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ccasal
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Reged: 05/11/09

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M51 - Orion G3 Mono Tests new
      #5785439 - 04/08/13 08:40 AM Attachment (45 downloads)

Hi all,

I have been imaging with a DSLR for 4 years now and I am considering moving to a Mono CCD. While I decide on the camera to buy I bought an Orion G3 Mono CCD to start getting acquainted with monochrome imaging.

My DSLR has 6.4 micron pixels (1.32"/pixel) and the G3 has 8.6 micron pixels (1.77"/pixel).

This is a test of M51 using the G3 and I am finding I can go with longer subs than using the DSLR.

Is this related to the well depth of the G3, which is (50000)?

Resolution should be a bit better, compared to the DSLR, when I integrate color data to the image, even though pixels are bigger. Correct?

Your thoughts and comments are appreciated.

8 x 180s
Orion 10 F/3.9
Atlas EQ-G
Guiding Orion SSAG + Miniguider 50mm
Stacked in DSS and some processing in PS


Edited by ccasal (04/08/13 08:42 AM)


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Raginar
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Reged: 10/19/10

Loc: Rapid CIty, SD
Re: M51 - Orion G3 Mono Tests new [Re: ccasal]
      #5785510 - 04/08/13 09:32 AM

Carlos,

The CCD you purchased is really a fancy guide camera with cooling. That's about what I'd expect from it.

Your DSLR probably can go longer but it will suffer from more thermal issues.


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ccasal
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Reged: 05/11/09

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Re: M51 - Orion G3 Mono Tests new [Re: Raginar]
      #5787803 - 04/09/13 10:53 AM

Hi Raginar,

I understand this is an entry level ccd, I am just using it to get acquainted with mono ccd imaging. I still deciding which ccd to move to. (currently contemplating moving to an Atik 460ex).

My questions are regarding well depth and resolution.

Is the well depth responsible for me being able to shoot longer exposures with the G3 than with the DSLR?

Or putting it another way:

With my cooled Canon 350D I can go for 3 minutes before the histogram goes beyond that 1/3 of the way.

With the G3 I have gone for 5 minutes without seeing the effects of sky background saturation.

Why is this? I'm I not seeing the effects because I have not integrated color?


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Inverted
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Reged: 01/19/13

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Re: M51 - Orion G3 Mono Tests new [Re: ccasal]
      #5787895 - 04/09/13 11:53 AM

Going longer is probably somewhat well depth, but probably more noise. I think likely some of the "sky-background" was actually camera noise. Also, the gain settings are probably different which will have an effect. I don't think the G3 is a fancy guide camera though, it uses a very low noise Sony ICX419, has relatively low read noise and for all intents and purposes should be as good as most typical mono-ccds. Actually, I looked at it as a guide camera, but the download time is slow to use as a guide camera, and it isn't really marketed as such... The limitation is mainly that it's a really, really small chip compared to a DSLR, or Kodak 8300 etc... Overall though, I don't think length of exposure time necessarily means much, other than it's a different camera with different properties. The end result is more important.

As far as resolution, you stated the DSLR is higher resolution. The DSLR will lose a lot due to the bayer matrix though. The actual resolution you end up with however, may not have anything to do with the camera if your limited by seeing and tracking. Your stars are elongated, so, you are loosing resolution to tracking error and possibly seeing as well.


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ccasal
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Reged: 05/11/09

Loc: San Juan, PR
Re: M51 - Orion G3 Mono Tests [Re: Inverted]
      #5788016 - 04/09/13 12:43 PM

Thanks Inverted!

Sensor is really really tiny!!

Can we say that the DSLR having a pixel scale of 1.32"/pixel given the debayering process will have an effective resolution of 2 x 1.32"/pixel => 2.64"/pixel or is that a totally misguided assumption?


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Inverted
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Reged: 01/19/13

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Re: M51 - Orion G3 Mono Tests new [Re: ccasal]
      #5788060 - 04/09/13 01:03 PM

Sort of. My understanding is that the debayering algorithms can improve that mathematically. I'm not exactley sure by how much. I don't think algorithms such as drizzle may also improve undersampled images a bit more.

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