The Hunt for Sirius B
I'd just like to point out that Stargazers Lounge is solely responsible for me deciding last week, after 5 years of ignoring 'Stars' and treating them like sign-posts to everything else, that wait a minute, there may be something interesting about them after all. The thread on Sirius B - soon launched me out the door onto the driveway to have a look for the impossibly tricky double that is Sirius and Sirius B.
Here's what happened:
I setup my 8" Astro-Tech AT8In on CG5 ASGT Mount on the driveway. This is an F/4 scope and so certainly is not the ideal tool for double star splitting. Probably the 8" SCT with its longer focla length would make sense. But the AT8IN is 'the new scope on the block' and wowed me with its light gathering abilites compared with the C8, so I decided to try it out.
I began by slewing to Rigel which also has a close companion, with almost the same separation as Sirius from Sirius B. However, Rigel and its companion are not as widely separated in magnitude and this is a much easier double to observe.
I had a couple of other goals tonight. One was to try the CG5's Software Polar Alignment for the first time. Up until now, I've always used a polar scope. I also wanted to test the Baader Coma Corrector for the 8" Newtonian.
I did a 2 star alignment followed by 2 calibration stars, then selected 'Polar Align' from the menu (my version of the Hand Controller was 4.13). Half way through my second star aligment the power failed! I restarted and decided to pick 'last alignment'. This worked find and I slewed to Rigel.
I found the Rigel pair fairly easy to split after a few minutes. But it could be missed if you are not aware it has a companion star. As I aligned the scope I checked for doubles on a few other stars - noting Polaris' quite faint companion well separated from it.
Sirius was now approaching the Meridian (the East/West border) due South and so was moving towards its highest and best position for observation. Even so it would not climb above about 35 degrees in altitude.
I used a 4.3mm W70 Antares eyepiece for 186x on my 800mm FL 8" Newtonian - this worked well for Rigel. For Sirius I doubled this up to 372x. Sirius at first sparkled then later was a little muted by the thin cloud that was affecting its appearance on and off.
I was not seeing Sirius B and had intentionally not looked up its position so as not to cloud my judgement on detecting it. About 40 minutes into observing, for just a few seconds, a fleck of light persisted very close to Sirius. I moved my eye position around to try to confirm it. But after about only 5 seconds it was gone.
There were numerous annoying reflections in the eyepiece which had to be discounted. I cannot blame the eyepiece for this, as a very bright street light bores almost directly down the scope tube when I'm looking South. Despite an OTA that extends well in front of the focuser and a 2 foot long Dew Shield, the light still spills well into the scope tube.
The CG5 had tracked Sirius well past the meridian and the motor housings were close to touching. I broke off the pursuit for now. I attached the camera - a Nikon D5000 - and took a few test images of The Pleiades to check for star quality.
I then went back, first to Rigel and then Sirius, to see if I could pick up the elusive Sirius B on my DSLR. After that I took another 20 minutes using 372x (a 4.3mm eyepiece with 2x Barlow) on Sirius to try to split its companion. I made a drawing of the position of another possible candidate that seemed to be flitting in and out of view just above a diffraction spike, but later after working out its position angle, I ruled it out.
Below:
Rigel with its companion hiding in the lower diffraction spike. About 20 minutes earlier it was easier to see visually because of cloud movement.
Below:
Sirius and Yes, Sirius B, at the 10 O'clock position. The white halo is a result of thin high cloud which kept chaing the appearance of Sirius during observation.
Below:
Sirius and Sirius B (again at 10 O'clock). I confirmed the star field and Sirius B's position with an image from Tuscon-Skies.
These images were all taken at prime focus (800mm FL) with a Nikon D5000 DSLR - exposure on Sirius was 10 seconds at ISO 3200.
An enjoyable challenge. Although I did not see Sirius B visually, I was pleased to photograph the elusive 'Pup' as its called. Also having knowlege of its appearance I think will make it just a shade easier to detect visually under more transparent skies. A good 2 1/2 hours under the starry skies instead of in front of the TV!
The crescent Moon and some high thin cloud were lighting up the sky. On the ground I had a Victorian 'full radiation' street light, and several unshielded neigbhours lights bearing down on me.
The best defense turned out to be a fur hood! I flipped this over my head and the eyepiece while observing.
Above: Orion, Taurus and The Pleiades above the scope. Sirius is above the EZ Finder to the left. It was -1 C and ice formed on the scope and camera gear.
I look forward to trying again for a visual observation of Sirius B when the skies are more transparent!
The SW Polar Alignment was fine for visual, but not good enough for photograhy. To be fair I did not take much time over it. Adding more alignment stars should improve its accuracy. I will try it again to decide if I can beat the accuracy of aligning with the polar scope. I would sure welcome not having to crawl around on the ground under the polar scope. Its well worth perfecting so I will try a few ideas on refining it.
The Baader Coma Corrector - not sure as there was drifting on my images. But the star shapes are nice and round. I will also have to try this again to decide if the image has improved.
Clear skies!
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