#1
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ASTRO: M22
There seems little agreement on its size and distance. I've seen
reports of 10,400 light-years to 8,500 light-years for its distance and 200 light-years to 50 light-years for its diameter. It appears the latter differences are due to how the edge of it is measured. Just the star ball would give the smaller diameter, including further stars would lead to a larger diameter. Since this one is located against the stars of the Milky Way, how you define its "edge" is extremely difficult. Still, the wide disagreement surprised me. My image is rather poor. This object is located at about -24 degrees. My seeing goes to pot about -15 degrees. I finally had an extremely good night so gave it a try. At higher declinations stars were about 2" of arc in size or smaller in some cases but down low it was about 3.25". Far worse than I normally would process but likely the best I'll do from this location. I'd hoped to see the planetary but only its central star shows. The nebula is lost in the large size of about 7" of the central star. It just won't show at my latitude, too much atmosphere to distort the image. It might show in an OIII image but I don't have that filter. It contains no hydrogen so H alpha is useless on this planetary. It's also strong in IR but my sensor has little IR sensitivity so that doesn't help either. Stars are rather elongated due to atmospheric refraction. This low I really need to use a pseudo lum image made from the RGB frames aligned to eliminate the chromatic refraction of our atmosphere this low. I did do that for the RGB part of this image. This resulted in smaller stars in the RGB image even though they were taken at 1.5" per pixel than I had in the luminosity image at 1" per pixel. But I took too few and too short RGB images to get a sufficient signal to noise ratio to use these as a pseudo luminosity image. I may go that route if I ever get a good enough night. Actually it would take nights as I can only image this one for about 2 hours at best thanks to my Meridian Tree being in the way. I have an hour or so on either side of the tree before it gets so low seeing is really awful. If I could cut down the tree (that's illegal) I'd have nearly 4 hours of image time a night not 2 and those additional hours would be in the best seeing. Where are those beavers anyway? 14" LX200R @ f/10, L=6x5', RGB=2x10', STL-11000XM, Paramount ME 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". |
#2
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ASTRO: M22
Rick,
very good result for such a low object. I would probably consider to image a HII region that low with a short focal length, but a globular is very difficult in the "bad seeing zone". Stefan "Rick Johnson" schrieb im Newsbeitrag . com... There seems little agreement on its size and distance. I've seen reports of 10,400 light-years to 8,500 light-years for its distance and 200 light-years to 50 light-years for its diameter. It appears the latter differences are due to how the edge of it is measured. Just the star ball would give the smaller diameter, including further stars would lead to a larger diameter. Since this one is located against the stars of the Milky Way, how you define its "edge" is extremely difficult. Still, the wide disagreement surprised me. My image is rather poor. This object is located at about -24 degrees. My seeing goes to pot about -15 degrees. I finally had an extremely good night so gave it a try. At higher declinations stars were about 2" of arc in size or smaller in some cases but down low it was about 3.25". Far worse than I normally would process but likely the best I'll do from this location. I'd hoped to see the planetary but only its central star shows. The nebula is lost in the large size of about 7" of the central star. It just won't show at my latitude, too much atmosphere to distort the image. It might show in an OIII image but I don't have that filter. It contains no hydrogen so H alpha is useless on this planetary. It's also strong in IR but my sensor has little IR sensitivity so that doesn't help either. Stars are rather elongated due to atmospheric refraction. This low I really need to use a pseudo lum image made from the RGB frames aligned to eliminate the chromatic refraction of our atmosphere this low. I did do that for the RGB part of this image. This resulted in smaller stars in the RGB image even though they were taken at 1.5" per pixel than I had in the luminosity image at 1" per pixel. But I took too few and too short RGB images to get a sufficient signal to noise ratio to use these as a pseudo luminosity image. I may go that route if I ever get a good enough night. Actually it would take nights as I can only image this one for about 2 hours at best thanks to my Meridian Tree being in the way. I have an hour or so on either side of the tree before it gets so low seeing is really awful. If I could cut down the tree (that's illegal) I'd have nearly 4 hours of image time a night not 2 and those additional hours would be in the best seeing. Where are those beavers anyway? 14" LX200R @ f/10, L=6x5', RGB=2x10', STL-11000XM, Paramount ME 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". |
#3
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ASTRO: M22
It took me 5 years to have a night I could do this. Rather rare event.
I need a really super dry day with a north wind to keep the gunk layer from forming over the lake. Then seeing has to be super. Not common with wind here. Wind seems to mix the air too much creating horrid fast seeing so you can't begin to find a focus but this night was the exception. Still that low red and blue didn't line up with green and even Registar couldn't handle it very well. I should have taken more RGB frames at normal binning and ignored L since it just couldn't handle the prism effect of the atmosphere. If I ever can try again I'll know better. Rick On 4/21/2010 2:33 PM, Stefan Lilge wrote: Rick, very good result for such a low object. I would probably consider to image a HII region that low with a short focal length, but a globular is very difficult in the "bad seeing zone". Stefan "Rick schrieb im Newsbeitrag . com... There seems little agreement on its size and distance. I've seen reports of 10,400 light-years to 8,500 light-years for its distance and 200 light-years to 50 light-years for its diameter. It appears the latter differences are due to how the edge of it is measured. Just the star ball would give the smaller diameter, including further stars would lead to a larger diameter. Since this one is located against the stars of the Milky Way, how you define its "edge" is extremely difficult. Still, the wide disagreement surprised me. My image is rather poor. This object is located at about -24 degrees. My seeing goes to pot about -15 degrees. I finally had an extremely good night so gave it a try. At higher declinations stars were about 2" of arc in size or smaller in some cases but down low it was about 3.25". Far worse than I normally would process but likely the best I'll do from this location. I'd hoped to see the planetary but only its central star shows. The nebula is lost in the large size of about 7" of the central star. It just won't show at my latitude, too much atmosphere to distort the image. It might show in an OIII image but I don't have that filter. It contains no hydrogen so H alpha is useless on this planetary. It's also strong in IR but my sensor has little IR sensitivity so that doesn't help either. Stars are rather elongated due to atmospheric refraction. This low I really need to use a pseudo lum image made from the RGB frames aligned to eliminate the chromatic refraction of our atmosphere this low. I did do that for the RGB part of this image. This resulted in smaller stars in the RGB image even though they were taken at 1.5" per pixel than I had in the luminosity image at 1" per pixel. But I took too few and too short RGB images to get a sufficient signal to noise ratio to use these as a pseudo luminosity image. I may go that route if I ever get a good enough night. Actually it would take nights as I can only image this one for about 2 hours at best thanks to my Meridian Tree being in the way. I have an hour or so on either side of the tree before it gets so low seeing is really awful. If I could cut down the tree (that's illegal) I'd have nearly 4 hours of image time a night not 2 and those additional hours would be in the best seeing. Where are those beavers anyway? 14" LX200R @ f/10, L=6x5', RGB=2x10', STL-11000XM, Paramount ME 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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