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Rookie question. How dark is MY sky?
A question but first some background by way of introduction...
I've gone the typical route of a lifelong "journal interest" in astronomy that started (and ended in practical terms) with a dept store refractor. A recent bonus (some 30 years later) made it possible to indulge a long-term lust for a Meade GOTO scope. So about 4 weeks ago I bought a used 10" F/10 and have since spent nearly as much again on a micro focuser, dew control, eyepieces, filters (on back order) and books. CCD will have to be funded with the next bonus :-) I've followed a (disturbingly) typical learning curve on this scope too (only 5 sessions so far): 1. Digest MAPUG, absorb loads of theory and opinion, buy an LX200 2. Setup, look ETX90 (other new scope - another story) is better! 3. Decide cool-down time must be critical (didn't believe). Next time 4. Setup, cool down, look improvement, but still not good. So 5. decide collimation is MUST do too, not just "should do". Next time 6. Setup, cool down, (deep breath) collimate, look ecstatic!!!!! 7. discover looking is a skill which improves with practice too! 8. Next time, clarity and seeing better now understand the effects 9. Friday night best views yet including (possibly) difficult objects Although I "knew" all these things from reading, it was just theory and I got problems from lack of practical experience. Which leads me to my question as that's related to lack of experience too and I hope you seasoned observers can answer it for me. I have read much about the joy of "dark skies" and intend to travel to find some. But what I saw in my last session makes me wonder if I already have them over my house (5 miles S of Buckingham in the UK)! I have no prior experience to compare against so can someone confirm if the following couple of observations sound like they're from a great site (or not)? 26/7/03 @ 0200BST. Using 10" F/10 LX200 (non-UHTC) + 12mm Nagler. The air was not stable enough for more mag than this (211X)). The Milky Way was prominent to the naked eye; almost horizon to horizon. The dark lanes were clear and the nebulous clumps in Cygnus looked semi-solid. No moon and clear sky, but faint haze and light pollution below about 35 deg to the South. Andromeda visible to the naked eye. With the scope, I got acres of black between both components of the double-double. I also saw 3 diffraction rings around the stars (in focus) during a moment of particularly stable air. Is that a sign of good skies as well as good collimation (the rings were a bit broken due to turbulence, but there was clearly 3 concentric "layers" there)? M27 wasn't a dumbbell! It was vaguely rectangular with faint semi-circular extensions to each side (as in the astrophoto in Burnhams but I didn't think you could "see" images like that). Central star was a faint blue spark in direct vision, but vivid blue with averted vision. Like the central star of M57, I expected this to be too faint to see. Mag 13.9 isn't it? The question is, can I improve this (very pleasing) performance by travelling elsewhere or should I save time and petrol? At 77 metres I know getting higher will improve seeing (less air), and I don't discount the social aspects of star parties etc. But in general terms, am I wasting time looking for darker skies? If I will only achieve marginal improvement over what I get at home, then I would consider it a pointless exercise. What reference objects do you use (and how) to empirically compare clarity and darkness of skies between one place and another? Cheers Beats |
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Rookie question. How dark is MY sky?
On 30 Jul 2003 11:07:56 -0700, (justbeats)
stepped up to the plate and batted: and how) to empirically compare clarity and darkness of skies between one place and another? I always use Attila Dankos sky clock pages Check out the sky clock closest to you from http://www.cleardarksky.com/ Once there, click the light pollution map link for a clor coded map of light pollution levels. General light pollution levels can be defined using the Bortle scale, a description of which you'll find he http://novac.com/light/def.htm Hope this helps. G../0 |
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Rookie question. How dark is MY sky?
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Rookie question. How dark is MY sky?
Shankar Bhattacharyya wrote in message . ..
Ben Nevis is a molehill. My father, who walked and bicycled over a good bit of the UK in his student days, says it has a certain dramatic, spare beauty and is well worth a visit. Still, it is a molehill. Your father is right; Ben Nevis is a very attractive, and altogether respectable summit. Tiny in terms of height above sea level, but not tiny in terms of height from bottom to top, nor in terms of weather. There are plenty of 6000 meter summits in the Himalaya that are smaller from top to bottom than Ben Nevis. Unfortunately, in northern Europe, as in my own part of the world (eastern U.S.), altitude is actually counterproductive for astronomy, because the proportion of cloudy skies increases rapidly with altitude. There *are* times when the summits will be in clear air over an undercast, but the opposite is much more common. - Tony Flanders |
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