Hi, This has probably been debated before but I'll ask anyway. Since completing it several months ago, I have been enjoying using my 16'' version of Mel's...
16258
Michelle Stone
plettstone
Dec 1, 2006 3:06 pm
Well... I build and sell telescopes that don't use shrouds, so I will admit a bias. But I suggest you try it for yourself and see. You might want to make...
16259
buck8one2
Dec 1, 2006 3:23 pm
Tim I'm not going into the baffles-n-contrast debate, but I am a firm believer in protecting the mirror from STUFF. I say number 1, but maybe a breathable...
16260
mauro_dalio
Dec 1, 2006 7:02 pm
I recall that i did some sensitivity evaluations, but on the 2" thickness. I am not surprised of you findings: 1) they agree with the overall amount of...
16261
Dale Eason
atmpob
Dec 2, 2006 12:47 am
I have a more detailed analysis of my earlier latteral testing. I discovered that what I had measured was not the difference between two and one peg support....
16262
paul_winalski
Dec 2, 2006 2:04 am
Tim, From what you said about the baffling you've done on your scope, it seems that you've gone to considerable trouble to prevent stray light from entering...
16263
Bruce
wd9aqs
Dec 2, 2006 3:05 am
I can agree with a shroud protecting the primary from stuff. On my 12" truss Dob I often use a lawn garbage bag with the closed end cut off. It slides down...
16264
mauro_dalio
Dec 2, 2006 2:38 pm
Compliments! You hev shown that the positon of the support may cause astigmatins in the range -0.7 to + 0.7 waves (thus discussion of differente designs that...
16265
Raphaël GUINAMARD
rguinamard@...
Dec 2, 2006 4:56 pm
Very interesting study Dale ! It is now clear for me that the astigmatism problem I have on my 24" 1.6" thick mirror is certainly due to a problem of placement...
16266
Dale Eason
atmpob
Dec 2, 2006 7:07 pm
Mauro, Just a slight correction to your statment. The astigmatism PV wavefront range is .7 not -.7 to +.7. I realized I have the data to analyze trefoil. I...
16267
mauro_dalio
Dec 2, 2006 8:24 pm
I meant the range you can control: that by moving the support point you can achieve from -0.7 waves PV (vertical diameter wrt horizontal diameter, or 0.7 waves...
16268
Dale Eason
atmpob
Dec 2, 2006 8:37 pm
Mauro, Thank your for the clarification. I understand now. Dale ... you can achieve from ... waves horizontal to vertical) ... horizontal) when the ... ...
16269
Dale Eason
atmpob
Dec 2, 2006 9:57 pm
Here is my analysis of trefoil caused by 2 peg lateral support. http://doeason.home.comcast.net/lateral_test/trefoil.pdf This should be studied further to see...
16270
robert hoffman
roberth_jr
Dec 3, 2006 1:25 am
Dale, I have a 20" Obsession with a Galaxy mirror. I've noticed that at very high power, sometimes, I see a bit of astigmatism in my mirror. Also, I have a...
16271
Dale Eason
atmpob
Dec 3, 2006 4:47 am
Yes a sling causes similar distortion if not placed on the mirror's center of mass. I once tested an 18" obsession mirror it was surprising how important...
16272
gnowellsct
Dec 3, 2006 9:11 am
I have no idea whether baffling and controlling light scatter is a good idea or a bad idea, I note simply, that in the refractor world it is a matter of high...
16273
Scott Tannehill
scotttannehi...
Dec 3, 2006 3:35 pm
Tim, That's a beautiful looking scope. I'm curious. Has your primary ever dewed up, with that exposure to the sky? I'd bet you won't notice a thing in terms of...
16274
rolandlinda3
Dec 3, 2006 9:23 pm
We notice a difference when we do not use the shroud on the Eastern Seaboard of the US. Above 50% humidity or so, after a couple hours the shroud protects the...
16275
Bob Bunge
bungerob
Dec 4, 2006 2:09 pm
... Yes. With a refractor the exit pupil is looking straight up the optical train - at the sky and anything else up there. The low incidence of angle along...
16276
mauro_dalio
Dec 4, 2006 10:34 pm
... surprise surprise... I have done a quick check for my 16x2 mirror. I have considered the restraint to be concentrated at the back point of the lower mirror...
16277
Bob Bunge
bungerob
Dec 4, 2006 10:38 pm
... Most of this thread has been above my head, but if your mirror was distorted by a 1/2 wave, wouldn't you notice that at the eyepiece? That's pretty...
16278
Peter
peterpekurar
Dec 5, 2006 12:48 am
Hi, There is nothing special about refractors. A couple of years ago I looked through Peter Ceravol'os open refractor. It only had lenses and baffles (no tube)...
16279
Dale Eason
atmpob
Dec 5, 2006 3:55 am
http://doeason.home.comcast.net/lateral_test/sling_study.pdf Some have asked that I do a study of the sling for supporting thin mirrors. Here it is. I had a...
16280
Dale Eason
atmpob
Dec 5, 2006 4:10 am
Yes an experienced observer and star tester would be able to see the error. This was done at worst case simulating the mirror pointing at the horizon. As you...
16281
John Mahony
jmmahony
Dec 5, 2006 7:34 am
... There's still plenty of room in the photos section. -John ____________________________________________________________________________________ Do you...
16282
mauro_dalio
Dec 5, 2006 1:24 pm
... exactly ath ... NO!! 0.5 waves is the result of calculations IN CASE the mirror is resting on ONE pont located at the backplane on the lower edge. In fact...
16283
mauro_dalio
Dec 5, 2006 1:30 pm
... Exactly: i made a quck simulation which was intended to reproduce Dale's case with the support point near the back plane. Dale finds 0.7 waves for a 1"...
16284
mauro_dalio
Dec 5, 2006 1:38 pm
... Ok the file is loaded on the photo section (1-point support at lower edge backplane point)....
16285
John Mahony
jmmahony
Dec 5, 2006 4:07 pm
Which folder is it in? I can't find it. -John ... ____________________________________________________________________________________ Yahoo! Music Unlimited ...
16286
mauro_dalio
Dec 5, 2006 9:07 pm
... hi hi hi... it is in Collimation devices by gnowellist (do not ask me why--- it happende there :-)) ...
