Bottletopburly Posted December 31, 2020 Share Posted December 31, 2020 Found this on APT forum may simplify working out dither distance https://aptforum.com/phpbb/viewtopic.php?f=19&t=3157 First calculate the constant K for your system using the equation below. K = 2 x (FLi / FLg) x (Pg / Pi) where: FLi = imaging telescope focal length (mm) FLg = guide telescope focal length (mm) Pg = size of guide camera pixel (microns) Pi = size of imaging camera pixel (microns) Second, set Scale in the PHD2 Dither Settings (Global tab in Advanced settings) to 1. Third, the Maximum Dither Distance (MDD) in image pixels = K x [Dithering Distance]. Dithering Distance is set in APT in the Gear/Guide/Guide Settings menu. EXAMPLE: For my new system (about to order ASI1600MM camera package with filter wheel and filters): FLi = 348 mm FLg = 160 mm Pg = 5.2 microns Pi = 3.78 microns K = 2 x (348 / 160) x (5.2 /3.78) = 5.98 ~ 6 If Dithering Distance = 1 the MDD = 6 image pixels If Dithering Distance = 2 the MDD = 12 image pixels If Dithering Distance = 3 the MDD = 18 image pixels +RonC 1 Link to comment Share on other sites More sharing options...
Bottletopburly Posted December 31, 2020 Author Share Posted December 31, 2020 my mdd works out at 12 pixels so approx correct Link to comment Share on other sites More sharing options...
8472 Posted January 2, 2021 Share Posted January 2, 2021 I picked up on this one a few days ago, David. It's a very useful formula from which I created a spreadsheet to automatically calculate the numbers for my range of optics. I had terrible walking noise prior to this with APTs default settings. Once I set my optics to dither 15 or so pixels, the problem disappeared. Good to see they "stickied" it. Bottletopburly 1 Link to comment Share on other sites More sharing options...
Bottletopburly Posted January 3, 2021 Author Share Posted January 3, 2021 11 hours ago, 8472 said: I picked up on this one a few days ago, David. It's a very useful formula from which I created a spreadsheet to automatically calculate the numbers for my range of optics. I had terrible walking noise prior to this with APTs default settings. Once I set my optics to dither 15 or so pixels, the problem disappeared. Good to see they "stickied" it. Could you share the excel sheet , I thought that could be made into an excel formula but beyond me it’s one of those invaluable tools saves getting the calculator out , I haven’t noticed walking noise since dithering plus saves taking darks with a dslr which they says pretty useless unless temperature matched mega time saver . Link to comment Share on other sites More sharing options...
8472 Posted January 3, 2021 Share Posted January 3, 2021 8 hours ago, Bottletopburly said: Could you share the excel sheet , I thought that could be made into an excel formula but beyond me it’s one of those invaluable tools saves getting the calculator out , I haven’t noticed walking noise since dithering plus saves taking darks with a dslr which they says pretty useless unless temperature matched mega time saver . Of course, David https://drive.google.com/file/d/1LYcBtO_LhWqeD1jXeIxBeJ7A3iXPjdJp/view?usp=sharing As i say, I dither around 15 imaging camera pixels, but you may not need to go to that extreme. Simply enter your numbers into cells B4 through to B8 and it will do the rest for you. I had drop down cells for my dual pixel scale QHY294m and various optics, but this just complicates things further. Clear skies, Kev Bottletopburly 1 Link to comment Share on other sites More sharing options...
Bottletopburly Posted January 3, 2021 Author Share Posted January 3, 2021 CHEERS KEV 8472 1 Link to comment Share on other sites More sharing options...
Bottletopburly Posted January 3, 2021 Author Share Posted January 3, 2021 @8472 Kev would I be correct in assuming you don’t use APT ? Link to comment Share on other sites More sharing options...
8472 Posted January 3, 2021 Share Posted January 3, 2021 37 minutes ago, Bottletopburly said: @8472 Kev would I be correct in assuming you don’t use APT ? No, I am an APT user. Link to comment Share on other sites More sharing options...
Bottletopburly Posted January 3, 2021 Author Share Posted January 3, 2021 8 minutes ago, 8472 said: No, I am an APT user. your formula didn't look right to me using the formula off apt site ,my lad done a formula according to APT formula https://drive.google.com/file/d/18wes9gwRxnjXt4bm8O67HmdqIdTFqHW1/view?usp=sharing Link to comment Share on other sites More sharing options...
8472 Posted January 3, 2021 Share Posted January 3, 2021 That's odd. I've blinked my subs in Pixinsight and the dithering looks fine to me. I did have to remove some formatting for your copy, as it had all my data write-protected and/or in drop down boxes. I can't access your lad's formula, as it's restricted at my end. Link to comment Share on other sites More sharing options...
8472 Posted January 4, 2021 Share Posted January 4, 2021 Had another look at my sheet, and you're quite right. The formula omitted the constant K. Revised excel sheet here. https://drive.google.com/file/d/1DizHTaAd5IzxNOhrGpy25wyN2zyzw2Pg/view?usp=sharing Well spotted, Kev Bottletopburly 1 Link to comment Share on other sites More sharing options...
Bottletopburly Posted January 8, 2021 Author Share Posted January 8, 2021 (edited) Cheers Kev @8472 i managed to find how to edit values to my scopes cameras on the last sheet you posted and check against my lads sheet all seem to work out the same 🖖 Edited January 8, 2021 by Bottletopburly Link to comment Share on other sites More sharing options...
8472 Posted January 9, 2021 Share Posted January 9, 2021 Nice one, David. 👍 Link to comment Share on other sites More sharing options...
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