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Old 25-01-2008, 09:50 PM
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Terry B
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Imaging Sirius B

Dear All
Has anyone succeeded in imaging sirius B?
I took a 10sec exposure last night as a trial using my 40D and the cropped result is below. It was taken with the moon up and some high cloud so the conditions were pretty poor. There is a star to the NE but it is too far away to be the pup. The cropped image below is 12.8 x 9.2 arcmin in size.
I have seen a pic taken by one of the members of our club of the pup. He was using slow film on a widefield astrograph with a long exposure.
Any suggestions how to do it?
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  #2  
Old 26-01-2008, 01:02 AM
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Starkler (Geoff)
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The big issue is that Sirius B is almost 10,000 fainter than A.
Mag 8.44 vs mag -1.47, and no imaging media has anything like the dynamic range capability of the human eye. I wonder if its possible to catch by imaging twice, with one exposure having the brighter of the pair physically masked.
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Old 26-01-2008, 01:17 AM
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Hi Terry,
I would strongly suggest making a mask for Sirius,
Don't ask me how but the principle is sound.
Bit like looking for coronal flares.
Cheers,
Duncan
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Old 26-01-2008, 04:22 AM
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skwinty (Steve)
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Hi Terry
In 2008 Sirius B separation is 8.2" and 2009 8.6".
Diffraction is the main problem as sirius B is almost due east of Sirius.
Rotate your scope so that your diffraction spikes are not covering due east.
Use your highest power eyepiece and when Sirius is highest in the south.
Rigel is very similar to Sirius in separation but the magnitudes are +0.1 and +7.6. Rigels companion is SSW. Try Rigel for practice.
Happy hunting.
I cant wait for my OTA rings to arrive (next week I hope) and then my 40DH will swing into action.
Regards
Steve
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Old 26-01-2008, 05:31 AM
AJames
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Exclamation Try the Trick!

Best to use a Hexagonal Diaphragm to improve telescopic resolution are several clever techniques originally designed to measure close pairs. This method amazingly destroys the Airy disk completely!
A mask cut to be a six-sided hexagon is placed over telescope aperture, creating six very bright sparks of light are seen from the central star which is in part the distributed light within the Airy Disk. Resolution here is improved about 15% to 20% compared to without the diaphragm.
Separation of the stars can be judged either by placing the faint companion in one of the six dark zones, or estimating the space between the two light rays from both components. This tends to work best for stars with some difference in magnitude, as the component of such pairs usually lurks with in the Airy disk itself.
You might have to do some trial and error with the exposure, and making small rotations until you get the best possible position for the Pup.
This technique as old as the hills, and works well.

Make sure you tell us if your successful!

Regards and Good Fortune,
Andrew
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Old 26-01-2008, 03:40 PM
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This sound like an interesting idea. Do you make the mask almost as big as the scope. It will then have the secondary inside it as well or make it an off axis thing without the secondary?
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Old 26-01-2008, 04:11 PM
AJames
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Smile

Quote:
Originally Posted by Terry B View Post
This sound like an interesting idea. Do you make the mask almost as big as the scope. It will then have the secondary inside it as well or make it an off axis thing without the secondary?
Terry

All you need to do is to make the hexagon the outer opposing points being as large as the aperture, with the six edges blocking the edge. It is best to make the aperture to cover the end of the telescope tube. You don't need to do anything else - except observe the image. To change the orientation, just move the hex aperture stop about 10 to 20 degrees, and see if you can observe the Pup. Ie. It also does work visually.

Hope this helps.
Andrew
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Old 27-01-2008, 08:09 AM
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The current issue of US Sky & Telescope (this is the third one in a row I have received now, but that is another story) has an article on Le Verrier and the observation of Sirius B. They have some pictures of Sirius and Rigel as a comparison, also a picture of the hex mask. Hopefully this article will be repeated when the next Aussie issue comes out, it is a very interesting article and not totally "US" centric either!
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Old 21-02-2008, 06:19 PM
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http://www.youtube.com/watch?v=K9m5MW5HMl4

Buy a Gstar-ex!
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  #10  
Old 22-02-2008, 07:59 PM
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Merlin66 (Ken)
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Double star software

If you're serious about imaging close doubles, you should try Florent's Reduc program. It's free for the asking florent_losse@yahoo.fr
Gives some great hints on imaging and measuring doubles. Highly recommended!!!
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Old 23-02-2008, 02:37 AM
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The full aperture hexagonal mask will work, as Andrew already mentioned.
I have an old picture somewhere that shows the mask in place on a 14" Celestron.
The 'pup' is easily seen.
You'll need calm, clear conditions.
Good luck.
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Old 23-02-2008, 12:09 PM
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You need a very long Focal length, small pixels and a hexagonal mask (as previously mentioned)

Dennis Di Cicco at S&T imaged Sirius B some time ago using a Hex mask and C14....and some mystical substance called TP2415
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Old 23-02-2008, 05:48 PM
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Looks like everyones ignored astrojunks offering. Great video of the pup and so clear.well done .Today i saw a similar pic by Johnathan Bradshaw posted on the g star ex yahoo group today. Seems like the g star is a silenced achiever??
philip
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