Hemisphere:  Northern  ·  Constellation: Ursa Major (UMa)  ·  Contains:  Bode's Galaxy  ·  M 81  ·  NGC 3031
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Technical card

Imaging telescopes or lenses: William Optics Zenithstar 73 II

Imaging cameras: ZWO ASI 178 MM

Mounts: SkyWatcher EQM 35 Pro SynScan GoTo

Software: FreeAstro Siril  ·  Darktable  ·  KStars Ekos/INDI  ·  Pleiades Astrophoto PixInsight  ·  Astro Pixel Processor

Filters: Meade Blue Filter for CCD  ·  Meade Red Filter for CCD  ·  Meade L (UV & IR-Cutoff) Filter for CCD

Accessory: Raspberry PI4 4GB

Dates:Feb. 19, 2021Feb. 23, 2021March 3, 2021March 10, 2021March 12, 2021March 14, 2021March 16, 2021March 17, 2021March 25, 2021March 26, 2021March 27, 2021March 30, 2021April 1, 2021April 2, 2021April 6, 2021April 7, 2021April 9, 2021April 10, 2021April 11, 2021April 12, 2021

Meade Blue Filter for CCD: 1564x10" (4h 20' 40") (gain: 300.00) bin 2x2
Meade Green Filter for CCD: 1093x10" (3h 2' 10") (gain: 300.00) bin 2x2
Meade L (UV & IR-Cutoff) Filter for CCD: 3992x10" (11h 5' 20") (gain: 300.00) bin 2x2
Meade Red Filter for CCD: 1691x10" (4h 41' 50") (gain: 300.00) bin 2x2

Integration: 23h 10'

Darks: ~15

Flats: ~15

Flat darks: ~15

Bias: ~15

Avg. Moon age: 16.33 days

Avg. Moon phase: 41.22%

Bortle Dark-Sky Scale: 6.95

Temperature: 12.75

Basic astrometry details

Astrometry.net job: 4416073

RA center: 9h 55' 33"

DEC center: +69° 3' 54"

Pixel scale: 1.134 arcsec/pixel

Orientation: 276.156 degrees

Field radius: 0.411 degrees

Resolution: 2112x1532

Locations: Home, Athens, Attiki, Greece

Data source: Backyard


Almost two months' worth of M81. For every channel there were approximately +10% more subs which I didn't keep (20% for L).

With 10 second subs I didn't have to guide, but every 60-70 subs I would pause, plate solve and correct my position (staying within 5-10 arcsecs of the target). This is essentially dithering every 60-70 subs and combined with the thousands of available subs made the raw material ideal for 2X drizzle.

I used Siril for quick integration of my material, to see what channel I needed more data for. It is super fast. And the R,G,B channels in the final image were done with Siril. But I ended up using AstropixelProcessor for L, because I found it gave slightly better SNR. Most of the linear post processing (LRGB combination, gradient removal, color calibration, stretching) was done in APP and most of the non linear finishing touches were done in Darktable. But Pixinsight did help at the very first stage (I used DynamicCrop and star alignment to register the L,R,G,B master subs) and in the middle (HDRMultiscaleTransform on the image that came out of APP and some curve work before forwarding it to Darktable).


Sky plot

Sky plot