Another old find...

[bf79]

Hi folks, a while ago i posted on here about some mirrors and eyepieces that had been found packed away for years in my wifes loft... long story short, her dad was a keen astronomer and had built his own telescopes many years ago. Unfortunately he passed away long before we met and all his stuff had been packed up and stored away.

Well, Ive now found another box which ive just opened and found a rather nice mirror, its 30cm wide and other than a bit of dust looks in great condition.  

 

Im still very much a beginner to this hobby so I dont know the first thing about it, other than this is most likely the first time this has seen daylight in about 30 years. 

 

As much as i love the idea of putting this to use myself, its way beyond my skill or knowledge level, so im looking to see if anybody can give me advice on it. 

Is there a market for these kind of things? Are they valuable? Is it of any use for building a scope or is it outdated?

Any advice or info most welcome

Thanks

Brian

Edited April 7, 2020 by bf79

[laser_jock99]

Nice - wonder what F ratio?

 

[bf79]

2 minutes ago, laser_jock99 said:

Nice - wonder what F ratio?

 

Any idea how would i find that out?

[bf79]

Its 53mm thick, and theres no markings on it 🤔

[John]

No markings on the edge or back ?

 

[bf79]

Its got “No 6” written in pencil on the side, and also on the outside of the wooden box its in, other than that nothing

[bf79]

[Rob]

Looks really nice, And well made. Nice thick glass.

[RT65CB-SWL]

This may help---> 

 

[mikeDnight]

Hold a comb in front of your eye so you're looking through the teeth. At the same time, shine a torch through the comb so you see the reflection of the torch and comb teeth in the mirror and walk backwards, keeping the image of the expanding comb teeth in your vision. At the point when the comb teeth begin to topple over, you have reached the focal point. Measure the distance between the mirror surface to where your comb and eye was when the image toppled and you have your focal length. The comb teeth act like a basic Ronchi grating.

Edited April 7, 2020 by mikeDnight

[saac]

Brian that is a cracking find giving you the makings of very sound 12 inch Dobsonian telescope; that would be a very capable beast.  Constructing a Dobsonian would not be as challenging as perhaps you may think and it's certainly and enjoyable and rewarding project. If you think you may be interested in going down that line then this site would be a good starting point https://stellafane.org/  . 

Jim