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Dark sky site or not?

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#1 psugrue


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Posted 12 August 2022 - 10:45 PM

OK so having been an astronomer for a little over 2 or 3 years now, I think I am starting to work some things out. Please correct me if I am wrong. So in terms of AP, everything is a dark site target. However some more than others. The moon for example does very well in light polluted areas as does Jupiter but maybe not quite as well? Then we have M42 which is pretty bright AND you can use NB filters so that does OK. The worst target for urban settings is The Milky Way (I just got a 24mm f1.4 so I can have a crack at this.) And M31 is pretty bad and unlike M42 that I can do from my drive way, I should just suck it up and drive for 2 hours to go somewhere nice and dark!


Again, please let me know if any or all of this is rubbish.





#2 dave85374


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Posted 12 August 2022 - 10:58 PM

Dark sky is always better, but determining if you want to drive a long way to get to one is another.  It sky might be nice from your back yard or 15 minutes away but it might be worse two hours away.  I say that because some people in England (per notices out here on this site) have that problem and then they spend all the time getting there and back plus the hotel for the night.  The finally figured that a HyperStar with one filter loaded inside the HS made all the difference.


Out dark sky site is 35 miles away with Bortal 4.5 vs out local 6.0 and my HS makes a big difference in my back yard.  But I will admit that I definitely see more stars out there than my back yard.  We go out there once or twice a month depending on the weather but my back yard gives me much pleasure.  I guess the question is are you satisfied with your views in your local area and how far do you have to drive to get darker.  I could get darker with a 75 minute drive but I would have to go out there by myself which poses a problem for my.

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#3 Pantilas


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Posted 13 August 2022 - 01:44 AM

The moon and the planets are very bright. You don't need to go to a dark site to image them. For these targets seeing is far more important then a dark site. Wait for a good night of seenig or go as high as you can. This site make some predictions, but I don't know how accurate they are. Probably enought to decide if it's worth it to image: https://www.meteoblu...rsports/seeing/

For emission nebulas you can use narrwoband filters to overcome a lot of light pollution.


Broadband targets suffer the most under light polluted skies, because you can't filter out the light pollution.
When I go from my B4 to the B2, I choose dim targets and dark nebulas / dust clouds. NGC7023 is a good example. You get much more of the dark dust around the nebula when imaging from a dark site.

M31 is relatively bright and you can image it from a B6. You should get decent results with a few hours of integration.

Generally, the key is an automated and easy to use rig. When it takes you 15min to setup everything and it captures the data automatically during the night, you end up with a lot more total integration time for your final image, because you'll do it more often.

Edited by Pantilas, 13 August 2022 - 01:45 AM.

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#4 speedster


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Posted 13 August 2022 - 03:31 AM

Not rubbish but certainly something to deal with.  I'm in B8 urban light pollution but I don't hesitate to go after whatever target strikes my fancy.  I decided to image where I am rather than travel to a darker site because I'll do much more work in the convenience of my backyard than having to plan, travel, and spend so much time setting up and tearing down.  Bright skies are by no means hopeless but they do take some different technique and some processing frustrations to overcome sometimes.  For me, it's relatively short exposures, never more than 90 seconds, and an L-enhance filter on all DSOs, even broadband targets.  Also more time on target.  I try to get 6 hours on anything and twice that on some.  When my capture and processing technique get so good that the only thing between me and an APOD is sky brightness, then I'll get serious about a truly dark site.  Until then, I've made peace with suburban skies and don't let it slow me down.  This jellyfish nebula needs star reduction and some things I'll do on another processing run but you can see what is very doable under B8 skies.  C11 and ASI071 for several of these. Some C8 and Sony A6000.


jellyfish ps2 sm.jpg


For more B8 images, https://www.mccathren.com/astronomy/

Edited by speedster, 13 August 2022 - 03:32 AM.

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#5 Borodog


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Posted 13 August 2022 - 02:48 PM

Going from my B5 back yard to B4 15 minutes away makes a massive difference in imaging time. I calculated I can reach the same SNR on a target in 36% of the time.

However . . . I probably won’t be doing it much. Setting up in my backyard, I can actually SLEEP. Last month when I shot the Pelican nebula at the dark(er) site, except for the social interaction (was a star party) it was a pretty miserable experience. I made it to 2am before I thought I was going to die and packed up and left.

Edited by Borodog, 13 August 2022 - 02:49 PM.

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#6 danny1976


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Posted 13 August 2022 - 03:32 PM

In the wintertime I rent a airbnb for a couple of days. I search for a dark location and ask the owners if there are any lights on at night. This way I have 12h imaging time and don’t need to stay outside all the time. 


Some people laugh with this but for me that’s the only way to image at a dark location.

Edited by danny1976, 13 August 2022 - 03:34 PM.

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