Sept 17 Star Party
Well, it certainly looked like a bust all day, with the clouds coming and going. But by the time I got to SPOC around 6:45, the sun was shining with a lot of thin cirrus clouds challenging the potential evening. The sun was sweet! But I had to get a peek through Steve’s refractor at night – just to compare. The sunset was quite colorful and beautiful, but that color translated to lots of thin clouds. It looked like it was going to be an early night, but FINALLY Vega poked through – barely- directly overhead. So it might end up being a “sucker hole” night. That’s when just one part of the sky clears and everyone turns their telescope to that place and then it clouds over, but another break in the clouds appears elsewhere so everyone turns their telescopes to that point and then... “sucker!!” Slowly, over time all those thin clouds disappeared and the night turned into a true joy. Oh, and BTW, Steve’s got a great refractor --- but my refractor is better than his (certainly in my own mind). He had epsilon lyrae split with 90 magnification. He didn’t see it, but I did, although it wasn’t rock solid - they were “footballs” with occasional dark lines between. At 220 mag, it was a clean split, as it should have been. Bruce had the 11” “handicap” scope out there and it’s image of M13 was spectacular. Might I say “resolved to the core?” I challenged both Steve and Bruce, who had Gotos to look at Alpha Hercules. Neither of their gotos had it in their database, even by star name. Finally I looked at Bruce and pointed to the proper place in the sky and said “Geez, it’s right there!!!” Like a seesick (not seasick) sailor, Bruce had to get his star hopping legs back, but he managed (hehe) AND NO, I am not starting up the goto pushto debate again. It was just a “funny” moment. The real debate was the color of the pair. I just wanted to see what people thought. For those of you who missed it you are S.O.L. for those of you who took the chance, it was a blast.
Joan: I heard from several members tonight that it "was great to see you out" with us again. We all enjoyed your company and hope you will come out for a few minutes and stay for hours again soon. I couldn't possibly give a better report of the nights events than you have. It did indeed turn out to be an outstanding night out for all those who took the chance. If you would have pointed at Alpha Herculis for me we could have gone there. Since I had no idea where to look it didn't work out so well with the goto. Next time just remind me that it also goes by a traditional name. Rasalgethi is easy to find in the goto's double star catalog. I guess I need to get back in the habit of taking star charts to public star parties. Hope to see you all again, soon. Steve
From: jcarman6@q.com To: utah-astronomy@mailman.xmission.com Date: Sun, 18 Sep 2011 00:46:13 -0600 Subject: [Utah-astronomy] Sept 17 Star Party
Well, it certainly looked like a bust all day, with the clouds coming and going. But by the time I got to SPOC around 6:45, the sun was shining with a lot of thin cirrus clouds challenging the potential evening. The sun was sweet! But I had to get a peek through Steve’s refractor at night – just to compare. The sunset was quite colorful and beautiful, but that color translated to lots of thin clouds. It looked like it was going to be an early night, but FINALLY Vega poked through – barely- directly overhead. So it might end up being a “sucker hole” night. That’s when just one part of the sky clears and everyone turns their telescope to that place and then it clouds over, but another break in the clouds appears elsewhere so everyone turns their telescopes to that point and then... “sucker!!” Slowly, over time all those thin clouds disappeared and the night turned into a true joy.
Oh, and BTW, Steve’s got a great refractor --- but my refractor is better than his (certainly in my own mind). He had epsilon lyrae split with 90 magnification. He didn’t see it, but I did, although it wasn’t rock solid - they were “footballs” with occasional dark lines between. At 220 mag, it was a clean split, as it should have been. Bruce had the 11” “handicap” scope out there and it’s image of M13 was spectacular. Might I say “resolved to the core?”
I challenged both Steve and Bruce, who had Gotos to look at Alpha Hercules. Neither of their gotos had it in their database, even by star name. Finally I looked at Bruce and pointed to the proper place in the sky and said “Geez, it’s right there!!!” Like a seesick (not seasick) sailor, Bruce had to get his star hopping legs back, but he managed (hehe) AND NO, I am not starting up the goto pushto debate again. It was just a “funny” moment. The real debate was the color of the pair. I just wanted to see what people thought.
For those of you who missed it you are S.O.L. for those of you who took the chance, it was a blast.
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Steve, If your "goto" is made by Meade, get into the "Constellations" section on your hand held controller (I have no idea about Celestron). Once there, you can choose prominent stars. Alpha Herculis will he listed as the first target. From: Steve Fisher <iotacass1@hotmail.com> To: utah-astronomy@mailman.xmission.com Sent: Sunday, September 18, 2011 2:06 AM Subject: Re: [Utah-astronomy] Sept 17 Star Party Joan: I heard from several members tonight that it "was great to see you out" with us again. We all enjoyed your company and hope you will come out for a few minutes and stay for hours again soon. I couldn't possibly give a better report of the nights events than you have. It did indeed turn out to be an outstanding night out for all those who took the chance. If you would have pointed at Alpha Herculis for me we could have gone there. Since I had no idea where to look it didn't work out so well with the goto. Next time just remind me that it also goes by a traditional name. Rasalgethi is easy to find in the goto's double star catalog. I guess I need to get back in the habit of taking star charts to public star parties. Hope to see you all again, soon. Steve
From: jcarman6@q.com To: utah-astronomy@mailman.xmission.com Date: Sun, 18 Sep 2011 00:46:13 -0600 Subject: [Utah-astronomy] Sept 17 Star Party
Well, it certainly looked like a bust all day, with the clouds coming and going. But by the time I got to SPOC around 6:45, the sun was shining with a lot of thin cirrus clouds challenging the potential evening. The sun was sweet! But I had to get a peek through Steve’s refractor at night – just to compare. The sunset was quite colorful and beautiful, but that color translated to lots of thin clouds. It looked like it was going to be an early night, but FINALLY Vega poked through – barely- directly overhead. So it might end up being a “sucker hole” night. That’s when just one part of the sky clears and everyone turns their telescope to that place and then it clouds over, but another break in the clouds appears elsewhere so everyone turns their telescopes to that point and then... “sucker!!” Slowly, over time all those thin clouds disappeared and the night turned into a true joy.
Oh, and BTW, Steve’s got a great refractor --- but my refractor is better than his (certainly in my own mind). He had epsilon lyrae split with 90 magnification. He didn’t see it, but I did, although it wasn’t rock solid - they were “footballs” with occasional dark lines between. At 220 mag, it was a clean split, as it should have been. Bruce had the 11” “handicap” scope out there and it’s image of M13 was spectacular. Might I say “resolved to the core?”
I challenged both Steve and Bruce, who had Gotos to look at Alpha Hercules. Neither of their gotos had it in their database, even by star name. Finally I looked at Bruce and pointed to the proper place in the sky and said “Geez, it’s right there!!!” Like a seesick (not seasick) sailor, Bruce had to get his star hopping legs back, but he managed (hehe) AND NO, I am not starting up the goto pushto debate again. It was just a “funny” moment. The real debate was the color of the pair. I just wanted to see what people thought. For those of you who missed it you are S.O.L. for those of you who took the chance, it was a blast. _______________________________________________ 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
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You're right Steve, but I couldn't remember the name of the star to tell you! and Ras.... is a mouthful, no wonder I didn't remember. I was just saying good bye to everyone when Bruce looked it up on his chart and then he was bound and determined to check it out (hehe). He has an older goto so the star name wasn't there. It sounds like you had it by name in your catalogue. I could have/should have gone back to you, but then Jupiter was up, right between the trees where I stood (but not where your scope was! I really would have liked to see Jupiter in your scope. The planets are best with a refractor! I surprised myself by getting into my "star party" mode and was talking to strangers in the dark and loving it. ----- Original Message ----- From: "Steve Fisher" <iotacass1@hotmail.com> To: utah-astronomy@mailman.xmission.com Sent: Sunday, September 18, 2011 2:06:10 AM Subject: Re: [Utah-astronomy] Sept 17 Star Party Joan: I heard from several members tonight that it "was great to see you out" with us again. We all enjoyed your company and hope you will come out for a few minutes and stay for hours again soon. I couldn't possibly give a better report of the nights events than you have. It did indeed turn out to be an outstanding night out for all those who took the chance. If you would have pointed at Alpha Herculis for me we could have gone there. Since I had no idea where to look it didn't work out so well with the goto. Next time just remind me that it also goes by a traditional name. Rasalgethi is easy to find in the goto's double star catalog. I guess I need to get back in the habit of taking star charts to public star parties. Hope to see you all again, soon. Steve
From: jcarman6@q.com To: utah-astronomy@mailman.xmission.com Date: Sun, 18 Sep 2011 00:46:13 -0600 Subject: [Utah-astronomy] Sept 17 Star Party
Well, it certainly looked like a bust all day, with the clouds coming and going. But by the time I got to SPOC around 6:45, the sun was shining with a lot of thin cirrus clouds challenging the potential evening. The sun was sweet! But I had to get a peek through Steve’s refractor at night – just to compare. The sunset was quite colorful and beautiful, but that color translated to lots of thin clouds. It looked like it was going to be an early night, but FINALLY Vega poked through – barely- directly overhead. So it might end up being a “sucker hole” night. That’s when just one part of the sky clears and everyone turns their telescope to that place and then it clouds over, but another break in the clouds appears elsewhere so everyone turns their telescopes to that point and then... “sucker!!” Slowly, over time all those thin clouds disappeared and the night turned into a true joy.
Oh, and BTW, Steve’s got a great refractor --- but my refractor is better than his (certainly in my own mind). He had epsilon lyrae split with 90 magnification. He didn’t see it, but I did, although it wasn’t rock solid - they were “footballs” with occasional dark lines between. At 220 mag, it was a clean split, as it should have been. Bruce had the 11” “handicap” scope out there and it’s image of M13 was spectacular. Might I say “resolved to the core?”
I challenged both Steve and Bruce, who had Gotos to look at Alpha Hercules. Neither of their gotos had it in their database, even by star name. Finally I looked at Bruce and pointed to the proper place in the sky and said “Geez, it’s right there!!!” Like a seesick (not seasick) sailor, Bruce had to get his star hopping legs back, but he managed (hehe) AND NO, I am not starting up the goto pushto debate again. It was just a “funny” moment. The real debate was the color of the pair. I just wanted to see what people thought.
For those of you who missed it you are S.O.L. for those of you who took the chance, it was a blast.
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Hmmm. I wonder if I should say anything at this point? DT From: "jcarman6@q.com" <jcarman6@q.com> To: Utah Astronomy <utah-astronomy@mailman.xmission.com> Sent: Sunday, September 18, 2011 12:16 PM Subject: Re: [Utah-astronomy] Sept 17 Star Party I was just saying good bye to everyone when Bruce looked it up on his chart.
Hmmm, you will most likely say "something" so why not now?
Date: Sun, 18 Sep 2011 13:48:03 -0700 From: outwest112@yahoo.com To: utah-astronomy@mailman.xmission.com Subject: Re: [Utah-astronomy] Sept 17 Star Party
Hmmm. I wonder if I should say anything at this point?
DT
From: "jcarman6@q.com" <jcarman6@q.com> To: Utah Astronomy <utah-astronomy@mailman.xmission.com> Sent: Sunday, September 18, 2011 12:16 PM Subject: Re: [Utah-astronomy] Sept 17 Star Party
I was just saying good bye to everyone when Bruce looked it up on his chart. _______________________________________________ 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
I had a good session Saturday night. There was a short window from full astrotwilight at 9pm till moonrise some time after 10:30pm. I wanted to see the three globulars along the bottom edge of the teapot. Gary Seronik has them featured in his colum in Septembers Sky and Telescope. I was using my 20x80 binoculars while sitting in a portable lawn chair. The sky was riddled with cirrus patches, the water in the air column was up to 23mm and Sagittarius was low to the horizon. But Gary's map made it easy enough to follow the line between zeta and epsilon and I was able to tease them out from the skyglow. Next I went up to the "other wing" of Lyra. two stars eta and theta have a fine open cluster next to them called ngc6791. Oddly this is in the pocket skyatlas but not on the skyatlas 2000. Then I went for the comet 2009p1 Garradd. It was set on the line between 109 and 110 Hercules and was bright with a fine tail. Jeff Porter helped Ray Druian set up his new 14 dob. Views through this were the hit of the night. Jupiter, M13, and the usual suspects. DT
I truly wished and wanted to be there. Alas, I want to be over this pneumonia but it is very frustrating and I'm just stuck until the antibiotics work. I hate the side affects as much as the pneumonia and its cough and hard to breathe. Oh well, thanks for listening and keep the reports so I have something positive to read. On Sun, Sep 18, 2011 at 6:32 PM, daniel turner <outwest112@yahoo.com> wrote:
I had a good session Saturday night. There was a short window from full astrotwilight at 9pm till moonrise some time after 10:30pm.
I wanted to see the three globulars along the bottom edge of the teapot. Gary Seronik has them featured in his colum in Septembers Sky and Telescope. I was using my 20x80 binoculars while sitting in a portable lawn chair. The sky was riddled with cirrus patches, the water in the air column was up to 23mm and Sagittarius was low to the horizon. But Gary's map made it easy enough to follow the line between zeta and epsilon and I was able to tease them out from the skyglow.
Next I went up to the "other wing" of Lyra. two stars eta and theta have a fine open cluster next to them called ngc6791. Oddly this is in the pocket skyatlas but not on the skyatlas 2000.
Then I went for the comet 2009p1 Garradd. It was set on the line between 109 and 110 Hercules and was bright with a fine tail.
Jeff Porter helped Ray Druian set up his new 14 dob. Views through this were the hit of the night. Jupiter, M13, and the usual suspects.
DT _______________________________________________ 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
-- Jay Eads
Nice report, Daniel. Thanks! ________________________________ From: daniel turner <outwest112@yahoo.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 I had a good session Saturday night. There was a short window from full astrotwilight at 9pm till moonrise some time after 10:30pm. I wanted to see the three globulars along the bottom edge of the teapot. Gary Seronik has them featured in his colum in Septembers Sky and Telescope. I was using my 20x80 binoculars while sitting in a portable lawn chair. The sky was riddled with cirrus patches, the water in the air column was up to 23mm and Sagittarius was low to the horizon. But Gary's map made it easy enough to follow the line between zeta and epsilon and I was able to tease them out from the skyglow. Next I went up to the "other wing" of Lyra. two stars eta and theta have a fine open cluster next to them called ngc6791. Oddly this is in the pocket skyatlas but not on the skyatlas 2000. Then I went for the comet 2009p1 Garradd. It was set on the line between 109 and 110 Hercules and was bright with a fine tail. Jeff Porter helped Ray Druian set up his new 14 dob. Views through this were the hit of the night. Jupiter, M13, and the usual suspects. DT _______________________________________________ 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
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. ;-)
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
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
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
On 9/18/11, jcarman6@q.com <jcarman6@q.com> wrote:
Refractors do not have central obstructions. They take ALL the light from a source and focus it at a single point.
ONLY if the source is itself a point. Virtual images of planets and lunar features have a real size, they are most certainly not points. This illustrates a common misconception in that a typical image of say, a star field, is composed of many light cones spread across the entire FOV. Each cone corresponds to a single star in the field. The primary (be it lens or mirror) does not focus all light in the field to a single point, as I've heard some people express. Anywhoo, I understand what you say about the resolution of refractors being very good, but lets face it- Dawes' limit is Dawes' limit. I just played the aperture trump. Bigger aperture can and will give you better resolution. With identical apertures, it would depend on the individual quality and cleanliness of the telescopes being compared. And what about an unobstructed reflector? There goes the central obstruction complaint. I'm working on 3 six-inch refractors and a five-inch at present, as well as 3 50mm refractors (not the solar scopes). Obviously I like the sharpness of refractors. But from my experience, with the right reflector, the comparison with refractors is much more favorable. I'm not choosing. I'm going to keep using both and have it both ways. :o)
On 9/18/11, jcarman6@q.com <jcarman6@q.com> wrote:
Refractors do not have central obstructions. They take ALL the light from a source and focus it at a single point.
Ok, it occured to me that you were referring to the Airy disk. But refractors do not focus all the light to a point. They tend to bring more energy into the central spot but they do have interference fringes around the spot. There is no perfect optical system.
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