[SJAAboard] tests of mirror for #8 (14" homebuilt)

[Gary Mitchell]

Rob Hawley wrote:

> Gary and I did a Ronchi test of the mirror on Saturday.  At first blush it
> looks good.

I must hasten to point out that neither of us are expert at Ronchi testing.
We'll have to do a foucault test and run the numbers to see what the curve
actually is before declaring the mirror good.  I made up a mask, so we can
do that next time, if Rob is willing to drag the mirror down once again. :)
Maybe we can do others at the same time.  We have Houge reserved for one
last mirror making class on Dec. 27 at 7:30 PM.

Gary

>  The main problem is that it is 40 lbs.  That is roughly twice
> what a current commercial mirror would weigh. At 40 lbs there is really no
> way to permanently mount the mirror and still stay under 50 lbs.  50 lb is
> the most weight that you should reasonably expect people to lift.  If
> someone cannot picture how heavy this is I will be happy to bring a 50lb bag
> of cat litter for them to try.
> 
> I am going to recommend we sell the optics for #8 and either the club buy or
> accept the donation of a 12" Meade Lightbridge
> 
> http://preview.tinyurl.com/3b8uz7
> http://www.meade.com/lightbridge/index.html
> 
> 
> Vendors are currently offering a rebate so we probably need to decide
> quickly on this.
> 
> I had a customer for #8 so the Lightbridge would likely be loaned
> immediately.
> 
> I suspect whenever Craig tires of #7 we will have a similar discussion with
> it.  I do not think either the Highe or Obsession Truss design would work
> well for an f/7 scope. 
> http://www.sjaa.net//loaners/No-7.JPG
> 
> but that is a topic for another day.
> 
> 
> Rob Hawley 
> 
> 
> 
> 
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