From: Milton Aupperle <milton@outcastsoft.com>

Date: February 24, 2010 2:11:31 PM MST

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] REPORT: Experiment with a pretty big focal length (C11 @ f.92 = 26 meters)

Alberto;

On 24-Feb-10, at 1:07 PM, albe albo wrote:

Thank you Milton thank you Ray.

Milton the teoric limit is the one I'm trying to verify with such try.

Theoretical resolution for a C11 is 0.42 arc seconds, under perfect skies.

I know the mathematical formulas: they seems absolute but... perhaps for a single shot without atmosphere.

The summing method and the seeing seems to modify a little that possibility.

The summing method won't reduce the resolution, Your really shooting with empty resolution anyhow and just spreading resolvable detail out over 5 to 10 pixels instead of a single pixel.

I'd like to find that perhaps with such focal length i could resolve less than 10 pixels... perhaps 7 or 6.

6 pixels is about 0.2 arc seconds at F92. 

Binning 4x4 would still be below that threshold. But you still need to crank the gains way down to reduce the noise level.

Watching the video while i was grabbing it sometimes showed some nice detail.

I'm only basing my analyses on the single (hopefully represnetative) in the frames you showed though. That shows are vague soft changes spread over multiple pixels.

For such reason i'd like to own a ideal camera that could allow me to go to 60 fps with good brightness and no noise.

Your not going to find such a beast.

An EXHAD CCD will be 1.4 to 2 times as sensitive as your TIS Super HAD CCD Camera is. If you have a camera with larger CCD pixels, that will brighten the image up, but your image scale is smaller. I graphically showed this in the past for a 7.4 micron versus a 4.65 micron CCD camera.

Still your gain settings are amplifying the brightness by about 40 times, so your still 10x higher than the best case scenario.

The diagonal pattern is moving. Summing the frames UNALIGNED produce a pattern free stack while aligning even a gray flat patterned field produce a patterned stack.

Well aligning a flat gray frame (with low noise of course) will home in on the pattern that is there. That isn't a surprise to me it gets amplified by aligned stacking.

Here the link to the files that i sent to TIS:

http://dl.dropbox.com/u/1094920/DMK31AF03.AS-Pattern-Mayer-NoMovies.zip

I have the 100 frames original movies too and it would be not important to recompress them if necessary.

Your logs also show you've pushed the Gamma way down too. In one you were at 0.37 and the other at 0.69. That's pretty excessive and reduces the contrast even more. Your using it to brighten the already amplified gains image, which just makes the noise even worse.

About the sharpness/contrast.

Ok for what you say about smallest details but about the...macrosharpness (big details) i was thinking to the possibility to increase the contrast a lot (only temporarily during the estimation process)  and to assign a variable blur radius in order to cut off some  medium-high frequencies  (noise and not precious details in this case) allowing to choose among details of a certain given size.

It's not going to work. Boosting the contrast will Boost the noise even worse. And the noise isn't medium frequency it's very small frequency. Individual pixels are changing in value +/- 14 (likely higher because of the low Gamma usage) now, where as your brightest part of the image is only 60. So the pixels themselves are changing by +/- 25% between frames because of the high gains (and Gamma) and low brightness.

You could improve this signal to noise ratio if the image was brighter, but only if it is brightened without increasing the Gains or Gamma.

Watching my movies:

What about downloading my IR movie (for thr moment) already cropped and aligned and recompressed APPLE-PIXLET highest quality?

Nope. I will not work with post compressed movies. It has to be the original footage or it's not worth working on. It alters the pixels and that can change things drastically. I've been down this road and it simply is not the same.

I compared pixel x pixel the 2 compressions and the difference is really minimal so that i always recompress my movies after my processing including the DSO.

Did you quantify it? The only way to say it is has no effect is if you subtract the two frames (one uncompressed the other compressed) and sum the absolute differences between the two. If it isn't "0" for a sum, they are different and it could be significant. And of the wavelet or JPEG type compressors are altering pixels and do so by data loss. I've dealt with many compressors and lossy compression code in the past, they never produce the exact same images as the source does. It may be visually similar, but at the pixel level it has been altered.

TTYL..

Milton J. Aupperle