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vlaiv

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Everything posted by vlaiv

  1. No need to take the bias if you took darks that match in exposure length. One of the subs or multiple have either bad column kind of artifact or row of dead pixels or similar. Softer edges are due to subs alignment and bilinear interpolation that DSS uses. If it is only single sub - sigma clip stacking should get rid of it - but it can be present on all the subs - in that case you need to "interpolate" defective pixels.
  2. It is usually best not to process data in DSS other than stacking. You can export your data from DSS in 32bit fits format and then process it in Gimp for example. If you like, you can export data and attach it here and people can give best tips on hot to get the processing right.
  3. Excellent information given by @Budgie1 That is only the first step. You'll need to weigh your color information later ( ASI533 is very strong in green and images tend to have green cast that you must balance out). If you have issues with pale colors - it could be that DSS messed up things. There is option on background calibration and certain options tend to wash out colors: If you notice issues - try changing background calibration setting (but do pay attention that sigma clip stacking depends on frames being normalized - and you can get worse results if your LP levels c
  4. You need to debayer your images as part of your workflow. What software are you using for stacking and what is your workflow?
  5. As have been mentioned - you'll need ASCOM and EQMod installed on your laptop and you'll need cable to connect the mount to your laptop. You can buy ready made cable or DIY one yourself (not very hard to do - just connect some wires to connectors).
  6. You have a guiding setup, but you are not guiding. What you are doing with your finder scope and guide camera to polar align with sharpcap is OK and you should continue to do so, however, after you do that and before you start imaging - you should run guider software - PHD2 usually and let it command the scope by examining image from camera and then making corrections - that is what guiding is. What you are doing now is just camera assisted polar alignment. There are several videos on youtube that you can watch that explain how to autoguide with PHD2 or similar guiding software. You
  7. What do you mean by that? Did you mean - you both guided and used sharpcap polar alignment routine, or did you mean by any chance that you "guided via sharpcap polar alignment routine". I ask because there is issue with your guiding - subs appear as if they are not guided at all. You have problem with RA axis - what is most likely periodic error. This is normal with budget mounts (and some more expensive mounts) - and that is the reason people guide. If you are indeed guiding - how are you guiding? What software are you using, what is your guide scope / OAG and guide camera and
  8. Shifted flats. If you stack your subs without flats - you'll see dark patches in the places where you now see this artifact. When flats shift - flat correction creates "bevel / emboss" effect in places of the dark patches: Same effect - only produced on dust shadow circles. Question is - why did your setup move between lights and flats? Do you have something loose in optical train - like loose focuser? If you put your scope horizontally to take flats - gravity might be causing shift of loose component. Even if you think you have everything tight - if you use 2" no
  9. Hi and welcome to SGL. Yes, that is quite "normal" (although we all wish it was not the case). What you are seeing is periodic error of the mount. Worm turns every 638 seconds and in those 638 seconds - pattern will roughly repeat itself. This happens because gears in the mount are not perfectly round. Yes, you have made a belt mod and that removed some of the gears - but main reduction remains - worm and worm gear and these are not round enough. There are two things that you can do to fix this to some extent: 1. Guide - this is what most people do. Guiding will sort out me
  10. Don't think that you'll be close to what the mount can handle in terms of weight. OTA weighs about 6.5Kg - and camera is not very heavy. Guide scope + guide camera are not really heavy either - that is about 3Kg extra weight tops. Overall - you are at 10Kg and that is fine with HEQ5 given that scope is relatively compact (not large OTA). You'll be probably a bit oversampling with 1.41"/px most of the time (2" FWHM seeing) - but in good seeing, you'll be quite close to optimum sampling rate (which would be around 1.55"/px - for your guiding and 1.5" FWHM seeing). It can easily ha
  11. Why is that? What sort of guide RMS are you getting at the moment? What resolution do you expect to work with once you get your Esprit 100?
  12. Rough measurement gives ~ 0.12437"/px That in turn gives 4810mm of focal length with 2.9µm pixel size. 305mm is aperture, so effective F/ratio is ~F/15.772 You were using IR pass filter with 685nm cutoff frequency. I'd say that you are roughly twice over sampled - but we can calculate it more precisely. Indeed, critical F/ratio for this combination is ~ F/8.47 - almost the half of what you used. Not only that you don't need to drizzle - you can in fact bin your data x2
  13. Lens are hardly ever diffraction limited. Telescopes are diffraction limited and corrected for infinity. They will always outperform lens on astro images (except very cheap achromat vs lens costing many thousands of pounds). By the way - that is very nice M42 image.
  14. SGL just scales image depending on screen size (smaller on thread page and a bit larger in image display page). You can always open the image in separate window (right click - open link in new tab) and look at it at 100% zoom level. That is how I usually look at all images - at their proper resolution and not scaled.
  15. In order for drizzle to have any chance of bringing improvement - you need to under sample to begin with. What F/ratio were you using for ASI290? In any case - here is non drizzled version upscaled to drizzled version and again - blinked:
  16. Since you posted two images - I just compared the two - did not mean to imply anything. I just did this in my browser (these are respective screen shots - one scaled to 67% its size and other at 100% that way they match in pixel scale) Maybe I just wanted to point out that there was no real need to drizzle as it did not contribute anything - in fact, more aggressive sharpening creates better image. I did not analyze sampling rate and pixel scale. Could be that image is over sampled as ringing is visible (consequence of wavelets / sharpening).
  17. I see no major difference between the two. Second one is just a bit more aggressively sharpened - and that is good, but if you resize them to the same size - they are virtually identical (nothing gained by drizzle).
  18. I regularly use ImageJ for that purpose as long as you export the data as 32bit fits (it is free and open source). I think some other free software may also have it - like Iris (and now looking at Siril - there is discussion if they should implement it???). As far as I know - PI has it under integer resample (choose average method).
  19. Really no much of a contest. 70D has almost double quantum efficiency compared to 300D. 500D has somewhere in between. 26% vs 38% vs 48% (300D, 500D and 70D) 70D has the smallest pixels of the lot - so you'll need to bin your data. Since it has 4.1µm pixel size, I would recommend that you do the following: stack image normally at full resolution and once you are done stacking, while data is still linear - bin x3 in software before you begin processing it further.
  20. Color shift is due to the fact that LP filters have quite a bit of gaps in their response curve. This throws off color balance and even prevents you from properly recording some colors (lowers camera gamut). Here is comparison between couple of LPS filters. Notice that R, G and B are not as much affected as for example - neutral grey/sand color of the background. This is because designers of filters tried to get primary colors properly balanced - but that is not the problem - problem is in mixed colors. You can do couple of tricks to restore this color balance - but they are qui
  21. Not all narrow band has this. OIII often has higher FWHM than Ha. Atmospheric influence. Shorter wavelengths bend more than longer wavelengths and Ha is at red end of the spectrum. Often, lunar imagers use narrow band filters in Ha to lessen atmospheric influence. For this reason if usually creates very tight stars - simply not scattered around as much as shorter wavelengths.
  22. I'm for using LP filter in combination with regular filters. Depending on your optical train, there are several options. You can use LP filter instead of lum filter. I used to do this because I had 1.25" version of LP filter and had problem of using two 1.25" filters stacked. This prevents most of the gradients in luminance - but color data suffers from light pollution. You can use 2" LP filter on top of your regular imaging train (say first thing after focuser - like screwed into CC or similar) - and that is probably the best option in light polluted location - however, you nee
  23. I've noticed that DrizzleIntegration is often used and I believe that one or more tutorials out there shown it being used and that is the reason why people use it - most just follow a good tutorial. However, as you have seen yourself - that actually hurts the image if used improperly.
  24. Indeed - mosaic that contains celestial pole will be "180° rotated"
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