As previously reported (see Flame & Frogs), there’s a lot going on around the Auriga constellation at the beginning of the year, which I was able to capture well using the Samyang 135 rig in January.  For some reason and assisted by an unusually long period of clear skies, I then spent the rest of the month imaging the same area of sky and beyond again but with the William Optics GT 81 rig, with the aim of getting better resolution of the myriad objects that are found in this busy region – which would mean the need for a mosaic.

I generally avoid mosaics, (a) because they take too long and suitable weather windows in the UK are usually short, (b) because I find them a lot of hassle and (c) I now have the Samyang 135 rig to take care of such widefield framing.  Notwithstanding, 15-hours imaging time later, I completed 3-panels which incorporated Alnath, IC 405, IC 410, M36, M38 and more and I had the basis for my mosaic.  Unfortunately, the most southern panel including Alnath turned out to devoid of anything of interest, so in the end I decided to use only two panels for the final HOO image (see top of the page), which then broadly approximated to the aforesaid Samyang image i.e. why bother?

I have previously used Microsoft’s built-in mosaic software but this time decided to try out PixInsight’s inevitably complicated but excellent Photometric Mosaic script; earlier this year I set-up the new PI Gaia catalogues which provide the basis for identifying all stars in an image and furthermore, provide their individual photometric data, which can then be used for accurate colour calibration and exact mosaic matching!  Put simply, using the said database each mosaic panel is plate solved so that the image then contains the underlying detailed spatial and colour information.  Finally, using PI’s Gradient Merger Mosaic script this information is used to match and combine each panel with pixel accuracy to produce a seamless mosaic image.

Whilst I’m pleased with the final outcome and even enjoyed using the PI mosaic scripts, in this case I’m not convinced that the image is much better than the previous Samying 1135 version.  However, should the day come again when I get the mosaic urge, I’m now well prepared!

  

	IMAGING DETAILS
Object	IC 405 The Flaming Star Nebula + IC 410 The Tadpoles Nebula, M36 & M38
Constellation	Auriga
Distance	1,500 & 12,000 light-years
Size	Approx. 5.79o x 8.14o
Apparent Magnitude	+6.0 & +10
Scope  / Lens	William Optics GT81
Mount	SW AZ-EQ6 GT + EQASCOM computer control & Cartes du Ciel
Guiding	William Optics 50mm
	+ Starlight Xpress Lodestar X2 camera & PHD2 guiding
Camera	ZWO ASI 294 Pro mono CMOS sensor
	FOV 2.87o x 1.97o Resolution 2.50”/pix  Max. Image Size 4,144 x 2,822pix
EFW	ZWOx8 EFW & 31mm Chroma 3nm narrowband filters
Capture & Processing	Astro Photography Tool + PHD2 + PixInsight v1.8.9-1
Image Location              & Orientation	Centre: RA 05:19:54.329      DEC +05:27:50.250                         Right = North   Top = East
Exposures	Panel-1 Ha x24, OIII x24, SII x18 x 300 sec = 5hr 30m Panel-2 Ha x23, OIII x24, SII x18 x 300 sec = 5hr 25m  Total Integration Time: 10 hr 55 min
	@ 120 Gain   30 Offset @ -15oC
Calibration	10 x 300 sec Darks 20 x Flats & Flat Darks
Location & Darkness	Fairvale Observatory – Redhill – Surrey – UK        Typically Bortle 5 – 6
Date & Time	January 2023 @ +18.30h
Weather	Approx. <=2oC   RH >=80%                  🌙 +80%