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Hi Dear AstroBinners, once again my fate is in your hands. This time my question will be very straightforward and simle. I have 3 different sets of frames. I need to combine them into one. How do I do that? I assume I would pre-stack each of the 3 batches, but then the question would be how do I re-size them to fit into each other? Batch 1 is shot at 200mm (4022x6024px) DSLR Batch 2 is shot at 150mm (4022x6024px) DSLR Batch 3 is shot at 250mm (1080x1920px) Seestar S50 I assume drizzling in DSS would help with bringing the S50 resolution up to DSLR level But them would I be able to stack only the co-intersecting part, or could I still preserve the wide field while adding that extra to the center part where the nebula is? Even only if the center part could be stacked, how do I make them match their pixel/arcsec scale? Are there any software for that? Here are the sample frames, hopefully that helps you visualize: 150mm  200mm  250mm  Thanks a lot in advance! |
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I don't know about DSS, but something like this works like a breeze in Pixinsight or Siril. I describe the Siril way, because its free to use and you could try it out for yourself. You stack every session separately with the "OSC_preprocessing" script and then look in the "process" folder of your working directory for the "pp_light" files. Those are the preprocessed lights of your session you currently looking into. You can take all the pp_lights from your sessions, copy them into a separate folder named "lights" and choose this as your new working directory in siril. Now you can use the "OSC_preprocessing_withoutDBF" (without Darks, Flats, Bias; because those lights are already calibrated) to stack them into one big master file. Siril does not care about Sampling or FOV, it just stacks, but later on you will see the high SNR region (the center) vs the lower SNR outer regions and the clear SNR cuts of the different FOVs. I always cropped to the FOV that matched every session. Regarding drizzling, as far as I can tell Siril has no proper Drizzling implementation, so you would have to use your Seestar sessions at native sampling rate. Maybe someone else has more Siril experience to share. Hope this can bring you closer to your goal, good luck! Regards |
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I just did this with the double cluster, combined 2 hours of subs from 2019 with an Espirit 100 and 6D with new data using a 61EDPH + 294mc pro and FRA300 + ASI071 I use Astro Pixel Processor, highly recommend you try it or switch to Siril. DSS is like 2010 lol with APP I loaded lights and calibration frames for each scope / camera separately, and then saved the calibrated lights for each scope / camera combination. So then I had like 200 fully calibrated lights from 3 different scopes and ran APP to combine them, unchecking “same scope and camera” option in registration you can see the result on my page |
7.56
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Tobias: Of course it can:=commandnameregister  [url=reference external=https://siril.readthedocs.io/en/latest/genindex.html] [/url]=highlight-text notranslate=highlightregister sequencename [-2pass] [-noout] [-drizzle] [-prefix=] [-minpairs=] [-transf=] [-layer=] [-maxstars=] [-nostarlist] [-interp=] [-noclamp] [-selected]=lineFinds and optionally performs geometric transforms on images of the sequence given in argument so that they may be superimposed on the reference image. Using stars for registration, this algorithm only works with deep sky images. Star detection options can be changed using SETFINDSTAR or the Dynamic PSF dialog. The detection is done on the green layer for colour images, unless specified by the -layer= option with an argument ranging from 0 to 2 for red to blue.=line =lineThe -2pass and -noout options will only compute the transforms but not generate the transformed images, -2pass adds a preliminary pass to the algorithm to find a good reference image before computing the transforms, based on image quality and framing. To generate transformed images after this pass, use SEQAPPLYREG. -nostarlist disables saving the star lists to disk.=line =lineThe option -transf= specifies the use of either shift, similarity, affine or homography (default) transformations respectively.=lineThe option -drizzle activates the sub-pixel stacking by up-scaling by 2 the generated images.=lineThe option -minpairs= will specify the minimum number of star pairs a frame must have with the reference frame, otherwise the frame will be dropped and excluded from the sequence.=lineThe option -maxstars= will specify the maximum number of star to find within each frame (must be between 100 and 2000). With more stars, a more accurate registration can be computed, but will take more time to run.=line =lineThe pixel interpolation method can be specified with the -interp= argument followed by one of the methods in the list no[ne], ne[arest], cu[bic], la[nczos4], li[near], ar[ea]}. If none is passed, the transformation is forced to shift and a pixel-wise shift is applied to each image without any interpolation.=lineClamping of the bicubic and lanczos4 interpolation methods is the default, to avoid artefacts, but can be disabled with the -noclamp argument. |
1.20
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You can process every stack separately and register them using Registar and then combine them with pixinsight or PS. Just make sure when you process the stacks, the backgrounds are equalized. Here is an example of a combination of a widefield of M45 taken with camera lens and DSLR and a close up taken with 98mm WO and ASI 294mc. https://astrob.in/368968/D/ |
3.15
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I would recommend you try to stack everything to one image instead of stacking multiple stacks and then stacking them, because you get better signal to noise ratio with 1 stack than with multiple stacks (maybe not the Seestar data - more later). Batch 1 and 2 are quite similar in field of view and Siril will stack them to 1 image easily, you just need to manually stack the frames instead of using the script. You can still grab the pp_light files (they are your calibrated frames) after running the script and use those for registration and stacking manually. You need to choose which reference frame you want to have, and with it your pixel scale. The reference frame and the pixel scale applied to every image is chosen by the first frame you input into the sequence in the "Conversion" tab. You should choose the widest field of view for this purpose (the 150mm data). Siril will also stack the Seestar data to batch 1 and 2 without any complaints should you choose to do so, but i am not so sure its a good idea. You can try, but you will have some visible artifacts around the area where the Seestar data ends and the next dataset starts (such as background issues, different SNR - tricky to process out to an image that looks like it was one scope from the get go which i am assuming is the goal, granted this issue also exists with batch 1 and 2 because of the difference in field of view, but its not so drastic). As for Siril Drizzle which was mentioned before, it is not "true" drizzling like with DSS/APP/PI, it is a simple 200% upscale applied to the subs at registration. You dont need to do this, nor is there probably any use for it for what you wanted to do here (or in general - few cases where one would want to do that anyway). You can also manually stack at any scale you want to with some trickery, here is how: Choose your registration frame and resample it to whatever you want, lets say 133% and then use that as the first frame in the Conversion tab. Then run Global star alignment in the Registration tab and every sub that comes after that will be resampled to fit that so you can in fact choose any pixel scale you want to this way and dont have to go with any of the 3 options you have. |
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Robert Huerbsch: I just wanted to agree with Robert here. APP makes this job of integrating data from different focal lengths very easy, also good for mosaics. |
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Oskari Nikkinen: That implemented in Siril (from Iris and that from IRAF) is actual drizzle. Which is only meaningful if the original images are undersampled, which isn't the case here. |
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3.15
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andrea tasselli:Oskari Nikkinen: From Siril documentation: The button =guilabelSimplified =highlightedDrizzle x2 activates the simplified =highlighteddrizzle algorithm for the processing of this sequence. An up-scale (x2) will be applied to the registered frame or during stacking depending on which registration is chosen, that will result in higher resolution images. This option is adapted for under-sampled images, i.e, when the telescope focal length is too short for the pixel size. One may consider that the system is under-sampled when FWHM is smaller than 2 pixels. The correct name of this method should be super-resolution stacking, but for a more convenient understanding we called it Simplified Drizzle x2. If things have changed in Siril and it now does proper drizzling, link me to the page that says that. And i am being pedantic here, but i think Drizzle is not really useful even for undersampled images, at least if we are slightly undersampled (the 2 pixel fwhm that Siril recommends to drizzle with is fine, no need to drizzle). Drizzle was created for the Hubble space telescope, so this leads us to the question of if we are operating HST or not? If no, then dont drizzle, easy guideline. |
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Oskari Nikkinen: It's the same operation that was used in Iris under the same name so "simplified drizzling" is the proper name (since does not reject, weigh or normalize results) but I expect the same affine remapping between under-sampled and final image with a drop of 0.5 is operating here. Need to look at the code though. And, yes, you are being pedantic here as several forms of actual drizzling, more or less refined with respect to the original code developed for the Hubble's WFC, are in use in astronomical image processing codes and operating *on* the HST images (as opposite operating *the* HST, unless you are NASA) is no prerequisite for it to be used and useful as long as the two main requirements, i.e., 1) enough dithered frames to cover the whole of sub-sampled image space and 2) FWHM < 2.5 are met. I suspect most of the people that uses drizzle do not operate under both conditions but that it's another story. |
