Re: [ATM] New home built 12" ultralight dob

["Olivier Biot" <olivier.biot@versateladsl.be>]

From: Alan Scott

>I just finished a 12" ultralight dob, and wanted to ask for feedback. Any 
>ideas on how to make it lighter or smaller?
>
> Also, does anyone have any experience on making 3/4" aluminum tubes that 
> split in the middle, yet are very stiff? How about graphite? I use a 
> torsional attachment of the truss tubes with the mirror box.

I'd like to know what you mean with a "torsional attachment". Does this mean 
that you slightly twist 'n bend the trusses in order to fit them into the 
hles you foresaw for them in the mirror box?

> http://www.xmission.com/~alanne/Astronomy.html

Nice web site!

I however have some questions on your mirror cell. My main concern with your 
approach is that your coil springs apply pressure directly to the wooden 
disks. This may severely deform your mirror's surface (no rotational "tilt" 
freedom). I'd rather use a pair of "locking nuts" on your supporting 
collimation bolts, with a washer between the locked nut pair and the 
springs; this way the springs will apply much less deformation on the back 
of your mirror. Of course, as you seem to have a rather thick mirror, this 
deformation may get unnoticed.

Best regards,

Olivier 


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