Alpha Geminorum (Castor)

[DarkerSky]

Castor in Gemini is a visual multiple star system. Sketched this on 6 Jan through my 12" at x70 magnification. TFOV 1.03 degrees

Castor A to the SW is Mag 2.0 and slightly brighter than Castor B, which is at Mag 2.9. Separation is 4.6 arc seconds I believe, and is currently widening slightly each year. There is an orange/yellow star to the south of the main double. This I think is Castor C at 9th magnitude.

The view was mesmerising. Two brilliant white gems held so close together in the eyepiece. Highly recommended viewing !!

[Nexus 6]

Hi Darkersky, nice sketch. I was out myself for an hour having my 1st views with the 13mm Nagler I got for crimbo. I had some really nice views of several subjects including Castor, was so captivated by the quality of the view I did'nt notice Castor C but will be looking out for it next time I'm out.

Alan

[Macavity]

Nice. It slightly miffs me that I never looked at Castor until a very few years ago. My "Epoch 1950"(!) book implied it would be a "difficult" double, with my scopes? But, as you say, the A-B separation is now about 4" (arc), so I guess it's now a "good test"? But I was pleasantly surprised...

[DarkerSky]

Nice. It slightly miffs me that I never looked at Castor until a very few years ago. My "Epoch 1950"(!) book implied it would be a "difficult" double, with my scopes? But, as you say, the A-B separation is now about 4" (arc), so I guess it's now a "good test"? But I was pleasantly surprised...

I've just done some reading up on the Castor system. As seen from Earth, minimum separation was just 1.8 arc secs in 1969/70 - so yes, would be a difficult double by 1950 epoch standards. In fact, anytime from late 50s to early 80s would have been challenging.

I think what is fascinating is the way the position angle has changed. B was due south of A in the 1950s. It's now more than a quarter turn around, oriented to the north-east.

Stellar astronomy in motion!

[valleyman]

Looked at Castor a few weeks ago and was blown away, I rate it as good as Albiero

Neede to go to max magnification but it was worth it

[perrin6]

It's a great sight in my ZS 66 - nicely seperated.

[Doc]

Love looking at Castor in the 16" dob, just breathtaking

[John]

Castor is great - looks like car headlights at 320x with my 6" refractor !.

Another good one, but a tougher test, is Porrima, Gamma Virgo which is starting to get to a decent altitude from around 1:00 am now. It's an equal brightness double with a separation of around 1.5 seconds of arc the the moment - it's been gradually widening over the past couple of years.

[perrin6]

Castor is great - looks like car headlights at 320x with my 6" refractor !.

Another good one, but a tougher test, is Porrima, Gamma Virgo which is starting to get to a decent altitude from around 1:00 am now. It's an equal brightness double with a separation of around 1.5 seconds of arc the the moment - it's been gradually widening over the past couple of years.

Ah yes, I remember when porrima was easy & then closing up and becoming more and more difficult - makes me feel old to hear that it's widening again now !

[philj]

Nice one, I was looking at that last night.

Ive never really given it much attention before but I just took a quick peek last night and was smitten, it really is a nice sight. Car headlights describes the main comonents nicely.

Philj

[John]

Ah yes, I remember when porrima was easy & then closing up and becoming more and more difficult - makes me feel old to hear that it's widening again now !

I have that ageing feeling as well - I was 1st able to split Porrima with my old Tasco 60mm refractor - I don't think that will be possible for a couple more years yet although I still have the scope so I hope to do it again one day, for old times sake

[chiltonstar]

What is the consensus opinion on the colours of the Castor doublet? In my Mak 127mm at 185x I would say orange and "electric" blue (although listed as "white", I think I can see some slight colour difference at high mags??) - is this how others see them? Even in tonight's poor seeing, they were very well separated - last time I looked (70s in a 4" refractor), I couldn't split them.

Chris

[Mikea]

Darkersky's lovely sketch inspired me to try this one. It was quite a job with my 130P plus x2 Barlow and 8mm EP (162x), but I was eventually rewarded with a shining pair of diamonds. Rather envious of the "car headlight" version though! - must think about getting some money from the piggy bank.....

[lunator]

DS

Very ggod sketch Castor is always a great view

[Mr Flibble]

Just split Castor for the second time tonight. Mag x68. Really chuffed because the last time I split it I needed a mag of x83. I guess the seeing must have been better this evening.

And finally for the first time ever I discovered that my collimation is good because when I ramped Castor up to x187 I got my first ever good, stable, airy disk (a pair of them) just like the textbooks show

[lunator]

Hi David

Well done on the split

It is amazing to thing that the 2 stars you see are doubles in themselves so you are looking at 4 stars

YY Gem the faint star near by is also a spectroscopic double so you are looking at a 6 star system.

Cheers

Ian

[Mr Flibble]

Hi David

Well done on the split

It is amazing to thing that the 2 stars you see are doubles in themselves so you are looking at 4 stars

YY Gem the faint star near by is also a spectroscopic double so you are looking at a 6 star system.

Cheers

Ian

Thanks Ian.

Clear skies again last night so I had another look at it. That star system would be absolutely bonkers if we were able to see it close up