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geoflewis

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Everything posted by geoflewis

  1. Clouds rolled in about 30 mins ago, but I got 5 x 15 min subs, so something to play with when I get my laptop back or buy a new one.... Currently shooting new flats
  2. Thanks Donal, it’s been one thing after another recently..... Geof
  3. First time out in a few weeks for me and first time since I had the QSI583 camera serviced. I have shot a new darks library, so now testing 15 min Ha subs on M57 to see how they compare with the 5 min subs shot previously. Sky isn’t great with poor transparency, but this is as much a test that everything is working as it is capturing meaningful data. I won’t be able to process anything for a while as my main processing laptop had a fatal BSOD about 10 days ago, so that’s in the repair shop with my fingers crossed that it can be recovered, not least because all my processed astro images from the past 2 months were on it and not backed up..... If the laptop is U/S, then I’m looking at another ~£1500 outlay to replace it
  4. Hi Mick, welcome from another Norfolk located retiree.... I look forward to seeing you around here. Cheers, Geof
  5. Hi Kev, I have the Meade F6.3 reducer, which I used to use with my old 10" LX200 that I no longer have, so the reducer is redundant. I previously listed it last year, but didn't get any interest, so I still have it in my obs, boxed and unused. How much are you willing to pay for it? Cheers, Geof
  6. It’s clear and windy here, but won’t be imaging. I got my QSI camera back from a service today, so I’m currently shooting a new darks library, this time including 900s (15m) subs at bin 2x2 so that I can shoot longer lights exposures with my Ha filter. Will probably continue with more darks tomorrow at Bin 1x1. It’s going to take several hours to get them all ready. Plan is for 20 darks at 120s, 300s, 600s & 900s for both bin 1 & bin 2. Then I need to shoot new flats and flatdarks for all 5 HaLRGB filters.
  7. Hi Vlaiv, I didn't get any reply from the software developer, but I did hear back from one of the more experienced users, who also happens to use the same model camera (QSI583) as me. We had a few email exchanges, too long to copy it all here, but here are a couple of extracts from what he told me.... Geof, Just because a pixel has a value of 0 does not mean that it is clipped. If the master dark for a given pixel has a value of 300, with no photons reaching the sensor, then the "dark subtraction" process reduces the value of that pixel in the light frame by 300, assuming that 300 ADU of the light value is due to a thermal noise contribution. Geof, I reported the pixel values that are displayed in the IP status bar, at the right-hand end. They are 8 bit values. Below is the histogram of the 25 minute master dark. It shows 99.9% of the pixels with 8-bit values of 0 or 1 and an average 16-bit value of 261.  Geof, 5 minutes for Ha is not very long, so it is not surprising to me that you have a lot of 0 data after calibration. I usually shoot twice that for luminance data 1x1 and 8 minutes for 2x2 color. I wonder if you tripled that time where your data would be. So nothing conclusive there other than I've been shooting way too short exposures, so I'm wondering whether that is distorting my results. I've sent my camera off to be serviced as I'm wondering whether the cooling is not as reported, since I noticed that one of the fans stopped working, plus I needed to have the desicant recharged anyway. When it comes back I'm going to shoot a new darks library for longer exposures at both bin1 and bin2, probably 10 min and 15 min initially as I'm not ready to go longer. I will also shoot some new flats, flat darks and bias, so that I can revert to also including bias in my processing. Once that is done I can try imaging again with longer exposures to see what difference I get. Once I have a bunch of data to process, I'll probably download the trial for APP to see how calibration, stacking, etc. compares with my existing ImagesPlus software. I'm also tempted by PI, but from what I read that software eats computer resources for breakfast and I'm not ready to splash out multi £k on a new computer. I feel that I've learnt a huge amount from this discussion, not least finding some tools in my existing astro software that I'd not previously used, so many thanks for your detailed analysis and explanations. Cheers, Geof
  8. Hi Nigel, I’m interested in your observation, so what would you recommend please? Regards, Geof
  9. Thanks Vlaiv, I thought it would be too easy a solution . I have posted the question to the ImagesPlus User Group and will see what answers, if any, that I get. The software developer used to be very active on the user group and in the early days even directly supported me via email, with me in turn helping him with beta testing. However, this has not been so in the past couple of years, so I'm not sure that he is actively supporting the product anymore. Also there have been no development releases for maybe 3 years, or more. If there is no response via the user group, then I will write to him directly, but I'm increasingly reaching the conclusion that it is time for me to invest in an alternative like APP or PI, where there are more users worldwide, more ongoing development and more active support is available. Up until now I have been put off by the steep learning curve of a new processing application, but there comes a point...... Regards, Geof
  10. Thanks Vlaiv, Sorry for my slow reply, but being on holiday I was out with my wife much of the day and your analysis is too complex for me to review on my phone, so I'm only just now reading it on my laptop. Good points about using sigma clip for my calibration masters, something that I never paid any attention to previously, just using the default in my software of average. I will certainly make that change in future and indeed I have resacked them that way and now there is no cosmic ray hit showing in the mast flatdark. I already use sigma clip combine method for my calibrated light frames, and yes, I do dither my lights, but I also use an additional filter in the software to correct any residual hot pixels not fixed during calibration, so usually my final stack lights are good. Regarding the banding in the corners of my master flats, yes, it is something I have noticed, but I don't think that it shows in the final processed image, not least because that reagion is usually cropped out. I don't know what causes it. Maybe it is something to do with my LED light panel, which has a slight flicker when on the low intensity that I need to shoot flats at my target range of 25k ADU. I have been thinking of increasing the ADU to say 30k to see if that makes any difference. The panel has variable intensity, but for all the LRGB flats I have to use the lowest intensity setting or the camera shutter is captured during the exposure. I could increase the intensity for the Ha flats to reduce the required exposure from the rather high 90 secs, but I just used the same intensity as set for the LRGB filters. I will definitely exeriment some more after I get home the week after next. Thanks for the link to your notes on ImageJ calibration, but I think this is going to be too complex for me to follow. As you advise, I think the better way forward is to trial something like APP, again something that I can do once I get home. In the meantime, I intend to write to the developer of ImagesPlus to ask him about the auto calibation process and why it is black clipping so may pixels. The software does include a manual calibration process, which uses the same calibration frames as auto. The manual calibration set up option also includes a dark scaling setting with the default set at 1.0. I found that when I set this to say, 0.75 then the number of clipped pixels was dramatically reduced to ~100. Even with dark scaling factor at 0.9 the 0 pixels was a few thousand rather than the sevearl hundred thousands at scaling of 1.0. I really don't understand what this dark scaling factor is as I can't find any explanation for it in the limited documentation that I have for the software, so I'm going to ask about that too. I wondered whether the setting in the manual calibration set up might carry through to the auto image set processing calibration, but that seems not to be the case the dark scaling factor getting reset to 1.0. Do you have any ideas what the dark scaling option might be Vlaiv? Here is a screen shot of the set up screen fyi... Many thanks, Geof
  11. Thanks Olly, I think it's an example of great minds think alike Cheers, Geof
  12. Brilliant, I never thought I’d see anything as good as that from an iPhone, but I’m sure the 28” helps a lot . I prefer the x2500 video over the x12000 - not at all miserly in IMO..!! Cheers, Geof
  13. Vlaiv, Again many thanks for your analysis. It's reassuring to know that the raw light, raw dark and master dark look ok, so now I have to understand what went wrong with the calibration, but I have no idea how to do that. The astro processing softwarwe that I use (ImagesPlus) provides an auto calibration tool where I load lights, darks, flats, flat darks and bias (though actually I don't use bias) frames. I then hit the 'process' button and it runs throught it's steps automatically with the output being the calibrated, aligned and combined stack ready for post processing. See screenshot below... Is it possible that my flats and flat darks are the problem? I use an LED light panel for my lights and with the Ha filter the flat exposures were a fairly long 90sec, which I matched for the flat darks. Here are a single flat, the master flat (from 20), singe flatdark and master flatdark (from 20).... C14+Optec-Flats(-10C)_2019-09-20_Flat_Ha_90sec_2x2_Ha_frame1.fit C14+Optec+QSI(-10C)_20Sep2019_Ha_MasterFlat.fit C14+Optec-FlatDarks(-10C)_2019-09-20_Dark_Ha_90sec_2x2_Ha_frame1.fit C14+Optec+QSI(-10C)_20Sep2019_Ha_MasterFlatDark.fit I am interested in your suggestion to use ImageJ (though I never heard of it previously) and your tutorial for it. I did just Google it and it looks frightening to me..... I have also been thinking to switch to PixInsight (PI) or Astro Pixel Processor (APP) as I hear more and more that these are the best astro image processing tools, especially APP for calibration and stacking. I await you next lesson please . Geof
  14. Hi Olly, Thanks for your observations. 0.43"/px is precisely why I bin 2x2 with the C14 and as you suggest I have considered 3x3, but never used that other than for plate solving where I actually use 4x4. My guide RMS is typically around 0.5"-0.6" total, with lower values for RA and Dec (typically 0.3"-0.5" each). That is clearly more than half my image scale of 0.85" when binned 2x2, so please could you explain the target of half image scale. As you will have concluded from my discussion with Vlaiv on this thread I really understand very little of the science of this hobby . Up until now I've just guessed, but now I'm trying to better understand what I should be doing and why. Thanks for the explanation of how to improve star colours. I'm not familiar with MartinB's tutorial, so will look for that. I have just purchased Noel's tools last week and had a play, including with his 'increase star colour', but it didn't seem to have much effect - maybe I was expecting too much. I like the layer approach in PS that you [proposed, so I will give that a try, though I'm something of a novice with PS too.... Many thanks, Geof
  15. Hi Vlaiv, I've now checked into my holiday lodge, but there is no wifi here, so I'm using my phone as hotspot, so that may be a little unreliable. I checked my darks and was very surprised to discover that the master dark was only 8 bit, so I've reprocessed the dark stack as 24 bit. Here is a single dark off the camera and the master dark from 20 dark frames. QSI-Darks(-10C)_300sec_Bin2x2_frame1.fit MasterDark.fit I checked and there are no zero values in the single dark, where the minimum seems to be ~400 ADU. The minimum value for the master dark is ~500 ADU. I then looked at singe uncalibrated frame and the same frame after calibration. M57_300sec_2x2_Ha_frame1.fit C_M57_300sec_2x2_Ha_frame1.fit The raw file off the camera shows minimum at ~400 ADU, this just 1 or 2 pixels, rising to ~500 ADU by the time 1000+ pixels at that level. Checking the calibrated same image shows a huge number of pixels with 0 ADU, so for sure the calibration seems to be making the difference. If calibration simple deducts the dark frame value per pixel this makes sense, as anything in the raw file with ADU <500 will move to 0 if the dark master has min ADU value of ~500. It makes me wonder how a dark frame has >ADU per pixel than a light frame even when using Ha filter, but perhaps I'm still not understanding this well enough. Truth to say, I've never really thought much about this previously, so this is definitely a journey of discovery for me and I very much appreciate your help and look forward to your reply. Best regards, Geof
  16. Thanks Steve, it is very helpful to have your input. As I found in my discussion with Vlaiv, I was wrong in thinking that more shorter exposures gives better SNR than few longer exposures. I will go back to 10 min or maybe even 15 minute exposures, but I'm also very interest to learn more from Vlaiv more about this so will continue the thread with him by providing the dark frames that he requested. Cheers, Geof
  17. Hi Vlaiv, I am just leaving home to go on holiday for one week - actually to a local uk star party, so I cannot send these to you immediately, but I will take my laptop with me and see if I can upload them later today. I very much appreciate you helping me diagnose all this for me and helping me better understand what is going on. Regards, Geof
  18. Hi Vlaiv, Thanks again, here is a 32bit FIT file - at least I think that it is. C_M57_300sec_2x2_Ha_frame1.fit I usually perform processing (calibration, align, combine) at 32 bit Fit in Images Plus, then save as 16 bit Tiff for post processing as tools that I use, e.g Registar and Photoshop (CS2) do not read the Fit files. Even at 32 bit level I think I'm seeing 16% (~339k) at 0, so what does this mean? Regards, Geof
  19. Excellent gif Donal and yes, it sure is moving along at a good lick
  20. Hi Vlaiv, One more time please? I checked the background ADU for a series of Ha image that I captured last night. The exposures were 300sec and background ADU is ~50. So if target ADU is ~4100, then approx optimum exposure is 300s x 4100 / 50 = 24,600s or 410min (6.8 hours) - surely ~7 hour exposures cannot be right, so what did I do wrong? Does a background ADU of just 50 at 300s seem likely? I live in a bortle 4 location with readings that night of 21 SQM, so reasonably dark. I've attached the calibrated Tiff for you to check if that is possible please. C_M57_300SEC_2X2_HA_FRAME1.tif Thanks again, Geof
  21. Vlaiv, Thank you so much for taking the time to explain this using my example ADU readings. I think that I finally get it, or at least I feel much more comfortable in my understanding. Thanks also for explaining your use of the x5 multiplier, which makes sense. I will continue to re-read this thread (probably many times to get it fixed in my brain), but at last I feel that I have some logical methodology for determining exposure durations for my different rigs and different binning. Oh and BTW (by the way) my reference to NB for M13 was not Narrow Band, but Nota Bene (Latin for note well). Of course I do not shoot narrow band for globular clusters . Many, many thanks. Geof
  22. It's clear, but poor transparancy here tonight. I'm packing ready to head to Kelling Heath star party tomorrow for the next week, so I won't be doing any astro tonight. I'm not taking any gear, just like to catch up with friends and hopefully take a peek through some of the big dobs there if the skies clear.
  23. Vlaiv, Many thanks again. I have found a statistics tool in my astro software ImagesPlus, so tried some tests on both binned 2x2 and unbinned 1x1 images. I only use the 1x1 when imaging with my 4" APO, whereas binned 2x2 is always with my C14. I'm not sure what if any significance these different configurations make as it is the same camera. Here is what I found checking some L subs.... 4" APO unbinned 600 sec sub - ADU = ~3200 If I understood you correctly I need to multiply that by 4 for comparison with binned 2x2 which gives 12,800 - I must say I'm not understanding this part....?? C14+Optec lens binned 2x2: -300 sec sub - ADU = ~1400 -120 sec sub - ADU = ~800 (NB for an image of M13 the background ADU was ~600, but if I shoot much longer surely the globular cluster core would become blown out) Of course the results vary depending whether there was a moon in the sky, hence recent subs from M57 had ADU of ~1800 at 120 sec. Based on my understanding of what you are saying the 600 sec sub binned 1x1 with the 4" APO looks to be too long duration, which I find very surprising, whereas both 120s and 300s subs with the C14 binned 2x2 is much too short. Please can you explain some more. Many thanks, Geof
  24. I'm finding the same Neil, so have also been updating old crappy versions with better ones, but likely it will be a never ending project.....
  25. Thanks Vlaiv, I understand the advice about LP noise v read noise, but I have no idea how to measure them, nor how to convert ADU to electrons - actually I don't even understand what that means. What software do I need for that? I also understand that more shorter exposures is better than few longer exposures for improved S/N, provided each exposure is sufficient to dominate read noise, so why do many of the best imagers I see shoot exposures lasting 10, 15, even 30 minutes? I've never been able to get my head around that? I also understand that short exposures can be used to restore star colours, but I've never been much good at that, so I guess that don't know the correct processing steps. One of the problems of beinf self taught I guess.... I sure wish that I understood all this much better than I do currently.... Cheers, Geof
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