A Quick Double Star Session

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A Quick Double Star Session

Postby Aratus » Wed Aug 24, 2016 5:41 pm

Tuesday 23rd August 2016

After a very hot day, the sky began to cover in thin cloud. However by 2230 the sky had cleared.
The temp was still 20̊C with light winds. This is possibly my warmest evening observation.

I decided to image a typical range of double stars visible in the same part of the sky. I took a series of images of alpha Capricorni, (Giedi), and beta Capricorni (Dabih). Giedi is an optical double, and can be seen with the naked eye. The photograph shows a nearby 9th magnitude star near to α1 which seems to be brighter than it should be. Dabih is a closer double, half the distance between them compared to Geidi. Although easily split with a telescope, I’ve never seen the double with the naked eye.
The final double was gamma Delphini. (the nose of the dolphin!) At just 9 seconds of arc, it is 1/42 of the distance between the stars of Giedi, and 1/23rd of the distance between the Dabih double. It wasn’t difficult to split with 8" SCT using the 32mm eyepiece. (63x), but was at the very limit of my old 40mm refractor. After 2300, I spent some time observing M31 the Andromeda Galaxy. I was initially confused when a faint patch of light appeared in the eyepiece. I quickly identified it as the M110 galaxy just north of M31! The Andromeda Galaxy looked great in the 32mm eyepiece, but I think it would look better on more transparent night. The M32 galaxy was also easily visible. By 2330 the thin cloud was returning, and the moon rising.

For comparison. Giedi, Dabih and Gamma Delphini
Image
Image
Image
They are all iso3200 and 10 sec exposures. However the stars of Gamma Delphini are 2 sec exposures superimposed on the original star field. The original stars were so close together that they merged into one. This was the only way to see the separate stars and the star field.
Last edited by Aratus on Wed Aug 24, 2016 7:47 pm, edited 1 time in total.
I use an 11" Celestron SCT (CPC 1100) on an equatorial wedge, housed in a 2.2m Pulsar observatory. I use a ZWO ASI1600MC and Canon 500D for imaging.
Aratus
 
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Re: A Quick Double Star Session

Postby andrewscomputers » Wed Aug 24, 2016 6:02 pm

Hi Aratus I like the double stars I have now bought a Cambridge star atlas to help me navigate the sky.
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Re: A Quick Double Star Session

Postby Aratus » Thu Aug 25, 2016 2:18 pm

Hello Andy. I've always found a star atlas very useful. Good ones also contain a lot of information and lists. They have the advantage of being able to mark them with a pencil. I always keep a planisphere handy to remind me where each constellation is in the night's sky. A book containing constellations and the varied objects in each one is a good buy too.

Double stars are interesting to observe, and there are lots of them to see - even in a small telescope.
I use an 11" Celestron SCT (CPC 1100) on an equatorial wedge, housed in a 2.2m Pulsar observatory. I use a ZWO ASI1600MC and Canon 500D for imaging.
Aratus
 
Posts: 840
Joined: Tue Jan 12, 2016 2:17 pm
Location: East Lincolnshire

Re: A Quick Double Star Session

Postby andrewscomputers » Thu Aug 25, 2016 5:54 pm

Hi Aratus I have also got a planisphere and a few books about what to look for in the sky,also recently got a book on astrophotography to try and learn about taking images with my gpcam.
Andy
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