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Re: [ATM] Lateral mirror support test cases measured
I see not much difference between bottom or 120deg pegs. What worries me
more is that the surface error is in the order of two waves (12.10^-5cm =
1200nm)
How is your sling mounted, as a U or a V?
Arjan
> That is very interesting. According to this:
> http://astro.umsystem.edu/atm/ARCHIVES/APR02/msg00872.html it appears the
> one bottom point is better than two points at 120 degrees. Seems one point
> on the bottom ain't so bad! Fig 12 & Fig 13. I'm glad you verified the two
> points at 45 degrees is the best.
>
>
> And nobody ever answered my question, is the common seat-belt sling Fig 9
or
> Fig 11?
>
> Thank you,
>
> John
>
>
>
>
>
>
>
> ------------------------------
>
> Message: 11
> Date: Wed, 29 Nov 2006 23:45:59 +0100
> From: "Vladimir Galogaza" <vladimir.galogaza1@zg.t-com.hr>
> Subject: [ATM] is mirror thermal equilibrium important
> To: "ATM List" <atm@atmlist.net>
> Message-ID: <002301c7140a$b78c4440$500dfea9@piv555a133b59e>
> Content-Type: text/plain; format=flowed; charset=iso-8859-1;
> reply-type=original
>
> "Anything that can happen, will happen"
>
> So sprah James:
> >The final result had 18 1k ohm resistors @ 12v (2.6watts) heating the
> >backside of each
> >primary with the existing 4" fans blowing ambient air across the front of
> >each
> >primary.
>
> Imagine, after tons of discussions about indisputable need for mirror
> temperature equilibrium, e.g.. while on test stand, while waiting for
> observations, while pressing... etc), one demonstrably
> practical & working solution is using forced heating of backside
> and forced cooling of the front side of the mirror while in use.
> Thus warranting lasting temperature gradient across the mirror.
>
> Is this end of one more dogma ?
> Very likely yes, because it comes from very reliable source.
>
> Thermal equilibrium redefined:
> It does not necessarily mean that
> all parts of mirror are or should be at the same temperature as
> environment.. It may mean that it does not hurt if
> temperature gradient is present if it is temporally and spatially
constant.
> Because in this situation mirror figure, whatever it is, will not change.
> That it will be different than at test stand is another story.
>
> Regards
> Vladimir.
>
>
>
> ------------------------------
>
> Message: 12
> Date: Wed, 29 Nov 2006 17:32:00 -0800
> From: "Jack Swaton @ Starry Host" <jswaton@starryhost.com>
> Subject: Re: [ATM] is mirror thermal equilibrium important
> To: "'Vladimir Galogaza'" <vladimir.galogaza1@zg.t-com.hr>, "'ATM
> List'" <atm@atmlist.net>
> Message-ID: <00a901c7141f$557940e0$0402a8c0@dell1>
> Content-Type: text/plain; charset="us-ascii"
>
> I think this is a more pragmatic definition of thermal equilibrium in the
> light of heavy dew:
> If you're dewed up you don't observe, no matter what the figure is!
>
> :-)
> Jack
>
> -----Original Message-----
> From: atm-bounces@atmlist.net [mailto:atm-bounces@atmlist.net] On Behalf
Of
> Vladimir Galogaza
> Sent: Wednesday, November 29, 2006 2:46 PM
> To: ATM List
> Subject: [ATM] is mirror thermal equilibrium important
>
>
> "Anything that can happen, will happen"
>
> So sprah James:
> >The final result had 18 1k ohm resistors @ 12v (2.6watts) heating the
> >backside of each
> >primary with the existing 4" fans blowing ambient air across the front of
> >each
> >primary.
>
> Imagine, after tons of discussions about indisputable need for mirror
> temperature equilibrium, e.g.. while on test stand, while waiting for
> observations, while pressing... etc), one demonstrably
> practical & working solution is using forced heating of backside and
> forced cooling of the front side of the mirror while in use. Thus
warranting
> lasting temperature gradient across the mirror.
>
> Is this end of one more dogma ?
> Very likely yes, because it comes from very reliable source.
>
> Thermal equilibrium redefined:
> It does not necessarily mean that
> all parts of mirror are or should be at the same temperature as
> environment.. It may mean that it does not hurt if temperature gradient is
> present if it is temporally and spatially constant. Because in this
> situation mirror figure, whatever it is, will not change. That it will be
> different than at test stand is another story.
>
> Regards
> Vladimir.
>
> _______________________________________________
> ATM mailing list http://www.atmlist.net/
>
>
>
>
> ------------------------------
>
> Message: 13
> Date: Wed, 29 Nov 2006 20:45:38 -0500
> From: Mark Holm <mdholm@telerama.com>
> Subject: Re: [ATM] is mirror thermal equilibrium important
> To: Vladimir Galogaza <vladimir.galogaza1@zg.t-com.hr>
> Cc: ATM List <atm@atmlist.net>
> Message-ID: <456E37C2.3010702@telerama.com>
> Content-Type: text/plain; charset=ISO-8859-1
>
> Vladimir,
>
> Have you been to Florida? On a dry day there, you have to carry a
> baseball bat to knock down the catfish swimming through what Floridians
> jokingly refer to as air! On a wet day, the Navy leaves for drier ground!
>
>
> --
> Mark Holm
> mdholm@telerama.com
>
>
>
> ------------------------------
>
> Message: 14
> Date: Wed, 29 Nov 2006 21:09:01 -0500
> From: "Jerry" <wa4guu@verizon.net>
> Subject: Re: [ATM] Updated pictures of 8"f6 mirror............
> To: "'Mike Lockwood'" <melockwo@uiuc.edu>, "'ATMList'"
> <atm@atmlist.net>
> Message-ID: <003c01c71424$8188e8c0$0100a8c0@D85SJB21>
> Content-Type: text/plain; charset=us-ascii
>
> Hello Mike:
>
>
> Just a few points of disagreement. Hee Heee! John will have finished his
> mirror and we'll still be debating pitch hardness. Then he will tell us he
> used spar varnish.
>
>
>
> Mike Lockwood wrote:
> The problem is we still have no measure of how the pitch is behaving,
> we can only guess. And that's what we've been doing.
>
> My reply:
> You may be guessing, but I am not. There are the results to give us an
idea.
> There are several sessions of experience with the lap. Consideration of
the
> work applied under the stated conditions should say a lot about the
behavior
> of the lap. If results does not indicate suitability of the lap, we are
> wasting our time even thinking about changing pitch or any other property
of
> the lap. Why would we alter the properties of any thing involved in the
> process if it did not impact results? What guessing I have been doing is
> what will result using the lap under conditions other than what has been
> used in the previous known work sessions.
>
>
>
> Mike Lockwood wrote:
>
> In my experience it takes a fairly large rise in temperature (10F or
> more) to make hard pitch significantly softer. So, I choose to use
> linseed oil to soften my pitch rather than crank up the thermometer.
>
> My Reply:
>
> Why do you think his pitch is too hard? Could it be too soft? Could it be
> just right?
>
>
>
> Mike Lockwood wrote:
> Keeping my work/testing area closer to the temperature it naturally
> wants to be makes for less air currents when testing, too, and that is
> a big consideration for useful testing results.
>
> My reply:
> "Keeping" might be a problem.
> John's work area is.... I believe he said a garden shed. In day light the
> sunlit wall will have rising air and the opposite wall will be where it is
> coming back down. There will be a continual rotation. I think he will be
> doing most testing on cloudy days or at night. Or more likely he will
bring
> it indoors for that. The work temperature will be varying.... lets say
> "wildly".
>
>
>
> Mike Lockwood wrote:
> Well of course other factors can affect the channel closing time (CCT),
but
> this is the best we can do over email when we are on opposite sides of
> the world. Let's face it - most people aren't going to build a pitch
> tester, so this is the next best thing.
>
> My reply:
> Obviously I do not think it is the best we can do. I agree most will not
> make a pitch tester. Ruling out the pitch tester, channel close time is
not
> the best. I'm not saying CCT is of no interest at all. You seem to imply
> that if the mirror results are excellent but the channels closed "too
fast"
> or "too slow" a new lap of different hardness is needed.
>
>
>
> Mike Lockwood wrote:
> If we are ever going to learn to help people with mirrors over this
> list we need some standard questions and indicators that will help us
> determine what is going on. So I ask again, how long are the channels
> taking to close up?
>
> My reply:
> Standards should not ignore results.
> John has answered:
> The laps made with a lap mould from pitchlaps.com. Followed the
> instructions ok. After a few hours of work the channels are about 50%
> closed.
> And here we see the vagueness of CCT. His answer is as specific as can be
> expected. Yet if he had said 3 hours you would be no more certain of the
lap
> condition than if he had said 5 or 6 hours.
>
>
> Should I apply the spare varnish with a brush? Do I have to brush in only
> one direction? Do I have to use thinner, if so how much?
>
> Jerry
>
>
>
> ------------------------------
>
> Message: 15
> Date: Wed, 29 Nov 2006 21:27:42 -0500
> From: hermit <hermit@outofoptions.org>
> Subject: Re: [ATM] Updated pictures of 8"f6 mirror............
> Cc: 'ATMList' <atm@atmlist.net>
> Message-ID: <456E419E.5040008@outofoptions.org>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Jerry wrote:
> > Hello Mike:
> >
> >
> > Just a few points of disagreement. Hee Heee! John will have finished his
> > mirror and we'll still be debating pitch hardness. Then he will tell us
he
> > used spar varnish.
> >
> >
> >
> >
> Grind more, worry less? ;) For those of us that love the process, it is
> all a learning experience any how.
>
> Ken Lowther
>
>
> ------------------------------
>
> Message: 16
> Date: Wed, 29 Nov 2006 21:53:44 -0500
> From: "Jerry" <wa4guu@verizon.net>
> Subject: Re: [ATM] Updated pictures of 8"f6 mirror............
> To: "'hermit'" <hermit@outofoptions.org>
> Cc: 'ATMList' <atm@atmlist.net>
> Message-ID: <004201c7142a$c1199650$0100a8c0@D85SJB21>
> Content-Type: text/plain; charset=us-ascii
>
> Onya mate! (How's that John? ... Uhhh... I hope that isn't a Strine
insult)
>
> Jerry
>
> -----Original Message-----
> From: hermit
>
> Jerry wrote:
> > Hello Mike:
> >
> >
> > Just a few points of disagreement. Hee Heee! John will have finished his
> > mirror and we'll still be debating pitch hardness. Then he will tell us
he
> > used spar varnish.
> >
> >
> >
> >
> Grind more, worry less? ;) For those of us that love the process, it is
> all a learning experience any how.
>
> Ken Lowther
>
>
>
>
> ------------------------------
>
> _______________________________________________
> ATM mailing list http://www.atmlist.net/
>
> End of ATM Digest, Vol 35, Issue 32
> ***********************************
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