Finally, a decent night of seeing
It's been 2 1/2 months since I had a good night of seeing. I set up the TV-102 refractor on the Losmandy GM-8 mount to view some doubles, planets, and the moon. I was surprised to see the "C" ring on Saturn. I saw a clean split of the Cassini Division plus detail on the globe at 125X. Instead of reaching for the 5mm Radian, I grabbed the 4mm Radian. It was an awesome view at 220X. I've never seen Saturn this good in this telescope. It made we wish I had a 3mm Radian and a 6" refractor. I first checked the seeing with Theta Aurigae. It was an easy split at 125X. I thought Ithis is supposed to be a tough one. Then I went to Epsilon Canis Majoris. I could see the faint secondary star at about the 4 o'clock position. It was a clean split tonight. Then I went on to Kappa Puppis. This is a 3.8 and 4.0 mag, 9.9" almost equal matched pair. It was a pretty sight at 125X. I went north to Eta Puppis, a 5.1 mag, 9.8" equal matched pair. This was also a pretty double. My next target was the Tau Canis Majoris cluster, a pretty open cluster despite the light pollution from the half moon. I just love viewing this cluster. I viewed it on March 19th with the 15" and it is one of my favorite star clusters in the Milky Way. Just to the north of this cluster is the "Winter Albeiro", a pretty 27" wide gold-blue double with a striking color contrast. Nice view at 40X. My next target was the triple star Beta Monocerotis. This is a 4.7, 5.2, and 6.2 mag triple with 7.2" and 2.9" separations. I got a clean split at 125X. All three stars are white. My last double was Gamma Leonis, a striking bright pair of yellow suns. I turned my scope to Jupiter and I could see much detail at 125X with the 7mm Nagler. When I put in the 4mm Radian(220X), Jupiter was larger than life. The Great Red Spot was readily apparent and I could see a smaller storm to the left of the Great Red Spot. After looking at all the bands of Jupiter I thought I'd take a high power look (220X) at the moon. The craters along the terminator were amazing. I felt like I was hovering over the moon in a spacecraft. The mountains on the moon almost looked 3D. I can only imagine how Jim Lovell saw it on his Apollo 8 mission. Clear Skies, Debbie
Deb, Nice report, however, it only adds to my already bad case of "refractor envy" ;o) Rich --- UTAHDEB@aol.com wrote:
It's been 2 1/2 months since I had a good night of seeing.
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Mine too! Especially 'apo-refractor envy'... Dave On Wednesday, March 31, 2004, at 01:49 PM, Richard Tenney wrote:
Deb,
Nice report, however, it only adds to my already bad case of "refractor envy" ;o)
Rich
--- UTAHDEB@aol.com wrote:
It's been 2 1/2 months since I had a good night of seeing.
In my experience looking through refractors, I have been struck by the fact that the apos are not as sharp as the achromats. I am not saying the image in an apo is bad - to the contrary. They are great. The image through a good achromat just seems sharper to my eye. Yes, there is the secondary color you have to deal with, but you learn to "see through" that very quickly. The apo is not optimized for a better image, but rather is optimized to reduce the secondary color. I understand that it seems like this should add to the contrast, but the MTF should be no different. The MTF is diameter dependant. Since the secondary color is in the shorter wavelengths, the human eye cannot focus them well anyway, especially when focusing on a low light level image rich in longer wavelengths. One must also consider that there are more surfaces in a true apo than in an achromat. The more surfaces, the more chance for errors. At least this is the current model of the situation in my mind. This is like adding filters - they REDUCE detail. I demonstrated this to a few folks in St. George in Feb 2003. Chime in if you remember the tests we did on Jupiter with my 12.5" dob. Now, I have seen some absolutely STUNNING images throuh an apo, but I think those of an achromat are superior. What has been the experience of this group? BTW, the fact that I own a large achromatic refractor does not and should not have any bearing on this postulate nor remarks. Brent __________________________________ Do you Yahoo!? Yahoo! Finance Tax Center - File online. File on time. http://taxes.yahoo.com/filing.html
Has it occurred to anyone that Douglas Adams was wrong? The answer is surely not 42, but is 37. It is written in the stars, and there can be little doubt of his folly. If you don't believe me, just look at NGC2169. Brent __________________________________ Do you Yahoo!? Yahoo! Finance Tax Center - File online. File on time. http://taxes.yahoo.com/filing.html
That must be from an earlier run of by the great computer ...
I've seen that cluster, but I'm still not so sure. What if it's not base-10? The mystery continues... C. --- Brent Watson <brentjwatson@yahoo.com> wrote:
Has it occurred to anyone that Douglas Adams was wrong? The answer is surely not 42, but is 37. It is written in the stars, and there can be little doubt of his folly. If you don't believe me, just look at NGC2169.
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Brent, I've always liked doublet refractors, and, like you, learned to "look past" the purple haze. One only has to examine the essentially perfect diffraction rings of even a mass-produced doublet to appreciate the resolving potential of the objective. But I think the apo advantage is an aesthetic thing and hard to pin down exactly, for me anyway. I haven't had enough experience with my own apo yet to really say with certainty that either it or the classical doublets have the "detail" advantage. The appeal is more like analog recorded music. It just sounds "alive" and "breathing" to me, whereas digital, though technically excellent, lacks that spirit, that spark, "life". At this point, it's still just a joy to use a refractor with no color to speak of. But now that you mention it, I'll be sure to see if I find myself leaning one way or the other as time passes. Without the unfocused color, the impression is certainly one of a sharper, more detailed image. Perhaps color, or spectrum, of the target has an effect on resolution in a classical doublet, eh? I would also ask if you've looked through as many apo's as doublets? Could the sample size be skewing the results? Interesting post. C. --- Brent Watson <brentjwatson@yahoo.com> wrote:
In my experience looking through refractors, I have been struck by the fact that the apos are not as sharp as the achromats. Now, I have seen some absolutely STUNNING images throuh an apo, but I think those of an achromat are superior. What has been the experience of this group?
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I have looked through many apos. I would estimate that I have looked through as many apos as achromats, although the amount of time spent is probably 95%achromat, 10% apo. The doublets just have an image that appeals to my eye more than the apos. I have seen some really great views through apos, though. Brent --- Chuck Hards <chuckhards@yahoo.com> wrote:
Brent, I've always liked doublet refractors, and, like you, learned to "look past" the purple haze. One only has to examine the essentially perfect diffraction rings of even a mass-produced doublet to appreciate the resolving potential of the objective.
But I think the apo advantage is an aesthetic thing and hard to pin down exactly, for me anyway. I haven't had enough experience with my own apo yet to really say with certainty that either it or the classical doublets have the "detail" advantage. The appeal is more like analog recorded music. It just sounds "alive" and "breathing" to me, whereas digital, though technically excellent, lacks that spirit, that spark, "life".
At this point, it's still just a joy to use a refractor with no color to speak of. But now that you mention it, I'll be sure to see if I find myself leaning one way or the other as time passes. Without the unfocused color, the impression is certainly one of a sharper, more detailed image.
Perhaps color, or spectrum, of the target has an effect on resolution in a classical doublet, eh?
I would also ask if you've looked through as many apo's as doublets? Could the sample size be skewing the results?
Interesting post.
C.
--- Brent Watson <brentjwatson@yahoo.com> wrote:
In my experience looking through refractors, I have been struck by the fact that the apos are not as sharp as the achromats. Now, I have seen some absolutely STUNNING images throuh an apo, but I think those of an achromat are superior. What has been the experience of this group?
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I have found the images in the Takahashi 5" Fluorite FCT (just two elements) to be superior to the 5" three element apo's in side by side comparison. Both kinds are virtually color free but perhaps the two elements gives superior detail to three. I have also compared the 5" Fluorite to a good 6" achromat and I think the 5" is superior in both detail and contrast. Clear Skies Don Colton -----Original Message----- From: utah-astronomy-bounces+djcolton=piol.com@mailman.xmission.com [mailto:utah-astronomy-bounces+djcolton=piol.com@mailman.xmission.com]On Behalf Of Brent Watson Sent: Wednesday, March 31, 2004 3:40 PM To: Utah Astronomy Subject: [Utah-astronomy] The Refractor In my experience looking through refractors, I have been struck by the fact that the apos are not as sharp as the achromats. I am not saying the image in an apo is bad - to the contrary. They are great. The image through a good achromat just seems sharper to my eye. Yes, there is the secondary color you have to deal with, but you learn to "see through" that very quickly. The apo is not optimized for a better image, but rather is optimized to reduce the secondary color. I understand that it seems like this should add to the contrast, but the MTF should be no different. The MTF is diameter dependant. Since the secondary color is in the shorter wavelengths, the human eye cannot focus them well anyway, especially when focusing on a low light level image rich in longer wavelengths. One must also consider that there are more surfaces in a true apo than in an achromat. The more surfaces, the more chance for errors. At least this is the current model of the situation in my mind. This is like adding filters - they REDUCE detail. I demonstrated this to a few folks in St. George in Feb 2003. Chime in if you remember the tests we did on Jupiter with my 12.5" dob. Now, I have seen some absolutely STUNNING images throuh an apo, but I think those of an achromat are superior. What has been the experience of this group? BTW, the fact that I own a large achromatic refractor does not and should not have any bearing on this postulate nor remarks. Brent __________________________________ Do you Yahoo!? Yahoo! Finance Tax Center - File online. File on time. http://taxes.yahoo.com/filing.html _______________________________________________ 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.utahastronomy.com
Debbie I printed out your post and took my SkyAtals 2000 outside and with my Orion ED80 I tried to chase the doubles you mentioned. I had to put in a 4.8mm eyepiece to achieve 125X. The stars looked like satellites crossing my eyepiece. The wind stirred up a lot of dust today and I couldnt identify Monocerotis or Puppis let alone their constituents. I could barely make out Epsilon Canis Majoris but I couldnt split it. I believe I found Theta Aurigae but again I couldnt split it either. This was really fun though. Chasing doubles is very compatible with a bright moon. Even though I was not successful, I am hooked on chasing doubles on moon lit nights; what else can you do?. I have to start with some easier ones and work up. The 4.8mm is really pushing the little 80ED but for bright objects the Nagler works well and gave a beautiful view of Jupiter. I took a look at the moon. Now up on top (North) the Sinus Iridium is fully in the light where as last night only the Northern point was exposed. The crater Sharp is quite distinct above Iridium. As you come down the black Mare along the terminator until you are parallel with Copernicus the crater Aristarchus has just come into view. In a few more days the white rays from Aristarchus will be more apparent. Then continuing down the terminator in the bottom quarter you will see a very large crater called Gassendi. It is 110 km (68 mi) wide and the central peak is very promenant. Gassendi is right on the edge of Mare Humorum. Jim UTAHDEB@aol.com wrote:It's been 2 1/2 months since I had a good night of seeing. I set up the TV-102 refractor on the Losmandy GM-8 mount to view some doubles, planets, and the moon. I was surprised to see the "C" ring on Saturn. I saw a clean split of the Cassini Division plus detail on the globe at 125X. Instead of reaching for the 5mm Radian, I grabbed the 4mm Radian. It was an awesome view at 220X. I've never seen Saturn this good in this telescope. It made we wish I had a 3mm Radian and a 6" refractor. I first checked the seeing with Theta Aurigae. It was an easy split at 125X. I thought Ithis is supposed to be a tough one. Then I went to Epsilon Canis Majoris. I could see the faint secondary star at about the 4 o'clock position. It was a clean split tonight. Then I went on to Kappa Puppis. This is a 3.8 and 4.0 mag, 9.9" almost equal matched pair. It was a pretty sight at 125X. I went north to Eta Puppis, a 5.1 mag, 9.8" equal matched pair. This was also a pretty double. My next target was the Tau Canis Majoris cluster, a pretty open cluster despite the light pollution from the half moon. I just love viewing this cluster. I viewed it on March 19th with the 15" and it is one of my favorite star clusters in the Milky Way. Just to the north of this cluster is the "Winter Albeiro", a pretty 27" wide gold-blue double with a striking color contrast. Nice view at 40X. My next target was the triple star Beta Monocerotis. This is a 4.7, 5.2, and 6.2 mag triple with 7.2" and 2.9" separations. I got a clean split at 125X. All three stars are white. My last double was Gamma Leonis, a striking bright pair of yellow suns. I turned my scope to Jupiter and I could see much detail at 125X with the 7mm Nagler. When I put in the 4mm Radian(220X), Jupiter was larger than life. The Great Red Spot was readily apparent and I could see a smaller storm to the left of the Great Red Spot. After looking at all the bands of Jupiter I thought I'd take a high power look (220X) at the moon. The craters along the terminator were amazing. I felt like I was hovering over the moon in a spacecraft. The mountains on the moon almost looked 3D. I can only imagine how Jim Lovell saw it on his Apollo 8 mission. Clear Skies, Debbie _______________________________________________ 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.utahastronomy.com --------------------------------- Do you Yahoo!? Yahoo! Small Business $15K Web Design Giveaway - Enter today
participants (8)
-
Brent Watson -
Chuck Hards -
David L Bennett -
Don J. Colton -
Jim Gibson -
Joe Bauman -
Richard Tenney -
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