Posted 19 May 2004 - 05:29 PM
Posted 19 May 2004 - 08:31 PM
Posted 19 May 2004 - 09:51 PM
I was just kidding about the germs, of course!
Oddly enough, I once got hold of a packet of lens tissue that had a silicone treated surface. It was very difficult to get THAT off the glass!
Posted 20 May 2004 - 01:25 AM
Posted 20 May 2004 - 07:07 AM
If you haven't cleaned already, you might also want to get some white cotton gloves to wear when you do it. These are readily available at the pharmacy and will help to prevent oils from your fingers from being dissolved into the cotton balls/alcohol solution and being deposited onto the glass surface.
PS. I wouldn't use plastic or latex gloves, since these usually have plasticizers or other processing additives in them which could dissolve into the alcohol solution, with similar results.
Posted 20 May 2004 - 09:23 AM
P.S. My dew shield arrived last night...... couple days after the fact, of course.....just my luck, eh?
Posted 20 May 2004 - 09:35 AM
Posted 20 May 2004 - 10:28 AM
I use soft tissue without scent and an isopropyl alcohol/water mix from the drug store. A drop or two of ammonia in the solution helps with sludge, but you won't need it for a corrector plate.
Make sure you blow the surface dust off first. The first wipe may remove some more dust that is stuck on the corrector, so rub very gently. The second "wash" (a second one is always necessary to remove streaks) can be with a little more pressure.
Use a bright light at an angle to illuminate the surface. When it's clean and free of streaks, you'll know.
The iside of the corrector tends to "haze" from time to time. It may be dew, or outgassing from the painted tube interior, or simply smog, but it happens. Remove the screws and the pressure ring that surrounds the corrector plate. You will see a few cork or plastic shims around the edges of the corrector plate. These do not have to be removed for this procedure, but make a note of where they are in case one moves and has to be replaced. These hold the corrector plate in the center of the tube without the tube having to press against the edge of the corrector.
You will notice that there is a scratch or white spot on the edge of the corrector with a matching scratch or white dot on the tube end beside it. These are the registration marks that will allow you to return the corrector to the exact rotation necessary to give the best images.
Grab the secondary mirror edge which protrudes from the corrector plate and gently lift the corrector plate out of the tube.
Turn it over, and grabbing the baffle tube surrounding the secondary mirror, replace the corrector in the tube.
At this point you can clean the inside of the corrector exactly as you cleaned the outside.
Then, reverse the corrector plate again, line up the registration marks, replace the pressure ring and lightly tighten the screws that hold the ring on. Use only light pressure to snug them up.
Next time out, check the collimation on a star. It may have moved (but it won't be much) and therefore require a little touch up.
I've done this yearly and my scope is 11 years old. The mirrors are still clean, and the corrector is spotless and unscratched.
Everyone thinks eyepieces, lenses and corrector plates are very delicate. They aren't. But if there is dirt on the surface, you can end up scratching the surface. This, in itself, won't hurt your scope, but makes you feel as bad as accidentally stepping on your cat's tail.
Just be careful on the first "wash" not to press very hard or go back over the same spot too often.
When cleaning, the tissue should be "wet", never dry. After the corrector is completely cleaned (maybe twice), you can "burnish" a spot with a dry tissue. Just don't press too hard or go too long.
And though one's breath is not completely distilled vapor, it is acceptable to fog up a section with the breath before wiping. I watched Roland Christen do the corrector on a Houghton Cassegrain this way, and it was clean! when he finished.
After my last cleaning, I stored my SCT with the corrector plate down (as I usually do), and, unbeknownst to me, a small gnat had gotten in the tube. It died, fell on the corrector plate, and stuck! It's been there a year now, and hasn't affected the image at all. I'm going to flock the tube this month, so I'll remove it when I take everything apart. I think I'll miss my mascot, though. It's been a lot of places with me.
Good luck. Once you do it, you'll realize how little there is to worry about and a periodic cleaning after heavy dew is a good thing to do. Especially in the eastern US, where the dew is acidic.
Posted 20 May 2004 - 12:54 PM
Posted 20 May 2004 - 04:10 PM