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geoflewis

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geoflewis last won the day on June 25 2020

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  1. Thanks for posting this Carole, it is very sad news indeed. @wookie1965 I believe that you have one of these vintage scopes, so if possible please could you let Carole @carastrohave an idea of their 2nd hand value. Many thanks
  2. Looks pretty good to me, but maybe a bit low in contrast, so maybe you could get something more punchy with further processing. FYI I also took some test luminance images with my C14 on Saturday night (actually early Sunday morning) and this is what I've extracted from 2hours data (12x10m subs). I captured at Bin 2x2 then as an experiment, I further binned 2x2 in software, before post processing....
  3. Thanks Vlaiv, that sounds good enough for me, so I will continue to experiment with binned and unbinned processing in software. I will continue to bin 2x2 all my subs in camera when shooting with the C14, so a further bin 2x2 in software might be too much. I know that I've struggled with all of this, but actually feel as if the fog is begining to lift, so thanks for your significant contributions over the last few days on that. BTW I did send an email to the ImagesPlus developer, Mike Unsold, but haven't heard anything back yet; that might be just early days, but I suspect that he doesn't want to take the lid off that particular box again, since he announced over 1 year ago that he's no longer supporting, or developing it and made it a free download, which if your are interested in checking out is at http://www.mlunsold.com/ILOrdering.html Many thanks,
  4. So when it boils down to it, as far as you are conserned I can bin the stacked linear image, regardless of the align methodogy and no one will ever know (see) the difference?
  5. Absolutely, at least I certainly hope so, which is why I am so appreciative of very generous people like @vlaiv who are prepared to indulge folks like me, with their time, to try and share their knowledge.
  6. I just love this statement! I was getting to the point that I thought that I no longer understood English.....
  7. Thanks again Vllaiv, this I think I understand. I have no idea what method ImagesPlus uses for alignment and since the developer no longer supports the product, I am unlikely to be able to find out. The auto image set processing tool starts with me loading all my raw data (lights, darks, flats, flatdarks, bias) and ends by kicking out a calibrated, normalised, graded, aligned and combined image using whatever combination method I specify, e.g. Min/Max exclude, average, one of Sigma clip options, etc. I have been using Median Sigma combination, but saw that you recommend Average instead of Median, so I will change to that in future. I can stop the process after calibration, but then normaisation, grading, aligning and combining the calibrated images becomes a tedious manual process, that I'd prefer not to do. I will email the developer to see if he will answer about the alignment method, e.g. is it bilinear?, but I'm not hopeful about getting a reply. If I don't get a reply, can I just take the risk of binning the stack, i.e. what is the risk of a bad result and how bad could that be? Best regards,
  8. Thanks again Vlaiv, I feel that I've reached the end of the road with my undersranding, or in reality, lack of it. I am going round in circles and getting nowhere. I want to understand why, when and how to use resampling and/or software binning to improve my AP workflow. Up to now I never tried it, as I didn't understand it; I did not know what benefit it would be trying to achieve. I thought I understood in camera (CCD) binning (better sampling rate for oversampled camera scope configuration as with my 5.4 micron camera pixels and F11 C14 scope + x0.63 telecompressor), but now even that is not so clear. I really appreciate your patience with me and you sharing your deep knowledge of this topic, but I just don't get it, sorry....!!
  9. Thanks again Vlaiv, so clearly I still not understand this. I will keep trying, but it is difficult over forum chat. As requested, below is a screen grab of the same region displayed 3 ways. The top left is the original (not resampled) image binned 2x2 (add) and zoomed 400% to show the blocky pixelated stars - can you see it? The bottom left image is the resampled x2 (upsampled) image then binned 2x2, viewed zoomed 200% so that image dispays the same dimmensions as the top left, not resampled image - the stars are not blocky. The image on the right is the same as bottom left image (resampled x2, plus bin 2x2) zoomed 400% for comparison and the stars are still not blocky. Any ideas why it is not as you expect? I could zoom everything in even further to show the blocky stars in the not resampled image better. What does this mean? Should I only bin the raw images before calibration and stacking? Would that mean that I also have to bin all my calibration frames at their Raw off camera status, not the unbinned calibration masters? I am really not understanding how anyone would use binning in software if I can't bin a calibrated, but otherwise unprocessed stack of raw image data. Thanks again
  10. @vlaiv and others, as promised I've re-read this thread a few times and am gradually becoming more comfortable with the terminolgy around resampling and binning. I had a play in my ImagesPlus astroprocessing software and took a look as some tools in there that I never used, as I'd not understood them. One of them is a Resize Files tool and from looking at that I now see that it is a resample tool, that amongst other things allows an image to be resampled by a fixed factor including decimels, not just integers, and values below 1 (so downsampling?). As you can see from the below image the resize tool offers Bilinear, Bicubic and nearest neighbour resample options, with Bilinear being the default. As an experiment I applied a resize factor of 2 (x2 bilinear) to an unprocessed stack of 2hrs lum subs of the M90 galaxy that was captured at Bin 2x2 in camera with my QSI583 CCD, due to oversampling with that camera and my C14 combo. I then binned that resampled stack 2x2 in ImagesPlus (using the Add operation), which got me back to a same dimensions images at the original, but now binned 2x2, so a brighter starting point. Next I applied a quick ArcSinH stretch (with an nth Power X'n prestretch to darken the background). Interestly I found it much easier to reveal the fainter details in the image, including the outer galaxy arms, so I think may be a useful way of processing data in future. I need to experiment more with that though. Please note that I found that if I did not resize by x2 before binning 2x2 in software, I noticed that the stars started to become blocky, but by first resizing, then binning their roundness (I know that they are not very circular to start with) was preserved. I'd be very interest to have you observations on what I did and my initial findings. Many thanks,
  11. Yep, I popped out to my observatory at that time and was just in time to see the ISS pass close to the Moon, then pretty much directly overhead. It was certainly very bright....
  12. Oh wow, so much to read. I've been out all day today, so only now getting to this. Thanks @vlaiv for aswering my questions, but on first reading of your reply I still am very confused. I did pick up one thing very quickly.... Doh, there am I using max 65k ADU for saturation at 16 bit, when in fact I'm processing at 32 bit float.... stupid me I need to spend much more time reading the discussion points on this thread to see if I can undersand it any better Again thanks everyone for their contributions.
  13. @vlaiv - Again thank you for the reply, but I am still not clear which option I should use when. I understood the mathematical differenaces between add, average and median and useually use median for sigma stacking as I understand that it handles outliers better. When it comes to binning I was thinking average as I process at 32bit floating so was thinking average would be best. Did you mean add and average are the same, or median and average are the same? Add seems completely different to me, as you also state..... This is what makes me think that add in software binning is not a good option, as if I have a region of 4 pixes with ADU values of say 15k, 18k, 18k, 20k, the their sum is 71k, but max is ~65k, so result will be saturation, which isn't good. Which are identical? All 3 or just Average and Median? If all 3 then how can setting white point 'correct' a saturated binned pixel from Addition, like in my example above - addition above 65k ADU is stuck at 65k regardless of the value of the binned pixels. Vlaiv, you are really helping to gradually unlock some of this for me, so I hope that you don't mind the slew of questions while I continue to pick away at this. Best regards,
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