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Re: [ATM] strange (collimation?) problem
This is one of the things I never check, because I never had a problem with
it. I will check tonight.
Jan
http://home.wanadoo.nl/jhm.vangastel/Astronomy/
----- Original Message -----
From: "A. Suijkerbuijk" <a.suykerbuyk@wxs.nl>
To: "Atm-List" <atm@atmlist.net>
Sent: Monday, June 20, 2005 5:48 PM
Subject: Re: [ATM] strange (collimation?) problem
> Hi Jan,
>
> Are you sure there is not a problem with the focuser, seems it is not
> parallel to the optical axis.
>
> Adrie Suijkerbuijk
>
> ----- Original Message -----
> From: "Jan van Gastel" <jhm.vangastel@wanadoo.nl>
> To: "ATM List" <atm@atmlist.net>
> Sent: Monday, June 20, 2005 9:05 AM
> Subject: [ATM] strange (collimation?) problem
>
>
> > Yesterday I startested my selfmade, not yet aluminiumized 300 mm f/5 30
mm
> > thickness (Pyrex) mirror (its my first mirror). To be able to do that I
> > made
> > an extra collimatable platform with a 6-pointcell on the mirrorbox of my
> > 300
> > mm f/6 telescope. Two round teflonpads at 90 degrees act as lateral
> > supports
> > (see: http://home.wanadoo.nl/jhm.vangastel/Astronomy/scope3.jpg ).
> >
> > What I saw inside of focus: nice round diffraction pattern with clear
> > round
> > diffraction rings. No sign of astigmatism. Nice outer ring. Secondary
> > shadow
> > well centered.
> >
> > And outside focus: more turbulence, nice round diffraction pattern as
> > well,
> > Rings a bit les clearly seen then inside focus. Secondary shadow breaks
> > out
> > a bit later (but clearly less later then in my other 1/8 lambda P-V
> > mirror)
> > as compared to inside focus (new mirror tested 1/13 lambda P-V; .98
> > Strehl,
> > using Figure XP; undercorrected edge).
> >
> > BIG DIFFERENCE as compared to inside focus: secondary shadow not
centered
> > but very clearly offset to one side. When I centered the secondary
shadow
> > during the startest in the outside focus pattern, it became decentered
> > inside focus and was then also clearly off collimation as seen in the
> > cheshire.
> >
> > I can't imagine I did the collimation wrong. Collimated the secondary
with
> > a
> > laser and the primary with a cheshire as I always do.
> >
> > I have never expierienced this before and don't have a clue about the
> > cause
> > of the problem.
> >
> > Jan
> > http://home.wanadoo.nl/jhm.vangastel/Astronomy/
> >
> >
> > ----- Original Message -----
> > From: "David Harbour" <scarab2@cox.net>
> > To: "Stan Truitt" <s.truitt@verizon.net>; "ATM List" <atm@atmlist.net>
> > Sent: Sunday, June 19, 2005 3:03 AM
> > Subject: Re: [ATM]: What do they offer:
> >
> >
> >> Re: [ATM]: What do they offer:Stan-
> >>
> >> You are too generous! All I can tell you is that this little bulb, the
> >> one
> >> that the hardward stores carry on their flashlight lamp charts (the
only
> > one
> >> that is threaded, and for which radio shack has a socket and leads to a
> > two
> >> cell "D" cell battery holder), never caused me heat problems. In fact,
I
> >> cannot believe how good my experience with this tester was, over the
> > years.
> >> I built five testers. This one was ready when I destroyed my McIntosh
> > tester
> >> (#4) by failing to put counterweights on the extension to the platform
of
> > my
> >> very long optical bench, to test a very long mirror. Glad I had it
ready.
> >> You can see it here:
> >>
> >> http://www.atmsite.org/contrib/Harbour/Tester.html
> >>
> >> My neat little (large, actually) McIntosh tester disintegrated in a
> >> shower
> >> of flying parts when it fell to the concrete floor.. But I was ready
with
> >> #5!!! Someone kept it. (I expected this). It's okay; I was never going
to
> >> use it again. I hope he loans it to others, whoever he is (the guy who
> > kept
> >> it).
> >>
> >> It is hard to believe that it was so bright that it caused me to have
> >> SERIOUS difficulty reading shadows on coated mirrors, but it was. Maybe
> >> we
> >> should form a club: "Not Happy with LED Illumination" club. On the
other
> >> had, everyone on the list would probably just get mad at us, and shun
us,
> >> forever.
> >>
> >> Thanks,
> >>
> >> Dave
> >>
> >> P.S.- Late stuff, since my website, courtesy my dear friend, Master
> >> GORDON
> >> TULLOCH:
> >>
> >>
> >> http://www.gordtulloch.com/harbour/index.html
> >>
> >> Dave
> >>
> >> All of you guys are the best club anyone could be a memeber of (ATM
list)
> >>
> >>
> >> ----- Original Message -----
> >> From: Stan Truitt
> >> To: atm@atmlist.net
> >> Cc: scarab2@cox.net
> >> Sent: Saturday, June 18, 2005 6:35 PM
> >> Subject: Re: [ATM]: What do they offer:
> >>
> >>
> >> Aloha Dave,
> >>
> >> <Will someone offer me an explanation for what the "advantages" of LEDs
> > are,
> >> <compared to VERY BRIGHT incandescent filament lamps? I just have never
> > been
> >> <able to figure this out. I'm sure it's not a fad;' it's just probably
> >> <because I am stupid about these things.
> >>
> >> While being a fan of incandescent Tungsten, and to a lesser extent
> > Zirconium
> >> arc lamps, I would like to share an experience relating to LED sources.
> > In
> >> an ellipsoid being tested with the knife at it's long focus and the
> >> source
> >> at the focus closer to the mirror, convection currents from the heat
> >> dissipated within the light path seriously disturbed data
repeatability.
> >> Efforts in ducting away the heated air, and water cooling the lamp
> > surround,
> >> improved the setup; but not without blocking an unacceptably large area
> >> at
> >> the mirror's center. Switching to the vastly more efficient LED source
> >> while retaining a bit of the water cooling resulted in excellent
> >> repeatability of the data, even with the water flow turned off.
> >>
> >> Perhaps you are not "stupid about these things", rather than highly
> >> enthusiastic about those things that worked for you. Patient
forbearance
> > of
> >> others' curious investigation of alternate avenues seems, to me, a good
> > way
> >> to go! Pontificating is, at least for me, not.
> >>
> >> Tungsten ribbon lamps are a practical necessity in the double bounce
from
> >> uncoated Cass secondaries in Hindle sphere setups. Not to mention
> > providing
> >> a fine place atop the lamp housing to set my pyroceram coffee cup!
> >> Coherence effects in porting my HeNe beam to this setup make the
filament
> >> approach all the more desirable.
> >>
> >> I enjoy many of your messages to the ATM list. Some, for me, have been
> >> valuable. Your kindness and generosity garner my appreciation and
> > sometimes
> >> admiration.
> >>
> >>
> >> Sincerely,
> >>
> >> Stan Truitt
> >>
> >>
> >> _______________________________________________
> >> ATM mailing list http://www.atmlist.net/
> >
> > _______________________________________________
> > ATM mailing list http://www.atmlist.net/
> >
>
>
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