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ASTRO: First light, AP155EDF f/7 and PL39000C, target M8/M20
I have been attempting to use the '155 f/7 with the PL39K for three weeks
now. The faster focal ratio, f/7 versus the f/9 of the '180edt, means nearly a 2x improvement in light gathering rate with a modest increase in image scale: 1.15 versus 0.87 "/pixel. Finally the weather cooperated on Saturday night. I took 4.75 hours of exposure on Sat night using 15 minute subexposures. the full 39 megapixel resolution on the linked page below is interesting: there are a lot of stars in there! http://www.narrowbandimaging.com/m8_...pl39K_page.htm |
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ASTRO: First light, AP155EDF f/7 and PL39000C, target M8/M20
Richard Crisp wrote:
I have been attempting to use the '155 f/7 with the PL39K for three weeks now. The faster focal ratio, f/7 versus the f/9 of the '180edt, means nearly a 2x improvement in light gathering rate with a modest increase in image scale: 1.15 versus 0.87 "/pixel. Finally the weather cooperated on Saturday night. I took 4.75 hours of exposure on Sat night using 15 minute subexposures. the full 39 megapixel resolution on the linked page below is interesting: there are a lot of stars in there! http://www.narrowbandimaging.com/m8_...pl39K_page.htm Nice resolution on the central "star" of M20. Well resolved. Glad someone sees sky. At least lately the clouds have given up some rain. Well shy of what's needed but it helps. Still two solid months of clouds and only 2" of rain is not a good trade. I'm a bit lost on the image scale. 155mm at f/7 is 1085mm focal length while f/9 at an aperture of 180mm is 1620 or a 49% increase. Increasing ..87 by 49% gives a 1.3" pixel. Does the flattener make the difference? Rick -- Correct domain name is arvig and it is net not com. Prefix is correct. Third character is a zero rather than a capital "Oh". |
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ASTRO: First light, AP155EDF f/7 and PL39000C, target M8/M20
"Rick Johnson" wrote in message ster.com... Richard Crisp wrote: I have been attempting to use the '155 f/7 with the PL39K for three weeks now. The faster focal ratio, f/7 versus the f/9 of the '180edt, means nearly a 2x improvement in light gathering rate with a modest increase in image scale: 1.15 versus 0.87 "/pixel. Finally the weather cooperated on Saturday night. I took 4.75 hours of exposure on Sat night using 15 minute subexposures. the full 39 megapixel resolution on the linked page below is interesting: there are a lot of stars in there! http://www.narrowbandimaging.com/m8_...pl39K_page.htm Nice resolution on the central "star" of M20. Well resolved. Glad someone sees sky. At least lately the clouds have given up some rain. Well shy of what's needed but it helps. Still two solid months of clouds and only 2" of rain is not a good trade. I'm a bit lost on the image scale. 155mm at f/7 is 1085mm focal length while f/9 at an aperture of 180mm is 1620 or a 49% increase. Increasing .87 by 49% gives a 1.3" pixel. Does the flattener make the difference? You are right about image scale Rick. I went by memory thinking my focal length was 1215mm. It is 1085 as you said. the image scale is 1.27"/pixel instead of the 1.15 I stated above. so moving from the '180 f/9 at 1620 to the '155 f/7 at 1085mm gives me 1.27"/pixel instead of 0.87"/pixel I did a lot last week: Sunday I flew to Taipei and had a week's worth of biz meetings, flew home friday evening, drove to the ranch upon landing, set up the scope and imaged. I got crap for data that night but found the warts and fixed them for sat night. I guess in the confusion I just did not remember my focal length correctly.. thanks for double-checking! here is the view from my hotel room.... that's Taipei 101, the tallest building in the world (at least today it is). |
#4
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ASTRO: First light, AP155EDF f/7 and PL39000C, target M8/M20
Mighty image Richard.
The faster setting suits the camera well obviously. 0.87"/pixel were probably a bit of an "overkill" for those large nebulae, so you probably didn't lose anything by going for the shorter focal length. Stefan "Richard Crisp" schrieb im Newsbeitrag m... I have been attempting to use the '155 f/7 with the PL39K for three weeks now. The faster focal ratio, f/7 versus the f/9 of the '180edt, means nearly a 2x improvement in light gathering rate with a modest increase in image scale: 1.15 versus 0.87 "/pixel. Finally the weather cooperated on Saturday night. I took 4.75 hours of exposure on Sat night using 15 minute subexposures. the full 39 megapixel resolution on the linked page below is interesting: there are a lot of stars in there! http://www.narrowbandimaging.com/m8_...pl39K_page.htm |
#5
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ASTRO: First light, AP155EDF f/7 and PL39000C, target M8/M20
Richard Crisp wrote:
"Rick Johnson" wrote in message ster.com... Richard Crisp wrote: I have been attempting to use the '155 f/7 with the PL39K for three weeks now. The faster focal ratio, f/7 versus the f/9 of the '180edt, means nearly a 2x improvement in light gathering rate with a modest increase in image scale: 1.15 versus 0.87 "/pixel. Finally the weather cooperated on Saturday night. I took 4.75 hours of exposure on Sat night using 15 minute subexposures. the full 39 megapixel resolution on the linked page below is interesting: there are a lot of stars in there! http://www.narrowbandimaging.com/m8_...pl39K_page.htm Nice resolution on the central "star" of M20. Well resolved. Glad someone sees sky. At least lately the clouds have given up some rain. Well shy of what's needed but it helps. Still two solid months of clouds and only 2" of rain is not a good trade. I'm a bit lost on the image scale. 155mm at f/7 is 1085mm focal length while f/9 at an aperture of 180mm is 1620 or a 49% increase. Increasing .87 by 49% gives a 1.3" pixel. Does the flattener make the difference? You are right about image scale Rick. I went by memory thinking my focal length was 1215mm. It is 1085 as you said. the image scale is 1.27"/pixel instead of the 1.15 I stated above. so moving from the '180 f/9 at 1620 to the '155 f/7 at 1085mm gives me 1.27"/pixel instead of 0.87"/pixel I did a lot last week: Sunday I flew to Taipei and had a week's worth of biz meetings, flew home friday evening, drove to the ranch upon landing, set up the scope and imaged. I got crap for data that night but found the warts and fixed them for sat night. I guess in the confusion I just did not remember my focal length correctly.. thanks for double-checking! here is the view from my hotel room.... that's Taipei 101, the tallest building in the world (at least today it is). That's one massive building. The Asians seem to be building "The Tallest Building" every few years. I think it is too many years as a CPA but when numbers just don't work something in my brain goes off. I know its wrong, just not what or by how much. But I have to figure it out or go nuts thinking about it. I hate long flights all cramped up. Going east always gives me a three or four day period I'm worthless for anything. No way I could have even tried imaging after that return trip. West doesn't seem to bother me. Lived next to a Pan Am pilot for years when I lived in Lincoln Nebraska. He flew a round the world route from LA returning to Kennedy about 6 days later. They only set those routes going west. East flights were only one leg if crossing more than 2 time zones. He had the seniority that he could and did refuse anything going east. Not bad gig, fly around the world once every two weeks, work for 6 days and be off for 8. Rick -- Correct domain name is arvig and it is net not com. Prefix is correct. Third character is a zero rather than a capital "Oh". |
#6
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ASTRO: First light, AP155EDF f/7 and PL39000C, target M8/M20
"Stefan Lilge" wrote in message ... Mighty image Richard. The faster setting suits the camera well obviously. 0.87"/pixel were probably a bit of an "overkill" for those large nebulae, so you probably didn't lose anything by going for the shorter focal length. Stefan Thanks Stefan the only reason it was first used on the '180 was because it was set up already for the PL9000 and robofocus. My key obstacle to deploying it on the '155 was coming up with a way to connect my robofocus to it. That wasn't very hard: it was harder waiting three weeks for the skies to clear..... |
#7
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ASTRO: First light, AP155EDF f/7 and PL39000C, target M8/M20
"Rick Johnson" wrote in message ster.com... I hate long flights all cramped up. Going east always gives me a three or four day period I'm worthless for anything. No way I could have even tried imaging after that return trip. West doesn't seem to bother me. Lived next to a Pan Am pilot for years when I lived in Lincoln Nebraska. He flew a round the world route from LA returning to Kennedy about 6 days later. They only set those routes going west. East flights were only one leg if crossing more than 2 time zones. He had the seniority that he could and did refuse anything going east. Not bad gig, fly around the world once every two weeks, work for 6 days and be off for 8. I finally managed to sleep on the return trip. Slept most of the way. Biz class seats make a huge difference! usually going East is the killer for me. This time it was heading west: the departure from SFO is 1:40AM so it has already been a long day. Then the flight is 14 hours and when yuo land it is 6am.... the beginning of yet another long day. Only way to make this work is to find a way to sleep on the way over.... But I was whacked all week over there.... I do this every month now :-( |
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