23 replies to this topic

[jdbastro]

This is my first foray into the world of imaging off of a Gen3 Image intensifier. This shot was taken thru a Mewlon 250 scope in heavily light polluted skies. A 12nm narrow band H-alpha filter was attached to the input end of the intensifier.
Here is the HorseHead Nebula shot in 8 seconds:

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[jdbastro]

Here is a shot of the flame (8 second exposure):

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[jdbastro]

This is the crab nebula (8 second exposure):

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[jdbastro]

Finally everyone's favorite, M42 (in about 1 second):

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[jdbastro]

The camera used was a Panasonic Lumix G5 with a 20mm f1.7 lens looking into the eyepiece of the image intensifier unit (a Micro Monocular) - afocal photography.

Cheers.

[nytecam]

The camera used was a Panasonic Lumix G5 with a 20mm f1.7 lens looking into the eyepiece of the image intensifier unit (a Micro Monocular) - afocal photography.
Cheers.

These are great images especially liked the crisp Horsehead and the Crab M1 - well done and more please

[Lightning]

They are really quite remarkable. Really ghostly in appearance. Have you tried taking a number of pics and stacking them in DeepSkyStacker or such?

Great work, cheers for sharing,
Cam

[highfnum]

great job

[StarStuff1]

Excellent!! I especially like the details in the Crab.

[mattflastro]

very interesting . Not knowing much about gen 3 intensifiers, are those many bright little dots stars or intensifier noise , and if they are at least some of them noise, how can it be reduced?

[GlennLeDrew]

The multitudinous specks are indeed noise, or scintillation, as it's called with intensifiers. Stacking a number of images would significantly reduce their impact.

Another strategy would be to use a scope working at a faster f/ratio, and/or employ a focal reducer. This would form an image having higher surface brightness, thereby increasing signal to noise. The result would be a smoother, 'lusher' image, especially if the gain can also be dialed down.

[mattflastro]

The multitudinous specks are indeed noise, or scintillation, as it's called with intensifiers. Stacking a number of images would significantly reduce their impact.

Another strategy would be to use a scope working at a faster f/ratio, and/or employ a focal reducer. This would form an image having higher surface brightness, thereby increasing signal to noise. The result would be a smoother, 'lusher' image, especially if the gain can also be dialed down.

I wonder what's the duration of each of these scintillations . How fast of a frame rate could be used , assuming I had a camera capable of let's say 500 -1000 fps and stacked 5-20 frames on the fly , would it reduce them significantly? That way the device would still send live video but hopefully less noisy ? Increasing sgnal to noise by reducing noise is more work but addresses the problem without saturating the highlights .

[dtripz]

Well done! I'd love to see some more if you have. Out of curiosity how do these compare with looking through the tube with your own eye, also what light pollution zone are you in?

[StarStuff1]

Generally speaking, the stronger the filtration the more the scintillation. My 12nm Ha filter shows a lot, less in darker skies. My Orion SkyGlow photographic and my Lumicon Deep Sky show noticeably less, even in more LP environs. All experiences with naked eye viewing, not photographically.

BTW Glenn, my IIE has automatic gain and I think most, if not all others, are the same. So gain is not normally adjustable on IIEs. Think of looking over the battlefield and an artillery burst happens nearby. Self survival for the image intensifier tube.

Agree with dtripz, more pics if available.

[mattflastro]

Generally speaking, the stronger the filtration the more the scintillation. My 12nm Ha filter shows a lot, less in darker skies. My Orion SkyGlow photographic and my Lumicon Deep Sky show noticeably less, even in more LP environs. All experiences with naked eye viewing, not photographically.

BTW Glenn, my IIE has automatic gain and I think most, if not all others, are the same. So gain is not normally adjustable on IIEs. Think of looking over the battlefield and an artillery burst happens nearby. Self survival for the image intensifier tube.

Agree with dtripz, more pics if available.

Is this effect of the stronger the filtration the stronger the scintillation due to the skyglow being amplified and becoming bright enough to hide the scintillation ?

[StarStuff1]

If I understand your question, yes. When using the IIE in a small optic for simple night vision in the neighborhood and with no filtration there is little or no scintillation. Very smooth.

[highfnum]

filters cause a certain amount of photon starvation
that forces gain to increase
more gain more noise

but for Ha it still worth it
you get more than you lose

[PEterW]

The figure of merit for intensifiers is equivalent background illumination, essentially the brightness of the output with no input, which your deep sky objects need to be able to poke through. You also want to be below f4 as well, the faster the better.
Be interested in the visibility of nebulae and amount of scintillation with transparency and stray light. I assume nebulae disappear with the other light pollution filters, brighter sky and less scintillation though. I get the same with my rg630 light pollution elimination filter, have to try my CLS filter. So the intensifier equivalent of averted vision is mentally averaging the scintillation. How do things get as the bandwidth drops, thought 10nm was about optimum?

Cheers
PeterW

[highfnum]

if you can do a series of shots and stack you reduce noise
I did a test a while back
http://www.cloudynig...5229288/page...

[GlennLeDrew]

The more aggressive the filtration, the more sky glow is reduced, and the more prominently the scintillation presents itself against the darker image. This is why a faster f/ratio is required. For example, an f/8 scope equipped with a 0.5X focal reducer works at f/4. Image surface brightness scales as the inverse of the f/ratio squared, and so the f/4 image equals (8 / 4)^2, or 4 times brighter.

Trying to reduce scintillation in images by shortening the exposure time may not be of significant help. But given that the noise in the intensifier's output is already high, you can crank up your camera's ISO setting without fear of that noise source being too detrimental. Then it's a matter of selecting an exposure which reasonably well fills in the darker end (left side, by convention) of the histogram.

Ultimately, as Hifnum's linked-to post showed via some example images, stacking is the best bet for a rather more nicely smooth result.

[jdbastro]

Well done! I'd love to see some more if you have. Out of curiosity how do these compare with looking through the tube with your own eye, also what light pollution zone are you in?

My light pollution zone is a suburb of Los Angeles. So there's lots of sky glow. When viewing the intensifier with my eye, on the Flame, and HorseHead, only the faintest outlines are visible. On the Crab, again only the outline is visible - can't see any of the 'vein-like' structures.

If I view these nebulae from a much darker location like Mount Pinos, CA (altitude 8300 ft), the Flame and Horsehead appear at about 80-90% of the detail in these photos. The Crab, although showing brighter, still does not reveal the 'vein' structures.

I took pics of some other nebulae, but I need to see what I've got before I post more.

Also, I plan to shoot similar objects in some of my faster scopes (f7 and f5.6). Both of these scopes are faster but have smaller aperture than the Mewlon. BTW, the Mewlon 250 is f12 - pretty slow.

My ultimate objective is to shoot video with the G5 camera, however I need a faster lens on the camera or some other coupling with less light loss between the camera and intensifier output to make video work. I know someone else on CN has posted some impressive videos using an image intensifier.

[GlennLeDrew]

For extended objects like nebulae and galaxies, f/ratio controls image surface brightness and aperture controls image scale at given f/ratio.

A 3" f/6, a 6" f/6 and a 12" f/6 system will all produce equally bright images, because the f/ratio is the same. As far as extended objects are concerned, the only difference is image scale and hence the level of detail recorded. However, for stars, a larger aperture will record fainter ones.

An f/1.2 lens on your camera is plenty fast, and you'll be hard pressed to find anything faster. That's not the weak link. Strive for the very fastest light cone obtainable from the telescope, yet which is not too badly aberrated in the off-axis part of the image.

[jdbastro]

OK, here's a shot of M82 using an Astronmik CLS light pollution filter at 240 power (f24!) taken in about 1 second):

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[Lightning]

Considering the F-ratio, that's an awesome pic!

Would you mind trying your lowest F-ratio and taking a number of short pics and stacking them with DSS? I'd really like to see just how smooth an image is possible.