From: "Jim Miller" 
To: "Garth Arsenault" , 
Reply-To: "Jim Miller" 


garth

congratulations on the primary! don't use epoxy on the secondary! it will
induce strains that will ruin it's figure. i'm not sure what i'd use on a
wooden dowel. i used silicone to fasten my 13oz secondary to my aluminum
secondary holder. never one big blob, instead use three or four spaced dots
sufficient to hold the weight securely.

you need ~20x per inch of mirror or more to do a star test. that would mean
a 7mm or so eyepiece or a 3x barlow for your 25mm eyepiece.

good luck

jtm

----- Original Message -----
From: "Garth Arsenault" 
To: 
Sent: Wednesday, July 16, 2003 11:08 PM Subject: ATM secondary mirror



Hi list,

I have just finished figuring my 10" BVC mirror (what an ordeal!) I
ended up doing my figuring with a full sized lap and it only took about 25
figuring sessions (groan) to get my figure. I am anxious to star test to
verify if the 1/25 wave error is accurate from my foucault test. I have the
rest of my truss style dob almost complete. What is the best material to
fasten the secondary mirror to the diagonal wooden dowel. Should I use
silicone, epoxy or another adhesive?

Also, To date I have only a 25mm eyepiece, will this be sufficient to do my
star test or do I need to have more power than this will give me? My mirror
has a focal length of 57.5 inches which will give me about 60X mag.

Thanks

Garth

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