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Astrofriend

DIY, High efficient narrow band camera system

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Hi,

What can you do during a rainy and boring day?

Yes, write something about about old project ideas that newer have been realized.

For many years I have been wondering how to construct a beam splitter system to make more efficient use of exposure time when doing color or narrow band imaging.

I have today written down my ideas here:

http://astrofriend.eu/astronomy/projects/project-high-efficiency-narrow-band-imaging/project-high-efficiency-narrow-band-imaging.html


There are a lot of interesting links there too to read.

/Lars

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I'm not an expert but wouldn't the split beams be dimmer than the input beam thus you'd have to increase the exposure time?

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That's a very interesting idea. So a beamsplitter doesn't spread the different wavelengths out like a normal prism? Of course, if it did then the idea wouldn't work as the different blue wavelengths, for example, would hit different parts of the sensor.

59 minutes ago, kbrown said:

I'm not an expert but wouldn't the split beams be dimmer than the input beam thus you'd have to increase the exposure time?

I believe the idea is that the "blue" sensor would receive all the blue wavelengths, just like using a filter.

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Here's the theory of it:

https://en.wikipedia.org/wiki/Dichroic_prism

If anybody feels particularly brave, then how about a wrecked 3ccd broadcast camera as a source of a tricroic prism bloc:

https://www.ebay.co.uk/itm/Sony-DVCAM-DSP-WS-Studio-Broadcast-Camera-USED-DAMAGED-835/222731637408?_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20131017132637%26meid%3Dd56ec756752b488ca2ce9b8cbcb2b792%26pid%3D100033%26rk%3D6%26rkt%3D8%26sd%3D272800656087&_trksid=p2045573.c100033.m2042

https://www.ebay.co.uk/itm/Sony-Power-HAD-EX-Professional-Video-Camera-USED-DAMAGED-832/222731627942?hash=item33dbd6eda6:g:1xIAAOSwvD5aGEW3

(DISCLAIMER: the guy selling these has not mentioned model numbers, they both LOOK like pro 3CCD models, but I'm not putting my neck on the line)

CCD targets are probably bonded to the prism, so not easy to remove, but would be worth a punt for anybody interested in playing with the idea.

Me, I'm finding controlling one camera difficult enough:icon_biggrin:

 

Huw

 

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Hi,

It will catch three wavelength in parallel, one telescope, three cameras. Normally you only have one camera and one filter, then to get a rgb color from a mono chrome camera you have to take three exposures. Of course you can have three telescopes and three cameras als, then no need for a beam splitter.

Normally when doing rgb photos with mono cameras you block 2/3 of the incomming photons.

With other beamsplitters you can divide the incomming light in one visual and one IR beam. Then you need a mirror telescope. Some use the IR beam to autoguide on.

Lars

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