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#11
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ASTRO: NGC 2244 (Rosette nebula)
Nice widefield view of one of my favorite nebulas!
Jon Christensen "Stefan Lilge" wrote in message ... I recently used a night with exceptionally good transparency to image the Rosette nebula. My only previous attempts on this object were done with my Canon EOS300D DSLR camera and some closeups with small CCD chips that only got a small part of the nebula. This time I used a 200mm f/3.5 lens and was quite surprised how bright this object is when imaged with a "proper" CCD camera as it was tough with the DSLR. I will attach a "normal" version and a link to one where I used "drizzle processing" in IRIS. The drizzled version shows more detail, but is also noisier, so I reduced it's size (which was 2x original size) to 75% which helped a bit. Unfortunately I lost one hour of data when the nebula was in it's best position. Taken from the middle of Berlin with a 200mm f/3.5 lens, SXV-H9 camera, AStronomik 13nm Halpha filter, 30x5 minutes. The images can also be found at http://www.slilge.de/temp/2244-30x5gut.jpg http://www.slilge.de/temp/2244-drizzle30x5gut.jpg Stefan |
#12
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ASTRO: NGC 2244 (Rosette nebula)
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#13
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ASTRO: NGC 2244 (Rosette nebula)
"Rick Johnson" wrote
... Thanks for the explanation. Not having used Drizzle I wasn't all that familiar with it. I just posted my partial shot of this nebula. Came out far better than I thought it would. Rick Rick, et al: Drizzle takes advantage of info spread across the images to extract extra resolution when you are forced to under sample. It was invented by the HST guys back when the first camera really under-sampled. The price you have to pay is getting at least 5 good exposures that are slightly shifted, and to be prepared to handle noise. I've always wanted to fool around with it but I haven't taken many under-sampled images. I'm glad to see what great results Stefan got with it on this image. George N |
#14
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ASTRO: NGC 2244 (Rosette nebula)
"Rick Johnson" wrote
....... When the budget allows I'll have to get a good wide angle scope to put atop the LX200R. I had the rings made so I can attach something up there easily......... Rick, I don't know what you had in mind but I was thinking of getting one of those new Meade 127mm APO's. However, a friend has good results with an old Cave 6" F/4 Newt and a coma reducer. Perhaps a Meade 6" Schmidt Newt tube would be a good and inexpensive "toy" for wide-field imaging? It would probably need a new focuser, but lots of people buy them to get the mount and then sell off the tube. At NEAF I was trying to get David Nagler to discuss using Televue's new coma lens (designed to screw into the STL cameras) with the Meade SNT's, but he said that he thought that the Meade SNTs were already coma corrected. I had planned on using our "finder" (80mm Brandon APO) on the 20RC but the focuser needs to be fixed and that won't happen until next month. George N |
#15
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ASTRO: NGC 2244 (Rosette nebula)
"Stefan Lilge" wrote ... I recently used a night with exceptionally good transparency to image the Rosette nebula......... Stefan, Great image! The resolution in your 'drizzle' version is quite impressive. George N |
#16
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ASTRO: NGC 2244 (Rosette nebula)
George Normandin wrote: "Rick Johnson" wrote ....... When the budget allows I'll have to get a good wide angle scope to put atop the LX200R. I had the rings made so I can attach something up there easily......... Rick, I don't know what you had in mind but I was thinking of getting one of those new Meade 127mm APO's. However, a friend has good results with an old Cave 6" F/4 Newt and a coma reducer. Perhaps a Meade 6" Schmidt Newt tube would be a good and inexpensive "toy" for wide-field imaging? It would probably need a new focuser, but lots of people buy them to get the mount and then sell off the tube. At NEAF I was trying to get David Nagler to discuss using Televue's new coma lens (designed to screw into the STL cameras) with the Meade SNT's, but he said that he thought that the Meade SNTs were already coma corrected. I had planned on using our "finder" (80mm Brandon APO) on the 20RC but the focuser needs to be fixed and that won't happen until next month. George N As as stop gap measure I was thinking of that STL lens you mention with my Optical Craftsman 6" f/4. I'll have to replace the spider as it is warping so I couldn't keep it in collimation. Move the scope to the other side of the meridian and it lost all collimation. It had been adjusted so many times over the 45 years I've owned it it just won't hold any more. The mirror in that scope is fantastic. It easily beat the best RV-6 mirror of the era in our club at high power even with the huge secondary. So if I can get it to hold collimation and that lens works it would be a cheap way to go. As is, with the ST-7 it has almost exactly the same FOV as the 14" with the STL-11000! So if you hear anything about those at f/4 let me know. Think they are designed for f/4.5. With the 11000's large chip that may not work at the corners. 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". |
#17
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ASTRO: NGC 2244 (Rosette nebula)
Stefan, Nice shot!
dirk "Stefan Lilge" wrote in message ... I recently used a night with exceptionally good transparency to image the Rosette nebula. My only previous attempts on this object were done with my Canon EOS300D DSLR camera and some closeups with small CCD chips that only got a small part of the nebula. This time I used a 200mm f/3.5 lens and was quite surprised how bright this object is when imaged with a "proper" CCD camera as it was tough with the DSLR. I will attach a "normal" version and a link to one where I used "drizzle processing" in IRIS. The drizzled version shows more detail, but is also noisier, so I reduced it's size (which was 2x original size) to 75% which helped a bit. Unfortunately I lost one hour of data when the nebula was in it's best position. Taken from the middle of Berlin with a 200mm f/3.5 lens, SXV-H9 camera, AStronomik 13nm Halpha filter, 30x5 minutes. The images can also be found at http://www.slilge.de/temp/2244-30x5gut.jpg http://www.slilge.de/temp/2244-drizzle30x5gut.jpg Stefan |
#18
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ASTRO: NGC 2244 (Rosette nebula)
"Rick Johnson" wrote As as stop gap measure I was thinking of that STL lens you mention with my Optical Craftsman 6" f/4. I'll have to replace the spider as it is warping so I couldn't keep it in collimation. Move the scope to the other side of the meridian and it lost all collimation. It had been adjusted so many times over the 45 years I've owned it it just won't hold any more. The mirror in that scope is fantastic. It easily beat the best RV-6 mirror of the era in our club at high power even with the huge secondary. So if I can get it to hold collimation and that lens works it would be a cheap way to go. As is, with the ST-7 it has almost exactly the same FOV as the 14" with the STL-11000! So if you hear anything about those at f/4 let me know. Think they are designed for f/4.5. With the 11000's large chip that may not work at the corners. Rick, You might have to put a new focuser on the 6-inch F/4 because focus is so tight at that f-ratio. However, with the good mirror I'd bet that you could get the OC scope to work with a coma lens. My friend with the Cave 6" F/4 put a Moonlight focuser on it and uses a coma corrector from Baader (http://www.alpineastro.com/). He's using a camera with a chip about the size of an ST-7's. However if the coma gets too much in the corners of the STL-11k just cut the corners off! I got use to round images back in my days of using a Lumicon 4x5" camera (3.8" circle of film exposed). You would get a huge field even if you lost a little and it would be fun getting the old 6-inch scope working for imaging. George N |
#19
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ASTRO: NGC 2244 (Rosette nebula)
George Normandin wrote: "Rick Johnson" wrote As as stop gap measure I was thinking of that STL lens you mention with my Optical Craftsman 6" f/4. I'll have to replace the spider as it is warping so I couldn't keep it in collimation. Move the scope to the other side of the meridian and it lost all collimation. It had been adjusted so many times over the 45 years I've owned it it just won't hold any more. The mirror in that scope is fantastic. It easily beat the best RV-6 mirror of the era in our club at high power even with the huge secondary. So if I can get it to hold collimation and that lens works it would be a cheap way to go. As is, with the ST-7 it has almost exactly the same FOV as the 14" with the STL-11000! So if you hear anything about those at f/4 let me know. Think they are designed for f/4.5. With the 11000's large chip that may not work at the corners. Rick, You might have to put a new focuser on the 6-inch F/4 because focus is so tight at that f-ratio. However, with the good mirror I'd bet that you could get the OC scope to work with a coma lens. My friend with the Cave 6" F/4 put a Moonlight focuser on it and uses a coma corrector from Baader (http://www.alpineastro.com/). He's using a camera with a chip about the size of an ST-7's. However if the coma gets too much in the corners of the STL-11k just cut the corners off! I got use to round images back in my days of using a Lumicon 4x5" camera (3.8" circle of film exposed). You would get a huge field even if you lost a little and it would be fun getting the old 6-inch scope working for imaging. George N It isn't a coma problem at the corners, but a curvature problem. If focus is dead on there is no distortion at the corners. It happens only if the center is focused in to the maximum F/10 allows. That puts the corners just barely at the out extreme of focus. If it cools any the focus moves out just a tad and there go the corners but the center is fine. Robo-Focus's temp compensation handles this when I can get it to turn on. If I can't then I just have to manually focus and cross my fingers. 6" F/4 already has a JMI motor focus on it that is run by the Paramount. It works very well. I used it as my scope for a couple months waiting for the LX200R OTAs to hit the market. For a while Meade only sold them on their fork mount. Scope was nice and fast and with the ST-7 had almost exactly the same FOV as the LX200R with the STL-11000 but usually no sooner did I collimate the spider than I'd park the scope to roll the roof and that motion would cause it to go out of whack again. Gave me large stars on the right side of most images as the field was tilted. I've got to replace that spider before I try the lens and make sure it will hold in place. To fully illuminate the STL-11000 I'll need an even larger secondary. Might just live with the vignetting and flat field it out. 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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