Dwarf Galaxy NGC 7793

Object Details:

Designation:  NGC 7793                   Constellation:    Sculptor            
Visual magnitude:   + 9.2                  Apparent size:  10.4′  x 6′ 
Diameter:  36,900 light years.         Distance:  12 million light years

Not much to say about this little galaxy. Too many other things going on, making it hard to concentrate but it was good to get out on my front driveway observatory, despite the blinding new street light glaring down at me.

Everything behaved itself, although my polar alignment over some recent outings has been less accurate than I would have hoped for. This time is was almost 2 arc-min and last time it was just under 4 arc-min. Before that I’d had a run of alignments well under 1 arc-min.

2 arc minutes seems a remarkably tiny angle – one thirtieth of a degree – but it translates to about two and a half Jupiter diameters, so room for improvement again.

Also in image:  See my image with Astrometry.net annotated overlay.

Technical stuff:

Image & Processing:

Date:  2019-10-27
Exposure:   56 x 88.3 sec   =  82 min.
Gain:   184

Location:  outer suburban.
Conditions:  clear sky, no Moon
Sky brightness:   0.45 e/pixel/sec . 

Image acquisition:  SharpCap.
Method: Live stacked.
Darks: 6x

Image post-processing:  GIMP.
Cropping: yes


Telescope: SkyWatcher Esprit  Type: 120ED triplet refractor
Focal: 840 mm F/7 Mount: SkyWatcher EQ6-R Pro
Camera: ZWO ASI 071 MC Pro
Type: CMOS 28.4mm 16 Mpx
Optical aids: Flattener: Y; filter: LP Guiding: PHD2
Polar aligning: QHYCCD PoleMaster Polar Error: 1’57”

Geek Log:

[ZWO ASI071MC Pro]
Debayer Preview=On
Output Format=FITS files (*.fits)
Capture Area=4944×3284
Colour Space=RAW16
Hardware Binning=Off
Turbo USB=40
Frame Rate Limit=8 fps
Timestamp Frames=Off
White Bal (B)=50
White Bal (R)=53
Cooler Power=43
Target Temperature=-5
Auto Exp Max Gain=300
Auto Exp Max Exp M S=30000

Auto Exp Target Brightness=100
Mono Bin=Off
Anti Dew Heater=On
Banding Threshold=35
Banding Suppression=0
Apply Flat=None
Subtract Dark=C:\Users\Roger\Desktop\SharpCap Captures\darks\ZWO ASI071MC Pro\RAW16@4944×3284\88.3s\gain_184\dark_6_frames_-4.9C_2019-10-27T10_24_41.fits
#Black Point
Display Black Point=0
#MidTone Point
Display MidTone Point=0.5
#White Point
Display White Point=1

Images © Roger Powell

2018-03-10 Telescope & Roger




  1. Holy Toledo ! You are one smart dude. All those accomplishments are really impressive, I can’t wait to open your postings.

    Liked by 1 person

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