Cygnus Loop, Filamentary Nebula, Veil Nebula - you can chose the name you like

[bobharmony]

I have recently completed my first mosaic - a 4 panel version of the Veil Nebula in Cygnus. I started planning this in April and had all good intentions of imaging in the July dark sky period. The weather had other ideas so I wound up with my first imaging session in September instead and got a lot less time on the target than I had hoped for.

I started by using the Mosaic tool in Cartes Du Ciel to lay out the 4 panels. The tool gives coordinates for the center point of each panel and a rotation offset for the camera. The center points were exported to Astrophotography Tools as custom objects, which I used to build the script that controls the scope during acquisition. As I don't have a rotator in my imaging stream, the camera angle has to be adjusted manually at the time of the session.

This is where I ran into an issue. CdC reported an angle of 340 degrees, which it turns out was incorrect. The correct angle is closer to 26 degrees (as I confirmed later with various platesolvers and astrometry.net). So my first nights results all were centered correctly, but were at such a bad angle that getting a workable mosaic built from them was not possible. The second night I had time to try a different camera angle but limited shooting time due to clouds rolling in. Finally the third night I was able to get a better camera angle and a full nights worth of data.

I used Microsoft ICE to stitch the mosaic together after processing each panel separately in StarTools. Here is the result:

Each panel got 50 minutes of time, which is all I can get between astronomical dark at 2045 and when the targets dives behind the trees at 0130. This consisted of 25 120" subs for each panel position. Data was calibrated with darks, flats, and dark flats. I may add more data to this next year, and I may try to get individual images of the Eastern and Western Veil using the data from all three nights if that is possible.

Comments and questions welcome!

Bob

[MariusD69]

Wonderful! Great work, Bob!

[messier 111]

Superb work , thx .

[Juno16]

Cool mosaic Bob!
I have yet to try a mosaic and the way that the weather has been, I may never get the opportunity!
I can’t imagine getting four separate images processed so close that they can be stitched together seamlessly. Nice work!
Did you do any star reduction? There must be a gazillion stars!

[bobharmony]

Cool mosaic Bob!
I have yet to try a mosaic and the way that the weather has been, I may never get the opportunity!
I can’t imagine getting four separate images processed so close that they can be stitched together seamlessly. Nice work!
Did you do any star reduction? There must be a gazillion stars!

Thanks, Jim. I did enjoy trying out a mosaic although I would have preferred getting a start on it in July if the weather had permitted. I think I will limit myself to two-panels editions in the future.

The processing was very simple because the data I had to work with was very good. Your old D5300 is very sensitive compared to the Canon and having the infrared mod was great for this target - it was a pleasure to work with! I used a flow that applied a lot of default values in StarTools, my contributions were selecting the ROI in Autodev and making sure the green was capped in the Color module.

You are right, there are an incredible number of stars in the area. I used the StarTools "Shrink" module to try and get them under control a bit.

Bob

[Jockinireland]

Its good to see you back imaging and posting - seems you had the same summer as i did! Thats a nice image to start off the season.

[Graeme1858]

That turned into a real labour of love Bob!

Looks like it was well worth the effort. Nice to see an image of the whole thing.

Regards

Graeme

[OzEclipse]

Lovely mosaic Bob. Thanks for sharing.
Joe

[bobharmony]

FWIW, I was able to figure out what the issue was between CdC and APT WRT to camera rotation angle. I communicated and worked with Patrick in the skychart@group.io board and Ivo for the APT side of things.


It turns out that both programs use the top of the image facing North as their 0 position, but they measure rotation in different directions. CdC increases camera angle counterclockwise, and APT increases the angle in the clockwise direction. This makes it pretty easy to figure the corresponding numbers fairly easily. To get the CdC angle from APT subtract the APT measured angle from 360 degrees. The analogous process for switching from CdC to APT is to subtract the CdC angle from 360 degrees.


Both Ivo and Patrick are aware of the issue. I don't know whether either of them will do anything to address it. In any case, I will be better prepared when I do my next framing critical run on M31. If I get better weather next summer I may revisit the Cygnus Loop as well. What I got was a nice start but I would have preferred a lot more integration time on it.


Bob

[SkyHiker]

Beautiful mosaic, well done!