide? i got the idea from this website i think Cleaning Optics

@dweller25 thanks for those cleaning links, they are much appreciated. i will go over them when i get the chance.

[wolfdogg]

@nightfisher

the optics arent so bad, i dotn think they need a recoat. ill see if i can take a picture of it. but im not sure if i can post it being a "Vacuum" still

[swamp thing]

Only the last water you rinse the primary in at the end will make any difference to water marks on the surface.

This is what the use of Distilled water avoids.

Normal tap water can be used to wash it. Trust me it won't hurt it.

The only reason we use Distilled water is to make sure that any moisture left on the surface evaporates without trace.

All mirrors have a silicone overcoat that is pretty hard, tap water will not hurt it.

If you wish to use Distilled water for the whole process is up to you, but it's an expensive way to wash it.

I have always used tap water to wash my mirrors, finishing with a Distilled rinse. Never had a mark on em.

Regards Steve

[swamp thing]

I would be more concerned about using cotton wool. Unless it is very pure this may scratch the surface much worse than use of your fingers. I use ny fingers (using no pressure) to gently wipe the surface whilst in the tap water cleaner solution.

Obviously wash your hands thoroughly first.

I have cleaned my mirrors this way for years without any worries.

Regards Steve

[wolfdogg]

i tend to think cotton might scratch as well. and i love the idea of using fingers under tap. i just need to know its clean enough before i do this. how do i get it clean enough to know when im ready to rub it with anything that i wont scratch it with any contaminants that are already on the surface? i think thats my problem. Have you ever washed something really dirty under water with no scrubbing? the dirt doesnt go anywhere. so im worried about the smallest grain. so how do i start, or atleast get past this point when i know its safe to start the light finger pressure?

and i think might just do it the way you say, tap water, fingers, then a distilled rinse. question though on this, will a distilled rinse, left to dry on edge leave nothing, or will i need to dry it off with some sort of air to get any drops off. i know that process itself is endles though, there will always be drops left to dry themselves, so these will be just fine?

oh and i took a look today closely and took some pics, it might be mainly my corrector, its as if the last time i cleaned it, i messed up, or something got in there from the time celestron cleaned it maybe, but its as if static has caused layers of dust on it, along with thick dew streaks :-) .

ive been so anxious to clean this, its coming soon!

[nightfisher]

my advice would be remove and clean the corrector first, but while corrector is of have a good look at primary, you might find it does not need cleaning, you would be surprised at how mucky looking a mirror can be before in intrudes on the view

[swamp thing]

I start, by rinsing using a shower attachment this will remove any loose dirt. Then I use the cleaner and tap water using my fingers to very gently wipe over the surface if you feel anything stuck to the surface, you can kinda roll it gently off with your finger. The water itself providing the lubricant to avoid any scratches. Then I rinse with the shower attachment. I normall go over the mirror a few times like this. Anything that doesn't come of with very gently pressure LEAVE ALONE. It won't effect optical performance and you may cause more damage than good trying to remove it.

After Ive finished washing and rinsing I place the mirror on a guitar stand ( this holds it upright). Then, pour Distilled water all over the surface. This final rinse washes all the previous water off and just leaves the pure Distilled water on the surface. I just leave it on the guitar stand to dry. Distilled water dries without leaving any trace.

Just make sure the water is Distilled not de-ionised as de-ionised still has impurities in it and will leave water marks.

HTH

Regards Steve

[wolfdogg]

@nightfisher yeah i planned to do that, onec the corrector was off i will be checking out the primary before pulling it. I was looking at teh scope yesterday and was thinking the primary may not be all that bad. but the corrector is shameful. The funny thing, all of the crud is on the inside. i cant figure how it got so bad. theres even what appears to be a fingerprint full of heavy dust, that most likely is celestrons cleaning shop from about 20 years ago, that much dust has adhered to it. i took some pics too. ill post them up in a bit.

@swampthing

ok,from what you mentioned i think i like that the best

i will take it to the shower / bath (combo)

run it under the bath spout (holding under the backside center with one hand, stabilizing it with the other) to give it a good soak and loosed up anything on it

then run it under the pressure of the showerhead

then back to bath spout where i will ever so gently rub only a few inches at a time then rub and rinse fingers each time, rinse and repeat (pun intended)

once the entire glass has been stroked, i will then stroke it a bit more liberally with my fingers across the length in larger swaths until i cover the whole lens again

then i will rinse good under bath spout then to shower head for a hard rinse,

then i will give a thrrough rinse with grocery distilled water (1 gallon jugs)

then off to a coated stand, i dont have a guitar stand, ill have to find something, maybe set it edge up on top of a towel on the kitchen counter top and lean it against a lint free cloth against the wall, and i wont worry about any drying spots.

i want to do this to the corrector mainly, unless the plastic housing, and metal screws will be a problem, but i think not as long as its thoroughly dried.

anything sound wrong with this procedure?

[wolfdogg]

Heres the RIG

heres the best image of teh primary i can come up with

but heres the damning evidence of some malpractice on the corrector, i was able to catch the dust just right in the sunlight on an angle. i have never seenit this bad

NOtice the residue on the inside im referring to, only thing i can figure is thats from repeated dew, also theres even a big dust collected fingerprint on the inside, but i think celestron was the last ones who cleaned it when i had it serviced by them about early to mid 90's.

if those images dont just want to make you cry, or have you shivvering then i dont know what will, well, to say the least its time to disassembly anyhow.

[swamp thing]

i want to do this to the corrector mainly, unless the plastic housing, and metal screws will be a problem, but i think not as long as its thoroughly dried.

anything sound wrong with this procedure?

Whoa boy. This is how to wash the primary mirror. I'm not sure about a corrector plate. This may need a totally different approach. I am not a SCT owner so cannot offer advice on corrector lens cleaning.

If its just your corrector lens that needs a clean I wouldn't be in any hurry to dismantle the OTA just to clean that.

I would think all you need is some sort of proprietary lens cleaner.

Looking at your pictures the primary mirror is certainly not needing a clean yet.

Most Newts get a lot dirtier than that before we even start thinking of giving em a wash.

I would hold fire until another SCT owner can advise you on the correct procedure for cleaning the front corrector.

Regards Steve

[wolfdogg]

yeah, i was figuring you would say that, however, im entirely comfortable washing the corrector as mentioned, but that only depends if the secondary comes off, or if theres no confusion in that area. But the process i mentioned was for the mirror mainly. I was going to use very careful discretion depending on the secondary mirror assembly, however the method you mentioned, if it works on a coated mirror it should surely be safe on a corrector. I have cleaned it before, but it was with lens cleaning equip, and i wasnt happy with the results with that, so i took it into the shop then.

I will be pulling off the corrector first and wasnt planning to hull out the back end unless the primary is as bad as i thought it was, but i think its the corrector im seeing. you know when you look at the primary in an SC, if your not careful of what transparent image your looking at, it actually looks like the mess is on the primary, because it hard to tell what piece of glass your actually seeing because of all the reflections going on.

But im thinking if the inside of the corrector is that bad, its got to provide some kind of hint at what the primary would look like. Also, since its the first time, and i want to play with the scope at a deeper level than just observing, if its even barely dirty, im up for it, since i will be cleaning everything else. I dont want to leave just that partially dirty and have everything else spotless. :-)

thanks for the tips too!

[dweller25]

I have cleaned SCT correctors by first rinsing with warm water and detergent and then with distilled water - very easy and the coatings are very hard so very low risk of scratches.

The biggest problem was getting the corrector off !!

The corrector had stuck to the OTA so I gently heated the edges of the corrector with a hair dryer and eventually it worked itself free.

Also you must mark the orientation of the corrector with respect to the main tube so you can re-install it at the same position and you should do the same thing with the secondary if you remove that.

[wolfdogg]

how do you guys mark it, with a permie marker on the edge of the glass, or what?

happy new year by the way. im still up partying. i just love this forum so i keep a couple tabs open in my browser (google chrome)

[arbacia]

Hi,

Wolfdogg, when I received my old orange C8 (1978) it was in worse state than yours. I disassembled it completelly and clean all the mirror under the tab (at home the water is OK, no residuous). Later I did the same with many others, including one like yours.

Wolfdogg, at least the Schimdt plate should be cleaned. Remove the Schimdt plate. First the six screws, then the aperture retaining ring. Then use a felt permanet marker to mark the position of the Schimdt plate. Use a marker in both: frame and Schimdt plate to place again in the same place. Paint sevral marks as during the washing can be deleted!

There is a some small cork strips in the edge of the plate. Remove them and record their position. Usually there are three of them.

Grab the secondary holder and try to lift the plate. rotate something. Be careful. As the time flyes, the plate can be "glued" itself. If doesn't go out easily check if it is glued to the suppot. In this case some drops of water, or medical alcohol in the edge can help. Left for minutes or hours rehydrating and softenen the adhered parts. Once soft, grab again the secondary holde and pull.

Clean the Scmidht plate as any optical glass (which includes glasses, by the way. Usually people take care of telescope lens but not of the glasses).

Probably it can be cleaned with no removal of the secondary mirror and holder.

Check the state of the primary. If primary mirror needs to be cleaned I will give some tips. basically once extracted from the tube don't remove it from its holder

Patricio