Gueri & Fred's astronomy


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Sirius A and B

Like many people, I have try to observe Sirius's components. But each time a fail to observe it. When  looking at the figures, the target seems easy but this is not as simple as it look.

  Magnitude Separation
Sirius A -1.46 3" to 10"
Sirius B +8.50

 source : sky map 7 and sky catalogue 2000.0 ed 1985

Actually, Sirius B is mostly hidden Sirius A's halo. And that why even is in theory this double could be split using a 60 mm refractor. But it's very difficult to separate the two stars. More over, for me, Sirius's maximum altitude is 25.

After many unsuccessful observation, I have decided to try the same techniques I use for planetary imaging. I set up my refractor with a powerMate 5x and a HX516 camera ( with square pixel ). This configuration give me 0.5" per pixel.

I try several exposure. A too short, and Sirius B won't appears. A too long, and Sirius A will be too bright.

I had some results using 5x10-3s and 10-2 s. But 10-2s is better.

Date : December 26th 2004

Exposure : 10-2 s (single frame)

A 4x enlargement gives :


Using Astro-Art, it's possible to determine the separation between A and B : This separation is about 6.5" (2")


Data sheet


All pictures are copyright Frederic Pertuisot and may not be reproduced without permission