Might as well stay home?

[Bruce D]

OK, I'm pulling the pin...

Something I've been wondering about for a while now, maybe yoou can clue me in.

We all love the images you people take during trips to Stellafane, AH, and other dark sites but honestly, I don't think they look any better than the images you all take from here at home. Is the trip to dark sites a waste of gas? Or are you choosing targets that you couldn't image from home? What gives-

[AstroGeek]

Bruce,
Post-processing can do wonders for light pollution removal. The glow from Bridgewater State College, the prison, Brockton and Taunton is most likely what killed my visual observing days. I still think, however, that images show fainter nebulosity and finer detail from a dark site to begin with.
Just my two-cents worth...
Steve

[Mark G]

I agree with Steve, and not to mention sharing the dark sky with 30 other ASSNE members, camping.

[Bruce D]

Right Mark, it's fun to hang out with 30 ASSNE members even when it's raining!

It would be interesting to see some "Stellafane/Home" images of the same objects so we can compare the differences. Good point Steve, the eye can't do post-processing

[Pete]

Theoretically a single 10 minute exposure should have a higher signal to noise ratio than a stack of five 2 minute exposures. Skyglow is the major source of image noise, and urban skyglow will sometimes limit the length of exposures. In this context, imaging from a dark site is superior.

In practice, imaging from a remote site requires a whole lot of effort.

One can post-process much more detail from an image with a high signal/noise ratio. And judging from the excellent results we’re seeing posted the S/N in the Stellafane images would appear to have been very high.

It should be noted that use of filters or the stacking of additional images, and the proper matching of pixel size and focal ratio will also improve S/N for those imaging under less than pristine skies.

Pete

[Paul D]

Right Mark, it's fun to hang out with 30 ASSNE members even when it's raining!

It would be interesting to see some "Stellafane/Home" images of the same objects so we can compare the differences. Good point Steve, the eye can't do post-processing

Bruce in order to properly compare two images the conditions would have to be exactly the same. I dont think you could actively compare two images because of such unstable conditions.

I can remember one night at Marks many years ago when we were looking at a fragmented comet. If I remember correctly it was an astro day night. Mark and I were seeing individual elements of this fragmented comet as well as atmosphere on Mars through my dob. It was the best night I ever had and this was from a Westport sky not a Stellafane night. So with all that said I think that in a dark sight you would tend to pull out some of the finer details of the object that you are imaging. My knowledge on this subject is limited but I would also imagine the number of stacked images can also make a difference.

Now with all that being said though you get more detail with images you limit yourself to just a few objects a night. For a visual observer the trips out allow me to go just that much deeper in the night sky. People who image I must say I admire, they shoot all these images, then spend massive amounts of time in the post processing. Something I dont think I would have the patience for. Though I must also say that Dan S has a way of slowly dragging me into this imaging thing when he convinced me to buy a tripod at Stellafane to mount my camera on and take some milky way images which I may attempt at Arunah Hill...

[Rotorhead]

Stay home or go someplace dark??? Hmmm. All those astroimagers out west who are buying into Arizona Sky Village, or the new place in New Mexico must have one of two reasons to move: they just want to get away from non-astronomers, or they are onto something.

[Pete]

For "clean" noise-free imaging of extended objects, working with a dark sky gives one a very significant advantage. I've just completed reading a series of 5 articles posted by Dr Craig Stark (of PHDGuiding fame). The lengthy article starts at
http://www.cloudynights.com/item.php?item_id=1966
and it examines signal to noise ratios exhaustively. Only now do I understand why one can successfully run PhotoShop's levels & curves routine to bring out great detail on some images while other images will fall apart.

For extended objects such as the really faint outer arms of a galaxy, the total electron count in a given pixel may run 2050, and of that total count, 2000 of those electrons may be noise. Skyglow can be a major source of this noise. After subtracting the noise, the remaining 50 electrons isn’t much signal to "expand" and pull all kinds of gray scale detail from.

It turns out that short focal length scopes with fast f/ratios are typically superior to long focal length higher f/ratio scopes when it comes to imaging extended objects. Long focal length SCTs like mine are superior for high resolution work but are terrible for aesthetic imaging.

So yes, imaging from a dark sky site will produce cleaner individual exposures, and require a whole less imaging time than would be required to achieve equivalent quality locally. For example, a stack of 15 one-minute images taken at Stellafane might produce a great quality highly detailed noise-free image, where one may have to stack more than 100 images taken locally with the same setup to achieve the same result. It’s all about S/N. I think.

Pete

[Dan S]

...

[NGC7000]

Well, Bruce, I'm not sure anymore. last night I was out in my Light Polluted backyard with the little ETX60. I didn't even put it on a tripod. I had it table top, not level, and approximated the CNP. I attached the DSI 3 with a low profile nose and took 21 second exposures of M27 along with some darks. The temperature of the sensor was 25 d C

So go figure. I had a nice time observing and imaging.. slept in my own bed..not much to break down, and Voila!











Tom