Scope Cleaning

[orbital1]

I have just purchased a used scope that is somewhat dusty. What is the best way to remove dust from the eyepieces and corrector plate? I thought I'd use my air compressor first, but if there is still some stuck on there I don't want to scratch everything up with a paper towel and Windex if that is a no-no. Thanks.

[Jon Hickman]

Andrew:

Here is a clipping from the LX200 manual concerning care of the optical surfaces:

"MAINTENANCE

LX200GPS telescopes are precision optical instruments designed to yield a lifetime of rewarding applications. Given the care and respect due any precision instrument, your LX200GPS will rarely, if ever, require factory servicing. Maintenance guidelines include:

a. Avoid cleaning the telescope’s optics: A little dust on the front surface of the telescope’s correcting lens causes virtually no degradation of image quality and should not be considered reason to clean the lens.

b. When absolutely necessary, dust on the front lens should be removed with gentle strokes of a camel hair brush or blown off with an ear syringe (available at any pharmacy). DO NOT use a commercial photographic lens cleaner.

c. Organic materials (e.g., fingerprints) on the front lens may be removed with a solution of 3 parts distilled water to 1 part isopropyl alcohol. You may also add 1 drop of biodegradable dishwashing soap per pint of solution. Use soft, white facial tissues and make short, gentle strokes. Change tissues often. Caution: Do not use scented or lotioned tissues or damage could result to the optics.

d. Do not, for any reason, remove the correcting plate from its machined housing for cleaning or other purposes. You will almost certainly not be able to replace the corrector in its proper rotational orientation and serious degradation of optical performance will result. Meade Instruments assumes no liability for damage incurred
to the telescope in this way.

e. If the LX200GPS is used outdoors on a humid night, water condensation on the telescope surfaces will probably result. While such condensation does not normally cause any damage to the telescope, it is recommended that the entire telescope be wiped down with a dry cloth before the telescope is packed away. Do
not, however, wipe any of the optical surfaces. Rather, simply allow the telescope to sit for some time in the warm indoor air, so that the wet optical surfaces can dry unattended."

[orbital1]

Ok...I think I'll just use the air on the scope. The eyepieces might have some smudges though. Guess I'll just have to be real gentle on those with my kleenex!

[Jon Hickman]

An air compressor is too much pressure, a small squeeze bulb from the local photography shop is much better. With the lens brush on it this will replace the kleenex (or other brand of facial tissue) too!

[SEmert]

Also, if you use the alcohol, it should be the 97 or 99% pure stuff, not the typical 70% stuff.

[youngsww]

If you can't find a camel hair brush, a cat hair mitt will work almost as well.

John

[rbubany]

Make sure the cat is asleep. Else it could scratch the primary.

[SEmert]

What is the best way to remove dust from the eyepieces and corrector plate?

Seriously, on the eyepieces: If you also have smudges from fingerprints or eyelashprints (??) or other such stuff on your eyepieces, the little LensPen cleaning device from Celestron and other places works wonders. One end is a retractible camel hair brush (no cats here) and the other end is a little round thing that looks like an itty-bitty suction cup, except that it doesn't stick like one, and has the ability to clean smudges off without scratching the eyepiece.

I bought one similar to the Celestron one the last time I was down at Cabela's.

Here's the link on Celestron's web page:

http://www.celestron.com/prod_pgs/acces ... ccessories.
LensPen™ - Optics Cleaning Tool, Item #93575

[Deane Clark]

An air compressor is too much pressure, a small squeeze bulb from the local photography shop is much better. With the lens brush on it this will replace the kleenex (or other brand of facial tissue) too!

Also, in my experience, air compressors tend to contaminate the air with oil. and I'm guessing you don't want oil on your corrector.

[Gomanson]

I was told at the astronomy flea market last saturday to use a q-tip with distilled water. However, I have a small refractor so this might only apply to lenses (i.e. my refractor lens and eyepieces.) I assume it would be safe for all eyepieces; don't know about mirrors though.

[Starforce2]

I was told a powerwasher. Blasting the mirror with water for several minutes. Anyone have an opinion on that?

[Jon Hickman]

If I sold replacement mirrors or mirror recoating services, I would recommend power washers for everyone!

The issue with brute force, whether air or water based, is that small pieces of dirt can be pushed across the surface causing greater damage to a mirror than just the dirt alone. Once the integrity of the surface is breached (dug into) it becomes easier for that area to see further damage (think a scratch in the surface of a car left untreated...). Dirt, dust, water stains, and the like have very little effect on the overall light gathering ability of a primary unless it is extreme, for example an inch of saw dust, or a cat (ask Bill!), would be very difficult to see through....

[Bill Bynum]

Orb,

Unless it looks like someone threw mud on your primary, the view won't be effected all that much.

Dusty optics with a good surface are MUCH better than clean optics with a haze of micro-scratches. No matter how careful you are, you will harm the surface of your optics every time you clean them. Timescale for optics cleaning should be no more than every other year, and can stretch out to once a decade (or never).

Try an experiment - while you are looking through the eyepiece, have someone hold up a ruler or their hand in the optical path.
Can you tell the difference? On my 14" newtonian, you can have your whole hand in the optical path and almost no change (and I think most of even that change is due to thermal effects from body heat).

There is a story about John Dobson doing a demonstration where he invites people to look through a 6" or 8" newt, then takes the mirror out, signs his name across the face of the mirror with a Sharpie and puts the mirror back in. No difference in image quality.

It's difficult when you are starting out. You worry about everything on your scope. Just remember there other things that effect your view more. Get obsessive about collimation. Make sure the optics are cool. Don't sweat about the dust.

[rbubany]

Well, I just finished cleaning my mirror following the Orion instructions. It looks OK at the moment.

I suppose it will all turn green or something tommorrow.

Anyway, I will follow Bill's advice. I.e., this was the final cleaning!

[orbital1]

Whenever I get around to pressure washing my fence or deck or patio I'll give my scope a few squirts. The concentrated cleaning chemicals should help eat away any dirt too!

But a little dust must not really matter much. I was looking at Mars this past week with my 8" LX200 and thought it was a little bit dimmer then I expected. Turns out 3/4 of my scope was being blocked by an awning type thing on my deck!! Oh well, I'm still a beginner....

[Starforce2]

not loosing the dustcaps helps too. I've had to clean crap off my 3" twice (mainly dust from roads) and somehow something dripped on it, but orion had an extra plastic eyepeice plug so no more crap gets in that one.

[imkirok]

I find that for really dirty lenses, sandblasting works great.

[rbubany]

I was out at an outreach event last night. It was cold.

This morning, when I brought in the telescope, the mirror immediately frosted up. It was totally covered with water, both big and small drops.

Just for the h... of it, I aimed it across the lake to see what the affect would be on viewing. To my surprise, the details across the lake jumped into clear, sharp view despite the watery covering on the mirror.

It would seem that the mirror would have to be a total mess to really affect viewing, so cleaning would usually be of no benefit and at the same time would be a risk of damaging the mirror.

Interesting.

[Jon Hickman]

Ron:

2 things: 1) Thanks for covering with Sarah last night; 2) John Dobson (and others) used to prove the point during alignment classes etc by signing his autograph across the entire mirror surface after placing a center ring for someone.

[MinnDon]

Also, if you use the alcohol, it should be the 97 or 99% pure stuff, not the typical 70% stuff.

Yeah, I think "rubbing alcohol" typically has lanolin in it - greasy. Don't know anything about mirrors, but you guys have scared me into ignoring that problem if it ever crops up.

As for eyepieces, I would think they could be handled like good camera lenses - use an optical tissue and put a drop of lens fluid on the tissue, not the glass. I saw instructions somewhere for cleaning eyepieces that suggested putting drop right onto the glass (maybe the manual for my C11), but I was told by some one, long ago, that the lacquer (?) used to hold the glass in place on camera lenses can be dissolved by solvents,... even mild solvents made for optical glass. True for eyepieces, too?

[Chris White]

Ron:

2 things: 1) Thanks for covering with Sarah last night; 2) John Dobson (and others) used to prove the point during alignment classes etc by signing his autograph across the entire mirror surface after placing a center ring for someone.

Jeez, good point but, I think I would have passed on the autograph.

[rbubany]

2 things: 1) Thanks for covering with Sarah last night; 2) John Dobson (and others) used to prove the point during alignment classes etc by signing his autograph across the entire mirror surface after placing a center ring for someone.

1) My pleasure, Jon
2) Despite all, I continue to have this little voice in my head saying "clean it! clean it!". It won't stop.

Aaaargh!

[rbubany]

As for eyepieces, I would think they could be handled like good camera lenses - use an optical tissue and put a drop of lens fluid on the tissue, not the glass. I saw instructions somewhere for cleaning eyepieces that suggested putting drop right onto the glass (maybe the manual for my C11), but I was told by some one, long ago, that the lacquer (?) used to hold the glass in place on camera lenses can be dissolved by solvents,... even mild solvents made for optical glass. True for eyepieces, too?

You have it exactly right. Same procedure as camera lenses - solvent on the paper, then start in the middle and work toward the edges. I do this all the time and have had no problems with the eyepieces.

DO NOT DO THIS TO YOUR MIRROR THOUGH