two mirrors gathering dust

janoskiss (Steve H) · #1 19-01-2005, 11:53 PM

I have two 4.5" long focal length (1.8--2.0m) mirrors I inherited from an optics lecturer at the old Physics Dept. of Monash Uni. I'd like some ideas on how to best put them to use.

Story goes like:...

I've had plans/dreams for these mirrors, including a home made telescope with two main mirrors, or a pair of giant astronomic binoculars. But I soon found that to make anything useful out of them would cost me not only effort but quite a bit of cash too.

The mirrors are coated in silver, but badly need recoating after many years in storage. The glass is very thick (1.5" ?), and is in a solid brass "sleeve" which is on a hand-made brass mount, with three alignment bolts and a central spring loaded tensioning bolt.

I used to view the moon with these. I'd just put the mirror on the ground (at roughly the right orientation) and look for the reflection of moonlight. Then I'd walk away from the mirror whilst keeping the moonlight in sight, and stop once an image of the moon came into focus. The image was always very clear and beautiful. (I could view for longer by getting someone else to adjust the mirror until I could view the image standing up comfortably. i.e., no tiptoe & no squatting)

For years the mirrors have been degrading in the cupboard, but still seem like fine hand-made would-be instruments, and I have a soft spot for such things.

Even if I can't find a use for these, I'm refuse to put them in the bin, that's for sure.

You guys/gals have any ideas?

rumples riot · #2 20-01-2005, 12:14 AM

I think the binos idea is the best. Binos from commercial makers can cost a lot more than a couple of thousand, so if you spent a third of that or even one half you would have a pretty mean set of binos.

Vermin (Tom) · #3 20-01-2005, 12:23 AM

Have a chat to Mark Suching at Deep Sky Optics (there's an email address at the bottom of the page):

http://deepsky.cia.com.au/optics/

He's built a 12" bino newt and will know about getting the mirrors re-coated.

Starkler (Geoff) · #4 20-01-2005, 12:38 AM

For those that don't know , Mark Suchting is Australias answer to Carl Zambuto in crafting of newt mirrors.

ballaratdragons (Ken) · #5 20-01-2005, 09:04 PM

If you want to keep the mirrors original (for nostalgia) why not re-silver them. You can re-silver at home!

janoskiss (Steve H) · #6 20-01-2005, 09:33 PM

Don't know anything about re-silvering, and there is not much "nostalgic" value to these mirrors.

They just look like your typical improvised equipment made in-house by underfunded researchers who can't afford to pay for quality, but can't put up with a cheap substitute either. I believe they were made by and/or under the supervision of Dr. Fred Robilliard, when he was still at Monash.

ballaratdragons (Ken) · #7 20-01-2005, 09:43 PM

Hi Janos,

If you did want to re-silver to keep the cost to bare minimum, I have the recipe and instructions.
It is in a book and my scanner bit the dust so I would have to type it all in, if you really wanted it.

Otherwise aluminising is the way.

janoskiss (Steve H) · #8 20-01-2005, 10:05 PM

Thanks, ballaratdragons! Just give me the reference, and I'll try to find a copy.

ballaratdragons (Ken) · #9 20-01-2005, 11:12 PM

Handbook for Telescope Making

N.E. Howard

SBN 571 04680 0

Printed in Great Britian by John Dickens & Co Ltd, Northhampton.

Or do a Google on 'Silver coating telescope mirror'.

I haven't tried to Google that myself yet!

janoskiss (Steve H) · #10 20-01-2005, 11:16 PM

Thanks! Found a copy at Monash, Clayton!

ballaratdragons (Ken) · #11 20-01-2005, 11:38 PM

Excellent! It's an old book.