Re: [ATM] 8" F/4.2 progress

[Jason Hissong <jhissong@gmail.com>]

Mike Lockwood wrote:

> Very next looking scope.  With it to allow star testing, you are about
> to learn star testing under almost ideal conditions - you get to test
> the mirror whenever you like.  Try it before you start figuring if you
> can.
>
Thanks Mike.  I am excited to finish it.
I will try to do the star testing prior to figuring (or very close to 
the beginning).  I need to get the focuser placed just right.  I think I 
know how I will be doing that.. I will be using a piece of 1/2 baltic 
birch, glued to the bottom of the secondary ring (I will route out a 
notch for it to sit in).  I just picked up the last remaining pieces so 
hopefully by this weekend, I will have an operating scope (with my 
non-operating mirror :)

> Typical symptoms of the disease.  There is no cure.  Beer may help.


My wife calls me obsessed... now I know why Kriege called his scope 
Obsession 1.  Beer does help.. but I have found a nice martini does 
better (the dry kind of course!)

>
> Once around the turntable?  How many minutes did that take?  For me
> it's a minute or two.  I would be surprised if it shaped up that
> quickly....


Took me about 7-8 minutes.  I am going pretty slow and using the weight 
of the mirror only.  I am not using any pressure myself.  The polish is 
a little thin which is what I thought I read I should do.  The lap is 
well charged.

>
> You're welcome!  If there's any place where it could be more helpful 
> or clear, let me know.


Not that I can think of... it is good material.  I finally get it.  Your 
examples really helped alot.  I really need to get practicing at 
foucault measurements.

>
>
> Why not?  You can learn what LOTS of undercorrection looks like.


Hey.. you're right.  Then it will look like an Ebay mirror!! LOL...  I 
was going to do that anyway.  I find it would be very educational to 
watch the star images change.  I am borrowing Richard Suiter's book (who 
used to be a member of my astronomy club BTW!!) to study it.  I should 
get familiar with the spherical abberation images.

>
>
> If you can take some pictures with a knife edge tester that would be
> useful.  It will probably tell more than the ronchi image, at least 
> for me.


I may do that too....  I find that I will be using the Ronchi test most 
at the beginning.. then when I start zeroing in on the figure, I will 
use the Foucault test.

When I finish this scope, I will be writing up an article on my website 
on building it.

Jason

-- 

"A long journey starts with the first step and an understanding spouse."
http://www.undermidnight.com - astronomy and astrophotography
http://www.n8xe.com - ham radio
http://www.jasonhissong.com - electronic music composition

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