Loading ...
Sorry, an error occurred while loading the content.

Re: [ccd-newastro] Re: Well depth of the 8300 chip

Expand Messages
  • Wodaski - Yahoo
    The depth of binned pixels is a mixed bag. Usually, the total electron count is not the sum of the 4 or 9 pixels involved; it is limited by the size of the
    Message 1 of 11 , Jan 2, 2010
    • 0 Attachment
      The 'depth' of binned pixels is a mixed bag. Usually, the total electron count is not the sum of the 4 or 9 pixels involved; it is limited by the size of the readout pixel. So even if you use four pixels, and the well depth of individual pixels is, say, 50k, that doesn't give you a 200k well depth. The max will be determined by readout limits. They might be (and often are) substantially lower. For most cameras, you can get this number from the manufacturer's spec sheet.

      Ron W

      On Jan 2, 2010, at 6:18 PM, Mike wrote:

      > Ron, with 2x binning does that effectively double the well depth?
      >
      > Thanks,
      >
      > -Mike
      >
      >
      > ------------------------------------
      >
      >
      >
      >
    • dannysperry
      Hi Ron, ... I m really glad to see you say this. A lot gets said about a chip s numbers but the chip is only the start of the story. It mostly comes down to
      Message 2 of 11 , Jan 4, 2010
      • 0 Attachment
        Hi Ron,

        >> In the end, nothing says anything as well as
        >> some actually images. The best thing to look
        >> at are calibrated sub-exposures that are long
        >> enough to overcome the read noise.

        I'm really glad to see you say this. A lot gets said about a chip's numbers but the chip is only the start of the story. It mostly comes down to the manufacturer's implementation of the support electronics and actual images are the only way to know if YOU'LL be happy with any given camera. The downside, of course, is that good sets of images are difficult to come by with newly released cameras.

        Best,
        Danny
        http://www.californiastars.net/


        --- In ccd-newastro@yahoogroups.com, Wodaski - Yahoo <yahoo@...> wrote:
        >
        > I would consider both of those cameras to be low in terms of well depth. I've used cameras with well depths up to 800,000 electrons, and that one also had read noise of about 1 electron, so it had a huge, huge dynamic range - and, yes, it was able to resolve small brightness differences magnificently.
        >
        > (In fact, you could see more dim details with that camera in a 10-minute exposure than with a 70-minute exposure from an ST-10XME.)
        >
        > So I wouldn't expect a huge difference, but I also can't quantify it for you in advance, because it's not just about the well depth. There are so many variables that it's hard to anticipate what a chip's images will look like. I remember when the STL-11000 came out from SBIG; no one had good expectations for it. But it became a widely used camera because the _combination_ of its qualities resulted in both pleasing images and useful data.
        >
        > In the end, nothing says anything as well as some actually images. The best thing to look at are calibrated sub-exposures that are long enough to overcome the read noise.
        >
        > Ron W
        >
        > On Jan 2, 2010, at 11:47 AM, chris provost wrote:
        >
        > > Thanks Ron. With that siad would you shy away from the 25,500 well depth of the 8300 chip? Will I see a obvious difference compared to my 2020 chip with a well depth of 40,000?
        > >
        > > Chris
        > >
        > >
        > >
        > > --- On Sat, 1/2/10, Wodaski - Yahoo <yahoo@...> wrote:
        > >
        > >
        > > From: Wodaski - Yahoo <yahoo@...>
        > > Subject: Re: [ccd-newastro] Well depth of the 8300 chip
        > > To: ccd-newastro@yahoogroups.com
        > > Date: Saturday, January 2, 2010, 2:43 PM
        > >
        > >
        > >
        > >
        > >
        > >
        > > Well depth, plus read noise, determines the dynamic range you will get from a camera.
        > >
        > > Read noise can be considered as a step size. So if full well is, say, 100k electrons, and your read noise is 10e-, then your dynamic range has 100,000/10 or 10,000 steps.
        > >
        > > If your well depth is 30k, and your read noise is again 10e-, then your dynamic range is only 3,000 steps.
        > >
        > > The smaller your dynamic range, the less able you are to resolve faint differences in brightness levels. For example, if you were imaging a comet, a greater dynamic range would make it easier to resolve subtle brightness differences in the tail.
        > >
        > > You can improve on this base dynamic range by taking additional images, and using sub-exposure durations that are long enough to bury the read noise in the shot noise.
        > >
        > > The ideal situation, of course, is to have deep wells, large pixels, high QE, low read noise, large aperture, fast focal ratio, etc. But that gets expensive!
        > >
        > > Ron W
        > >
        > > On Jan 2, 2010, at 9:34 AM, lineman_16735 wrote:
        > >
        > >> As I have posted earlier I am considering the purchase of an 8300 chip camera. A friend of mine mentioned that the shallow well depth should be something I consider. Can anyone explain what the drawback of shallow well depth would be? Is it something that should be a major concern to me?
        > >>
        > >> Chris
        > >>
        > >>
        > >>
        > >> ------------ --------- --------- ------
        > >>
        > >>
        > >>
        > >>
        > >
        > >
        > >
        > >
        > >
        > >
        > >
        > >
        > >
        > >
        > >
        > > [Non-text portions of this message have been removed]
        > >
        > >
        > >
        > > ------------------------------------
        > >
        > >
        > >
        > >
        >
      Your message has been successfully submitted and would be delivered to recipients shortly.