Atilla, Maybe I can chime in with my experience with Mike over the last year. I've never met Mike Lockwood in person and have no other tie with him than as a...
18319
John Mahony
jmmahony
Mar 1, 2008 3:58 pm
... You've probably heard of him here, since he's a member and has posted many times. He lives about 100 miles from me. I first met him at Astrofest, and the...
18321
Roger Greenwood
astrocrumb
Mar 1, 2008 6:12 pm
This is spam, right? -Roger (Via iPhone) ... [Non-text portions of this message have been removed]...
18322
Attilla Danko
attilladanko
Mar 1, 2008 6:15 pm
Yes. I've deleted the orignal post and the author is now moderated....
18323
Mike Lockwood
parabola30
Mar 3, 2008 5:59 pm
Hi, ... I wanted to thank John and Robert for their complements, and Dan for digging up and quoting Carl's. ... Well, John, mirror making is rapidly becoming...
18324
Jamey
jameyn1951
Mar 7, 2008 5:05 pm
I have been a member before and now I am back, planning to build an 18 inch Dob and of course would like to use the best design for a modern, lightweight and...
18325
kloster12000
Mar 8, 2008 1:27 am
Hi Jamey, Sounds like you live in a great place! Where is it if you don't mind saying? I live in Yorktown,VA and have to drive about 6 hours to get to really...
18326
Gregg
starryskyn
Mar 9, 2008 8:23 am
Here's a nice one just your size: http://www.synrgistic.com/astro/building.htm http://mailbot.onlineplayer.com/Ed/astro/18inch/ for another. ...
18327
Gregg
starryskyn
Mar 9, 2008 8:42 am
http://www.stathis-firstlight.de/atm/linkseng.htm has links to good Dobsonian ideas for your project. ... 18 ... modern, ... dark ... f4.5, ... that ... exotic...
18328
desvauxpierre
Mar 9, 2008 4:42 pm
Here in my website, there are perhaps some ideas: http://dobson.2005.googlepages.com/home Minimalist dobsons, inspired by Gregg Babcock, Dan Gray, and Mel ...
18329
Alan Scott
alanne1956
Mar 10, 2008 4:07 am
Jamey, I made a 16" lightweight and transportable dob. I wrote it up here: http://www.xmission.com/~alanne/DS4Main.html . It is easy to lift, and fits in the...
18330
davidfpitre
Mar 10, 2008 2:57 pm
I'm working on a cell for an 18" f/4.2 mirror that uses 45° whiffletree supports. These should be positioned at the plane of the center of gravity, and not at...
18331
Robert Houdart
rhoudart
Mar 10, 2008 3:27 pm
The Mirror Edge Support Calculator computes the position of the COG and some other useful data (sagitta and estimated mass of the mirror) for you. See...
18332
K. Anderson
kanders2faac
Mar 13, 2008 3:14 am
I am investigating large dobsonians for a semi-portable club telescope. Since faster scopes are shorter they are more transportable, and increase saftety due...
18333
Attilla Danko
attilladanko
Mar 13, 2008 3:21 am
High quality scopes like Starmasters, Starstructures and others are available in focal ratios as short as 3.7 and they work very well. I'd say the main...
18334
Scott Tannehill
scotttannehi...
Mar 13, 2008 5:12 am
Cost is one. They are harder to figure than a slower mirror to any given measure of quality. Accordingly, there are fewer who can (or will) make such large...
18335
Sebastian
pikibooicu
Mar 13, 2008 6:07 am
Equatorial Platforms make really nice fast focal ratio scopes with Kennedy Mirrors, all metal, and with their fancy new goto slipstream drive. Very pricey. ...
18336
C. Starks
cstarsnc
Mar 13, 2008 1:01 pm
Storage. Transport. EPs GoTo and tracking. I definitely would try to get the most aperture possible and still retain both feet on the ground (or nearly so)....
18337
tomofreno2000
Mar 13, 2008 1:25 pm
A faster primary requires a larger secondary, reducing contrast somewhat for planetary details if that is a concern. i think this is more limited by seeing...
18338
Roy Diffrient
roy_diffrient
Mar 14, 2008 3:40 am
Something not yet mentioned is that faster Newtonians have reduced tolerance for misalignment of the optics. For faster optics, better collimation is ...
18339
Attilla Danko
attilladanko
Mar 14, 2008 3:47 am
True. However, owners of high quality F/3.66 newts report seeing fine detail on planets (in times of good seeing) meaning that it is possible to build the...
18340
mharveyww1
Mar 14, 2008 6:51 am
... tolerance ... collimation is ... tube ... Which is one of the main reasons I chose a Starstructure telescope. They are 'overbuilt' in terms of structural...
18341
Nils Olof Carlin
nilsolofcarlin
Mar 14, 2008 8:38 am
Roy, Things may not be quite as bad as they may seem at first. The linear miscollimation tolerances are indeed proportional to the f/ ratio cubed, meaning the...
18342
tomofreno2000
Mar 14, 2008 3:00 pm
I think this issue of constrast as a function of central obstruction is complex. Harold Suiter graphs the MTF as a function of central obstruction and shows...
18343
Attilla Danko
attilladanko
Mar 14, 2008 3:24 pm
I my observing experience, I find that the size of the central obstruction is less of a distinguishing factor in seeing fine detail than telescope to telescope...
18344
tomofreno2000
Mar 15, 2008 1:23 am
Hi Attila, What do you attribute the "Oh wow" too? I think that is a very interesting, and real, observation. Your comment that "20% is actually quite a...
18345
Attilla Danko
attilladanko
Mar 15, 2008 1:58 am
I was referring to visual telescopes only. The "oh wow" effect is a instant visual sense that the image looks good that I've noticed in high quality...
18346
jpcannavo
Mar 15, 2008 12:31 pm
The other issue here wrt central obstruction that should be mentioned is that in very large scopes, the size of diffraction patern starts to become small...
18347
Roy Diffrient
roy_diffrient
Mar 15, 2008 2:43 pm
... Ah, but that's for a constant aperture, comparing focal lengths -- The goal is to increase aperture while keeping the focal length (and the trip up the ...
18348
tomofreno2000
Mar 15, 2008 2:51 pm
Huh? You've lost me here Joe. I don't understand comparing a feature in the image space to a scale defined in the object space (seeing in arcsec). The Airy...
