secondary mirror

[spacemanblue]

Where can I buy a secondary mirror on the web, from the UK.

Just built a plywood 6" f/5 reflector with an old primary mirror from a skip. Don't have a lot of money. Tried a small make-up mirror but got a double image from the glass.

Maybe I should buy the Celestron Firstscope and salvage the

parts ?

[Ad Astra]

The ordinary mirror didn't work because it is a 'second surface' mirror - the reflective bit is on the back of the glass. This protects the reflective surface, but as you noticed, you get double reflections - one (dimmer) off the glass surface and another (brighter) off the real mirror surface.

Dunno about supliers in the UK, but be sure you get a 'first surface' mirror this time!

Dan

[John]

These people may be able to help:

Galvoptics Ltd. Scientific and industrial optical components. lenses, mirrors, filters, prisms etc

As Dan says, it needs to be a 1st surface aluminised mirror. It is possible to use a diagonal prism as an alternative which I've seen in some DIY designs.

[tomw28]

Would the mirror from a cheap diagonal work?

[ronin]

It would work but is the wrong shape, may also be too small.

Galvoptics are the best ones to enquire of.

Then Oldham optics and Orion Optics.

Could ring a couple of local astro societies and ask if at the next meeting they could ask if anyone has an old one.

Think that the Galvoptics site says what size a secondary needs to be so check out their site and get one that is the right size.

[John]

Would the mirror from a cheap diagonal work?

It's not the right shape but it would work. The converging light cone coming from the primary will be circular in section so a square mirror (as found in mirror diagonals) may block more of the light than is needed. But it should work as a temporary measure or for testing purposes.

[spacemanblue]

Cheers guys, but I think I'l keep an eye on a salvage scope from ebay.

I have a four and a half inch Celestron and some bins to keep me going for now,

Just trying to build on the cheap, I'm enjoying knocking the wood about in the shed. thanx

[Mik3]

I've got an old meade 4504 you can have the mirror from that if you like? just PM my your addy and I will post it free tomorrow morning. You can have any other parts from it if you cover the cost of the postage. The focuser works but its not much cop, the eyepieces and focuser is 1.25" I was going to throw it out so if it goes to a good cause then all the better

[johninderby]

Telescope Service sells secondaries that aren't too expensive.

http://www.teleskop-express.de/shop/index.php/cat/c91_Selbstbau-----Optiken--Spiegel-Linsen-.html

John

[Moonshane]

I have been looking around for an 82mm secondary for my 16" f4 mirror. In the end I went with Orion Optics as this is where the primary is from and the price was not that different, plus I can collect.

[Mik3]

Here is the pic: