Telescope lens smudged. NEED HELP QUICK?

Question

well, I was trying to get a new telescope to work( a dobson design,) and I ended up unscrewing the thick lense from its place at the end of the telescope and it fell to the back of the telescope. Once I was able to set all the screws back in, I noticed that the mirror area of the thick lense had big smudges on it. is this bad?? can it be fixed?? PLEASE HELP!

Answer 1

Don't use rags.  Use microfiber cloth and turn it after every swipe, or cotton cloth (something like a soft towel) or balls, and don't use the same part of material for more than one pass over a section of the mirror.  

Smudges imply something that will need to be disolved.  

A solvent that doesn't affect the coatings (or your cleaning cloth)  and evaporates completely will be better than soap.

Answer 2

I'd clean it with cotton balls and acetone.  I learned about this method of cleaning from the late Thomas Back - a guy who designed premium telescopes.  

Dip a cotton ball in the acetone, make one swipe from the center of the mirror to the edge with the only downward pressure coming from the weight of the soaked cotton ball, toss the cotton ball, grab a fresh cotton ball, dip it and swipe again covering a different part of the mirror.  

Work your way around the mirror until the entire surface has been cleaned.  You may need to go all the way around the mirror a couple of times, or make multiple passes over affected areas to get everything.  

You'll use a lot of cotton, and acetone, but it's not going to cost very much for the supplies compared to paying to have your mirror resurfaced.  

The reason for only one swipe per cotton ball is to get rid of any contaminants it's picked up before you move to the next section of mirror.

Make sure your cotton balls are actually made of cotton.  Some places sell sythetic ones.  Also you can get large containers of acetone reasonably at the hardware store.  Pour it through a coffee filter into a jar to remove any impurities.

Cleaning it sooner rather than later is a good idea as there is a chance finger oils will etch the protective overcoat on your mirror.

Note:  Tom Back lived in Ohio.  Astro-Physics equipment isn't inexpensive, but is affordable enough that I own an AP scope, and an AP mount.  AP sells their own lens cleaning kits that include Purosol, plus other cleaners.

Answer 3

use rubbing alcohol and a soft rag or something soft. not kleenx. and wipe off the smudges

Answer 4

Most telescope lenses and optics have coatings that enhance night viewing.  Use of harsh chemicals can destroy your equipment.  Go to the website of the maker of your scope and search their help section for their recomended directions.  They know what their coatings are made of and how to preserve their integrity.  

Most solutions I have heard of are water with one drop of dish detergent and one tablespoon of rubbing alcohol per quart of water.

Dont rub or you can scratch lens with the dust particles which act like sandpaper.

Edit:

The mad thumbs down person is at it again!  Well, I hope that you have enough common sense to realize which answer is the safest and best for you.

Answer 5

"big smudge";  How would that have happen?  A smudge would suggest that you somehow contaminated the surface of the mirror, but it sound like the damage was the result of an impact, in which case you may have fractured the mirror.  If that is what you did then you will have to purchase a replacement  main or secondary mirror (I am not sure whether you are saying that you have fog on the mirror in front of the tube, or the larger mirror at the base.).  Either way, the manufacturer should be able to help you with this.

Answer 6

Since Newtonian telescopes on Dobson mounts don't have thick lenses up front with mirrors on them. I'm a bit concerned that you have something else like one of the Orion or Meade Maksutovs; Celestron also  puts out a few; impossible to say from your description.   Perhaps this is on some kind of altitude-azimuth mount similar to a Dobson, but that is unusual.  "The mirror area of the thick lens"  is quite specific and it seems to me that you are talking not about the primary mirror in the back of the scope but a secondary spot on a Maksutov design with a thick corrective lens up front.  If you have a Maksutov design and you've smudged the secondary mirror on the meniscus then you've got significant problems.    The secondary on any telescopic system is critical to keep clean, more critical than the primary.

Mirrors as a general rule can be recoated, but re-coating a Mak secondary is a more difficult operation, one it would be better to avoid.  And it's totally unnecessary for a fingerprint.

This is the Yahoo general problem area and it's hard to get people to spell out exactly all the details.  So I'm referring you to a general telescope Yahoo discussion group.  (link below)  You need to be able to interact directly with people and that Yahoo group will let you do that.  Make sure you spell out your make and model and scope type because good-natured advice from Newtonian owners is not optimal in this situation.  

  

Because all the light from the main mirror is concentrated on the secondary, very small marks there will degrade the image transmitted to your eyepieces.

There's a lot of things that will work more or less well.  Acetone is nasty to work with but it will certainly work: make sure your working area is ventilated, not near anything that will catch on fire, and not near furniture.  It will take the paint off anything it touches including your telescope; an acetone soaked cotton ball that accidentally touches paint will smear paint on your secondary.  Acetone by itself won't hurt the optics though.  If there is any plastic on your scope keep it away because acetone melts plastic.  There is however a big drawback: in humid parts of the world acetone sucks moisture right out of the air and you get water streaking from using "pure" acetone!  Alcohol will also do this.  (Acetone and alcohol are hydrophilic). Tom Back, who lived in Southern California until he died recently, had the benefit of dry air so acetone probably worked better for him than others of us.  Unfortunately just using mild dish soap and water will also lead to water marks.    Avoid rubbing alcohol: the oils use to make it gentle on the skin smear the optics with a light film.  Regular non-rubbing 93% pure denatured alcohol will work.

Your best bet for maximum spotlessness on a secondary spot on the meniscus of a Mak is Purosol.  Lay the tissues out on the mirror and spritz it wet with Purosol, then let it soak in for a while, say fifteen minutes.  Then pull it away in a radial motion away from the center, not scrubbing, just letting the wetted paper drag.  Then I lay down fresh lens cleaning paper and pull it away from the mirror using gentle radial movements.  The Purosol should clean up without streaking.  Purosol is used by Astro-physics which makes telescopes so expensive they're in the "we don't want to think about it" category.  Purosol is also recommended by Edmund optical which actually has a clean-your-optics tutorial (Edmund also has other cleaning liquids, but they'll kill you on shipping.) I don't use canned air, and I use Pursol instead of Edmund's in-company solution, but the dragging technique they describe (and the advisability of latex gloves--no powder--to prevent smugdes) is all on the mark as far as I'm concerned.   I've provided a link to their site.  They sell purosol in addition to their own stuff but as I say, they kill you on shipping.  Something close to fifteen bucks if I recall.  

Purosol is also excellent on your eyepieces which you should clean several times a year (if you use them often).  

I think that between Purosol, a Yahoo discussion group, and the Edmund tutorial you'll get out of this OK.  

Hope that helps,

GN