Info wanted on procedure for cleaning a VC200L Mirror

[1ponders] (Paul) · #1 14-09-2009, 01:31 PM

This mirror cleaning stuff is new to me, though I'm pretty sure I can handle it. However what I'm not sure on is the procedure for cleaning the VC200L mirror. The setup is slightly different to your average newt assembly.

Does any one have a guide for dismantling and reassembling? Thought I might have a read before i start pulling it apart.

Dennis · #2 14-09-2009, 02:02 PM

Hi Paul

It’s a very long time since I cleaned my mirror and it was in the pre-digital SLR days so I didn’t take any photos!

I don’t know if the design has changed, but I think I just unscrewed maybe 3 screws that held the mirror cell to the OTA and the whole cell/mirror/baffle assembly slid out?

Just make sure you mark everything so you know the exact orientation of the cell to the OTA and the mirror to the cell.

Cheers

Dennis

[1ponders] (Paul) · #3 14-09-2009, 02:17 PM

I'd have to check but it looks like I can remove the rear part of the OTA which holds the mirror cell. Then remove the ring that holds it in place. The thing that is got me scratching my head is do I need to remove the mirror from the whole assembly (baffle through the center and all that.) I guess it will be obvious as I start to pull it apart.

Oh yes I'll make sure I put marks along side anything that comes apart.

[1ponders] (Paul) · #4 14-09-2009, 02:24 PM

Well I did find a really good article for cleaning the mirror at the yahoo group link you posted in my other thread Dennis. Thanks for that. It seems much simpler now and without having to muck up the collimation too much.

leinad (Dan) · #5 15-09-2009, 01:53 AM

Interested also.
I might try this later this week, I believe with the right dishwasher solution and a shower spray you can carefully pat wash the mirror with your hand may work without scratching the surface.

Heres a useful link also:
http://www.mikesastro.com/analysis/vixen/index.html

multiweb (Marc) · #6 15-09-2009, 08:54 AM

Quote:

Originally Posted by [1ponders]

This mirror cleaning stuff is new to me, though I'm pretty sure I can handle it. However what I'm not sure on is the procedure for cleaning the VC200L mirror. The setup is slightly different to your average newt assembly.

Does any one have a guide for dismantling and reassembling? Thought I might have a read before i start pulling it apart.

I wouldn't dismantle anything. I cleaned my C11. I suspect the mirror arrangement is similar on yours? How dirty is the mirror? If it's only a couple of spots or sticky stuff, local cotton swab with acetone won't leave any mark. The whole water/detergent thing is more suited for newts or dobs where you can strip the mirror bare.

[1ponders] (Paul) · #7 15-09-2009, 09:04 AM

It does need a clean Marc, definitely. Fungus starting, finger print

multiweb (Marc) · #8 15-09-2009, 09:15 AM

Quote:

Originally Posted by [1ponders]

It does need a clean Marc, definitely. Fungus starting, finger print

Ouch! Sounds like it needs a major clean then and you have no choice. Take it off and stand it up right on a bench, because it looks like a salad bowl, you can fill it in with demineralised water with a dab of dish washing liquid, then clean it with cotton wool. Let it soak a bit then finish all the remaining dry evaporation spots with acetone.

[1ponders] (Paul) · #9 15-09-2009, 09:36 AM

My biggest concern is getting fluid down the join between mirror and baffle and then down into focuser. I'll need to look at this process carefully, especially as the fingerprint is right next to the baffle.

multiweb (Marc) · #10 15-09-2009, 10:37 AM

Quote:

Originally Posted by [1ponders]

My biggest concern is getting fluid down the join between mirror and baffle and then down into focuser. I'll need to look at this process carefully, especially as the fingerprint is right next to the baffle.

I saw the pictures of your mirror type and if you can safely remove it all together from the baffle then that's the way to go - wash it like a dob's mirror in a tub. On the C11 I couldn't do this because of the rubber/cork bond that sealed it on the baffle tube.

[1ponders] (Paul) · #11 15-09-2009, 11:43 AM

Quote:

if you can safely remove it all together from the baffle then that's the way to go - wash it like a dob's mirror in a tub

That's what I was thinking as well. As long as it isn't too major an engineering feat.

Bassnut (Fred) · #12 15-09-2009, 12:00 PM

Question. After tring several lame, inocuous liquids and ending up with streaks etc, I cleaned my mirror with Windex and its perfect, but I noticed (after) theres a lot of surfaces that you cant use it on, eek, I hope I havent done any damage, me thought.

I saw somewhere ppl get paranoid about all this and the coatings are pretty tough (with cleaners that is, not scratching), anyone know for sure how critical which cleaner is used?. I would have thought Acetone would be very agressive, if thats OK, what isnt?.

multiweb (Marc) · #13 15-09-2009, 12:21 PM

problem with the water/soap/alcoohol you always end up with "dry stains". I found acetone to get rid of all this as long as you keep the coton swab moving. You can actually leave absolutely nothing behind. I googled the net to see if it would dissolve aluminium coating and haven't found anything saying it would, if used sparingly I guess?

Anyway I haven't killed any optics (yet).

[1ponders] (Paul) · #14 15-09-2009, 12:26 PM

I'm even considering using the Bintel solution after initial rinsing to remove grit and dust etc.

DavidU (Dave) · #15 15-09-2009, 12:30 PM

It's the rubbing that does the damage to Aluminium coatings.
I use Acetone on lenses.

bert (Brett) · #16 15-09-2009, 07:28 PM

Just to raise the stakes a little higher...

You cannot have the mirrors coated in australia. The only way to get the coatings redone is by vixen in japan. The reason I have been told is some thing like the final figuring is ground into the coating.

I know of one person getting the mirrors aluminised locally and turned the scope into an expensive paper weight.

Brett

Ps Can you post some pics of the fungus?

DavidU (Dave) · #17 15-09-2009, 07:34 PM

Quote:

Originally Posted by bert

Just to raise the stakes a little higher...

You cannot have the mirrors coated in australia. The only way to get the coatings redone is by vixen in japan. The reason I have been told is some thing like the final figuring is ground into the coating.

I know of one person getting the mirrors aluminised locally and turned the scope into an expensive paper weight.

Brett

Ps Can you post some pics of the fungus?

I think Paul is just collimating and cleaning the mirror, no fungus

Doomsayer · #18 15-09-2009, 10:29 PM

Brett is correct about the coatings - they use a proprietary vixen coating. I own a VC200L which had its mirrors recoated locally by the previous owner. It gave awful images after that. It was later sent back to Vixen and now works fine in its new CF truss configuration.

If you remove the primary mirror, put a reference mark on its edge so you can relocate it. Also, do not tighten the rubber mirror clips too much. They really just need to be resting against the mirror, not pressing down - undue pressure can induce aberrations on this quite thin mirror.

It is also a good idea to centre spot the secondary mirror witth a fine felt tip pen - this will make collamation with tools or a laser much easier. You can make a spot template quite easily by pasting a series of ever reducing concentric circles in a graphics package - merely cut the paper circle to the secondary size and pierce the middle with a pin - you can then place the paper over the mirror and poke the fine felt tip through the hole.

guy

[1ponders] (Paul) · #19 16-09-2009, 09:33 AM

Oh no there is definitely fungus starting on it so I want to nip that in the bud.

Thanks Guy. I'm hoping that I won't have to do too much with the secondary as I won't remove it from the OTA tube. I will of course be calling on everyones expertise when it comes to collimating after cleaning. The cleaning won't occur until late next week at the earliest at this stage.

Sharnbrook (Mike) · #20 19-09-2009, 02:52 PM

Paul,

When removing the mirror, be sure to mark any washers and shims, and replace them in the same location when re-assembling. Whether this is true of not, I don't know for sure, but I have heard/read that the shims are part of the collimation, and whilst they may look the same, they are variable. Better safe than sorry.

As for killing fungus, UV light is one way to go, and the sun is a good cheap source of that. Leave the mirror/lens in direct sunlight for a couple of days. Here is a link to a number of sites.