secondary concerns

[lancerde]

Hi

Here are a couple of pics of the secondary on my newly acquired second hand Meade 10'' LB. There are misty patches and black spots on the secondary. Should I be concerned? I hope you can see them on the pics. I have not had the chance to test the scope under dark skies yet. Saturn was nice the last few nights even with my cheap eyepieces from my light polluted balcony. But I'm comparing the views with my old 6'' bird jones scope that I cannot collimate properly. NPLs, a Panaview and Bobs knobs are on order.

If it is goosed, is it possible to order a replacement. If so where from?

I don't seem to be able to add images to this post but they are on my only album.

Cheers

Jon

[NGC 1502]

Hi Jon, I found those pics on your album. On the centre pic, all looks fine, the closer pic, it's a job to tell.

If it were myself, I'd give the secondary a gentle wash with a mild soap solution and soft pure cotton wool, no pressure or rubbing, rinse with distilled water.

You don't need perfection, just quit while you are ahead, if you make it better than it was.

If it comes to it, you could get it re-coated at Image Optics at Basildon Essex. They also do replacements. You would need one as close as you can get in size.

Hope you sort it, Ed.

Edit - here's a link (they are also called Galvoptics, same firm) - http://www.galvoptics.fsnet.co.uk/telescope6.htm

[Peter Drew]

Hello Jon.

I haven't seen the pictures but in general your description is that of a well worn aluminised surface. The misty patches are usually where the aluminium has started to oxidise and the black spots are usually where the aluminising is pitted down to the bare glass. Carefull cleaning as suggested could result in an improvement if you are lucky. Having said this, reflecting at 90 degrees, the condition of the secondary is less critical than that of the primary and yours may well have plenty of life left.

[ollypenrice]

I've just replaced the secondary on our 20 inch, mainly to cure astigmatism caused by its not being flat. However, the old one was also rather dull and tarnished, though not too bad. The new one is certainly giving brighter images as well as far less astigmatic ones.

Olly

[lancerde]

Thanks guys.

In day light the secondary looks very bad, as if it has been breathed on. But under artificial light when viewed from a foot away it looks ok. Likewise the primary looks very good when viewed from the scope opening but at an angle it seems very dirty .From what I've read this may not be an issue.

My Vixen NPL EPs arrived this morning so as soon as we get a clear night over here I'll check out the image quality. This will give me a better idea of the performance of the secondary.This is my first large scope so I have no experience to draw on.

Jon

[Moonshane]

a good way to check coatings is hold the mirror up to a light source (be careful if using the sun of course) and look from the back. if the coatings are starting to fail then you will see little specks of light coming through. you may be able to do this with the mirrors in situ by looking down the top section at the back edges of the secondary and up the bottom section, both with the other section removed.

in reality, even if the coatings are failing, like dirt, there will have to be a notable deterioration (i.e. worse than they appear in the pics) before you will see much change at the eyepiece.

coatings can be reapplied as suggested by Ed, although I am not sure where you are living, Orion Optics in Crewe do a good service.

[lancerde]

Thanks Moonshane

Comforting words indeed. I live in North Germany. The cost of getting a mirror re-coated over here is ridiculous. It would be cheaper to send them back to UK. From the answers I've received on the forum this hopefully won't be necessary.

Thanks to you all.

Jon

[lancerde]

Meade Germany have just got back to me and can provide a new secondary for 62 Euros delivered free within Germany. Thats not a bad price I think? As soon as my Bobs Knobs turn up, so I can fully collimate, and of course I get a clear night I test the scope and decide if I want to replace the secondary.

[Moonshane]

I'd see how you go first. there's no rush. that's a decent price but secondaries do come up on AB&S occasionally. maybe a wanted ad for the right size would be worth it although I can see the attraction of a new one too.

[NGC 1502]

Hi Jon,looking at this pic from your gallery http://stargazerslounge.com/gallery/image/12865-img-0280/ the secondary is held in place by a clip, rather than a sticky pad or silicon.

If you do decide to get a replacement, it would need to be an exact fit. ( a glued secondary could be marginally different and be ok ) so the correct Meade secondary may be the simplest solution, and be a simple swap.

Hope you sort it, whichever way you should choose.

Regards, Ed.

[lancerde]

Just to finish the post having removed the secondary it was badly tarnished and not very shiny. Just received a replacement that is an exact fit and wow what a difference. The old one really was goosed. Can't wait to fit it and get it out side. I have not really been out much over the last year due to personal-family issues but now ready to get back in there. This is the link to the ebay seller that supplied the mirror. 

http://stores.ebay.de/Astromann?_rdc=1