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DSLR - how many megapixels to use?


xanthic

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i have only seen it in maxim on the camera window.... i assume you can do it from elsewhere though.


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i may be wrong but if you bin images, do you lose colour ? i understood they only come out in mono using binning method


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Guest Kheldar

i may be wrong but if you bin images, do you lose colour ? i understood they only come out in mono using binning method

 

Not to the best of my knowledge Rob ..

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i may be wrong but if you bin images, do you lose colour ? i understood they only come out in mono using binning method

I think you are right, well at least if DSLR work in a similar way to Colour CCDs then the colours are messed up at least with certain binning, dependant on the colour pattern I think...

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I think you are right, well at least if DSLR work in a similar way to Colour CCDs then the colours are messed up at least with certain binning, dependant on the colour pattern I think...

never heard that one Eddy, lots of the imagers like Per and Olly use binning i think? it has advantages.  chap did a test

and decided on balance to keep binning, interesting though 

 

http://www.lefevre.darkhorizons.org/articles/colorbinornot.htm

Edited by Sheila
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  • 1 month later...
Guest ollypenrice

I hardly ever bin and, apart from with some crafty modern sensors, I don't believe it's possible on one shot colour systems. In Bin 2 you combine 4 pixels into one combined super-pixel but those pixels will be a mixture of all colours on the Bayer Matrix, so how can the information from each be preserved? The super-pixel is read as one, so I can't see that it can be done.


 


Craving more and more pixels on your chip is a daytime thing to do. It is not at all what is wanted for most astro imaging applications. There are two reasons.


1) The seeing limits your resolution. Try to resolve below the resolution allowed by the seeing and you will fail. 2) This failure comes at a cost; each little pixel receives less light (less signal) than would a larger one, so your S/N ratio is inferior and you image dimmer and noisier.


 


The perfect pixel scale in arcsecs per pixel is much debated and depends on your site and the night. However, trying to go below 1 arcsec per pixel is, for almost anyone, a waste of time. In the UK many feel it's optimal around 2. I work between a silly 0.6 (because the SX H36 won't bin without artefacts) and a coarse 3.5 with the Atik 11000/FSQ106. If we could bin the H36 at 2.4 metres of FL we would because 1.2 arcsecs per pixel would still give great resolution and would be at least 1.6x faster. GRRRR!


 


Assuming you're somewhere near the 2 arcsecs per pixel mark or below, you can shoot unbinned luminance and binned colour, which you then resize to fit the luminance. Some will say this comes at no cost but I certainly disagree. It does work pretty well but you will not get the same quality stars. What is more, where possible I remove luminance from my stars because in RGB only they are smaller and less saturated, so more colourful. This assumes that your RGB was shot unbinned, though.


 


Olly


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I did read somewhere about Binning a colour camera for framing (don't remember where and haven't tried)


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Guest ollypenrice

I did read somewhere about Binning a colour camera for framing (don't remember where and haven't tried)

 

That's not a problem. I did it all the time when I had an OSC CCD. You just get a mono image for framing. A lum image from a mono cam is obviously about 3 times brighter but you can work around that without difficulty.

 

Olly

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