... 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...
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...
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...
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...
http://www.stathis-firstlight.de/atm/linkseng.htm has links to good Dobsonian ideas for your project. ... 18 ... modern, ... dark ... f4.5, ... that ... exotic...
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 ...
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...
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...
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...
I am investigating large dobsonians for a semi-portable club telescope. Since faster scopes are shorter they are more transportable, and increase saftety due...
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...
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...
Equatorial Platforms make really nice fast focal ratio scopes with Kennedy Mirrors, all metal, and with their fancy new goto slipstream drive. Very pricey. ...
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)....
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...
Something not yet mentioned is that faster Newtonians have reduced tolerance for misalignment of the optics. For faster optics, better collimation is ...
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...
... tolerance ... collimation is ... tube ... Which is one of the main reasons I chose a Starstructure telescope. They are 'overbuilt' in terms of structural...
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...
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...
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...
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...
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...
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...
... 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 ...
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...
Another comment, it seems that you could reduce the effect of anything that reduces the MTF, central obstruction, mirror figure, seeing...by scaling both f.l....
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