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Observing >> Double Star Observing

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MG1962
sage


Reged: 08/13/11

Has anyone ever tried this
      #5576724 - 12/18/12 01:28 AM

Would variable polarized filters have much effect on double stars where one companion is buried in the glare of the primary such as Sirius A and B

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Rachal
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Reged: 04/07/09

Loc: Alexandria LA
Re: Has anyone ever tried this new [Re: MG1962]
      #5577018 - 12/18/12 09:50 AM

If you have one, give it a shot on something easier like Rigel and see how it works. Interesting question. It would be nice if it would; one might have better luck with an occulting bar, however.

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MG1962
sage


Reged: 08/13/11

Re: Has anyone ever tried this new [Re: Rachal]
      #5577118 - 12/18/12 11:09 AM

I dont own one, and have never done enough Luna observing to consider the expense - Rigel would be an excellent target because I can already split that and can compare the performance

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Rachal
super member
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Reged: 04/07/09

Loc: Alexandria LA
Re: Has anyone ever tried this new [Re: MG1962]
      #5577568 - 12/18/12 04:39 PM

Years ago I made an 'apodizing' filter using window screen, which is "supposed" to help with double stars. You might do a search to see if this is something that would interest you.

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blb
Post Laureate


Reged: 11/25/05

Loc: Piedmont NC
Re: Has anyone ever tried this new [Re: Rachal]
      #5578142 - 12/18/12 11:28 PM

Quote:

Years ago I made an 'apodizing' filter using window screen, which is "supposed" to help with double stars. You might do a search to see if this is something that would interest you.




Easy to make and it works well.


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Asbytec
Guy in a furry hat
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Reged: 08/08/07

Loc: La Union, PI
Re: Has anyone ever tried this new [Re: blb]
      #5578227 - 12/19/12 12:35 AM

When apodizing, you really have to optimize the screen for high frequencies of double stars. Apodizing tends to slightly enlarge the spurious disc while greatly diminishing the bright ring pattern. This improves contrast at lower spacial frequencies starting about, say, 3 to 5 or more times the Raleigh limit depending on the mesh and radii used.

At these separations doubles would not qualify as close pair where ring brightness might matter. You might loose the dark space at the Raleigh limit observing a classic Raleigh pair and Dawes splits would be more difficult. Wider doubles might be more aesthetically pleasing, however, as well as larger planetary details.

Another trick to observing Sirius pup is to have very clean optics to reduce glare. Some folks have uses square aperture mask to change the shape of diffraction. But, a good neutral density filter might help, too.


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Ed Wiley
scholastic sledgehammer


Reged: 05/18/05

Loc: Kansas, USA
Re: Has anyone ever tried this new [Re: Asbytec]
      #5579358 - 12/19/12 05:52 PM

You might be interested in these articles by Jim Daley. JDSO is always a good source for innovative techniques.

http://www.jdso.org/volume3/number4/Daley.pdf
http://www.jdso.org/volume4/number4/Daley.pdf

Ed


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