Trichroic beam-splitter v RGB

[nytecam]

Anyone tried one of these beam-splitters (BS)? They permit separate RGB in one hit in one third of the exposure time of separate RGB imaging especially important for long exposure DSO imaging that can run to hours. The downside is cost of BS and 2 extra matching sensors :-)

[NickK]

I looked at these - some of the high end video systems use it. Also for DSO getting the image start and end points aren't as bad.

[nmoushon]

Still cheaper than buy 3 scopes and 3 cameras. Though you'd need a hefty focuser to hold all the cameras lol.

[nytecam]

I looked at these - some of the high end video systems use it. Also for DSO getting the image start and end points aren't as bad.

Thanks Nick - nice to find someone interested in innovation too   This is the type of trichroic beam splitter [Philips] I had in mind in pic - I've sure there are other permutations.  I've no idea as to QE for the three wavebands through the prisms but it must be fairly good.  Those who do H-alpha imaging could place a Ha filter over the red channel exit and before the sensor

I recall Panasonic's prosumer videocam of nearly a decade ago with three sensors - some must be on the scap market now for reuse/ adaption.   

My over-riding reason for post was the constant "mono+separate RGB is quicker" [than OSC] which ignores the waste of two waveband whilst the third is exposed - crazy waste of photons.   OK may be costly but not as much as three matched and aligned scopes+cams running on a massive new mount 

[laser_jock99]

These are common in high end video cameras, look out for an old spares or repair '3CCD'  camera, it might be possible to convert it to astro use or even just rip out the beam splitter. My old Sony TRV900E has 3CCD's - it's still working so I'm not about to cannibalise it yet!

I assume you are thinking of imaging fairly bright objects as the scopes brightness is effectively reduced to one third at each CCD. But the advantage is you can image your RGB simultaneously.

[nytecam]

These are common in high end video cameras, look out for an old spares or repair '3CCD'  camera, it might be possible to convert it to astro use or even just rip out the beam splitter. My old Sony TRV900E has 3CCD's - it's still working so I'm not about to cannibalise it yet!

I assume you are thinking of imaging fairly bright objects as the scopes brightness is effectively reduced to one third at each CCD. But the advantage is you can image your RGB simultaneously.

That's interesting LJ - perhaps more about than I imagined - however I'm happy with OSC camera so idea hyperthetical.  If such a system can take RGB via separate monochrome sensors, the object can be as faint as possible with a 'correct' long 'single' exposure - not considering video frame rates by any imagination.  

Was also wondered how the three channels could be combined in post processing to create a strong L [luminance] channel  - maybe G +RGB = L?  but it couldn't be as strong as an unfilter monochrome channel but that's not possible via tri-colour beam-splitter   

[Gina]

My over-riding reason for post was the constant "mono+separate RGB is quicker" [than OSC] which ignores the waste of two waveband whilst the third is exposed - crazy waste of photons.   OK may be costly but not as much as three matched and aligned scopes+cams running on a massive new mount 

It's still quicker than OSC but my triple imaging rig using three scopes or lenses with separate filters and three astro mono cameras catches the maximum number of photons   I would like matching imaging trains but can't afford it - at least, not yet.  I think 3 Esprit 80EDs with 3 Atik 460EX cameras on the EQ8 mount would be awsome.  Total cost of the imaging trains alone is about ten grand (£10,000) maybe more if you use the best filters and filter drawers.

[nytecam]

Hi Gina - perhaps I had you in mine for one of these fancy prisms with just one scope and three sensors - you're the one to do it :-)

[Gina]

I mostly do NB and that's more suited to RGB.  Ha and SII are both in the red - OIII is turquioise so don't know whether it would go into the green or the blue.  Interesting thought though

I guess one option would be to return the Esprit and buy another Evostar 80ED and save up for another two 460EXs - the Evostar is 510mm FL and f6.3 with the FR/FF - the Esprit 400mm and f5...  No I don't like that - I've fallen in love with the Esprit which will be great when replaced for one without the optical fault - and all that's in hand