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Re: [ATM] Re: ATM zones
Bob,
You didn't say if your mirror is pyrex or plate or
etc. That makes a huge difference. My 16 X 1 inch
plate takes all night to reach equilibrium. I have
tried blowing on it with a big fan but because the
basement floor in winter is 5 to 10 deg colder than
the air one foot above it and because the mirror stand
is on the floor tilted back at 20 deg the mirror gets
colder than room temp and that too causes problems. I
have a measured its temp and it is only about 1 deg
diff from room. Then the next day when it is the same
temp the figure is different. It does not change
after that. In fact with my automated Robo tester I
can set it to take measurments all night. The results
are that the figure changes for about 5 hours. I
measured using polarizers for strain and I did not
have any so I think it is the temp change.
It all depends on your situation.
Dale Eason
--- Bob Walker <tac@i1.net> wrote:
> wait for equilibrium before testing mirror--sounds
> right, but for us
> impatient types, is there an alternative? Reasoning
> that the evidence for
> the effectiveness of fans for keeping mirrors at
> equilibrium temperature
> during observing is now overwhelming, would the same
> thing work for
> figuring? During figuring my 16" f/5.4, I set it on
> the test stand
> immediately after figuring (and washing!) and set a
> 20" window fan blowing
> across it at a medium gale. I found after something
> like 15 minutes of
> this, the figure seemed the same as it was if I
> waited another couple of
> hours, or overnight. Has anyone else tried this?
> or am I the only one
> whose motto is "Patience is a wast of time"?
> I still haven't gotten my scope completed enough to
> do careful star testing,
> but during Mars' apparition last fall, it looked
> mighty good -- still
> uncoated. I've left further testing until I get the
> structure more
> complete -- also waiting for some semblance of clear
> skies!!
>
> ----- Original Message -----
> From: <atm-request@atmlist.net>
> To: <atm@atmlist.net>
> Sent: Friday, December 10, 2004 7:14 PM
> Subject: ATM Digest, Vol 12, Issue 10
>
>
> > Send ATM mailing list submissions to
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> > When replying, please edit your Subject line so it
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> > than "Re: Contents of ATM digest..."
> >
> >
> > Today's Topics:
> >
> > 1. cutting tube in the first generation
> > (Ina Ron Lippard Renaissance Reproductions)
> > 2. RE: Ray tracer for cheap? (Julio Sanchez)
> > 3. Cassegrain Secondary testing (Mike Lockwood)
> > 4. Re: FW: Oslo short (Woodchuck)
> > 5. Re: Square over Round Truss Tube (Bob May)
> > 6. Re: Set of specs. (Bob May)
> > 7. re Oslo (Ellen Mackenzie)
> > 8. Telescope Optics Workshop (Richard Schwartz)
> > 9. Re: ANY LENS IN DIGITAL PHOTOCOPY MACHINE ?
> (Dave Smith)
> > 10. Re: Square over Round Truss Tube (Arjan te
> Marvelde)
> > 11. Re: Ray tracer for cheap? (vladimir sacek)
> > 12. zones (David Williams)
> > 13. zones 1 (David Williams)
> > 14. Re: zones (Jerry B. Hillman)
> > 15. OT: Question for David Williams (GARY FUCHS)
> > 16. Re: Re: Ray tracer for cheap? (Guy
> Brandenburg)
> > 17. Re: zones (Guy Brandenburg)
> > 18. Re: Waineo/Jones null test question
> (Hiroyuki HIKITA)
> > 19. Re: Re: Holographic Foucault null test
> (Mauritz Andersson)
> > 20. Re: Holographic Foucault null test (Mauritz
> Andersson)
> > 21. Re: zones 1 (Bob May)
> > 22. Re: zones (Bob May)
> > 23. Re: zones (Jim Burrows)
> >
> >
> >
>
----------------------------------------------------------------------
> >
> > Message: 1
> > Date: Thu, 09 Dec 2004 07:15:24 -0500
> > From: Ina Ron Lippard Renaissance Reproductions
> > <renrepro@surfglobal.net>
> > Subject: [ATM] cutting tube in the first
> generation
> > To: atm@atmlist.net
> > Message-ID: <41B841DC.6040404@surfglobal.net>
> > Content-Type: text/plain; charset=ISO-8859-1;
> format=flowed
> >
> > If you don't have a cut-off saw but do have a
> bench and circular
> > saw,try this: Start by taking a block of squared
> wood and drive a 1 1/4"
> > bright finish nail 1/2" into it.Clip off the
> head and file it to a
> > point.The nail point should be on center to your
> tube.Rig up the skill
> > saw with a barn door arrangement(I'd get a good
> ball bearing door hinge
> > at a salvage yard for about $10) that acts like a
> chop saw.Screw the
> > assembly to the bench.A rail installed at the
> proper angle to the blade
> > is screwed to the bench.A wood clamp can act as an
> adjustable
> > stop.Scratch a mark along the side of the
> workpiece on the first
> > end.With a prick punch,lightly mark this
> line.After some trial and
> > adjustment,cut the first tube.If it looks to long
> either use some shim
> > stock inserted between block and workpiece or us a
> a light tap of the
> > mallet on the stop.After all pieces are cut and
> marked flip the pieces
> > and trim side 2 using the marks and block to line
> up both ends.If you
> > took the time to make your 'surface gage' it will
> keep your angles
> > aligned to one another.I'm taking up valuable
> space here to make a point
> > of value.That being,you can do some very close
> work with the simple
> > tools of doing everything the same way based upon
> a flat plane.A simple
> > bench vise can be made from 3 screws and a block
> of hardwood.The jaw is
> > shaped the same as the tube.It has a 1/4-20 long
> bolt that is threaded
> > thru the block you screw down on the bench using
> the other 2 screws.By
> > turning the bolt,the jaw closes on the tube,firmly
> holding it near the
> > saw.If you take your time making this jig,you
> should be able to hold a
> > tolerance of +/- .010 or less.Not everyone has a
> table saw or chop saw.
> > regards,Ron
> >
> >
> > ------------------------------
> >
> > Message: 2
> > Date: Thu, 9 Dec 2004 08:56:30 -0600
> > From: "Julio Sanchez" <jsanchez@skipanon.com>
> > Subject: [ATM] RE: Ray tracer for cheap?
> > To: <atm@atmlist.net>
> > Message-ID:
> <NNELKFNKFMLCIKADIHGAEECGCMAA.jsanchez@skipanon.com>
> > Content-Type: text/plain; charset="us-ascii"
> >
> > First of all, thanks to Jim, Vlad, and many others
> who have taken part in
> > the "Small Ritchie-Chretien" discussion topic. I
> am very glad I brought
> this
> > up.
> >
> > Can anyone recommend a good ray tracer that does
> not break the bank? I use
> > DBOptic and like it very much but would often like
> to have a "second
> > opinion" before committing to a design. For
> example, my trace of a 6" f:6
> RC
> > in DBOptic reports a flat field and all other
> aberrations much below the
> > tolerance. Is the software "smoking" something?
> >
> > Thanks,
> >
> > Julio
> >
> >
> >
> >
> > ------------------------------
> >
> > Message: 3
> > Date: Thu, 09 Dec 2004 10:01:30 -0600
> > From: Mike Lockwood <melockwo@uiuc.edu>
> > Subject: [ATM] Cassegrain Secondary testing
> > To: M/S Heald <maheald@octa4.net.au>
> > Cc: atm@atmlist.net
> > Message-ID: <41B876DA.3050208@uiuc.edu>
> > Content-Type: text/plain; charset=windows-1252;
> format=flowed
> >
> > Mike,
>
=== message truncated ===
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