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ASTRO: SH2-282
Sh2-282 is an emission nebula excited by HD 47432, an O9 star which is
the bright star that gave me fits in the upper left of the image. It seems to be surrounded by a faint bubble or maybe just an arc of HII emission. I thought it part of the horrid reflection it gave me but it is real. Galaxy map puts it about 5000 light years distant one place and another says it is about 4000 light years away. Take your pick. I can't fit it all into my frame so picked the more interesting, to me at least, part to include. Galaxy map says it contains 8 cometary globules. What I see are lots of dense shock fronts all pointing right to the exciting star. This is an HaLRGB image. HA was added to the luminosity data using the lighten mode. It was added at 80% to the red image, 10% to the green and 20% blue also using lighten mode. Stars were removed from the H alpha image before the blend so are pure LRGB. The image is noisy. I needed considerable more H alpha time. If I find time to get more I'll rework it. This data is from last January. 14" LX200R @ f/10, Ha=3x30' L=4x10' RGB=2x10'x3, 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: SH2-282
Excellent image -
I haven't imaged the winter Sharpless objects, I tend to favor wintergalaxies and the bright nebulae. On Tue, 16 Nov 2010 22:47:01 -0600, Rick Johnson wrote: Sh2-282 is an emission nebula excited by HD 47432, an O9 star which is the bright star that gave me fits in the upper left of the image. It seems to be surrounded by a faint bubble or maybe just an arc of HII emission. I thought it part of the horrid reflection it gave me but it is real. Galaxy map puts it about 5000 light years distant one place and another says it is about 4000 light years away. Take your pick. I can't fit it all into my frame so picked the more interesting, to me at least, part to include. Galaxy map says it contains 8 cometary globules. What I see are lots of dense shock fronts all pointing right to the exciting star. This is an HaLRGB image. HA was added to the luminosity data using the lighten mode. It was added at 80% to the red image, 10% to the green and 20% blue also using lighten mode. Stars were removed from the H alpha image before the blend so are pure LRGB. The image is noisy. I needed considerable more H alpha time. If I find time to get more I'll rework it. This data is from last January. 14" LX200R @ f/10, Ha=3x30' L=4x10' RGB=2x10'x3, STL-11000XM, Paramount ME Rick |
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ASTRO: SH2-282
Rick -
How dark is your sky, I ask because your exposure time seems to indicate dark sky's and the ClearSkyChart for Mantrap Lake doesn't have a light pollution map. I would love to live in a dark sky area but the boss (my wife) has veto power on those type decisions. Below is an out of date LP map for my location. There has been significant development to the west in the last few years, greatly adding to the LP. I pretty much limit my imaging to northeast quadrant and even then I'm fighting significant gradients. |
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ASTRO: SH2-282
On 11/17/2010 11:16 AM, glen youman wrote:
Rick - How dark is your sky, I ask because your exposure time seems to indicate dark sky's and the ClearSkyChart for Mantrap Lake doesn't have a light pollution map. I would love to live in a dark sky area but the boss (my wife) has veto power on those type decisions. Below is an out of date LP map for my location. There has been significant development to the west in the last few years, greatly adding to the LP. I pretty much limit my imaging to northeast quadrant and even then I'm fighting significant gradients. I'm in the middle of no where. Back before cataracts I could easily see 6.5 magnitude at the zenith. Younger eyes were reaching 7. I still don't have glasses since the surgery as one eye remains too swollen to fit for glasses so my vision isn't great. I was 20:1200 without glasses without cataracts I was so nearsighted. Also have several cylinders of astigmatism 3.5 left eye and 4.25 right. That isn't corrected though the lenses do give me nearly correct vision otherwise. Still too poor due to the astigmatism to know how it has helped me see the sky. Still, in summer I can see my fuzzy shadow on the deck and side of the house cast by the light of the Milky Way. My wife grew up in pot hole country of North Dakota where the nearest town was 20 miles away and had 120 people. So living here is just what she likes. She hated living in the city when we were working full time. So the move up here was not a problem. Though she might have preferred the family farm in ND. It's a 4 hour drive west from here so she gets back from time to time. Their skies aren't as dark however. Every farm has several "security lights" that, of course, provide just the light a crook needs to do his thing yet hide in the stark shadows while doing it. So crime is up about 500% since they went in! But farmers like them for working in the yard at night. Result is about 5.5 magnitude skies even though the population is still low. Not as low as here however. This time of the year all have gone south. There's only 4 families that live in this township all winter for a population of 18. Being heavily wooded the few "security lights" here are all well below tree line which is another 40 foot higher and blocks their light almost totally. While I can see nearly three miles across the lake I can see only ONE home or cabin, summer or winter. The only lights it has in summer are well shielded trail lights lighting the path from cabin to dock. They do run all night -- to let the bears find the water? In any case they aren't a problem but can be seen dimly. Other than that, even from atop my hill which is the highest around the lake, I can't see any other lights. Park Rapids has a rather nasty light dome to the SW so avoid imaging there. It has a population of only 3000 but is a tourist town. Each business out-lights the next trying to attract customers that don't exist this time of the year as only locals left now that deer season is over. Some snowmobilers will show once we get a snow base but they are weekenders from Fargo or the Twin Cities. All businesses complain about the high cost of electricity but yet waste it thinking lighting bellies of flying ducks attracts customers. It is so well lit that most drive at night without their lights on! You can see to drive fine but if your car is dark no one sees you. Result is lots of nightly accidents. Editor of the paper has constantly pleaded with folks to turn on their car lights at night and can't fathom why they don't. Comparing the famous night sky photo for Park Rapids at 3000 to towns back in Nebraska with populations of 30,000 you find Park Rapids brighter (though a smaller foot print but not by much). No business will be the first to cut back. Bemidji is 10 miles more distant to the north but has virtually no light dome from here. It too is a tourist town but hasn't gotten into the light trap of Park Rapids, besides, thanks to my Polaris Tree (actually 2 trees) I can't image to the north anyway. My main problem is air glow. It is far worse here than in Nebraska. It is really bad in winter. When it is low my typical background in a 10 minute 2x2 binned image is 250 ADU after dark subtraction. In winter it can hit 1200 or more. Far stronger in green and sometimes red. I've noticed the new Generation 2 filters have reduced the red portion considerably yet seem to have more red sensitivity to red stars and nebula making color balance far easier when I do have air glow problems. Even in green it isn't as much of a problem. No change in the L channel however. Now that the sun is getting active I expect air glow to worsen and faint all sky aurora to start to be a problem. So far I've lost only a couple good nights because of it. When it hits my background in L hits 4000 and I shut down. I expect that to start to be a problem. Most calculators for sky limited exposures say I need subs of over 1 hour. That's more than my normal total exposure time and would so saturate stars there'd be no color left in them. I figure with that low of sky noise I'm still ahead of many as far as total noise goes. I do use 30 minutes for H alpha. Even then my background is usually about 40 ADU after dark subtraction. I'd need 24 hour subs at that rate! 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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