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rotatux

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About rotatux

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  1. Very nice and natural colors, and with much structure & detail. (is what I would like to get if mine were a success) Peeping in the image, me thinks maybe there's also room for a bit of sharpening (wavelet / tone map / unsharp mask). Also, what's your gear and capture info for this ?
  2. Hello, I find that reprocess much better, at least there's much more dust structure visible. I wish you get more data to bring the blue reflections around. /me has waited for clear skies on weekend for nearly 2 months now to have a retry at imaging it (either cloud coverage or moon). Lucky you...
  3. From the album Alt-Az / NoEQ DSO challenge

    The Markarian Chain, with M86 and local friends. Taken while drowning west. Intended as a 4000 ISO test, had to suffer much wind and throw away most of subs. Gear: Olympus E-PL6 with Skywatcher 130PDS and SWCC at f/4.55 on Celestron Nexstar SLT tracking Alt-Az Exposure: 44 lights (/ 35% keep) x 30s x 4000iso, 38 darks Processing: Regim 3.4, Fotoxx 12.01+ Location: deep country 26km from Limoges, France; good sky (skm ~21.4)

    © Fabien COUTANT

  4. Not enough: you have to rotate the polar scope to either 1/ match your local longitude + date + hour, or 2/ match other constellations around NCP (such as Ursa Minor/Major and Cassiopeia). Otherwise you may be up to 2x40' (1.33°) offset from NCP, and that might explain your trouble.
  5. No need to ask and welcome to altaz imagers. That's a very nice image, with crips stars and beautiful colors (stars and nebula). The blue background is nice too, after all. Did you have any experience with astro imaging before ? if that's your first it's a very good one.
  6. It appears your CC introduces more vignetting as there was initially. Meaning you will *need* flats to correct your images taken with it The global level is also very different : 202 vs 217 (on the full-width bottom area below the label) which is about 7%. This is difficult to see (and hereforth quantify) with the eye+screen, so I used Gimp to measure (though I wanted the median, it only offered the mean, but that's another story). I think that result is not bad per itself (90-95% Tx factor is usual with good glass assemblies), but if you're comparing brightness variations between apertures, you should remember to apply that value as transmission factor of the CC. Such an interesting subject that I'm now planning myself to check exposure levels from all my lenses/scopes x apertures, just to try to clarify whether focal+transmission ratio play a role alone, or must be combined with focal (have seen both theories defendable). Just need to build a DIY light lab to keep things constant :-P
  7. Hi Ian That looks like an option to use DCRAW demosaicing when AA doesn't know how to do it. I don't understand, though, why it would not allow you to apply calibration frames. Those are pixel-level processing techniques which would apply correctly to either a grey frame or sub-component frames of a RGB image. In my early days with Regim I have used color darks (= debayered, and applied after demosaicing the lights) and they were giving good results; I now have reverted to the more traditional "before debayer" way of doing calibration, not because it was wrong but because processing 1/3 smaller images is much faster and takes less space on my storage. IMO the only drawback I could see, is a pixel level precision / resolution one. After demosaicing, some discrete (= integer) math has been applied to produce 3 image channels from one, so a bit of resolution is lost in combining adjacent pixel values -- actually I think not completely lost but rather distributed around in unpredictable ways. Typically a single hot raw pixel will give a few color-sticky pixels as output, but roughly the same distribution will occur in all images, so a dark should remain effective. Since that distribution of error/precision depends partly on input channel level and surroundings, the demosaicing algorithm cannot guarantee a value would be processed the same in a light and in a dark or flat. Thus your calibration frames, though applicable, won't give exactly the same result as would the traditional way, and you may in theory need a bit more frames to achieve the same level of precision as others (seen that way, the distribution I spoke of would look like another kind of noise). However we are talking of off-by-one cases, so I don't think that would be high enough compared to noises of other natures, that one would easily notice it.
  8. Fantastic. A7S' sensor seems to keep much sensitivity and range at 10000 ISO. I feel miserable with a try at roughly that FoV (a 200mm/4 for me) and 3200 ISO.
  9. Very interesting. Though, for the sake of comparison, I'd like to see the scope's result without CC, to account for just the mirrors' transmission, and starting the lens at f/4.0. Given that I've heard pixel individual illumination should be proportional to F ratio (all other conditions being equal), it's quite strange to observe your scope's F:5 result to be between the lens F:8 and F:11. That's a kind of flat images you made, but was your light source for them constant in intensity and distance ? BTW I don't believe in the T-stop explanation, as that would make the result even worse, i.e. the lens results around the scope's would not be F:8 and F:11 but more something like F:9 and F:12 (assuming 80% transmission). Don't forget that your 2 newton's mirrors each have typically 95% reflectivity so overall ~90% transmission.
  10. From the album Alt-Az / NoEQ DSO challenge

    The Trifid Nebula (M20) First attempt at it, trying to take advantage of my last days on a very dark site; Unfortunately failed to counteract too much wind, so it totaly lacks precision. Gear: Olympus E-PL6 with Skywatcher 130PDS 632mm/4.86 and SWCC at f/4.5 on Celestron Nexstar SLT tracking Alt-Az. Capture: 9 lights (/ 14% keep) x 30s x 3200iso, 23 darks Processing: Regim 3.4, Fotoxx 12.01+ Site: deep country 26km from Limoges, France Sky: good seing, SQM=21.4

    © Fabien COUTANT

  11. From the album Alt-Az / NoEQ DSO challenge

    The Laguna Nebula (M8) First attempt at it, trying to take advantage of my last days on a very dark site; Unfortunately failed to counteract too much wind, so it totaly lacks precision. Gear: Olympus E-PL6 with Skywatcher 130PDS 632mm/4.86 and SWCC at f/4.5 on Celestron Nexstar SLT tracking Alt-Az. Capture: 14 lights (/ 31% keep) x 30s x 3200iso, 23 darks Processing: Regim 3.4, Fotoxx 12.01+ Site: deep country 26km from Limoges, France Sky: good seing, SQM=21.4

    © Fabien COUTANT

  12. Also look at "Pinpoint stars" Android app (if you're on that kind of smartphone/tablet): tell it your camera and (focal) lens and it gives you a starting exposure time. It's for 60° declination, but times are easily divided by 2 to have the (minimum) value for celestial equator (Dec 0). It has shown to be pretty correct, though a bit optimistic at times, so take it as a start value and adjust.
  13. Nice animation... as always, I bit of explanation on how you took it would be welcome (equipment, settings, post-processing)
  14. ^ What others said + Depending on your camera (e.g. P&S vs Hybrid vs Reflex) your sensor may not have much color depth available. Thus you need to raise exposure more to counteract that limit and get some signal to stack: add time (limited by star motion on a tripod) or ISO (but stay below the "extension" zone, which is digitally amplified so not good for astro). For a starter, a "hand-motorized barn-door tracker" is quite simple to make and will buy you more exposure time (allowing to release the pressure on ISO).
  15. Interesting: so DSS does multiple iterations, while Regim does only one. Hence the very different "kappa" values. It might just as well fall back on my values range if using iterations=1. While I'm highly confident at the mathematical / statistical meaning of doing only one iteration, I'm more in unknown territory about doing many, especially as it will progressively shift the average value used as criteria. I still have to think about it as it seems to "just work" for many people. Is there some kind of synthetic report in DSS, where it would indicate the net proportion of kept pixels, so we can get an idea of the final selectivity of this algorithm ?