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Evaluating Bias/Dark Frames and Camera Power Suppl

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#1 buckeyestargazer

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Posted 28 February 2013 - 02:12 PM

I'm curious if there is a way to evaluate bias frames (or darks too) that shows changes in background or irregularities etc if there is a change in the voltage supplied to the camera.

Normally I power my camera and filter wheel with separate power supplies. But in an effort to streamline cables I'd like to power the camera and filter wheel from the same power supply using a splitter. I've been told by the manufacturer (Atik) that this should be no problem as long as the power supply has enough amps to cover the components draw. In the case of my Atik camera (max 2amps) and filter wheel (very low amps), a regulated 2.5amp power supply should be fine.

So I took some bias frames with the camera drawing a lot of power and the filter wheel disconnected, and some bias frames with the filter connected and rotating (of course, the filer wheel will never be rotating during exposures in actual practice!).

Is there a way to quantitatively measure the bias frames with and without the FW attached that would show any differences induced by sharing a power supply?

I really have no clue what I'm talking about here so if this is all a ridiculous question I apologize in advance! :lol:

#2 cn register 5

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Posted 28 February 2013 - 06:17 PM

The simplest way to evaluate bias or dark frames for noise is to take two images and subtract them. What's left is the noise.

You could try the different power supplies and see if there's a difference in noise or subtract an image using one power supply from one using the other and see it there's a difference.

What you're trying to do is the same as with any other scientific experiment, change the thing you are measuring while keeping everything else the same.

Chris

#3 wolfman_4_ever

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Posted 28 February 2013 - 06:32 PM

I doubt you would see any changes.. most power supply noise is transferred through an analog signal such as a video camera.. The a/d converter should dump any analog noise.

#4 buckeyestargazer

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Posted 28 February 2013 - 06:41 PM

I doubt you would see any changes.. most power supply noise is transferred through an analog signal such as a video camera.. The a/d converter should dump any analog noise.


Good to know, thanks.

#5 Mike7Mak

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Posted 28 February 2013 - 06:48 PM

I doubt you would see any changes.. most power supply noise is transferred through an analog signal such as a video camera.. The a/d converter should dump any analog noise.

Yeah, I wouldn't count on that. I've had cheap switching power supplies cause severe noise patterns in my DSIs, and my Atik occasionally picks up interference from the microfocuser.

#6 astrovienna

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Posted 01 March 2013 - 01:10 PM

The simplest way to evaluate bias or dark frames for noise is to take two images and subtract them. What's left is the noise.

You could try the different power supplies and see if there's a difference in noise or subtract an image using one power supply from one using the other and see it there's a difference.

What you're trying to do is the same as with any other scientific experiment, change the thing you are measuring while keeping everything else the same.

Chris


This is the way I would go. Craig Stark's writeup has pretty thorough instructions for how to do this. I learned a lot about my camera when I did this.

Kevin

#7 wolfman_4_ever

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Posted 02 March 2013 - 12:31 AM

Ground issue more than likely... who knows..

#8 buckeyestargazer

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Posted 02 March 2013 - 09:04 AM

This is the way I would go. Craig Stark's writeup has pretty thorough instructions for how to do this. I learned a lot about my camera when I did this.

Kevin


Thanks Kevin, that's good info and what I was looking for.






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