Jump to content

sgl_imaging_challenge_2021_annual.thumb.jpg.3fc34f695a81b16210333189a3162ac7.jpg

vlaiv

Members
  • Content Count

    7,720
  • Joined

  • Last visited

  • Days Won

    5

vlaiv last won the day on February 3

vlaiv had the most liked content!

Community Reputation

5,888 Excellent

About vlaiv

Profile Information

  • Gender
    Male
  • Location
    Novi Sad, Serbia

Recent Profile Visitors

8,161 profile views
  1. 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
  2. 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
  3. 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?
  4. 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
  5. 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.
  6. 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.
  7. 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:
  8. 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).
  9. 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).
  10. 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).
  11. 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.
  12. 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
  13. 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.
  14. 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
  15. 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.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.