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Thread: The no-cost 10-step checklist for a better image

  1. #21
    Alan Erickson's Avatar
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    Default Re: The no-cost 10-step checklist for a better image



    #4 has a typo. It is referring only to CCD cameras. Most DSLR cameras don't have a binning feature. Deconvolution is a form of deblurring. It is offered in some astro-imaging apps like Maxim DL. It's a tricky thing to use and get good results. It can be prone to sharpening noise.

    I always dither between subs. I use Maxim DL for auto guiding, and you can choose to dither through the auto guiding mechanism. In that case, Maxim is handling both the guiding and the exposure sequencing, so it knows when to move the mount. That may not be an option with your current setup, but it is something to advance to later. I think maybe Nebulosity and PhD guide could be a low cost way to get to automated subs and dithering.

    I haven't seen the Astronomy magazine article. Some who use bias frames and dithering don't use darks. Flats can account for both pixel-to-pixel variances in sensitivity and uneven illumination. Uneven illumination can be from vignetting or dust donuts. It is said that bias frame subtraction, dark frame subtraction, and flat fielding can themselves introduce noise, probably due to the small amount of noise still in those calibration frames. So that may be the motivation for leaving out dark frame subtraction, and even flats, although flats seem to be a net gain to me.

    Quote Originally Posted by jrkirkham View Post
    I have a couple of questions.

    (#4) What is binning and how do you do it one a DSLR. I always thought that was something done on a CCD, so I never paid much attention to it.

    (also #4) What is deconvolution?

    (#9) Do most of you dither between subs? Astronomy Magazine just had a short article on it, but the author suggested only shooting up to 16 frames and not using darks or flats. In his article he made some strong claims about the quality of dithered, stacked subs. I usually program my scope to take a series of subs and then do something else while the camera does it's thing. I didn't think about manually taking the subs so I could dither in between.
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  3. #22
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    Default Re: The no-cost 10-step checklist for a better image

    Quote Originally Posted by Alan Erickson View Post
    #4 has a typo. It is referring only to CCD cameras. Most DSLR cameras don't have a binning feature.
    Hi Alan,

    It is most definitely no typo!

    Have a look at post #21 where I explain the difference between hardware and software binning. Most DSLRs today do have a (software) binning feature ('low-light' mode) that reduces resolution to a quarter of the original resolution in exchange for reducing noise by 50%.

    Software binning is not something you would typically do at capture time though. It is something you do after stacking or at the start of post-processing, when you can better gauge the need for it.

    The following is an example of software binning;
    The first image is a 400% zoomed in crop that is scaled down to 35% of its original size using nearest neighbour sampling - this effectively retains noise levels as they were in the original crop.
    The second image is a 400% zoomed in crop that is binned down to 35%. The noise reduction is quite apparent.
    Notice that no actual detail was lost by scaling down, just noise. This is because the real detail occupies the lower frequencies (coarser details) in the image, as opposed to the noise which is mainly visible in the finer details.
    bin_example_400nobin.pngbin_example_after_400bin35.png
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  5. #23
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    Quote Originally Posted by Phil Leigh View Post
    #13 - Don't forget to fit the supplied rubber eyepiece blind to the DSLR viewfinder during long exposures. The blind is normally to be found fitted to the original strap that came with your camera (it can be removed from the strap, but don't lose it - I've not yet been able to source a replacement).
    The eyepiece surround needs to be removed first before fitting the blind - if you lose those, replacements are easy to find.
    www.bocaphoto.com

    You're welcome lol -- I use bought a eye piece blinder for my D7000 because the DX bodies don't come with a blinder built into the body like the D3S... Not does Nikon put that piece on the strap like Canon does. I went looking for it the other day and realized it was lost. Takes alittle while for the guy to ship the parts but he does. If I recall correctly its a one man operation. I have ordered parts from him every now-and-again over the past 3 years.

  6. #24
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    Default Re: The no-cost 10-step checklist for a better image

    Someone should start a similar thread for visual observation...

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    Default Re: The no-cost 10-step checklist for a better image

    Very nice starting points! Can you also help with selecting a new or lovingly used DSLR and how to have a qualified person modify the IR filter to allow a greater % of emission nebulosity through? I'll look for your knowledge and be a sponge.

    Thanks again.

  8. #26
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    Default Re: The no-cost 10-step checklist for a better image

    This is the most helpful thread on the forum. Thanks to all.

  9. #27
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    Default Re: The no-cost 10-step checklist for a better image

    Quote Originally Posted by rfluke View Post
    This is the most helpful thread on the forum. Thanks to all.
    Well yes apart from the bit about binning... DSLR's do not do binning.

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    Default Re: The no-cost 10-step checklist for a better image

    You can do software binning in DSS using the "Super Pixel" mode. It does a straight 4/1 reduction.
    Jim
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    Default Re: The no-cost 10-step checklist for a better image

    I want to also say thanks for this nice list. i am just starting AP and it is great to be able to use this forum to benefit from the lessons others have learned through blood, sweat and tears!

    Fred

  12. #30
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    Default Re: The no-cost 10-step checklist for a better image

    Please explain Binning and Dithering between Frames.

    Thanks for the pointers.

 

 
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