Active instruments: 4.25" f/6 Newtonian on altazimuth Springfield mount with crutch tripod -- telescope for the handicapped. 12" f/6 Newtonian Telescope maker since 1958; always more to come? Well maybe just one more and it will be something very special Stellafane Awards: 1977 1st award for 4" f/6 refractor 1978 1st award for 4" f/4 Lurie Aplanat 1983 1st award for Newtonian smoking pipe For Sky and Telescope articles, please see Bio info.
Money can't buy happiness, but it sure makes living with misery a lot easier!
"You're not afraid of the dark, are you?" - Riddick "The best scientists are humble. They seek to understand, not to ensure their legacy, but merely to understand." - Mori
6" F4.6(w/Paracorr) Reflector , 8" F11 Dall Relay Scope ,
6" F5 RFT Refractor w/Istar Obj , G11 Mount Gemini1 Level 4
Quote: So observe. it's not realistic to try for perfection in every aspect of doing anything.
20 inch f8 Chief Ed Jones designed and a 17 f9 Zanbuto Wide Band Chief Mike Jones designed .Both unobstructed telescopes .
Quote:Jon My 17 inch off axis Wide Band CHief can do anything a 17 inch APO can do . Ed good post
Quote:AH, you weren't reading closely. One of my precision optical windows negates the need for any spider diffraction whatsoever. No need for curved spiders or other cheats to spread the diffraction around.Ed
"The White Zone is for loading or unloading of passengers only. No Astrophotography." Cosmic Acres! Greatest restoration challenge: Tulley and Sons 3" achromat on Altazimuth mount, circa ~late 1820s
Celestron 8SE Dobstuff 13.1": Swayze refigured Coulter mirror, 6 pt mirror cell (2 pt edge support) and CF focuser board made by me StarBlast 4.5 ST80/PortaMount II Zhumell 20x80/Oberwerk 15x70 on a Seronik-style tripod boom mount Hubble Optics 18 inch F/4 mirror.
Quote:The ultra wide angle view thing is where small (or large) reflectors cannot compete with small refractors. An ultra wide angle 2" EP may have a field stop pushing the limit the 2" format supports (44mm or so), say the ES100 25mm, the Nagler 82 deg 31mm, or the ES82 30 mm. You won't get adequate illumination of that field stop without a secondary that is at least as large, and a 44mm secondary with a CO of not more than 30% would have to be at least 5.87", call it 6". And with a reasonable exit pupil it would have to be F/4.2 (the ES100 25mm), requiring a coma corrector pushing it to F/4.8, or else an F/5.2 outright, with FL of 730-800mm. OTOH, these EPs can be used with F/4-5 70-100mm objectives, and FLs of only 280-500mm with no CO light or contrast loss at all for extremely wide fields. If used for large nebula observing, with narrowband filters the CA aspect of the short achros disappears.
Dan1st Caveman Award!Maynard Clark 8" f/8The Horsetrail Cave 12.5" f/7.51975 Cave 8" f/7 Lightweight Deluxe1972 Cave 8" f/4.5 RFT DeluxeCriterion RV-6Logitech HD C615 Webcam for Imaging
Quote:Long focus newtonians should be renamed "hyperapochromats".Rant off.-Tim.
Every week I do something new to reduce light pollution. Eyes on the Sky is at 650,000+ views so far; more views = more awareness. Please consider sharing with others.
Vaughn :-) Observing from Dunedin, New Zealand. (45ºS) [100mm f/15 Refractor] [200mm f/13 Newtonian - under construction!]
-DannyMy warehouseMy Channel
7x35 and 10x50 sears tower binocs, 3" f/10 edmunds reflector, 2.4" f/11.7 manon refractor, 6" f/8 jaegers refractor, 10" f/11 R30 Istar refractor, 3" f/15.8 sans&streiffe refractor, 3.1" f/15 selsi refractor(towa 339), 2.4" f/15 sears refractor, selsi 30x30mm spyglass, criterion 5-draw 25x45x75x spyglass(1957), 4.25" f/14.8 tasco 20te.http://cleardarksky.com/c/OmahaNEkey.html
Quote:Pictures were shown of unobstructed images of a 6" f/10 APO and a 6" f/10 Newt with 16% obstruction. The difference was barely perceptible. In fact, Suiter and I agree that there is no difference at the eyepiece...Tell me the aperture of your APO and give me time to make an optimized Newt of the same size, with a precision optical window and a 12% obstruction. Special coatings all around.
Quote:Quote:Long focus newtonians should be renamed "hyperapochromats".Rant off.-Tim. I think I'll name my 6" f/10.9 reflector that, Tim!!
Quote:I found it! It's actually about an APO vs. Questar Funny and probably fitting for what this thread will turn out to.
Quote:Comments and pictures were shown on a thread concerning Herrig designs and I popped in and went off on a tangent.Pictures were shown of unobstructed images of a 6" f/10 APO and a 6" f/10 Newt with 16% obstruction. The difference was barely perceptible. In fact, Suiter and I agree that there is no difference at the eyepiece; anyone who says differently is thinking more of what he paid for his telescope than what he is seeing through his telescope in comparison.Tell you a story: I went on the Refractor Forum (EGads!) and made this offer. Tell me the aperture of your APO and give me time to make an optimized Newt of the same size, with a precision optical window and a 12% obstruction. Special coatings all around. Then, some neutral people would have to be picked to make an assessment as to what was what.The issue was to be imagery only; not the appearance of either telescope. Perhaps the Stellafane optical judges would be a good choice.In any case, no matter, win lose or draw, my telescope would be donated to charity.You know what? No one took the challenge against my 1/20 wave optics. Not one. Not one dared. I waited 6 months; the offer is withdrawn; why should I put up with all this "mighty APO" BS?
Jeff Morgan - Wile E. Coyote School of Telescope Making
Quote:I'd love to see you go ahead and build that closed-tube Newt and set-up next to the Astro-Physics tent at AstroFest or Stellafane. Perhaps you could invite some of the writers at Sky & Tel to stop by. Now that would create quite a stir!
Quote:I am now too crippled with rheumatoid arthritis to make another telescope or go to Stellafane.
Quote:But seriously, the best advantages of the APO aren't necessarily optical, but mechanical. That being the objective is farther away from the ground where one normally finds a rather sharp temperature gradient and it's detrimental effect on seeing. Sadly, by nature the primary mirror sits right in that gradient.
Refractors Reflectors Two Cats A few eyepieces
Quote:Too bad we can't get a likewise consensus on expensive big bucks eyepieces vs plain label orthos and plossls! Mike