Castor

[Peter_D]

Hi,

I'm new to observing double / multiple stars.  Castor was well placed last night so I had an enjoyable time observing the primary split with my 6SE SCT. 

I used my Zwo asi224mc to capture some images and stacked them like I would with Lunar / Planetary images. The first one is un-Barlowed and the second is 2x Barlowed.

I realise I should have recorded orientation and what eyepieces I was using but to be honest, I was just thrilled to be seeing the split 🙂

Thanks for reading

Peter

[Stu]

Nice shots @Peter_D, although I’m a bit confused by the second one. The first looks like the Castor pair, but the secondary in the second image is much too small to be Castor. Did you perhaps capture a different star?

[Peter_D]

I had to bring the exposure and gain right down Stu when I Barlowed..but now I am having doubts because there is such a discrepancy in the brightness between the two.

I see on this page that the orientation fits (coincidence?) but not the magnitude:

https://bestdoubles.wordpress.com/2010/12/08/castor-three-steps-to-take-you-from-aw-to-awe/

Maybe I need another session focusing on Castor!

Edited April 28, 2021 by Peter_D

[Stu]

20 minutes ago, Peter_D said:

I had to bring the exposure and gain right down Stu when I Barlowed..but now I am having doubts because there is such a discrepancy in the brightness between the two.

I see on this page that the orientation fits (coincidence?) but not the magnitude:

https://bestdoubles.wordpress.com/2010/12/08/castor-three-steps-to-take-you-from-aw-to-awe/

Maybe I need another session focusing on Castor!

Yes, I would have another go just to verify it. Gut feel is that even bringing the exposure down would not cause this level of difference, they are fairly even brightness but this looks more like the difference between, say, Polaris A and B. I look forward to seeing how this turns out 👍

[Cosmic Geoff]

According to the virtualcolony deep sky database, Castor has a faint more distant companion: of mag. 9 at 72", same PA.

http://virtualcolony.com/sac/star_search.php?con=GEM&sep=2.0&mag1=10.0&mag_diff=9.0&order=ra_hr

[Stu]

3 minutes ago, Cosmic Geoff said:

According to the virtualcolony deep sky database, Castor has a faint more distant companion: of mag. 9 at 72", same PA.

http://virtualcolony.com/sac/star_search.php?con=GEM&sep=2.0&mag1=10.0&mag_diff=9.0&order=ra_hr

Surely the brighter component would also show up still in the image, not just one star? This was at higher power. A bit confusing but I’m sure we will get to the bottom of it 😀

[Cosmic Geoff]

7 minutes ago, Stu said:

Surely the brighter component would also show up still in the image, not just one star? This was at higher power. A bit confusing but I’m sure we will get to the bottom of it

I'm not saying I'm right, but I've tried imaging unequal doubles, and given that the AC separation here is about 20x the AB and that  overexposed stars tend to bloat, if one tried to image all three Castor elements together, the second image is the kind of thing one might get.  I expect the answer may eventually emerge.

[Stu]

9 minutes ago, Cosmic Geoff said:

I'm not saying I'm right, but I've tried imaging unequal doubles, and given that the AC separation here is about 20x the AB and that  overexposed stars tend to bloat, if one tried to image all three Castor elements together, the second image is the kind of thing one might get.  I expect the answer may eventually emerge.

Could be. The primary is a little oval so may be the two bloated together...

[PeterW]

I randomly tried to split Castor a few nights back with my 70mm binoculars, I was seeing if I could use my 5mm eyepiece in them (80x), nice black gap between the components… pleasantly surprised, maybe should do More of this??

Peter