A few weeks ago I shared an image of Barnard's loop, taken with a simple modified DSLR setup (Barnards loop). That inspired me to explore the possibility of obtaining similar views but at a much higher resolution ie. both wide and deep. This image represents the start of that experimentation.

This is a 64 (8x8) panel mosaic of the Orion region taken with a RASA 8, ASI2600MC and an NBZ narrowband filter. The actual data acquisition phase was not nearly as daunting as I had imagined. I used an ASIAir to control the entire rig and mosaic management in the Air is now quite advanced and completely self-contained (no longer requiring input data from Telescopius, for example). It worked flawlessly over 5 short nights allowing me to acquire the base images. In order to keep this exploratory project under control I opted to take only 20 minutes of data per panel (20 x 60 second exposures) and so the total data acquisition time is actually only of the order of 20 hours or so, albeit punctuated by frequent slews of the mount and associated guider re-engagement etc (all handled by the ASIAir).

The data processing, however, was considerably more taxing! Most tasks were conducted in AstroPixelProcessor - its mosaic capabilities are, I believe, outstanding. For each panel the ~20 subs were combined to produce panel 'masters' and these were then individually corrected for light pollution gradients. At this point each (unstretched) FITS master made a brief journey across to Pixinsight for an application of BlurExterminator. Then they all came back across to APP and were registered and integrated together to form the mosaic. I had originally planned to make 4 intermediate (4x4) mosaics in order to lessen the computing burden but this didn't work out - you really need to do all the registration in one run

. Luckily this wasn't a major drama and was easily achieved in a few hours (Apple M1, 64GB, 10 cores).

Each of the 64 masters was around 312 MB in size (6241 x 4175 pixels) and so the resulting mosaic is very large. To preserve my sanity, a decision was made to downsample during integration. This resulted in a somewhat more 'workable' 4GB final FITS file for further processing. Stretching was done in APP and then a 2GB 16bit TIFF file was exported to Photoshop for minor tweaking. The 35MB JPEG shown here is a further significant degradation of that original image, unfortunately, to allow faster download..

Much of this project was very new to me and it took many different attempts to determine optimum settings for the mosaic generation. There are still many flaws in the image of course (such as a blotchy background due to variable light pollution adjustments to each panel early on in the process) but I am still on a steep learning curve and think that this can be relatively easily addressed in the future. The stars are also still narrowband form from the NBZ filter and I have not yet decided how to deal with RGB stars for similar mosaics - dealing with an additional 64 panels would not be fun! In fact I may actually just go with pure broadband down the track as the NBZ filter does also seem to produce an overtly red image - I would have liked to see more pronounced blue in there from areas of OIII.

For info, I did create a separate panel for M42 using 1 second exposures in an attempt to show the trapezium (the four major stars of which are clearly resolved with the RASA 8) but, with all the downsampling, they become just a mush so I decided to leave the existing, overexposed core of M42 in this image. I think that adds to the drama of the scene anyway.

Of course all the favourites are present in the image (Horsehead, Flame, M42, Barnards loop etc) but this was intended as an image to be explored in detail and there are in fact many far smaller but equally interesting objects to be seen in the wider field of view. Some were also quite unexpected finds - such as the small (2.5 arc minutes) planetary nebula Abell 13 which appears as a tiny red ring somewhere in the upper left quadrant (see if you can find it!). I hope that you have fun wandering around...