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Hi! While I look forward to narrowband images (SHO) to eliminate my light pollution problems (and more), I am not quite there yet. I am located right on the cusp between a very heavily light polluted area and a much less light polluted area (with heavy light pollution to the north and much darker skies to the south). While I know there is a lot of room for improvement in my images across the board from acquisition to process and everywhere in between, I am seeking to improve in any way possible; and based on the quality difference in my Eagle Nebula piece versus all others thus far, it seems that I may be getting higher quality subs by shooting objects in the southern skies. Is this a feasible conclusion or am I overthinking this? Thanks and Clear Skies! |
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Hi schmaks, It makes perfect sense to avoid the most light-polluted part of the sky, at least for nebulae and galaxies (it will still work okay for star clusters). For me it's W-SW that is excluded because most of the city resides in that direction (plus a rather annoying neighboor on the apartment right across the street with a huge TV bright enough for objects in my balcony to cast shadows even with the balcony lights turned on, although admittedly they never watch after midnight). Furthermore, all the low hanging fruit is in the southern half of the sky: Virgo, Orion, Scorpius, Sagitarius. You are lucky you live on that side of the light polluted area. Cheers, Dimitris PS: narrowband is almost immune to light pollution (manmade or moonlight) but is not the same as not having light pollution. You will not be imaging he same stuff, for starters. This is not to say you cannot produce very fascinating images, but subjects simply do not look the same as they do in broadband. Closest analogy that I can think of is a portrait of an individual vs a facial x-ray of that same individual. Admittedly not a very good analogy but you get the idea. Plus it brings in its own class of problems because it requires much longer exposures. It is not that you *can* take 5 or `10 minute subs. It's that you *must*. And you don't need longer exposures just for imaging, but also for focusing and target acquisition. Ever tried focusing when you need a `15 second exposure to see the out-of-focus stars? I just did. Can't say it was very pleasant. And the plate solving that is necessary for centering (or even just framing) targets would fail 5 times out of 6. |
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Cheers,Dimitris Thanks, Dimitris! This all makes sense. I am going to stick with the southern skies for now and see how things go. With southern skies in mind and a wide field (430mm) telescope... any must-shoot targets come to mind? I am thinking of the Helix Nebula for my next round since I should be able to get a lot of light from it this time of year. I know it'll be a bit tiny, but I'll see what I can do. Open to suggestions! I hadn't thought of the plate solving issue with narrowband imaging—how do folks get around this? On the focusing from, I suppose I could just leave a filter space open in the wheel and use that for focusing so long as you aren't focusing throughout the night, but I don't know about plate solving. I wonder if you could do something similar and have the filter programmed to the open filter spot in the wheel to plate solve. I use the ZWO ASIAIR PRO and would be curious if this is a possibility with it. Further down the rabbit hole, could I hypothetically get a color ZWO camera (or any astro camera for that matter) and do narrowband with it so I have the option of broadband imaging as well or would I run into issues? Thanks! |
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I am heavily in a huge light polluted part of a metropolitan area. I would suggest you just look straight up, in nearly any situation that is the least light polluted. But I would suggest doing the measurement for yourself. It doesn't take long--one image at the same exposure in each direction at the same time, and I would bet you would find the zenith gives you the lowest background by far, and also offers you much better resolution due to less atmosphere in your way. My telescope is always pointed way up, as much as I miss those low targets in the south. CS Rick |
