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Contains:  Extremely wide field
Getting plate-solving status, please wait...
Sandqvist 169 Dark Nebula and Starfield, 


            Gabriel R. Santos...
Sandqvist 169 Dark Nebula and Starfield

Sandqvist 169 Dark Nebula and Starfield

Technical card

Resolution: 2400x1600

Dates:May 18, 2018

Frames: 37x120" ISO400

Integration: 1.2 hours

Darks: ~20

Flats: ~20

Bias: ~30

Avg. Moon age: 3.38 days

Avg. Moon phase: 12.37%

Bortle Dark-Sky Scale: 4.00

Mean SQM: 20.60

Mean FWHM: 3.30

Temperature: 15.00 job: 2112732

RA center: 222.683 degrees

DEC center: -63.065 degrees

Pixel scale: 14.670 arcsec/pixel

Orientation: 354.136 degrees

Field radius: 5.877 degrees

Data source: Traveller


Sandqvist 169 is a rarely imaged dark nebula in the constellation Circinus. Lies near Centaurus, at a Southern decelination of -65º. It has quite a large angular diameter - this 135mm field could cover some 20 full moons in it (~9º)! The brightest star in the field is Alpha Centauri, the closest star system to the Solar System, being ~4 light-years away. The dark nebulas greatly contrast with the bright clouds of the Milky Way, creating a dynamic field. Sandqvist 169 is visible to the naked eye in dark locations (and with binoculars), but the main dark object in the nearby region is the much more famous and imaged Coalsack nebula.

This image is not perfect: the clouds are dwarfed by the starfield. The region doesn't feature any bright emission nebula - the end resultant field looks a bit monocromatic - the contrast is where all visual interest lies. The sky conditions were also not ideal: some frames were lost due to cirrus and fog, and the skies weren't as dark as they could. But I think the snapshot of this not-yet-imaged-by-me object was worth it.

This image was created in a very nice astro trip with fellow astroimagers of Southeastern Brazil, in a rural area. The skies were pretty good, but the weather was not ideal (again!). This was the 1st SE Brazilian Astrophotography Meeting, which had 11 setups up and running at night. I especially thank friends Joao Mattei, Jose Carlos Diniz, Sergio, Fernando Parmegiani, Fernando Menezes, Andre Brossel, Renata Sottomaior, Vinicius and Joao Fidelis that shared the skies and saw this image being born/captured. I also thank every other fellow astrophotographers that only got there on the 2nd night.

Constructive criticism, comments and suggestions are more than welcome in the comments section. Thank you for taking your time to look at this image.

Taken from Semi-Rural Skies (Bortle 4-5; SQM ~20.6*calculated), from Itirapina, SP, Brazil.

Date and Time: May 18, 2018, at 20:15 (start of capture)
Camera: Canon EOS 80D (unmodded), at ISO 400
Lens: Samyang 135mm f/2.0, operated at f/2.4
Mount: Sky-Watcher HEQ5, tracking, guided
Exposure Detail: 37x120s each; total 74 min



Gabriel R. Santos...
License: None (All rights reserved)


  • Sandqvist 169 Dark Nebula and Starfield, 


            Gabriel R. Santos...
  • Final
    Sandqvist 169 Dark Nebula and Starfield, 


            Gabriel R. Santos...

Sky plot

Sky plot


Sandqvist 169 Dark Nebula and Starfield, 


            Gabriel R. Santos...