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Pages: 1 | 2 | 3 | 4 | 5 | (show all) Peter in Reno Post Laureate Reged: 07/15/08 Loc: Reno, NV Re: Understanding stacking methods [Re: vpcirc]       #5252107 - 06/02/12 01:50 PM Edit   Reply   Quote Quick Reply   CCDStack seems to refuse to calibrate if I don't include Master Dark file. I am trying to calibrate lights with flat and bias but no dark but it seems I must include Master dark. My Sony CCD SXVR-M25C has very low noise and many times dark subtraction can actually be worse. I always dither images when capturing. Is there a way I can calibrate with lights without dark subtraction? Peter Post Extras:       freestar8n Carpal Tunnel Reged: 10/12/07 Re: Understanding stacking methods [Re: Peter in Reno]       #5252162 - 06/02/12 02:39 PM Edit   Reply   Quote Quick Reply   I don't know how ccdstack handles it or if there is a workaround, but you should be able to duplicate the bias and provide it as your master dark and it shouldn't know the difference. That is effectively your assumption here - that the dark is the same as the bias and dark current is minimal. I have an sx camera and that is how I process things - without darks - because the camera is not regulated and has very low dark current anyway. Images Plus is aware of this processing mode - interesting if ccdstack is not. Another related mode is to provide a master dark, but only use it as a hot pixel map - and not do an actual dark subtraction. This is also suitable for sx cameras. Frank Post Extras:       Peter in Reno Post Laureate Reged: 07/15/08 Loc: Reno, NV Re: Understanding stacking methods [Re: freestar8n]       #5252217 - 06/02/12 03:16 PM Edit   Reply   Quote Quick Reply   That's a great idea Frank. Why didn't I think of that?!?!?!? I always use darks to create Bad Pixel Map with Nebuloisty. I am experimenting with different methods to see which is best for my camera. This is going to be a long weekend. Back to re-processing all over again. Thanks, Peter Post Extras:       JoseBorrero Carpal Tunnel Reged: 09/04/09 Loc: MI Re: Understanding stacking methods [Re: Peter in Reno]       #5252232 - 06/02/12 03:29 PM Edit   Reply   Quote Quick Reply   I tried ccdstack tutorial at ccdware website. Is that enough? I used 50mins only on LRGB and maxim dl and DSS bringed better results. Post Extras:       elbee professor emeritus Reged: 05/02/09 Loc: Arizona Re: Understanding stacking methods [Re: Peter in Reno]       #5252259 - 06/02/12 03:52 PM Edit   Reply   Quote Quick Reply   Quote: CCDStack seems to refuse to calibrate if I don't include Master Dark file. you can calibrate without a master dark by specifying 'None' in the calibration manager. this blanks out the ability to specify a bias frame because on this page, the bias is only used if you are scaling darks. on the Flats tab of the calibration manager, there is also a place to specify a bias frame (or any frame) for dark subtracting your flats. i specify a bias frame when making master flats so don't use the option on this page. also have the choice to just specify a simple bias offset for dark subtracting your flats. Post Extras:       freestar8n Carpal Tunnel Reged: 10/12/07 Re: Understanding stacking methods [Re: elbee]       #5252278 - 06/02/12 04:07 PM Edit   Reply   Quote Quick Reply   What you describe seems ok - but only if the bias is subtracted from the lights. Is that how it works? You need (Lights-Bias) normalized by (Flats-Bias). You would not want (Lights) normalized by (Flats-Bias). Frank Post Extras:       Peter in Reno Post Laureate Reged: 07/15/08 Loc: Reno, NV Re: Understanding stacking methods [Re: freestar8n]       #5252346 - 06/02/12 05:07 PM Edit   Reply   Quote Quick Reply   Lee, Thanks for the explanation. This is exactly what I saw and it looks pretty unclear whether the lights can be calibrated with bias only and not dark. So if I do exactly what said, it would do what I want: calibrate lights with bias only? Peter Post Extras:       Peter in Reno Post Laureate Reged: 07/15/08 Loc: Reno, NV Re: Understanding stacking methods [Re: Peter in Reno]       #5252362 - 06/02/12 05:23 PM Edit   Reply   Quote Quick Reply   One other thing about CCDStack. It shows FWHM for each image but how does it know this? I never input focal length of my scope so how does it know the image scale? Can I input focal length of my scope in CCDStack. It already knows specifications of my camera. Thanks, Peter Post Extras:       elbee professor emeritus Reged: 05/02/09 Loc: Arizona Re: Understanding stacking methods [Re: freestar8n]       #5252375 - 06/02/12 05:34 PM Edit   Reply   Quote Quick Reply   Quote: What you describe seems ok - but only if the bias is subtracted from the lights. Is that how it works? You need (Lights-Bias) normalized by (Flats-Bias). You would not want (Lights) normalized by (Flats-Bias). the original request said he didn't want to calibrate with darks (darks/bias, similar). if you do want to subtract a bias frame from a light in place of a dark, simply specify that bias frame as a dark. if you specify "no dark" then nothing will be subtracted from the light frames and only flats will be divided into the lights (flats can be dark subtracted or not, as you choose). this is what i understood his original query to be about. if someone claims their camera needs no dark subtraction, this is the choice they can use. Post Extras:       elbee professor emeritus Reged: 05/02/09 Loc: Arizona Re: Understanding stacking methods [Re: Peter in Reno]       #5252377 - 06/02/12 05:37 PM Edit   Reply   Quote Quick Reply   Quote: One other thing about CCDStack. It shows FWHM for each image but how does it know this? I never input focal length of my scope so how does it know the image scale? the FWHM from ccdstack is in pixels... no assumption is made about image scale. Post Extras:       Peter in Reno Post Laureate Reged: 07/15/08 Loc: Reno, NV Re: Understanding stacking methods [Re: elbee]       #5252385 - 06/02/12 05:44 PM Edit   Reply   Quote Quick Reply   Thanks Lee. I think CCDStack should give the user more choices instead of forcing the user the use dark or no dark at all to calibrate with the lights. Peter Post Extras:       elbee professor emeritus Reged: 05/02/09 Loc: Arizona Re: Understanding stacking methods [Re: Peter in Reno]       #5252398 - 06/02/12 05:57 PM Edit   Reply   Quote Quick Reply   Quote: CCDStack should give the user more choices instead of forcing the user the use dark or no dark at all to calibrate with the lights. it does. maybe i mis-understood your initial question. specify whatever you want for a dark frame...(use the image itself to dark subtract if you want to Post Extras:       freestar8n Carpal Tunnel Reged: 10/12/07 Re: Understanding stacking methods [Re: elbee]       #5252414 - 06/02/12 06:12 PM Edit   Reply   Quote Quick Reply   Quote: the original request said he didn't want to calibrate with darks (darks/bias, similar). if you do want to subtract a bias frame from a light in place of a dark, simply specify that bias frame as a dark. if you specify "no dark" then nothing will be subtracted from the light frames and only flats will be divided into the lights (flats can be dark subtracted or not, as you choose). this is what i understood his original query to be about. if someone claims their camera needs no dark subtraction, this is the choice they can use. It is perfectly fine with an sx camera, or any camera with low dark current, to use bias frames without darks - but it is essential to subtract the bias from both the lights and the flats - otherwise the "calibration" is nonlinear and will not apply the flats properly if the bias is nonzero. So - it sounds like ccdstack does not support this mode as a formal option while other software does - and you need to provide a bias as a faux dark in order to calibrate using flats and bias - but no dark. Frank Post Extras:       elbee professor emeritus Reged: 05/02/09 Loc: Arizona Re: Understanding stacking methods [Re: freestar8n]       #5252421 - 06/02/12 06:22 PM Edit   Reply   Quote Quick Reply   Quote: it sounds like ccdstack does not support this mode as a formal option sorry, if i am not clear. ccdstack will easily support ANY combination you want for calibration. Post Extras:       Peter in Reno Post Laureate Reged: 07/15/08 Loc: Reno, NV Re: Understanding stacking methods [Re: elbee]       #5252428 - 06/02/12 06:31 PM Edit   Reply   Quote Quick Reply   CCDStack made it look like you cannot calibrate lights with bias and without dark. It was not trivial that I could trick CCDStack that bias can be treated as dark. CCDStack did not have to dim the bias selection if dark calibration was disabled. Peter Post Extras:       vpcirc Carpal Tunnel Reged: 12/09/09 Loc: Merced CA Re: Understanding stacking methods [Re: elbee]       #5252430 - 06/02/12 06:36 PM Edit   Reply   Quote Quick Reply   Ccdstack reads your camera model and figures noise levels based on manufacture specs. This plays into doing a better normalization if I understand correctly. Peter, I have some tips from Adam Block on OSC processing. I'll share them later this evening. If you look under camera manager you'll see your model and resolution. The FWHM is accurate. You can really see that come in to play if you try deconvolution. Any time you open an image from a different camera, the camera manger will open saying its detected a new camera and ask you to confirm the data. Post Extras:       vpcirc Carpal Tunnel Reged: 12/09/09 Loc: Merced CA Re: Understanding stacking methods [Re: vpcirc]       #5252704 - 06/02/12 10:34 PM Edit   Reply   Quote Quick Reply   Sorry Peter, the OSC section is video only and 90 mins long. I thought there was recap like the other parts, but no such luck. If you find you like the process, I would highly recommend Adams video tutorial. He can show you how to create magic from your data. Post Extras:       Peter in Reno Post Laureate Reged: 07/15/08 Loc: Reno, NV Re: Understanding stacking methods [Re: vpcirc]       #5252746 - 06/02/12 11:08 PM Edit   Reply   Quote Quick Reply   Thanks for looking into OSC information. After spending all day playing with CCDStack, PixInsight and Nebulosity, it's probably too early to say but I've concluded that all three software pretty much gave equal results. Maybe it's too difficult to compare for light polluted images. I don't think $200 for CCDStack is worth it since I already spend enough for other software I already own. $200 is quite a bit for limited processing as compared to PixInsight. Plus another $100 for Adam Block tutorial is a little steep for pre-processing and limited post-processing tools. Are there free tutorials around like there are many free tutorials for PixInsight? Plus I do not find CCDStack documentation well written or formatted. Peter Post Extras:       alpal Carpal Tunnel Reged: 06/15/09 Loc: Melbourne Australia. Re: Understanding stacking methods [Re: Peter in Reno]       #5252849 - 06/03/12 01:00 AM Edit   Reply   Quote Quick Reply   I think I'll stick with Deep Sky Stacker - I'm quite happy with it & it's free. I now make 2 stacks with DSS if I have an important galaxy image: Kappa stacking - seems to bring out more detail in the brighter areas. Mean stacking - seems to smooth the high noise background out. You can process the 2 images separately with 2 layers in photoshop & paint the galaxy in later with the brush tool if it's on a hide all layer. Post Extras:       BlueGrass Carpal Tunnel Reged: 07/25/09 Loc: Wasatch Front, UT Re: Understanding stacking methods [Re: Peter in Reno]       #5252850 - 06/03/12 01:06 AM Edit   Reply   Quote Quick Reply   Peter, Perhaps in the case of OSC processing you may be right. If you make the move to mono, take another look at it. Post Extras:       Pages: 1 | 2 | 3 | 4 | 5 | (show all)

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