I hate cleaning telescope lenses and mirrors. I know we're supposed to
seldom do it, but anytime I ever wanted to sell one of my optical toys,
I'd think the dust and spots were going to detract from the value,
especially after the camera flash, even though softened, would reflect
off of the lens/ mirror. So, I'd set about cleaning.

I've basically followed online suggestions and research and used the
method of first removing any dust and debris with a soft brush (or
canned compressed air IF kept level and IF already used just before
using on the lens or mirror), then patting with cotton ball soaked in
distilled water while wearing nitrile gloves, then patting once again
this time with distilled water/ drop of detergent (dawn) solution,
followed by distilled water again without detergent, and then drying
with dry cotton. I always wear the gloves and change cotton balls after
every pass. In between the detergent solution and final distilled water
rinse, I will use iso alcohol on cotton or acetone if allowed by the manufacturer for stubborn oils.

However, despite the above, and being as careful as possible, I always
end up with spots on the lens. Why is this? I see videos of others
using the process and ending up spot free. Frustrating!

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On Thursday, March 10, 2022 at 4:43:01 PM UTC-8, Ace Crysler wrote:

I hate cleaning telescope lenses and mirrors. I know we're supposed to
seldom do it, but anytime I ever wanted to sell one of my optical toys,
I'd think the dust and spots were going to detract from the value,
especially after the camera flash, even though softened, would reflect
off of the lens/ mirror. So, I'd set about cleaning.

I've basically followed online suggestions and research and used the
method of first removing any dust and debris with a soft brush (or
canned compressed air IF kept level and IF already used just before
using on the lens or mirror), then patting with cotton ball soaked in distilled water while wearing nitrile gloves, then patting once again
this time with distilled water/ drop of detergent (dawn) solution,
followed by distilled water again without detergent, and then drying
with dry cotton. I always wear the gloves and change cotton balls after
every pass. In between the detergent solution and final distilled water rinse, I will use iso alcohol on cotton or acetone if allowed by the manufacturer for stubborn oils.

However, despite the above, and being as careful as possible, I always
end up with spots on the lens. Why is this? I see videos of others
using the process and ending up spot free. Frustrating!

How?
Easy!
DON'T!!!!!!!

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On Thu, 10 Mar 2022 19:42:57 -0500, Ace Crysler <[email protected]>
wrote:

I hate cleaning telescope lenses and mirrors. I know we're supposed to >seldom do it, but anytime I ever wanted to sell one of my optical toys,
I'd think the dust and spots were going to detract from the value,
especially after the camera flash, even though softened, would reflect
off of the lens/ mirror. So, I'd set about cleaning.

I've basically followed online suggestions and research and used the
method of first removing any dust and debris with a soft brush (or
canned compressed air IF kept level and IF already used just before
using on the lens or mirror), then patting with cotton ball soaked in >distilled water while wearing nitrile gloves, then patting once again
this time with distilled water/ drop of detergent (dawn) solution,
followed by distilled water again without detergent, and then drying
with dry cotton. I always wear the gloves and change cotton balls after >every pass. In between the detergent solution and final distilled water >rinse, I will use iso alcohol on cotton or acetone if allowed by the >manufacturer for stubborn oils.

However, despite the above, and being as careful as possible, I always
end up with spots on the lens. Why is this? I see videos of others
using the process and ending up spot free. Frustrating!

For mirrors, I let soak in tap water with a bit of ordinary dish
detergent, then spray as hard as I can from the tap, then pour some
distilled water over it to wash away the tap water, then blow it dry
with a little hand blower designed to replace canned air (which I've
also used). I find that does a good enough job, and pretty much takes
off anything that's likely to come off. No spots. As advised, I don't
wash mirrors very often.

Lenses, I wash all the time. I don't tolerate any dust on them,
because that does impact performance. With my SCT, I probably washed
the corrector every week or two. I use ammonia-free Windex and
Kimwipes. Again, no spots.

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Den 2022-03-11 skrev Ace Crysler <[email protected]>:

I hate cleaning telescope lenses and mirrors. I know we're supposed to seldom do it, but anytime I ever wanted to sell one of my optical toys,
I'd think the dust and spots were going to detract from the value,
especially after the camera flash, even though softened, would reflect
off of the lens/ mirror. So, I'd set about cleaning.

I don't think a camera flash is really a fair test. Unless you're in a
clean room there is always dust floating around. Even if you were to
get your lenses immaculate they'll immediately pick up some dust when
you have them exposed to the open air.

Researching this question myself a while back, I stumbled on an
article at skyandtelescope.org[1] that references a Harold Richard
Suiter who, according to the article, claims in his book Star Testing Astronomical Telescopes that

The maximum amount of dirt [that a perfectionist] should tolerate on
the telescope optics is about 1/1000 of the surface area, the size of
a single obstruction about 1/30 of the diameter.” In other words, on a
10-inch-diameter telescope mirror you can have as much dirt as in a
completely opaque blot a third of an inch across. That’s quite a lot
of crud to have no effect at all.

“Don’t decide to clean mirrors on the basis of shining a light
down the tube at night,” advises Suiter. “All mirrors fail such a
harsh inspection.” After you’ve done what you can to prevent dust,
ignore it.

I've never gone straight to the source to verify its accuracy, but I
took this advice to heart and stopped worrying.

I've basically followed online suggestions and research and used the
method of first removing any dust and debris with a soft brush (or
canned compressed air IF kept level and IF already used just before
using on the lens or mirror), then patting with cotton ball soaked in distilled water while wearing nitrile gloves, then patting once again
this time with distilled water/ drop of detergent (dawn) solution,
followed by distilled water again without detergent, and then drying
with dry cotton. I always wear the gloves and change cotton balls after every pass. In between the detergent solution and final distilled water rinse, I will use iso alcohol on cotton or acetone if allowed by the manufacturer for stubborn oils.

However, despite the above, and being as careful as possible, I always
end up with spots on the lens. Why is this? I see videos of others
using the process and ending up spot free. Frustrating!

[1]: https://skyandtelescope.org/astronomy-resources/caring-for-your-optics/

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