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[ATM] My First Mirror is DONE!!!
My Mirror is DONE!!!
Yes, after 2 years, 2 weeks, and 3 days my 6" F/6.5 mirror is done!
I'll try and keep this reasonably short. I would like to put out my absolute
biggest thanks to the entire ATM community. I really don't want to start
with many names because there are simply way too many people to thank
personally and I don't wish to leave anyone out. So all of you out there,
you definitely know who you are if. I would though like to give an extra
special thanks to all the great people at our bi-monthly ATM Meetings.
Without their hands on help my first mirror story would have turned out VERY
different. Also if any of you were ever wondering the instigator of my ATM
fever it was started when I stumbled upon James Lerch's 8" Bino Dob page
where he discussed grinding two mirrors in a very short time and gave me the
confidence to try it.
So, the fruit of my labor:
The mirror has a 1/12.5 Peak-Valley Wavefront Error Rating! Strehl Ratio is
slightly above .98. The physical surface RMS error is 5.8nm. The overall
correction is .042, with the perfect being .048, so my mirror is only .006
undercorrected. As general opinion goes if you must leave a mirror one way
or the other Undercorrected is better than Overcorrected so my mirror is
good in that respect also.
Beside the numbers, the overall mirror is very good. The edge is fairly
good; there is a diffraction ring, though slightly dimmer on the right. The
very last mm or two is turned slightly down, estimated to be about 1/15 wave
or so. It is slightly accented by the fact that there is also an equally
narrow high zone just inside it from where my TDE and TUE originally merged,
just the tail end remnants of it. The surface is very smooth, only a very
slight roughness/artifact detectable in the center, but it will be covered
by the secondary. There was also no detectable astigmatism by the ronchi
test.
So all in all if I do say so myself this is not only an excellent first
mirror, but a very good mirror in itself!
Fun facts:
I did 194 wets of grinding total
I spend a total of 41 hours polishing and figuring
About 90 sets of Foucault readings were taken, many of them me practicing.
There are a countless number of just general viewing and ronchi tests
I went through about half dozen laps with Acculap and 2 with Pitch
(Other than the amount of grinding wets none of this includes the 7 Hours,
20 Minutes I polished for before I scratched my mirror and had to regrind)
The mirror is off to be Aluminized, and the mounting is nearly done; Just a
few odds and ends to tie up here.
For the full story see my website:
http://www.freewebs.com/mitchsspacepics/
I'll type up a little heart warming summary of my first ATM'ing experience
after first light,
Once again, THANK YOU ALL!!!
Mitch
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