Sirius B – The Hunt Continues

After getting proper calibration frames the night before I was able to measure the scale in my images which ended up being 0.315 arc-seconds/pixel. Armed with this and a good image of Rigel which has similar separation to Sirius A & B I headed back out into the cold on February 19, 2018 to try my luck again. This time around I used a sub-exposure of 0.1 seconds which I calculated from the Rigel image below and the difference in brightness between the Rigel and Sirius components.

Rigel Image (taken for reference)

Knowing roughly where to look for Sirius made all the difference. After collecting 122, 0.1 second sub-frames and stacking them to produce a stacked image in Images Plus, an arcsinH stretch was used to bring out the dwarf. Sirius B was just visible in the correct spot so the image was enhanced with sharpening and more contrast stretches. Finally the image was combined with my previous effort to show some field stars along with the resolved binary.

Sirius A & B

Measurements made from the image show that the stars have a separation of 11.3 arc-seconds with a PA of 72 degrees. This compares very well with the RASC Observer’s Handbook value of 10.94 arc-seconds with a PA of 72 degrees.

It is interesting to note that the star that I originally thought was Sirius B has been mistaken in several images and sketches I’ve seen, including some on the RASC Sirius B observing challenge page. I’d like to thank Dr. Roy Bishop, a mentor to the whole Halifax RASC Centre, for prompting me to re-examine my original data and to calculate the separation and position angle. If it were not for his coaching I would have made the same mistake as many others and reported the faint, blue star a little less than half way between Sirius A and the bottom of the cropped frame as the white dwarf.

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