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Perseus Double Cluster Real-Time HD Video thru IIE

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#1 jdbastro

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Posted 13 August 2013 - 11:39 PM

I know these are easy targets, but when is the last time you saw these at 90X? We start with NGC 869 which fills the FOV, and then GOTO over to NGC 884. Nice smooth frame rate since these are bright. Equipment is: Gen 3 thin-film image intensifier, Mewlon 250 scope at f9.2, Panasonic GH3 camera. Shot from Mount Pinos, Calif.

Perseus Double Cluster Real-Time HD Video Link

Here's a still of NGC 869 (1/2 sec exposure, ISO = 200):

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#2 jdbastro

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Posted 13 August 2013 - 11:40 PM

And NGC 884 (1/2 sec exposure, 200 ISO):

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#3 runner70

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Posted 17 August 2013 - 12:39 PM

Beautiful image! I have just started using a diy gen1 cascade tube; how does your output appear prior to entering the camera? My tube's output needs magnification- is putting it through a camera the only way to achieve a decent scale?

#4 jdbastro

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Posted 17 August 2013 - 06:22 PM

Beautiful image! I have just started using a diy gen1 cascade tube; how does your output appear prior to entering the camera? My tube's output needs magnification- is putting it through a camera the only way to achieve a decent scale?


My videos/photos are taken using afocal photography. This means that I have an ocular (eyepiece) attached to the housing that holds the Gen 3 image tube. The ocular is specifically designed to magnify the tube output and present a uniformly sharp image when viewed by eye with an apparent FOV of about 40 degrees. This ocular is used on a wide variety of Gen 3 intensifier housings (e.g. PVS-14, AVS-9).

I couple my micro 4/3d's camera to the ocular using a split ring adapter with 46mm male threads. This adapter is the attachment point for a 17.5mm f0.95 lens designed for a micro 4/3d's sensor (crop factor of 2).

So the ocular provides most of the magnification and produces an infinity view which the camera lens then captures while focused to infinity. I chose the 17.5mm lens based on earlier experiments with a micro 4/3 zoom lens to get a reasonable image size on the camera sensor.

My other option would be to use a relay lens specifically tailored to my tube housing (ITT Night Quest 6010) and remove the ocular and camera lens from the setup. I haven't tried this yet.

Can you obtain an ocular for your Gen 1 setup that gives you a suitable view for afocal photography? If not, perhaps a macro lens would work, or last option would be probably some type of relay lens coupled directly to you camera.

#5 runner70

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Posted 19 August 2013 - 03:24 PM

Thank you very much for the guidance- the specific part numbers are especially helpful. So far, I have used only standard telescope eyepieces as oculars. When using filters such as O-III or narrow H-alpha (~5-10nm), do you place the filter "before" the intensifier tube?

#6 jdbastro

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Posted 19 August 2013 - 04:53 PM

Thank you very much for the guidance- the specific part numbers are especially helpful. So far, I have used only standard telescope eyepieces as oculars. When using filters such as O-III or narrow H-alpha (~5-10nm), do you place the filter "before" the intensifier tube?


You're most welcome.

Please be advised that the ocular that I listed is intended to produce a sharp image when used with the curved output of a Gen 3 18mm intensifier tube. I'm not sure what results you would get with a Gen 1 tube. Does the Gen 1 have a flat output?

You want to put any filter intended for image contrast improvement in front of the intensifier tube, i.e. in front of (before) the intensifier photocathode. Narrow band H-alpha (6-12 nm) works very well to enhance emission nebulae and many planetary nebulae when used in conjuction with a Gen 3 intensifier (GaAs photocathode).

But I'm not familiar with the photocathode for Gen 1 nor it's spectral photoresponse curve. Is it similar to Gen 3 (GaAs)?

#7 jdbastro

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Posted 19 August 2013 - 05:14 PM

OK, regarding spectral photo response of photocathodes, I found this plot on the Photonis website:

Blue is Gen 3 (GaAs). Gen 1 is either the magenta (S25) or black (S20) curve.

Do you know what material your Gen 1 tube's photocathode is made of?

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#8 runner70

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Posted 26 August 2013 - 04:19 PM

It is a flat output of about 40mm in diameter. I have not been able to determine what sort of tube my cascade is; it has a purple color when viewed indoors.

#9 cnoct

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Posted 27 August 2013 - 08:08 AM

runner70,

Your cathode is of the S25 type. The behemoth pictured on the left uses the S25 type as well, though I do hope your tube is a bit smaller, couldn't imagine adapting this one to a telescope.

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