Castor and Uranus: Whats the connection ?

[John]

With Uranus being pretty well placed at the moment in Pisces I'll bet many astronomers are seeking out it's pale green-grey disk in their scopes. Despite being a giant gas planet, Uranus is currently a staggering 2.83 billion KM from us so it's 50,000 KM diameter disk subtends just 3.7 arc seconds in the sky. If you have yet to find a view Uranus with a scope, to get an idea what to expect in terms of it's apparent diameter take a look at the star Castor in Gemini, currently rising into the Eastern sky.

Castor is a well known and superb binary star system. The main two componants ( Castor A and Castor B ) are separated by around 4 arc seconds currently. A small scope using a magnification of around 100x should separate them. As you gaze at the tiny gap between these bright stars think that the disk of Uranus would fit neatly in between them. Gives you an idea of how small a handful of arc seconds are in the sky.

In 2035 Uranus will be in the constellation of Gemini but won't get close to Castor because the star lies just a bit too far off the ecliptic. Shame, because Uranus sitting between Castor A and B would make quite a sight 

 

[johnfosteruk]

That would be quite a sight John. I'm off to see if there are other similarly spaced doubles that'll be crossing paths with Uranus

 

[John]

I ought to add that this is a kind of observing report because I've been observing both Uranus and Castor this evening with my ED120 refractor

For kicks I used 450x on Castor to put as much black space between the A & B stars as possible then moved straight to Uranus to catch it's disk a tthe same power. It did indeed seem to be very close to the same apparent size as the separation between the Castor stars.

 

[Astro Imp]

Having read seen this thread a few days ago tonight I had a look at Uranus at 240x and then went straight over to Castor with the same EP. Unfortunately Castor was not well placed being low over a neighbour's house so the view was a bit unsteady but interesting to compare the two nonetheless.

Thanks John for the original interesting post.

[alan potts]

John, X450, did you take a magnification pill or was it the last album by Yes, the latter i imagine. Oh, nice report and information btw. 

Alan