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Equipment Discussions >> Electronically Assisted Astronomy

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sage


Reged: 04/24/13

A Survey of CCD’s Used In Astro-Video Cameras new
      #5863766 - 05/16/13 05:35 AM

interesting paper.

http://karmalimbo.com/aro/reports/Astrovideo%20Camera%20CCD%20Survey.pdf


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ccs_hello
Postmaster
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Reged: 07/03/04

Re: A Survey of CCD’s Used In Astro-Video Cameras new [Re: prefetch]
      #5863824 - 05/16/13 07:05 AM

It's an interesting paper. I saw the previous version of the paper and I have a few reservations. Since it's outside of the forum I'd say it's not fair to discuss/debate the subject without author's participation and his willing.

Clear Skies!

ccs_hello


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mclewis1
Thread Killer
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Reged: 02/25/06

Loc: New Brunswick, Canada
Re: A Survey of CCD’s Used In Astro-Video Cameras new [Re: ccs_hello]
      #5864222 - 05/16/13 11:15 AM

Jim (the author) does spend some time in the Mallincam Yahoo group and only occasionally around here. Perhaps an invitation there would be in order?

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mattflastro
Vendor - Astrovideo Systems


Reged: 07/31/09

Loc: Brevard County , FL
Re: A Survey of CCD’s Used In Astro-Video Cameras new [Re: prefetch]
      #5864349 - 05/16/13 12:03 PM

Quote:

interesting paper.
....




That paper claims to discuss and analyze cameras used in astronomy, but it doesn't address ANY camera with Sony SuperHAD 2 or Exview HAd II ccd's .

Simply put, that paper is frozen in time around 2003-2005 . It may have been relevant 5-10 years ago but making purchasing decisions today based on old data is not very wise.

Also while it has the appearance of a scientific paper, it is not. Hasn't been published anywhere except on the web , has NO professional peer review . Even the website where it is published doesn't allow comments .

For the average reader it would be impossible to tell if that paper is great or hogwash.

While it includes some cameras that are used in astronomy, it did not include any inexpensive cameras that are in widespread astro use such as the Samsung cctv models (the most glaring omission).
The Samsung sdc-435 and scb-2000 and many other cameras use the newer and better second generation Sony sensors, while the cameras the paper is discussing are stuck with the first generation sensors such as the icx418/428 .

Another problem is the general language of that paper.
It may seem logical and unbiased in its conclusions to people who have nothing to do with electronics but it's actually very biased (I'm not commenting whether involuntary or not) toward some camera brands .

One random example just to illustrate the point ,it states that the camera cooling system has to use very high grade components in order to not introduce noise into the image .

While such an assertion might seem plausible or reasonable to most readers , in reality the cooling system can introduce noise into the image by poor circuit design , NOT by the grade of its components.

The "high grade" components do only one thing, GIVEN THE SAME STRESS FACTOR they last longer than "lower grade" components .
But even this can be debated, because the stress or load can be changed by design .
For example, a "high grade" capacitor rated for 12V would last longer than a commercial grade capacitor rated for 12V , PROVIDED they operate at the same ripple currents and same ambient temperatures and numerous other conditions that qualify this statement.

A high grade 12V cap vs. a 25V commercial grade cap , the high grade operating at 12V and the comemrcial grade also at 12V, the high grade operating at a higher ripple current due to a different schematic, all bets are off .

However, noise CAN be introduced into a camera, in great amounts , by poor circuit design.
Bad grounding, bad power and signal routing , ground loops, long parallel traces, unmatched or mismatched loads , using the wrong part in the wrong place plus many many more .

High component grade does absolutely NOTHING to remove the noise that's introduced this way.
While it is understandable that the paper discusses performance mostly based on the Sony published data and is attempting to normalize it in order to perform a comparison, there is really no validation presented for the normalization method.

Also, while some measurements are not easily duplicated by amateurs, some other can be performed by anybody with a little bit of patience .

Camera noise can be analyzed using freely software and just the camera and some images taken with the camera.

True, using FFT seems intimidating to most readers but you don't actually have to understand what the FFT does, the software takes care of the process.

There are papers documenting how to do this even here on CN , for example the article series written by DR. Craig Stark :

How to Measure Camera Noise

Camera manufacturers use the FFT method too:

QSI Camera Noise FFT

There are others , like Tucsen etc.

That would be a direct comparison and could compare for example a camera using the Sony icx632 ccd , which is a 1/3" ccd rated by Sony at 3800mV sensitivity versus only 1600mV for the old icx428 .

Another problem with that webpage is that it mostly analyses features and technologies that are used in a certain camera brand that the author seems most familiar with , or perhaps was/is more closely associated with and it ignores other brands/features/technologies , which makes it either biased or incomplete.
Please note that I did not say the paper is biased on purpose, just that by picking some and ignoring others the result becomes biased.

I did like the tone of the paper and the amount of detail that was presented.

I did not go thru the numbers to see whether the analyses were correct , mostly because it deals with old CCDs of no interest today and also because some very important parameters such as sensor noise were not dealt with thoroughly .

Sony currently produces sensors that have much higher specifications than the venerable icx418 or icx428 .
Sony specifies the icx828 at exactly DOUBLE the sensitivity of the icx428 as a DIRECT comparison (not as the paper you refer claims that SOny is measuring each sensor under different conditions so a direct comparison couldn't be done).

Sony icx828 vs icx428

To sum it up, the paper you referenced would be a good read for people IF they already knew which claims to take seriously and which not (but people who already know those things don't need to read them) , and it would be dangerously misleading for people who don't know much about imaging electronics.

All in all, a good attempt but needs improvement in the areas of thoroughness , exactness and eliminating dangerous biases .


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C8er
super member


Reged: 09/15/12

Re: A Survey of CCD’s Used In Astro-Video Cameras new [Re: mattflastro]
      #6052789 - 08/29/13 03:23 PM

Can anyone tell me which model sensor is in the Samsung scb2000?

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mattflastro
Vendor - Astrovideo Systems


Reged: 07/31/09

Loc: Brevard County , FL
Re: A Survey of CCD’s Used In Astro-Video Cameras new [Re: C8er]
      #6052949 - 08/29/13 04:46 PM

Quote:

Can anyone tell me which model sensor is in the Samsung scb2000?



icx638


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C8er
super member


Reged: 09/15/12

Re: A Survey of CCD’s Used In Astro-Video Cameras [Re: mattflastro]
      #6053067 - 08/29/13 06:00 PM

Thanks very much for that Matt.

Cheers,
Chris


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