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RE: [ATM] Alan Scott's Deep Space telescope
Drew,
BLUSH. Thanks for the complement. I have really enjoyed making this
scope, and using it has even been nicer. Now, if we could just get the
skies here in New Mexico to stay clear, I would be a happy camper.
Double sided sticky tape. Yep, it has held like a champ. I would guess
that as it dries out, it will actually get stronger. Theoretically, the
double sided tape is strong enough to hold the primary. But, after
attaching the mirror cell to the back of the mirror, as a test, I lifted the
mirror (over a very soft towel) by ONE of the cell bolts, and shook the
mirror. So, now it had all of the weight of the mirror, PLUS a twisting
component (because I wasn't lifting in the center of the mirror). It didn't
budge at all. So, that says that I have AT LEAST three times the strength
that I need, if the mirror was ever inverted (which it isn't). As far as
the secondary goes, it has been stuck there for about 6 months now, upside
down, and is holding fine. YES - I would use double sided sticky tape again
in a second.
A second advantage (or disadvantage, if you like) is that the tape has a
thickness of a mm or so, so it tends to fill in rough spots on the surface
of the wood.
The tape doesn't expand/contract at all. I infer this because the
columnation doesn't change AT ALL as I lower the scope. We were looking at
Omega Centari the other day, and columnation seemed fine. (The seeing, on
the other hand was poor.)
Wire thickness - which note guitar string? Seriously, I don't know. I went
to an Ace hardware store, and picked up a clear plastic tube of 5 very thin
wires. I should have written down the size, but didn't. I was surprised
how thin they ended up. If you really want, I could go over there this
weekend (with the secondary ring as a comparison) and find out. Should I?
Vibration. For a truss telescope, I believe that vibration is BETTER than
most of the others in the club. I was the only person who finished a
Messier Marathon in March. Most of the big scopes had quit by about
midnight. I did have to run lower power most of the night. (22mm Superwide
Lanthanum) So, at this point, I am totally happy with the lack of vibration
of the scope. As an aside, the wire spider and secondary ring doesn't seem
to be a primary cause of vibration at all.
The two things that cut vibration was going to 3/4" aluminum tubing for the
trusses, and stiffening up the ground board.
Baffling. GROAN. This is still being worked on. Under dark skies, the
scope does very well. HOWEVER, if there is a moon, or someone shines a red
flashlight my way, , I DEFINATELY get light polution into the eyepiece.
With a moon, just having someone cast a shadow around the secondary ring and
upper baffle is a very noticeable improvement. So, I tend to not go out
when there is a strong moon.
I have picked up some corrigated plastic in black, but it turns out that i
cannot add that much weight to the top end of the scope, and keep the scope
balanced.
I have made about 4 black notebooks (without the metal back) into baffles
that go around the upper ring. I haven't tried this in action, however.
Does anyone know of a good source of flat black felt material to line
plastic sheeting with? Orion doesn't seem to have anything like that.
Alan
http://www.xmission.com/~alanne/Astronomy.html
http://www.xmission.com/~alanne/DS3Main.html
>From: DrewClan@aol.com
>To: atm@atmlist.net
>Subject: [ATM] Alan Scott's Deep Space telescope
>Date: Thu, 7 Apr 2005 13:45:52 EDT
>
><< Alan Scott writes: My telescope, and a wire spider:
> http://www.xmission.com/~alanne/DS3SecondaryCage.html >>
>
>
>Hiya, Alan! I like your telescope very much: it's clean and looks really
>functional. I've got a couple of questions on your construction:
>
>-how is the double sided tape holding up? You've used it on both the mirror
>cell and the secondary. Still sticking nicely? Would you go with it again?
>
>-which guitar strings did you use for the spider? The high E?
>
>-how are your improvements to reduce vibration and stray light coming
>along?
>
>Again, thanks for the great webpages detailing your excellent telescope,
>Jay in CT
>
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