More Double Stars in Ursa Minor

I have already done a little bit of double star hunting in Ursa Minor but on the last night out in my back garden I decided to go back and see a couple of others. I like looking at targets in Ursa Minor because it is pretty much always visible from my back garden and is high enough to avoid a fair chunk of the local light pollution.

An interesting thing I noted about these two stars I chose to look at tonight was that both have Struve in their name but one was coded as STTA and the other as STF which is the code I have seen before. I therefore did a bit of research and discovered that the reason for the different codes is that a fair amount of the Struve family have been involved in astronomy and here seems to be several double star catalogues related to them! Therefore if you try and look up Struve 143 you would find out that there is three of them, STF 143, STT 143 and STTA 143! 

Anyway, I have decided that for any star that I find with the Struve moniker I am just going to use the coded name from now on. So the stars I looked at tonight were STTA 143 and STF 1798 whose locations are shown in the image below.

STTA 143 (HIP 78761 / SAO 8415)
RA : 16 04 48.95   Dec: +70 15 42.0
Magnitudes: 6.9, 8.8
Separation: 46.6”
Position Angle: 83°

STTA 143 was my first target of the night which I found relatively easily with my GOTO handset. The reasonable magnitudes and wide separation distance of the A & B components meant it was a pretty obvious split to see. As for colour, well both stars looked white to me which ties in with the spectral classifications of A0 & F8. I was quite happy to see that they did match what I was seeing as I was beginning to wonder if I was maybe just missing colour when observing.

STF 1798 (HIP 67959 / SAO 7912)
RA : 13 55 02.30   Dec: +78 23 59.2
Magnitudes: 7.7, 9.7
Separation: 7.6”
Position Angle: 11°

Finding STF 1798 was actually the first real challenge in my astronomy adventure because my GOTO handset didn't have the SAO number in its database. I therefore had to use the Right Ascension and Declination to point my telescope in the right area and then use a print out from stellarium to actually centre in on STF 1798. It was actually quite fun to do as it felt like I was really working to find the star for once and I felt a sense of achievement when I did find it.

In regards to the star itself, it was slightly dimmer than STTA 143 and the separation was much smaller, in fact it was smaller than the separation in any other star I had successfully split so far. This meant that the B component was very close to the brighter A component and at times was lost it the glare. I could make it out most of the time although I was not sure of the colour as it was washed out by the white of the A Component with its F2 stellar classification.

Overall, STF 1798 was probably my favourite star of the night because of the extra challenge in finding it and due to the fact that it is smallest separation value I have split so far. I must have spent about 20 minutes just gazing through the eyepiece watching the component appear and disappear in the glare as atmospheric conditions changed.