Sirius B sighted

[jiahao1986]

Hi folks,

On Friday night NTU Astro Club organized an Geminids ob session at ECP. The meteor shower was OK, not as many bright meteors as past years. Anyway we managed to see a green fireball brighter than -6. Awesome view when we saw that fireball shinning behind clouds. There were around 20 people there including us. We all had much fun.

We brought our 10inch Orion dob there for DSO ob too. And it was a pleasant surprise that we saw Sirius B through the 10 incher. Initially I wanted to use Sirius to star collimate the scope. The scope was still collimated though it hit the wall several times during transportation. Then I suddenly saw a tinny dot above Sirius(240X was used). The angular seperation is about half of the apparent angular diameter of mars, i.e. 7 to 8 arcseonds, and the PA(postion angle) is about 270 degrees. Further inspection showed that the postion of the companion with respect to the diffraction spikes of Sirius changed over time. Later I could confirm Sirius B sighted, as shown in references for the PA and the seperation values for 2007.

It is a pleasant surprise that Sirius B being sighted so easily, though this sighting is purely accidential. I had expected much more difficulty. Aperture is important here, and seeing also needs to be good. Last night seeing was better than 8/10. The seperation of Sirius A and B is increasing now, and it will reach 11.5 arcseconds in 2025. However, now the seperation is already big enough for medium aperture scopes to split the double under good seeing conditions.

Best regards,
Jia Hao

[Robin Lee]

Hi folks,

On Friday night NTU Astro Club organized an Geminids ob session at ECP. The meteor shower was OK, not as many bright meteors as past years. Anyway we managed to see a green fireball brighter than -6. Awesome view when we saw that fireball shinning behind clouds. There were around 20 people there including us. We all had much fun.

We brought our 10inch Orion dob there for DSO ob too. And it was a pleasant surprise that we saw Sirius B through the 10 incher. Initially I wanted to use Sirius to star collimate the scope. The scope was still collimated though it hit the wall several times during transportation. Then I suddenly saw a tinny dot above Sirius(240X was used). The angular seperation is about half of the apparent angular diameter of mars, i.e. 7 to 8 arcseonds, and the PA(postion angle) is about 270 degrees. Further inspection showed that the postion of the companion with respect to the diffraction spikes of Sirius changed over time. Later I could confirm Sirius B sighted, as shown in references for the PA and the seperation values for 2007.

It is a pleasant surprise that Sirius B being sighted so easily, though this sighting is purely accidential. I had expected much more difficulty. Aperture is important here, and seeing also needs to be good. Last night seeing was better than 8/10. The seperation of Sirius A and B is increasing now, and it will reach 11.5 arcseconds in 2025. However, now the seperation is already big enough for medium aperture scopes to split the double under good seeing conditions.

Best regards,
Jia Hao

Jia Hao, thanks for sharing your finding. I thought it was impossible for this aperture range telescope. Now, I got a nice double-star reference to share to my club members.

[acc]

Yup interesting observation. Will try doing this too.