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

  1. #31
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    Default Re: The no-cost 10-step checklist for a better image



    A good explanation requires some writing/reading, so I'll point to some links that cover the topics instead;

    In regards to binning, I have an explanation and more information here.
    A great write up by Rowland Cheshire on the subject of dithering can be found here.

    Hope this helps!
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  3. #32
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    Default Re: The no-cost 10-step checklist for a better image

    I think the question was regarding "hardware binning". DSLRs don't. Software binning is always an option based on the PP tool. I have yet to dither, but apparently I'm missing out. Will definitely leverage the PHD to BYEOS compatibility to do so next night out.
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  4. #33
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    Default Re: The no-cost 10-step checklist for a better image

    Some great tips here, thanks to all that have contributed! After reading this sticky (a 2nd time) to double check all my settings are correct.
    I noticed I have been shooting with "picture style" set at standard, thinking about it I am guessing I should have it set to neutral instead?
    Thx again
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  5. #34
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    Default Re: The no-cost 10-step checklist for a better image

    For Canon DSLRs which only have the 100 ISO multiples, there's always Magic Lantern which uses the proper values. It's a bit intimidating at first but it turns your camera into a pretty powerful instrument.

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  6. #35
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    Default Re: The no-cost 10-step checklist for a better image

    Great tips. Time to cut and paste a single list.

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  7. #36
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    Default Re: The no-cost 10-step checklist for a better image

    Here is the entire modified list.

    1. If you use a DSLR, don't shoot in JPEG. You lose precision, you lose fidelity, and the camera performs on-board processing (such as stretching and sharpening) that is detrimental to signal quality later on.
    2. Use darks & flats. Just do it. Your images will be much easier to process and instantly look 10x better.
    3. Don't use in-camera noise reduction that is based on software (e.g. most of them). Chances are the noise reduction you can perform in post-processing is much better in preserving detail than the cheap&nasty noise reduction in your camera.
    4. If you use a DSLR, chances are the resolution of your CCD is way too high for your seeing conditions. Your images will be blurry when zoomed in. Use this blur to your advantage by binning (not scaling!) your images down to the level where the blur is not noticeable anymore. You'll lose resolution but again a great amount of noise reduction. Alternatively undo the blur using deconvolution.
    5. Take some time to get your focus right. A no/low-cost Bahtinov mask can really help, but using your DSLR with liveview can also help nail your focus.
    6. If you shoot many subs for long periods of time, check your focus again in between frames after a while. Chances are you'll find it's slightly off again.
    7. Don't apply deconvolution after stretching or after any other processing. It makes no mathematical sense. This is also a reason why you will want to have a signal that is as pure as possible (e.g. no JPEG, no stretching, no noise-reduction, just stacking) before you do this important step.
    8. Properly polar align your mount. Keep at it. You'll get better at it.
    9. Dither between subframes. Move the object by just a tiny bit, spiraling out from the initial position of your first sub.
    10. When using a DSLR, trust the color data you captured. Get to know the influences that are causing discoloration (ex. light-pollution, amp glow), model them, subtract them and be left with the real signal. Color correction (other than saturation) should not be necessary when using an off-the-shelf DSLR without filters in the imaging train.
    11. #11... If using a Canon DSLR that has 160 ISO multiples (160, 320,480,640) use them as they have the lowest sensor pattern noise. Avoid the 125 multiples as they have the highest noise. The 100 multiples (the so-called "native values") are in between.
    The 160 multiples do a 1/3rd stop digital pull on the sensor data, whereas the 125 do a similar push (gain boost).
    This barely matters in normal photography unless you are looking at low light shadow detail... But in AP everything is low light shadow detail :->
    12. (low cost if you already have one!) - if you have access to an AC outlet, use an AC adapter for a DSLR rather than internal batteries if you can... the lithium batteries get very slightly warm in AP use and this in turn warms up the sensor a little... this makes more noise!
    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.
    14. don't bother leaving a pause between multiple subs. It wastes your valuable time and the sensor won't cool down unless you leave a very long pause and it's better to have your subs at a constant temperature....and to have your lights and flats and bias frames at the same temp too.
    15. if your DSLR has a "silent shooting" mode (i.e. fully electronic shutter release) then see if you can use it. This will reduce shutter-induced vibration ... even if you are also using mirror lockup - assuming you can do that on your camera. This is particularly useful on short subs (< 30 secs) - on longer subs the vibrations will die away quite quickly and be lost in the overall exposure, but I still think it is good practice.
    16. Never use the lowest f ratio, as you'll get bloated stars and distortions. Keep it at f3.2 to f5.6 for optimal results. This may differ camera to camera, so the best way to find out is to take a night just to figure out where your sweet spot is.
    17. Don't use an AC-to-DC transformer, or a DC-to-AC inverter, unless absolutely necessary. These can induce a very slight 60hz ripple voltage that adds noise to the camera electronics. It can also add tracking errors in some mounts.
    18. Add a ground wire to your telescope setup when running on 100% battery power. I have a heavy copper wire attached to my aluminum tripod, which is attached to a long copper spike that I drive in the ground under my telescope. I also connect it to the negative side of my battery before I plug in my equipment (which all runs from the same 12v truck battery). This provides a solid 0v reference to the electronics and grounds out any RF energy the equipment might pick up. Think about it, long unshielded electrical leads, long aluminum or steel tripod legs, all act as antennas for whatever RF signals (or magnetic fields) are around. Grounding your equipment can significantly reduce the electrical noise introduced into your electronics by outside sources (especially nearby power lines). One thing, though. Make sure all of your powered equipment uses a negative ground on the chassis side (usually has a positive tip on the 12v connector).
    19. Put rubber pads under your tripod feet to reduce vibration. You can also use black rubber pipe insulation (held on with tight zip ties) around the aluminum legs to reduce unwanted tripod harmonics.
    20. Reduce unwanted light from entering your tube assembly any way you can. Light shields (dew tubes) work great, and can be made out of almost any lightweight tubing (I just started using a piece of 8" diameter cardboard concrete slip-form). Just line the inside with black rubber 1/16" hobby foam or flat black construction paper. In addition, put something between your scope and any nearby light sources. I often park my wife's Dodge Durango nearby, then throw a sheet of black plastic over it. This allows her to stay in the truck and read with the dome light on, but doesn't bother me even though I am only a few yards away.
    21. Be quiet when the shutter is open!! Loud noise, especially low-frequency bass, can reverberate down your optical tubes just like organ pipes.

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  8. #37
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    Default Re: The no-cost 10-step checklist for a better image

    Quote Originally Posted by Phil Leigh View Post
    #12 - (low cost if you already have one!) - if you have access to an AC outlet, use an AC adapter for a DSLR rather than internal batteries if you can... the lithium batteries get very slightly warm in AP use and this in turn warms up the sensor a little... this makes more noise!
    So I've found a few AC adaptors for my DSLR (Canon EOS Rebel SL2 (200D)) but some of the reviews mention an audible electrical hum that the adaptor creates when shooting video.

    Of course, I'm not going to be shooting videos of the Orion Nebula and so I don't care about mic noise but I'm wondering if you think that such noise would be limited to the mic or whether it might also create detectable noise in the sensor when taking long exposures?

    Clete

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

    Quote Originally Posted by Clete View Post
    So I've found a few AC adaptors for my DSLR (Canon EOS Rebel SL2 (200D)) but some of the reviews mention an audible electrical hum that the adaptor creates when shooting video.

    Of course, I'm not going to be shooting videos of the Orion Nebula and so I don't care about mic noise but I'm wondering if you think that such noise would be limited to the mic or whether it might also create detectable noise in the sensor when taking long exposures?

    Clete
    I did go ahead and purchase an A/C adapter for my Canon EOS Rebel SL2 and used it the other night for the first time. Here's a link to the actual product.

    It worked flawlessly! There was no difference between using that adapter vs. using the Canon branded battery that came with the camera except that I didn't have to worry about changing batteries.

    And, in answer to my own question (quoted above), there is no electrical interference generated that is discernible in the images.

    Clete

 

 
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