Sirius is the brightest star above us in the night sky. And it has a companion known by astronomers as Sirius B.

Since Sirius A (the main component) is part of the constellation Canis Major (the Great Dog) it was only natural to give it’s name “the Dog Star”. And since it’s companion is much fainter, the nickname for Sirius B is “the Pup”.

Well, there are many double stars in the heavens, so this pair shouldn’t be so special, but…it is. Besides the history, it is one of the toughest pairs to observe through a telescope, mainly due to the great difference in brightness of the components. But things have started to change in recent years, since the Pup is apparently moving away from it’s bigger companion, and that means that it becomes easier to observe in amateur telescopes. The separation variation between the two components is shown here.

Unfortunately, the negative declination means for my location that the Dog Star never rises to high in the sky. That being said, to properly observe component B of the system one must have some rather good seeing conditions.

Conditions which I just had on the evening of March 30, when, after a few weeks of planning, and one failed test with the 4.5″ APO Refractor (due to bad seeing mostly) I’ve finally motivated myself to get out with the C11 SCT.

This is what eventually resulted:

Sirius B

The strange shape of Sirius is due to atmospheric dispersion, which at the focal length of 2800mm is very well observable (unfortunately).

The “Pup” is easily seen at the 12 o’clock position.

Of course I had to confirm initially if what I was observing on the laptop screen was indeed Sirius B, so I’ve made a few experiments, including rotating the camera, using different filters and comparing the position and distance from the main component with the Rigel double system.

Sirius B observation

Well, maybe I shouldn’t have made so many tests, since component B was actually visible directly on the live recording window, as can be seen in this short movie. (Please watch the video at the highest resolution, since only then the small white dwarf will be observable).

Hopefully I will also get a chance of imaging Sirius B with the 4.5″ APO also. Soon I hope…


(April 1, 2014)



3 Replies to “Sirius B”

  1. Nice capture! I was able to visually observe the “pup” tonight, and if your cardinal directions are indeed correct, then I placed it in the correct position. I _may_ have observed it at the same location once before, but seeing was too spotty to tell. Tonight I am certain I was able to see it, however.

    1. Thank you Brandon! A slightly better shot from November 2015 can be found here.
      And “bravo” for seeing Sirius B visually! It’s a better result compared to just imaging it! I’ve also observed the B component visually, and I must say that it was a better reward compared to the final image…

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