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gorann

NGC1579 The Northern Trifid - RGB in full monlight

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I am back from the south Pacific to a wet and damp winter in Sweden. However, it did clear up on Sunday night and I aimed at the Northern Trifid Nebula. Since the moon was virtually full, my plan was to collect Ha with the Esprit 150 and ASI1600 mono. Since my Esprit 100 was sitting next to it, I though what the heck, I put my ASI071 on it and collect some RGB that I could maybe use for star colour later. I got about 7 hours with each scope, but the Ha data was quite uninteresting. Not much structure there and seeing was apparently not the best - probably ice crystals in the sky, so guiding suffered too (ca 1.3" RMS).

To my surprise, the RGB data looked much more interesting. Maybe it was because of running many short exposures (140 x 3 min) in an effort to not be totally blinded by the moon. Not sure that this is supported by theory (what do @vlaiv say?) but it may have been the reason why the data looked usable. So here it is, RGB from an OSC under a nearly full moon. Obviously, a really dark night with great guiding would have brought out more details, but.....

Comments most welcome!

20200112 NGC1579 RGB PS42smallSign.jpg

Edited by gorann
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Welcome back Goran!   Very nice object which I shall add to my to do list and impressive for OSC under a 95% Moon, what did the Ha look like and did you add it in?  

Dave

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Nice image. Too much red in the background that I can't seem to find on other renditions of this target - it is probably artifact rather than actual feature in the image.

Maybe try not to push the image that much? Btw, on topic of the Moon, situation is rather clear - it just acts as another source of LP, and it is same as imaging from large city center. If you otherwise have good skies - like mag21 or more, then these conditions (provided that the Moon was not directly in direction of target) - are pretty much the same as ones that many people (including me) have on regular basis - mag18.5 or so.

On night without moon - it would probably take you something like 1h or so to reach same quality of the image.

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31 minutes ago, Laurin Dave said:

Welcome back Goran!   Very nice object which I shall add to my to do list and impressive for OSC under a 95% Moon, what did the Ha look like and did you add it in?  

Dave


Thanks Dave! It will also remain on my list until I get a truly dark night.

This is what 38 x 10 min of Ha looked like. I ended up not adding it since it actually made no difference. All the Ha seems to be in the nebula and that was bright enough to be easily picked up in the RGB signal.

20200112 NGC1579Ha PS5(GradExt+darker sky).jpg

Edited by gorann
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3 hours ago, vlaiv said:

Nice image. Too much red in the background that I can't seem to find on other renditions of this target - it is probably artifact rather than actual feature in the image.

Maybe try not to push the image that much? Btw, on topic of the Moon, situation is rather clear - it just acts as another source of LP, and it is same as imaging from large city center. If you otherwise have good skies - like mag21 or more, then these conditions (provided that the Moon was not directly in direction of target) - are pretty much the same as ones that many people (including me) have on regular basis - mag18.5 or so.

On night without moon - it would probably take you something like 1h or so to reach same quality of the image.

Thanks Valiv! I will have a go at the red - could be a gradient issue from the moon. As you see from my Ha image above there was very little Ha in the sky around the nebula, so the red in the RGB should probably not be there.

As you say, the conditions were probably about the same as for many of you poor guys that suffer severe light pollution.

EDIT: Here is a version with desaturated red in the sky. Thanks for pointing it out @vlaiv!

 

 

20200112 NGC1579 RGB PS46smallSign.jpg

Edited by gorann
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