Cleaning shades and mirror?

[c_davidson]

The filters on my sextant are getting dirty/salty.  What should I do to clean them?

How about cleaning the index mirror?

Is there any concern about scratching the filters or the mirror?

Clendon

[CarlosPindle]

Clendon,

Spray some distilled water on mirror and wipe it off with a soft cloth. Same with the shades. That's what I do.

Carl P.

[stargazer]

I'm not experienced cleaning a sextant, but I have cleaned front surfaced (delicate) telescope mirrors, one worth $$$. I used distilled water, one drop of Dawn detergent in a gal of distilled. I first poured it over the mirror to wash away grit.

I then use more water and let soak a bit, then GENTLY wipe with the type of loose cotton you buy in a roll between papers in a drug store. Thoroughly rinse with distilled water. This is the generally accepted method.

I don't own a good sextant so I don't know what type of mirror. You want to avoid adding microscopic scratches to the surface. Normal water definitely will leave spots, minerals perhaps.

Since my telescope is worth more than my car I'm fussy about it. You decide about your instrument.

Here are some guys on youtube cleaning a smaller mirror out in the field, using the technique I use.


https://www.youtube.com/watch?v=py3CaZ0Y2JM

Edit: Just checked my cheap plastic Davis sextant and (naturally) it has rear surfaced mirrors, so the glass front is much harder than the reflective surface which is protected by the glass. Wouldn't need to be so fussy with it. For my "quality instrument" I might just rinse with rubbing alcohol and wipe with lens cleaning pads or microfiber.

[c_davidson]

That was a good video and the men were very careful in handling and cleaning the mirror.

Those are good ideas for cleaning the first surface mirror on my Astra III-B. When I clean the index mirror I'll use those techniques. Microfiber sounds like the solution to the scratching problem.

Thanks for replying.

The Davis plastic sextant is a nice one for the price. Not too accurate but it'll get you a fix +/-. And, it won't rust.

Does your name "stargazer" rightly mean you are an astronomer?

[stargazer]

Does your name "stargazer" rightly mean you are an astronomer?

Amateur only, since a child. I can actually still remember the first time I saw the stars, I was a babe in arms and the adults were pointing up (perfect black crystal night). I was looking at their hands at first. Then I saw the stars, wow! Standing on the door stoop facing west. Weird that I can remember that, being in someone's arms.

Got my first Gilbert 3 inch reflecting telescope on a tripod when I was maybe 6yr old. Hard to use. Saved and got a Criterion clock drive 6" on an equatorial, with rotating tube, rack and pinion focus, small sight scope, setting circles and 5 eyepieces when 11 or 12 yrs (took a long time to save up $). That was a super scope back then and I would run star parties at the grammar school and junior high. I still use it. I wanted my parents to sell the television and get the scope, but my Dad very wisely said if I saved half, he'd pay half. Teaching responsibility. When the time came he took the whole family to where they built them in Hartford, CT and there I met the builders and saw the possibilities of much larger scopes.....LUST!!

Took me a long time to get a 20" f 4.3 starstructure scope with a Vaughn Parsons mirror, I love it. Last I knew these mirrors were not attainable for us plebeians, only to NASA and the government, I had to track one down in Florida. So I consider it irreplaceable.

Scratching, just remember any tiny particles will scratch. The deep absorbent cotton tends to lift them. The cotton fibers will blow off when dry. You will need to blow dust and rinse before using microfiber, which doesn't leave fibers but doesn't have much depth to hold particles away from the surface.

[c_davidson]

That was an interesting from your youth up- you've lived the name you use. You father did make a wise decision.

Will take your advice about the cotton balls. It looks like the resilvering of Index mirrors, or replacement, is common and something I wish to avoid as long as possible.

Clean lenses,

Clendon

[stargazer]

That was an interesting from your youth up- you've lived the name you use. You father did make a wise decision.

Will take your advice about the cotton balls. It looks like the resilvering of Index mirrors, or replacement, is common and something I wish to avoid as long as possible.

Clean lenses,

Clendon

Just to clarify, the cotton I use is not the little balls, but the roll sandwiched between paper where you can tear off handfuls. I see they used that exact product in the youtube, where you see them tearing paper they are actually pulling out the cotton.