7.44
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Basically you must think of detail relative to the whole image. Even with a smaller sensor such as the IMX533, the Redcat gives a field of view that is 2.58 degrees or about nine thousand arcseconds across. Details smaller than 3-4 arcseconds simply do not matter. Even on print, they are really tiny. Might as well use a magnifying lens to inspect the pictures in a book, you will see there are only dots of cyan, magenta, yellow and black. Does it matter? Of course not  |
3.61
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DavesView:Byron Miller: Dithering is guider driven, it's mount backlash recovery/settling time you want to give space for but it's also super minimal on red cat (or non-existent if a good mount since these things even with image train are so small and centered compared to longer focals). You don't need much recovery since even a lousy RMS is within a single pixel in our average seeing and resolving power. Since we're so under sampled, I dither every sub no matter NB or Broadband. Dithering will reduce fixed pattern noise and improve the effectiveness of stacking (rejection and normalization) and in mitigating read noise. 1 pixel is NOT enough to do any of this and could introduce a pattern. I don't even think 3 pixels is enough to overcome fix pattern noise. make sure you dither on RA AND DEC, otherwise you will introduce walking noise. |
2.39
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Byron Miller: You guys know more than me. On my next outing I'm going to dither every shot at 5 pixels. This makes me wonder about something I've noticed in many of my images. After running NoiseX, there is a hint of mottling throughout the background that I have been dealing with. To get rid of it I use SelectiveColorCalibration/background. I wonder if this a product of not enough dither. But I am in a B7 sky with a huge soccer complex an eighth of a mile away. |
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3.61
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DavesView:Byron Miller: It wouldn't hurt to try a good dither to try and smooth out noise, but with a soccer complex nearby i presume its light pollution gradient more than anything. |
15.16
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astronomy.tools is wrong. it only considers seeing, but for small scopes like redcat, diffraction and aberration is way more important than seeing.
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8.34
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DavesView: Not dithering every frame is a time saver but always at least a bit sub-optimal. Do you want faster or do you want to squeeze every bit of advantage out of your process that you can in terms of quality? Yeah, I know someone will come along and say that dither every frame is a waste. My experience says otherwise. To be honest, at focal lengths under about 600 mm a great mount (think AP, Planewave, SB, 10 Micron) that will allow dither by mount unguided and using a model will save one way more time than skipping dithers. |
