Advice on how to remove diagonal mirror for recoating: Meade Schmidt Newt 8"

[Sponcom]

I'm looking to recoat my mirrors on a Meade Schmidt Newt 8" (lxd75) and looking for advice on the best method to separate the secondary elliptical mirror from the diagonal assembly.

I'm not sure how the mirror is bonded on. Looks like some kind of PVu? 

Before I try some heat and try to release it thought I'd ask here first.

Thanks all.

 

Paul

[Sponcom]

[pipnina]

Could you include a more face-on image of the mirror please? It looks like it might only be dirty, in which case not much action is required. At most you could get away with rinsing a warm tap over it, then using cotton buds and distilled water, using single-direction and single-use strokes. Change cotton bud with every wipe.

[davidc135]

If it does need to be removed you could try a cheese wire if there's enough of a gap.  David

[Sponcom]

Thanks both. It does require re coating along with the primary mirror that’s much worse.

(it’s been cleaned with a mixture of distilled water and isopropyl alcohol.)

I’ll be sending them both to scientific mirrors for recoating as they seem to be the best value currently. 

[Sponcom]

 

I managed to removed the mirror so thought I'd mention how I did it as it might help others. It was held on by what looks like some double sided tape . I tried a hot wire cutter with no succes and in the end used a multitool like the one below and managed to gently prise it off

.

 

[ewanv1970]

I've a Meade SN8 that was donated to my "Astronomy Donations" project and I had to do a complete teardown of the scope because the mirrors and corrector plate needed cleaning.  I've upgraded the focuser and added a stepper motor to it and will be passing it on to a new owner soon, with the understanding that the scope will need the primary recoating at some point in the not too distant future.  Fortunately, the secondary was clear.

I now have a Meade SN10 to dismantle because it needs a new focuser and the corrector plate aligning (the spacer under it has shifted and now sits part way across the glass).

Anyway, what I wanted to ask was would it be possible for you to post some before and after pictures for the resilvering?  I'd be interested to know how you get on with them as I've an F4 8" primary that needs doing before I can give that away.

[Sponcom]

I certainly will. One thing I would mention on the SN scopes is make sure there is a mark on the side of the mirror before removing/sending it off so that you can reassemble it in the same position relative to the front corrector. This will minimise how much fettling you might have to do when reassembling and aligning the optics. There's a good guide (on the weasner site I think) about how to align the optics on the Meade SN scopes.

I'm going to use scientific mirrors for the recoating. I considered Orion Hilux and have used them before but the cost is double from Orion. I haven't had any experience of scientific mirrors before but have used Galvoptics for a 12" GSO newtonian mirror and that came back fine. 

One thing I will mention from my experience is that any, say, black pitting where the coating has come off and affected the substrate underneath will not take recoating. Meaning that the black areas will still be there after but it will be such a tiny fraction of a percent it won't make any difference. 

Edited November 6, 2022 by Sponcom