gorann

Like it a lot! Wonderful colours and great detail.

I do my initial calibration and stacking in PI before I move over to PS. I save the original subs but throw out the intermediate files created by PI (calibartion, debayering if OSC/DSLR and star alignment since these can always be recreated). Then I also save all the steps I have saved in PS since I often go back and reprocess.. And I save it all on two 4 Tb hard drives and both are now getting quite full, so I will soon have to move over to two new ones. I should probably check the status of the old ones at least yearly and if one of them appear to fail, which they will do one day, I should back the old data up again.

Thanks Wim. Maybe "The Bubble's Dark Companion"? I have now seen it on at least one other image on the net, so it is real and not a result of a dust bunny and me refusing using light frames and instead trying to keep everything clean.

Cool! I found that Aladin (https://aladin.u-strasbg.fr/AladinLite/) is quite effective in finding names even on very small galaxies.

I spent Friday night collecting 13 hours on the well known Bubble nebula (NGC7635) together with two less known emission nebulas, Sh2-159 (down to the right) and NGC7538 (upper right). Aladin Sky Atlas gives no name for the black nebulosity in the centre. RGB collected with Esprit 150 and ASI071 (75 x 5 min). Ha collected with Esprit 100 and ASI1600 (27 x 15 min, Baader 3.5 nm Ha). Both side my side on the Mesu200 in my obsy. Ha added to the red channel in blend mode Lighten as 50%. The Bubble nebula came clearly out as more bluish-red than the others so expect there may be quite a bit of Oiii in it. Clouds moved in at 0100 and they have apparently decided to remian for at least a week.....

Thanks Martin. I think I found these by just surfing around on the sky near Auriga in the Aladin Sky Atlats on the net (POSS2 data).

These are two relatively rarely imaged nebulae in Auriga, and my rudimentary astro knowledge says that one is an emission nebula with a lot of Ha signal (Sh2-241) and the other a reflection nebula (vdb65). I had a bit of a fight with a gradient created by an empty OAG in the image train leaking in light. The reason being that I could not find any stars with the OAG prism and moved the camera to a guide scope. Lesson learned so now I know that I need to plug the camera tube of the OAG properly if not used. RGB collected with Esprit 150 and ASI071 (58 x 5 min) Ha collected with Esprit 100 and ASI1600 (24 x 15 min, Baader 3.5 nm Ha) Side by side on the Mesu200 from my home obsy.

Or maybe the dusty stuff really should be red in a HaRGB version since you have a lot of Ha signal there? But then your HaRGB image would look rather different from the "standard" RGB version of M42. If you do not put Ha into the red channel, but only use it as lum then it will make white dust rather than red dust since there is no strong red signal there to be picked up by the lum. So, in a HaRGB version of it, it probably should be red dust. Maybe make two versions of it, a standard RGB and a HaRGB? Would be interesting to see. And yes, the blend mode Lighten was something I also picked up from Olly, here on SGL.

Very nice Dave! When you blended in Ha with red (and found it too red), did you use blend mode Lighten? That one only puts Ha into parts where it is brighter than the red channel signal. Cheers Göran

Lovely Dave! I have no automatic rain protection so I just have to trust the forcast when I go to sleep and so far I have had no disaster.....🙄

Fantastic bino-imager you have there!

Not bad at all for 5 minutes. And you can use it to save the Trapezium if you also take some longer exposures.

Yes, very nice! The shapes of the stars in the corners indicate that you may not have the optimal distance between the reducer and chip. Could be worth exerimenting a bit with that distance - the distance suggested by the manufacturer is not always to be trusted.

My SQM usually lies between 21.0 and 21.6, so quite dark with no major city within 100 km. The problem with shorter subs is of course data storage and stacking time. In a good night with 5 min subs I may still get nearly 100 subs to stack,

The very best of luck Wim and do not trip over!

If ISO 1600 is optimal for your camera (the same with my Canon 60D) then reducing exposure time would be the way to go next time.

Last nigh was cloudless and virtually moonless but seeing was not great so my guiding was poor, ca 1.0 - 1.5 "/pixel. I was aiming at these neublae with my double Esprit rig. I collected RGB with Esprit 150 and ASI071, and managed to get 82 x 5 min (6.8 hours) before the obsy wall got in the way. Ha was collected with the Esprit 100 and ASI1600MM but after the flip around 22.00, the gain apparently got stuck at the very high setting I used for focusing, so while I took the dog for a last walk and then went to bed, it was just collecting blown out wite frames. So, I ended up with the 4 x 15 min Ha I had before the flip. I added this sparingly to the red channel. I should really get back to this object and collect more Ha and maybe Oiii. I had this problem with the ASI1600 before and assume it is a bug in the ASICAP software and I really should remember to restart the program after framing/focusing to be sure it has not happened. Here is what is written for an APOD image of these nebulae: Will the spider ever catch the fly? Not if both are large emission nebulas toward the constellation of the Charioteer (Auriga). The spider-shaped gas cloud on the right is actually an emission nebula labelled IC 417, while the smaller fly-shaped cloud on the left is dubbed NGC 1931 and is both an emission nebula and a reflection nebula. About 10,000 light-years distant, both nebulas harbor young, open star clusters. For scale, the more compact NGC 1931 (Fly) is about 10 light-years across. Comments most welcome. I know it is a bit soft due to the poor seeing.

This interesting thread has so far only been about gain, but you also need an offset setting. Like many others I always use gain 139 and offset 50 on my ASI1600 to keep things simple and limit the number of master darks needed. Then I adjust exposure time according to the object and filter. For NB I use 10 - 15 min and for Lum I use 2-5 min (or some shorter additional ones if there are very bright stars in there to be tamed). For M42 I would certainly use at least 2 different exposure times, I have not used RGB filters since I have a double rig and collect RGB with my ASI071 OSC. PS, On nights with many clouds passing then using many short exposures could be beneficial since less subs will have to be thrown out,

If I image for several hours I always have a small drift, at least several pixels, so maybe that helps, but I also think that the image integration routines in PI are very effective in remving hot pixels, just like the ones Olly @ollypenriceare using in Astro Art. In any case, after I moved from Nebulosity to PI for my stacking some years ago, I never notice hot pixels in my images (just like all satellite trails are magically gone).

Regarding dithering, my impression is that it is something that makes a difference with noisy cameras and many dead/bright pixels. With my cooled ASI CMOS cameras I have never seen a need to do it. Hot pixels are effectively removed using the stacking routines in PI. Or am I missing something? At least I would not attempt to do it on my dual Esprit rig.

Congrats Carole! would you mind posting your image here for those of us that so not subscribe to AN (I assume it is a British magazine)

Quite an effort Peter! Although I assume you did it all from a cosy armchair in London😉

Yes, excellent indeed, as always! Did you use the star pattern to frame it or was it anything to be seen in shorter subs?

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!

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.