I left out a word it should be - as long as there is *no* physical contact between - etc.
Don Dr E D F Williams http://personal.inet.fi/cool/don.williams Author's Web Site and Photo Gallery Updated: March 30, 2002 ----- Original Message ----- From: "Keith Whaley" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Monday, November 04, 2002 3:22 PM Subject: Re: OT: Re: Eclipse > > > Dr E D F Williams wrote: > > > > JC, > > > > I wish my 400mm Sigma APO produced results as sharp! > > > > If by mirror lens you mean something made specifically as a telephoto for > > terrestrial photography then your aversion to them may be justified. But > > consider the two Questars - 3.5" and 7". > > These are far superior to any telephoto that has ever been offered for > > sale to the public. > > This statement is without dispute. Questar hand figures their optics > as individual sets, for each and every instrument they build, to > _exceed_ the usually recognized standards or 'limits' of astronomical > telescope resolution. I know of no telescope available to the general > public, as Don indicates, that is made to such exacting criteria. > > I once had a 3.5" Questar, and it was so good, I was able to pick up > on the vibrations from cars passing by and others walking thru the > house... I had a very stout and stiff tripod, but it was the floor the > tripod was sitting on that was my problem. With other telescopes, you > couldn't notice it, mainly bacause you were power limited. Crank up > the power and very soon the image starts deteriorating badly, but with > the Questar, you could actually USE the power, if you could view thru > the eyepiece without touching the mount or instrument in any way! <grin> > Lovely instruments, with a price to match... > > keith whaley > > > Every time you > > see the launch of the space shuttle on TV its been taken though a 7" Questar > > specially adapted for the job - or so I've read anyway. I used the small one > > in my laboratory and sometimes out in the field. I have none of those > > slides, but I'm sure there are samples to be seen on the Questar web site. > > > > However, if you want sharp pictures with a Questar, or any really long > > telephoto for that matter, you need to go to extraordinary, and tiresome, > > lengths to get sharp pictures at high magnification. All the precautions > > used in photomicrography have to be applied. In a nutshell - as long as > > there is direct physical connection between the camera and the optics, half > > the battle is won. However, each part can be fastened to the same vibration > > free base. The shutter should either be replaced by an external one, or the > > exposure should be long - or very short indeed. > > > > Don > >
