Resolution and/or "sharper" is what I was referring to. I didn't mean to imply that you couldn't get good, even exciting, images of the moon and planets in reflectors. Bruce had Uranus last night and it was sweet. However, matching refractors to reflectors for size, the refractor will provide a sharper, more detailed image of the moon and planets than will a reflector. It has been my experience that part of the value of the light gathering ability of reflectors is "overpowering" when viewing moon and planets, less clear. There is too much light and it "bleeds" the image, making it less clear or less sharp. That is why reflectors, particularly dobs are stopped down when viewing the moon and planets. A reflector doesn't get light from the center of a bright object because of the central obstruction - just where you want to gather your light. But it gets plenty from the edges, which is overpowering. You're right about the column of air being smaller and less open to turbulence. However put a 6" dob or reflector against a 6" refractor on moon and planets and the image is decidedly sharper in the refractor. You can even put a 6" refractor up against a 8 or 10", even higher and, on the moon and planets, the refractor will win for sharper image. When observing Mars at closest approach, many years ago, I had my refractor and other much larger dobs at a public star party in Park City, very dark, and everyone (including the other telescope owners)admitted my view of Mars was sharper. A lot more subtle detail was seen in the refractor. We should put this to the test. Refractors versus reflectors on the moon - say Clavius. See how many craters can be counted. Or the straight wall. How sharply defined is the wall and surrounding details in each scope. Or the Epsilon Lyra split challenge. Dobs will split Epsilon Lyra, but they'll need a lot more magnification to do it. All of this may be nit-picking, as only truly experienced serious observers would discern the difference. ----- Original Message ----- From: "daniel turner" <outwest112@yahoo.com> To: "Utah Astronomy" <utah-astronomy@mailman.xmission.com> Sent: Sunday, September 18, 2011 6:57:22 PM Subject: Re: [Utah-astronomy] Sept 17 Star Party You're wrong Joan. The central obstruction boogyman is just not real. You can split stars and look at planets just fine with a reflector and star clusters are really great in them. Of couse the view through the reflector is different from that of a refractor, that's because the resolution of the reflector is much better than the seeing will generally allow. But when the seeing settles down the extra aperture of a reflector blows away the refractor. It's painful for people to believe that a telescope of one third the price can have better views. But it's true. DT From: "jcarman6@q.com" <jcarman6@q.com> To: Utah Astronomy <utah-astronomy@mailman.xmission.com> Sent: Sunday, September 18, 2011 6:32 PM Subject: Re: [Utah-astronomy] Sept 17 Star Party Oh, is this going to be a refractor/reflector debate? Refractors do not have central obstructions. They take ALL the light from a source and focus it at a single point. This works exceedingly well on the moon and planets (and the spliting of double stars). Planets are sufficiently bright that it is not how much light gathering ability you have it is what you do with it that counts most. Light buckets like dobs are best on the faint fuzzies, where gathering as much light as possible is more important. Many years of comparing reflectors to refractors is backing me up. Given the same size telescope, same eyepiece, the refractor will display a sharper image of the moon or planet than a reflector. On the other hand, my refractor (or any refractor) will lose the challenge if it is the Andromeda Galaxy. Just try splitting epsilon lyrae with a reflector at 90 magnification -- footballs, if you are lucky. They can't do it. Of course, quality of the lenses and mirrors are an issue. Some refractors aren't up to the challenge, but it is the same argument with the quality of the mirrors. We won't get into focal lengths that add mud to the water. But that is why refractors have not died out and been completely replaced by reflectors. Refractors have their uses and their value and that is why they are still around today. ----- Original Message ----- From: "Chuck Hards" <chuck.hards@gmail.com> To: "Utah Astronomy" <utah-astronomy@mailman.xmission.com> Sent: Sunday, September 18, 2011 3:33:20 PM Subject: Re: [Utah-astronomy] Sept 17 Star Party On 9/18/11, jcarman6@q.com <jcarman6@q.com> wrote:
The planets are best with a refractor!
Oh, Joan. (Chuck rolls eyes). I'm a refractor fan (have no less than 6 in progress as this is typed), but it's APERTURE that rules, everything else being equal. You know that. The planets are best with a big scope. Diffraction patterns are best with a refractor. ;-) _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php