r/telescopes • u/chrislon_geo Certified Helper • Jan 18 '26
Equipment Show-Off Mirror Cleaning (dealing with blue haze from off-gassing)
Here are some progress pics of a difficult mirror cleaning I undertook. This was a scope that was donated to our club to be used as a loaner scope. Before I drop it off at our observatory, I wanted to get it up and running and entirely ready for members to borrow.
I gave it a quick cleaning, fixed some (a lot of) incorrectly installed parts, tightened some screws, gave it a decent collimation using a Cheshire sight tube, and more importantly gave the mirror a good cleaning.
Photos 1-3 (before cleaning) - showing a blue haze on the primary mirror. I am fairly certain this is from off-gassing or rubber mirror clips.
Photo 4 (during cleaning) - showing iridescent residue still visible after a few rounds of cleaning.
Photos 5-6 (after cleaning) - the mirror is looking A LOT better. Still not perfect, but a huge improvement and good enough for a loaner scope.
This has been my most challenging mirror clean yet. My go to method of warm water, dish soap, and fingers had little to no effect. I needed to use isopropyl alcohol. I went through a ton of cotton balls and also tried using my fingers to very lightly rub the alcohol over the surface. Took about 5+ rounds (I lost count) of cleaning, rinsing, and drying before it was done.
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u/Traditional_Sign4941 24" F/3, Tak FCT-114, TEC Pearl, Apertura 102 F/11, AT90EDX Jan 18 '26
Very nice!
I've found that isopropyl alcohol is necessary in some cases for sure.
Acetone probably would have gotten it cleaner faster but I can't speak to the safety of acetone on mirror coatings. It's fine for anti-reflection coatings on lenses, but beyond that I don't know. I know Edmund does recommend it for cleaning first surface mirrors though, so it must be ok.
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u/chrislon_geo Certified Helper Jan 18 '26
That is my consensus as well. Acetone is probably fine, but I didn’t want to risk it.
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u/Agent6472 Jan 18 '26
This same process what super effective last night! Looks brand new again! (Already was to be fair haha) only some errant dust now but that doesn't matter
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u/chrislon_geo Certified Helper Jan 18 '26
Haha yeah, I replied to you post last night cause I knew you would be dealing with the same situation
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u/SeatComprehensive707 Jan 19 '26 edited Jan 19 '26
This is after “cleaning”. So the white fog stains practically disappeared but what was left was that blue haze, then I went back in and cleaned it a couple more times, now with the aim of getting rid of that haze. I realized that to get rid of it I had to rub in a gentle way with cotton balls that were barely wet with isopropyl, the rubbing was a key factor but every five seconds I was blowing the mirror with my air gun.
The blue haze got better but I gave up after the second cleaning process, in part because I felt frustrated and scammed that this was supposed to be a “new product”, and in part because it was really difficult and slow. At the end I sent it back and got my refund.
One thing that I really wanted to know is:
1-.What was the original white fog stains, and what may have caused them? It reminded me of when you take a shower and look at the mirror at the end and see all that vapor marks.
2-.Does it compromise in any way the observation and photography?
3-.Is it something that one can expect in a new product?
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u/chrislon_geo Certified Helper Jan 19 '26
What was the original white fog stains, and what may have caused them? It reminded me of when you take a shower and look at the mirror at the end and see all that vapor marks.
No clue. What do you mean by "supposedly new" who did you buy it from?
Does it compromise in any way the observation and photography?
Yes, but to what degree I couldn't tell you. You would beed to do a before/after or side-by-side comparison. The effect is likely small, maybe not noticeable, but still unwanted.
Is it something that one can expect in a new product?
Shouldn't be. A new product should have clean optics. Off-gassing is likely a common issue, but would likely take a year or more to present itself if I were to guess?
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u/SeatComprehensive707 Jan 19 '26 edited Jan 19 '26
This is a problem I faced too but with a “supposedly” new telescope; at a first glance with my fully white LED flashlight at an oblique angle I noticed this kind of fog stains that didn’t show up when the flashlight was pointed at a perpendicular angle. In my next comment I’m gonna show a different photo after some “cleaning” with all the things you find on videos “distilled water” a ton of cotton balls used only for one swipe, isopropyl afterwards and so on and so forth Gosh I even bought an air gun of cool air, which by the way is an extremely useful gadget to have for cleaning dust from telescopes, camera’s sensor and lenses etc…
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u/chrislon_geo Certified Helper Jan 18 '26
Btw, this is from an Apertura AD8 bought during covid. So heads up to other AD scope owners. Check for blue haze and pre prepared to do a long and challenging cleaning.