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geoflewis last won the day on March 20 2016

geoflewis had the most liked content!

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About geoflewis

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    Sub Dwarf

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  1. It's a clear moonlit sky here currently and been thus for the past couple of hours, however, I haven't been able to use it.... Firstly I got my main imaging laptop back from the IT guy who was able to bring it back to life sufficient to recover the data, but he advised that the machine itself, whilst currently working, is really for the scrap heap, so I took his advice and have ordered a new replacement. I spent much of the rest of today getting all the data and various program installers off the laptop to external hard drives ready to set up the new laptop when it arrives.... Secondly about 2 hours ago I thought I'd head out to the obs and try some new adaptors to connect my QSI camera to my 4" TSAPO. Currently I have to take the camera down and change the face plate between a standard 2" T-mount and a wider USA 2.156" mounting when switching between the C14 and 4" APO. Last week I purchased a 2.156" x 2" nose for the QSI to make the switch straightforward, so I was hoping to use that tonight, BUT as I now find that there is insufficient travel in the 4" APO focus tube to get sufficient back focus for the camera and after rummaging through all my various fittings and adaptors I don't have anything make up the difference. What I have is either too short or too long, so I have just ordered something in between - hopefully next time, I'll have what I need.... Thirdly, frustration and generally tiredness got the better of me, so I shut everything down and came back indoors. Sorry for the long moan, I will have an early night instead
  2. 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
  3. Thanks Donal, it’s been one thing after another recently..... Geof
  4. 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
  5. Hi Mick, welcome from another Norfolk located retiree.... I look forward to seeing you around here. Cheers, Geof
  6. 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
  7. 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.
  8. 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
  9. Hi Nigel, I’m interested in your observation, so what would you recommend please? Regards, Geof
  10. 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
  11. 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
  12. Thanks Olly, I think it's an example of great minds think alike Cheers, Geof
  13. 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
  14. 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
  15. 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
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