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wide screen dominance


happy-kat

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I'm always surfing new gear just to read about it and compare to what else is in the same area. Why are cameras coming out with such wide screen proportions, I've just read about the ASI462MC looks to be interesting on the infrared front which pits it against the ASI224MC also sensitive in infrared though the graph suggests not as sensitive as the new one but the older model has a nice 4:3 bias sized sensor. Wide screen looks to be pointless for planetary though perhaps it's just making use of sensors already developed by the likes of Sony then used by others on astro cameras.

What else am I missing in the point/drive for wide screen on sensors? Any enlightenment appreciated please.

 

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You have to remember that we're a niche market, so we have to make do with what the chip makers produce, and widescreen (Mainly 3:2) sensors are mainstream. About the only square format sensors are the 533 and the horribly expensive 37mm square offerings like the KAF16803 or Kepler 4040. Don't even think about the Kepler 6060 unless you are a university. The nearest would be the various 4:3 and 5:4 sensors such as the SX 694 or the 16200.

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  • 2 months later...

Pondering this further I have collated various cameras into a spreadsheet to look at pixel scale etc. I was looking at sensitivity information on the various Sony camera sensors and my stumbling block is I can't find a conversion for Digit to mV.

This is probably something @vlaiv might shed light on the conversion please.

image.png.2053231fd267e5856038698177aa61ab.png

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I don't think I'll be much of a help there.

It's the first time I've ever heard of a "Digit" being used as unit for something and I don't know much about mV as a unit.

I have an idea of what mV could be, but it is not "sensible" unit to compare to other units - it is "internal" measure - for Sony cameras, as far as I understand.

Sony has developed some sort of sensitivity measurement protocol where they use their "standard" light source, their "standard" lens and use something like 1/30 or 1/60 exposure and then measure voltage from electrons gathered in a pixel. At least I think so.

What we can do is try to figure out values from your table above.

ASI178 has saturation of 945mV and 15000e FW, so we have 15000/945 = ~15.873

ASI224 has 1210mV and 19200e FW => 19200e/1210mV = ~15.868

ASI290 => 14600 / 913 = ~15.991

ASI183 => 15000 / 942 = ~15.924

I would say that most pixels have ~15.9 conversion factor between mV and e.

As far as sensitivity goes, I'm not sure where you have your figures from, but here is for example screen grab of IMX178 sensor info (sensor in ASI178):

image.png.2726af4615101bec4e5eb86218a31126.png

found here: https://www.1stvision.com/cameras/sensor_specs/IMX178.pdf

In any case, that value is not telling much. Here is why:

image.png.770beab459b65076713c9205e39b4e2e.png

and look at QE graph of ASI224:

image.png.26f47fd9660934b10f804f289ade1a77.png

Green captures all the way up to 1000nm having significant peak (more than 50% of its max value) at 820nm. These wavelengths you won't be using in astrophotography unless you are doing IR imaging and using particular filter to capture only light above 800nm

If we have F/5.6 lens and 1/30 exposure - both cameras should capture signal that is in relation to their pixel surface and their peak qe.

for ASI178 this would be 2.4 * 2.4 * 0.81 /425 = ~0.011

for ASI224 this would be 3.75 * 3.75 * 0.8 (quoted value for peak QE is between 0.75 and 0.8) / 2350 = ~0.0048

It looks like ASI224 is twice as sensitive as ASI178 somehow, but what happens is:

image.png.9ef586848b7e4ff6b849da255a7cd5d7.png

ASI 224 has twice the surface under green QE curve than one would expect from regular camera that covers about 500-600nm for green channel.

Will this be useful for astro photography? if you use IR cut filter - no.

Don't look at published results from Sony (and others) - they are OK if you want to use camera in both day and night surveillance applications or similar - then yes, it will be twice as sensitive. Btw - this is where partial answer to original question lies - surveillance sensors often need to capture large horizontal areas - and not much in vertical axis - hence those wide formats.

Pixel size, peak QE, read noise - these are the things that you should compare. If camera has some "perks" like - ASI224 for IR imaging - that is a bonus if you plan to do that sort of thing.

 

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Thank you for replying. I had used Sony datasheets for values and it is odd that the latest data sheet now uses different metric for the same specification items.

I suspect I'm likely over thinking, but I like to expand learning when making decisions. The spreadsheet and use of the FOV calculator has helped narrow down that for me and the equipment that I already own the slightly larger pixels of 2.9 (larger than Neximage 5 at 2.2) will compliment and provide an opportunity to target the odd galaxy as well. Infrared is an interesting area and two of the cameras listed have that potential. 

Edited by happy-kat
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57 minutes ago, happy-kat said:

Thank you for replying. I had used Sony datasheets for values and it is odd that the latest data sheet now uses different metric for the same specification items.

I suspect I'm likely over thinking, but I like to expand learning when making decisions. The spreadsheet and use of the FOV calculator has helped narrow down that for me and the equipment that I already own the slightly larger pixels of 2.9 (larger than Neximage 5 at 2.2) will compliment and provide an opportunity to target the odd galaxy as well. Infrared is an interesting area and two of the cameras listed have that potential. 

What is primary interest? Is it planetary?

If so, pixel size and pixel count as well as format of sensor - have absolutely no bearing on decision - main two parameters should be QE and read noise.

If you plan on doing a bit of lunar as well - then you should take sensor size into account also - because it will take less panels to create full moon mosaic.

For solar, things again change as for EEVA / DSO imaging. For last two - sensor size becomes dominant factor as it enables you to pair camera with much larger telescope and get larger aperture for same field of view (which also requires heavier mount, etc, so all things need to be considered there).

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Imaging purpose is expand fun/use with what equipment I already have, which is neither a substantial mount or substantial aperture and not equatorial.

I can do full Moon disc and DSO with the 1100d and can do planets with Neximage 5.

I don't want to replicate the FOV that I already get the 1100d as I have neither mount, aperture or focal length, so it is left to manipulating FOV through pixel and sensor size,  which 2.9 fits, plus has opportunity for all sky camera and controlling through Android plus infrared.

QE and read noise of the ASI462 are very high/low respectively.

 

Edited by happy-kat
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