BIg Mirror

[Stub Mandrel]

Big surprise (literally) at last night's club meeting.

We've been donated an 18" mirror made in 1930, with a focal length of 120 inches and weighs 22kg. It has a long history and has been in 3 or 4 different scopes, I'm afraid I forgotten the makers name.. Lee's calculations suggest we can make a folded Newtonian that will fit (just) inside our observatory which is nearing completion.

 

[Saganite]

Made in 1930 and 18"means it is bound to be excellent quality I would suggest. Look forward to the build.

[Peter Drew]

Excellent start to an exciting project. If the colour of the mirror edge is true then it looks to be low expansion glass, even better news!. The mirror maker's name will be of interest and a possible pointer to the quality of the mirror. Don't get it re-aluminised until it's ready to use in the completed telescope.  ?

[Stub Mandrel]

1 hour ago, Peter Drew said:

Excellent start to an exciting project. If the colour of the mirror edge is true then it looks to be low expansion glass, even better news!. The mirror maker's name will be of interest and a possible pointer to the quality of the mirror. Don't get it re-aluminised until it's ready to use in the completed telescope.  ?

Others far more experienced than me will be leading the project.

Apparently it will have to have a 6" and 63mm secondaries (don't blame me for the mixed units!)

[estwing]

Very nice.

[solarboy]

It's a pity who  donated it hasn't got the secondry in the attic, shed it might be worth asking. 

Thay may have the secondry and not realise its part of it and with a stroke of luck thay may have the cell or the other bits. 

But a nice find. 

Regards Solarboy 

[Stub Mandrel]

7 hours ago, solarboy said:

It's a pity who  donated it hasn't got the secondry in the attic, shed it might be worth asking. 

Thay may have the secondry and not realise its part of it and with a stroke of luck thay may have the cell or the other bits. 

But a nice find. 

Regards Solarboy 

The story of the mirror makes that unlikely - the owner had died and the mirror was thought lost, but turned up in a shed when a remote property was being cleared. It appears to have always been used as a standard Newtonian and apparently the folded layout needs a special small eliptical 'tertiary' and big (round) secondary.

[Whistlin Bob]

I'm properly excited about this one Neil! ???

[Stub Mandrel]

I've already volunteered you to make the truss frame ?

BTW those rings are about 1 1/4" too big for me ? but thanks for the 'loan'. I'll bring them back at the next meeting - otherwise I will be tempted to buy an 8" mirror set. Buying mirrors just because you can get a set of tube rings is NOT a good idea... or is it?

[Whistlin Bob]

I would have thought it's all the excuse needed ?

[mapstar]

Very nice is that Lee B proudly propping it up! 

[Stub Mandrel]

28 minutes ago, mapstar said:

Very nice is that Lee B proudly propping it up! 

Indeed ?

[maw lod qan]

I can only imagine the finished project and it's second first light. I do hope you keep us remotely involved thru the forum.