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Re: [ATM] strange (collimation?) problem
I cured the problem. The secondary wasn't properly centered under the
focuser. I should have checked but I was so eager to startest my mirror,
that I forgot one of the most basic steps in collimation.
Thanks to everyone who responded.
Jan
http://home.wanadoo.nl/jhm.vangastel/Astronomy/
----- 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
>
> 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/
>
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