Problem during collimation

[SimpleMajority]

I was collimating my Orion XT8 and while adjusting the secondary mirror my finger slid off the side and brushed the mirror, now there is a finger print on the mirror surface and I need to know how to remove it (without removing the entire mirror assembly preferred). All the guides I have found so far only talk about the main reflector, and everyone has a difference chemical process.

[Saleratus]

Could you try to live with it for a while? It will probably not affect the images you see, since it is off the focal plane. At any rate, the secondary mirror is not as critical as the primary to performance.

[SimpleMajority]

That is what my friend was saying, but he said the other down side to it is the print will gather more dust. So I guess I will and maybe see if the place I purchased the scope from can do a cleaning down the road. I wish the book was a bit more specific to what the secondary mirror holder is and what it looks like. My friend did the initial collimation on it (as I didn't have a laser, and that cap sucks), and he was telling me what he was doing, but it was hard to see what he was holding on to and adjusting.

[x6gas]

Are your hands small enough to get past the spider vanes? IS so you could clean the finger print very gently with Baader wonder fluid (use a microfibre, lint free cloth and be very gentle...)

[faulksy]

as said badder cleaner and maybe strap the cloth to a pencil eraser side if your fingers are to fat

[scoobymike]

And if you're gonna clean the mirror in situ, make sure the OTA is on its side, that way if you drop something, it's less likely to fall on the primary... Personally I'd see how you go without touching it first, but I do understand your concern.

[umadog]

I'd take out the secondary to clean it. It's very easy to do. You will do a better job of removing the fingerprint if the secondary is in your hands and there's less chance you'll mess things up (believe it or not).

I'd try ethanol (as pure as you can reasonably get it). Just squirt it down with ethanol and leave it to air dry. Don't worry about the droplets whilst it's drying. They should all evaporate and leave no marks. If you try to mop them up with the corner of a tissue then you may get drying marks. That should be enough to get rid of the fingerprint. If not, you can try repeat the process or try acetone (BUT DO THAT SOMEWHERE WELL VENTILATED!). Acetone dissolves plastics but won't damage your coating.

It's worth keeping your coatings reasonably clean. A clean mirror tends to dew over less and when it does dew there is less chance of damage to the coating. Dew dissolves nasties on a dirty mirror and these can attack the coating. I wash my primary with distilled water about 4 times a year. I never touch it with anything but liquid. If you stick to that rule you will have clean optics and no possibility of cleaning-induced damage. I even wash it in situ so there's no chance of dropping it.

[x6gas]

I'd take out the secondary to clean it. It's very easy to do.

Truth.

Tho' the OP did say they'd prefer not to remove the secondary... but it is worth saying Umadog...

[SimpleMajority]

I can't get the telescope out and check the image quality right now as it has been cloudy the past few nights, but I am going to make another attempt tomorrow night. If I have to remove it I found a section discussing the removal and cleaning of the mirrors, and my only question is what is a few drops of dishwashing soap lol. That is what the manual says to use, as well as a cap full of rubbing alcohol, cotton balls, and distilled water for rinsing.

[kenmyers]

They mean a few drops of fairy liquid.

My primary on my F/5 looks like it has grown a beard! it has all sorts of fluff and dust and stuff covering it's entire surface along with no less than 3 fingerprints (I used to be very stupid)

BUT

My views are still wonderfull.

You shouldnt need to clean it. If you decide you DO, then you should go the whole hog and remove the primary and clean it carefully.

[umadog]

As Ken says, you will not have impaired views because of the print. You just don't want this stuff on your mirror for too long. I wouldn't mess about with cotton, or even the detergent. The ethanol is a one-step process.

[Astro_Baby]

Bit late now but thats why I always wear cotton gloves when handling stuff like that. Decent cotton gloves cost about a quid iin Boots. Alao always take off any jewellry....have seen a newbie scratch the secondary with a watch before and thats a lot harder to fix.