Mirror advice

[Rick King]

How do you clean the mirror at the back of my scope. I noticed last night that it has dust all over it. I'm not gonna try to take the back off till I know that I'm not gonna screw something up. 

[Cornelius Varley]

A small amount of dust won't affect the performance of the mirror, but cleaning it may scratch the surface coatings.

[Peter Drew]

If you can still see your face in it leave well alone.  

[N3ptune]

It's possible to remove the whole back assembly with the mirror installed on it and use a simple air blower to remove the big dust only, without ever touching the mirror with anything at all. The blower can remove at least 1/4 (or more) of the big loose scrap you see.

https://www.amazon.ca/FOTGA-Professional-Rocket-Keyboard-Cleaner/dp/B01E9W4U9Q/ref=pd_sbs_79_1?_encoding=UTF8&psc=1&refRID=NSE4WQGQH5ZYVVC2Y7N4

Personally, I think it's a good thing to learn how to remove and rebuild the primary mirror assembly and other parts of the reflector, to suppress fear, I did it once and I fear no more. Of course it's a laboratory grade operation, everything needs to be done perfectly, if you drop something on the mirror, there is no undo obviously.

It's +-6 screws to remove the assembly out of my tube, the position of the parts is secured with tape markers and paper schematic. 

http://imgur.com/zzSURsL

That's the assembly, 1 piece, I am removing the clips with a screw driver but don't do that of course. Just blow the mirror and put it back in the tube. Finally re collimate the instrument, mine was almost perfect after reassembly, I had to do minor adjustment only.

http://imgur.com/OS1tZr3

Most likely, it's not required to remove the dust away from your primary mirror and you should not do it. 

 

[Dave In Vermont]

Disassembly of your telescope's optical-system is a nerve-wrenching act of self-torture - at best - the first time one does it. And is a skill one should approach with much research and support of people like us. And there certainly should be a very good reason to do this in the first place. But for dust on the primary-mirror? That is misguided at very least. Ludicrous would be a bit more apropos.

As said before here, some dust will not affect the optical-performance of your mirror. Major observatories will, and do, agree. While there are some crooks out there who'd be more than happy to tell you otherwise, and sell you something hideous that will wreck your mirror to "clean it" with, feel glad you came here and asked us first! And we'll be here when the day arrives for you to go through the steps to disassemble & re-assemble your telescope and collimate your optical-system - the collimation itself can be done without the drastic steps of disassembly - but for now a good PHEW! is in order!

Something to tuck away for a rainy day is one of the best sets of instructions out there for collimation - and written by a member here in SGL, Astro_Baby. Who seems to have vanished along with her website and instruction-manuals. But some of us have copies of these missing documents for just such a possibility - hence my suggesting your tucking away such. So here is a copy of Astro_Baby's 'A Simple Guide To Collimating A Newtonian Reflector':

Astro Baby's Collimation Guide.pdf

Anyone heard anything from Mel? Or about her?

A bit worried,

Dave

 

[ronin]

To clean it you do have to take the mirror out, clean then replace it.

So taking the back off is kind of mandatory. It is the reassembly afterwards and then the resetting of the mirror in terms of position and collimation.

Cleaning is a problem area, usually it is a case of leave it alone but if you have worked in optics then absolutley nothing is left with dust or anything on it. You are constantly checking and cleaning components. If you see a single small hair on anything it is cleaned immediatly. Owing to this I know I could never have a "dusty" mirror. A bit of a strange situation.

I find that dust "sticks" - I tend to collect glass in various forms. On one handmade item I bought in Canada I found I had to spray it with a cleaner and really rub to get the accumulated dust off of it. That condition on a mirror would undoubtly cause damage, but it was just dust that had "stuck".

I suppose the options are leave alone, or little and often. Both have their positive and negative aspects.

[Waldemar]

If I combine this post with your other post, I think (forgive me if I am wrong) that you are an absolute beginner.
To be honest I would first collect more knowledge about optics, mounts and possibilities before I would even think about cleaning a telescope mirror with a bit of dust on it.
Not hindered by knowledge everything seems simple, untill you find out by experience it is more difficult than you thought... mistakes are irreversible...

Advise:  Just let it be, do not touch it and enjoy the night sky. You really will not be able to notice the dust! The scratches you will probably make on your mirror by trying to clean it are VERY visible because of the scattered light from the objects you are looking at...

[Cosmic Geoff]

Your primary mirror has a big secondary in front of it blocking out some of the light, so a few specks of dust won't make matters any worse. As someone else said, leave well alone so long as you can see your face in it.

[SteveA]

4 hours ago, Dave In Vermont said:

Something to tuck away for a rainy day is one of the best sets of instructions out there for collimation - and written by a member here in SGL, Astro_Baby. Who seems to have vanished along with her website and instruction-manuals. But some of us have copies of these missing documents for just such a possibility - hence my suggesting your tucking away such. So here is a copy of Astro_Baby's 'A Simple Guide To Collimating A Newtonian Reflector':

Astro Baby's Collimation Guide.pdf

Anyone heard anything from Mel? Or about her?

A bit worried,

Dave

 

Well that really is sad news, Mel's Astrobaby site was a terrific resource and I made use of it on numerous occasions. I'm not sure I would have even attempted striping down my EQ6 without access to her brilliant guide. 

I share your worries..

Steve

[Dave In Vermont]

Ronin: You have worked in optics? And no speck of dust is allowable? Then may I assume that if you have a Newtonian reflector - that you keep yours disassembled and the mirrors spend their time living in a sealed box, wrapped in plastic-wrap, in a glove-box under negative air-pressure? I mean - c'mon! Dust is a fact of life! Some of it even comes from outer-space (about 4%). I think I'd quit that job in a rather large hurry!

Leading experts of many fora and publications have been saying for years that dust does not diminish the ability of mirrors to reflect light - which is their task in how a 'reflector-telescope' works - and direct it where it needs to go - your eyeball. Perhaps we should keep our eyeballs in that box, too? Hmmm..... And I was just reading an article the other night (it was 3°F. out) on large obsy's and their policies of leaving dust alone - for the same reasons as us smaller-telescope users - to prevent unecessary wear & tear on their coatings for no perceivable benefit to their performance in their tasks.

Seems to me that, in the face of all the evidence and testimony given over the many years, to still feel a need to go after the "Dust-Boogyman" is not so much grounds to purchase a box of "Steri-Pads® Wipes" or similar - as it is a reason to make an appointment with a good psychologist to take a look at the situation from a fresh and objective perspective. At least I would.

There goes a house-fly! I gotta grab my hedge-clippers and go pursue now!! "I'll get ya! <CLAK!> I'll get ya! <CLAK!> Come back here!! <CLAK!>....." ~'°'~ 

( *< - KWAK!

Dave

 

 

[Paul73]

A bit of gentle rinsing won't hurt the mirror. Blow off the water drops.

But, a mirror has got to be properly gopping before it needs cleaning.

Always inspect the mirror in daylight. Even the cleanest of mirrors look like a horror story under torch light!

Paul

PS. I believe that Astro Baby is taking a break from Astro to pursue other hobbies. I guess that she may be back at some point.

[SteveA]

5 minutes ago, Paul73 said:

PS. I believe that Astro Baby is taking a break from Astro to pursue other hobbies. I guess that she may be back at some point.

That is at least good news....

Steve