Astronomy, DIY space

Amateur astronomer building telescope with 1.8 meter mirror

5 Comments

Truck driver and amateur astronomer Mike Clements is building a telescope with a 1.8 meter (70 in) mirror he got as surplus from a government auction:

Here is a fun TV news video about Clements from last year:

And here is their updated report from this week:

 

Update: Via the comments comes this pointer to the company supplying Clements with the spray system to silver the mirror:  Mike Clements  – Angel Gilding.

5 thoughts on “Amateur astronomer building telescope with 1.8 meter mirror”

  1. What I want to know is how he made a reflective coating for the mirror with a weed sprayer. Normally it takes having the mirror in a special vacuum chamber with vapor condensation of the aluminum coating.

      1. I don’t think so. That would require resurfacing about every 6 months or so to get a high enough reflectivity for practical use. That’s the reason why silver nitrate is no longer used because such resurfacing is a pain in the posterior. My guess is he may be using some kind of aluminum impregnated liquid polymer that dries in a very thin layer and may be polished down to insure the 1/8th wave surface tolerance needed for decent image quality. This would not have the high oxidative properties that produce the tarnish of metallic silver deposited via silver nitrate. But again, I’m just making an educated guess.

  2. OK, I see what is happening here. The spray being used is normally employed for silvering the back of second surface mirrors (mirrors where the reflective silvering is on the back of the mirror). The reflective surface of a second surface mirror is not exposed to air because the light goes through the glass to strike the silver and the back of the silver is coated with a protective paint that keeps the silver from oxidizing. A telescope mirror is a FIRST surface mirror and (in order to work properly) the reflective layer MUST be directly exposed to the air. Thus, Clement’s telescope will have to be resilvered probably twice per year after oxidation of the silver significantly lowers reflectivity. That is what they used to have to do to telescopes before the switch was made from silver to aluminum for the reflective layer.

Comments are closed.