more blemishes

[blink138 (Pat)]

hi everyone
i have only joined iceinspace today and what a find!
i have been researching for the past nine months everything about the modern telescope industry and very soon i want to make a decision on a system.The way i look at it i will either spend money on a five year plan or a ten year plan, which to me means 3K or 7K
There is an ad in star optics for a used rc lx400 12, but they have come clean and said there is a blemish on the primary complete with photo
I need to know (if someone looks it up) if the primary has cancer or if they think it is harmless.Obviously this will be a big investment for me and i want to put my hard earned to best use and if it is a lemon thats my life gone down the swany!
any advice would be gold
pat

[hulloleeds]

http://www.staroptics.com.au/catalog...nch-CON-02.jpg

Here you go
http://118.127.11.230/catalog/produc...3cd2abc860c7f1

[dannat (Daniel)]

if its just 1cm by 2cm big then when you compare that to the 700 odd centimetres of real estate mirror you have that is a negligible amount. If it s dropped onto the mirror as they day though why don't they just have it cleaned at bintel - i would send bintel the pics & ask their advice
Does seem like a bargain though

[DavidU (Dave)]

Re coat the mirror. Thats a dream scope (for me anyway)

[blink138 (Pat)]

thanks a lot guys for the advice
i wouldnt have a clue how much a recoat would be
and daniel i did phone star optics and they said that the owner wanted the onus on the prospective purchaser if they deemed it necessary
i think i will email the photo to bintel anyhow
thanks
pat

[DavidU (Dave)]

A re-coat may be around the $300 ish mark

[wasyoungonce (Brendan)]

1st stupid question for this .....doesn't the main mirror need to be removed form it's carrier to re-coat?

I thought the mirror was placed in a vacuum chamber & baked at temp then the pre-heated to high temperature aluminium was introduced into the chamber thru a 2econdary slot that kept the vacuum intact.

Then the lot was allowed to cool, slowly.

I believe most SCT main mirrors are glued to their carriers with a 2 part epoxy goop that will melt in at temps exceeding around 150°C .

Maybe I'm talking thru my hat...anyone else shed advice on this?

If you can get a re-coat for $300-$500...then it's a bargain scope indeed.

[DavidU (Dave)]

I'm pretty sure it's the low temp of the glass that aids the vaporized Al to coat the mirror. I don't think the mirror is heated. I may be corrected here. We used to use the same process to put the al onto polycarbonate discs to make CD's.

Originally Posted by wasyoungonce

1st stupid question for this .....doesn't the main mirror need to be removed form it's carrier to re-coat?

I thought the mirror was placed in a vacuum chamber & baked at temp then the pre-heated to high temperature aluminium was introduced into the chamber thru a 2econdary slot that kept the vacuum intact.

Then the lot was allowed to cool, slowly.

I believe most SCT main mirrors are glued to their carriers with a 2 part epoxy goop that will melt in at temps exceeding around 150°C .

Maybe I'm talking thru my hat...anyone else shed advice on this?

If you can get a re-coat for $300-$500...then it's a bargain scope indeed.

[blink138 (Pat)]

thanks again for the help but i guess i really want to know if the blemish is going hinder the overall optical performance or is it imperative that this blemish be fixed
any further clues?

[hulloleeds]

Originally Posted by blink138

thanks again for the help but i guess i really want to know if the blemish is going hinder the overall optical performance or is it imperative that this blemish be fixed
any further clues?

I honestly think this is a question to ask Meade. They can probably give you the most practical advice and also inform you of the process / cost of recoating (as I see there is some contention, here).

If I were you, I wouldn't buy it unless I was getting it recoated. Even if you had to send it back to meade at quite large cost. It just doesn't seem right to drop 6k on something that even the owner is shrugging their shoulders about.