Lightbridge mirror cover

[nmo]

Hi all,

Firstly great site, I've spent a lot of time reading it over the past few months and would have to say it helped me choose my last purchase.

I recently purchased a Meade 12" Lightbridge. Unfortunetly I dropped the flimsy plastic mirror cover onto the primary mirror and put a small mark on the mirror. While I don't think that this small mark will cause any significant issues I would hate to do it again so hence my question.

Has anyone made a mirror cover similar to those used on obsession style telescopes, ie It fits to the top of the mirror box and doesn't fit around the mirror, what do people think? is this a good idea or not?

I figure if it snuggly fits the top of the mirror box then it will be to wide to fall into the box.

Once again great site.

[Phil]

I did the same thing to my 16' the plastic cover is crap. I to mark the mirror but was able to get it of without any problems.
Phil

[JethroB76 (Jeff)]

It must be a good idea, I was pondering this very question just today

[RB (Andrew)]

Welcome to the forum NMO, I'm glad you've found it helpful.

Your idea is a very good one and well worth pursuing.

My daughter has the 8" LB and that's one of our concerns, that she may drop the flimsy plastic cover on the mirror.

[astronut (John)]

These covers can be a problem, the leading edge of the cover comes to a sharp edge and this is the part that scratches or marks the mirror, if dropped.
One other solution is to attach a strip of thin felt around the entire edge.
This softens the end so minimizing the possibility of mirror damage.
Go to the Yahoo Lightbridge site, there are examples of these mirror covers sitting on the tube top.

[nmo]

Thank's for the responses,

I signed up to the yahoo lightbridge group and I'm just waiting to get accepted, either way I went outside this morning and started cutting a disk out of 6mm MDF.

[JimmyH155]

It's very easy. I cut out a circle of plywood 3mm thick, the diameter of the mirror can. Then in order to get it to fit in between the trusses, I cut it in half and cut out those little squares where the trusses were, and then glued a lip on one of the straight edges to make a complete dust seal. I match marked the trusses and the plywood , gave it a coat of varnish and hey presto. To fit each half on, you can bend the ply a bit to make it fit. Very nice

[RB (Andrew)]

If you have some photos of it JimmyH155 I'd love to see how it looks.
Sounds great.

[JimmyH155]

Went into the shed last night with camera, took shots, then spent 2 hours trying to get the image onto the Lappy. I think either the cable or the camera is faulty. Then had a brainwave and discovered the lappy has a card reading slot So now I have the pic and cant remember how to get it onto this thread HELP....HELP....it is 375 Kb

[JimmyH155]

I think i have sussed it out here goes

[nmo]

Well I tried to make one that turned out similar to the images that have been posted. I must admit I'm a little worried that the design doesn't really fix the problem as each half could easily be dropped into the base and since it weighs a bit would do a fair bit of damage to the mirror.

The original design I had in mind would be a circle that had a diameter bigger than the top of the tube hence couldn't fall in.

I've got another possible solution I would like some opinions on (SEE PICS)

The orange is MDF smaller than the diameter of the tube so that it doesn't get stuck on the trusses.
The blue is foam, about the same size as the diameter of the tube.

The hooks go over the tube to stop the foam falling down and touching the mirror.

The idea would be that it would go in like a plug and stop any dust getting on the mirror, The 2 pieces of timber would hold it rigid. I might need to cover the foam in material.

Anyway's what does everyone think???

[JimmyH155]

If that cover is rigid, how will it fit on??
Yes, I realised that by making the cover in 2 pieces, then you are back to square 1 with problem of falling on mirror. Problem is that it is physically impossible (well to me) to make a cover same diameter as the tube, because the trusses get in the way and you cant force a rigid object into them or between them to sit on the tube.
Solution? tie a piece of string to each half maybe and secure to truss.(look awful) or perhaps you can get a really flexible one-piece cover that you could shove in between the trusses
The main reason for my plywood cover was not so much as trying to protect the mirror from fallling objects, but to keep the **** cat from jumping in I must say that I have never even looked like dropping the covers in - its all a matter of training

[nmo]

The timber section (orange) is smaller than the diameter of the tube, the blue section is a spongy foam or similar that will squash when you press it in and the spring back out making a dust tight seal,

At least that's the theory