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rotatux

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About rotatux

  • Rank
    Star Forming

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  • Location
    France
  1. rotatux

    The "No EQ" DSO Challenge!

    It's a nice image with regular stars on the whole field, but I can see the diffraction pattern of a closed diaphragm on bright stars... so are you sure it was wide open ? Anyway my collection only grew from trying several lenses to find an astro-correct one, and I will sell most of it ASAP but no Zeiss yet :)
  2. rotatux

    The "No EQ" DSO Challenge!

    My copy of the 200 (same "bokeh monster" variant as yours) is very soft at F/4, I must close nearly at F/5.6 to get decently shaped stars (esp. on borders and corners). This is why I ended getting another 200 (Olympus OM) which is fine wide open at F/4 (though it suffers another aberration). About 135mm I've got many, 2 M42/Pentacon F/2.8 (long and short) that are both good at F/4 (the long variant is a bit better), and 2 F/3.5 from Minolta and Olympus which I barely tested but need to be closed at F/5.6 (Minolta much better). Having to close is normal I think, the shortest the focal the bigger aberrations need to be corrected by closing; Only long focals would be kept wide open, at 200/4 you can find many good ones (don't know at 200/3.5), at 135 I didn't encounter any yet (but maybe some F/2.8 from Minolta, Takumar or Pentax) -- though if you have budget there's the Samyang 135/2 which is a wonder from what I have read everywhere.
  3. rotatux

    The "No EQ" DSO Challenge!

    Nice start. I've got the same 200, just wondering what aperture you used, is it full open (f/4) ?
  4. rotatux

    The "No EQ" DSO Challenge!

    Use an algorithm which selects best samples before combining. Such as those with "sigma clipping" or "range clipping" (just a wild guess, I'm not a DSS user). They will make a *huge* difference. When you have bad data (does not seem your case), use more selective parameters. From your number of frames, best is probably "average sigma clipping" because with a high number of frames, averaging statistically recovers more signal depth than median. Median is best with low number of frames because it converges faster (than average) to its target value, at the price of resulting precision (it would recover at most 1 bit of signal depth, when average could recover many more). Once you use the right algorithm, only way is more data, as Ken said. Most post-processing algorithms (such as median and other linear and non linear filtering) will only smear out your image, loosing detail; Some however will help, I personnally use wavelet denoising, but I'm too young on the subject to give advice.
  5. rotatux

    The "No EQ" DSO Challenge!

    That Sigma APO seems to fare surprisingly good ! (I like your Orion very much) How much did you have to close the lens' aperture ? or was it full open at 5.6 ? Seems only the DG version is available new on the market... did you hear how it compares (optically speaking) to your D version ?
  6. rotatux

    First image M45

    Hello, that's a good first anyway. To try some answers at your questions: about darker or lighter corners: which camera do you use ? with large sensors you have more vignetting, which needs flats to correct (given your FoV and focal I could bet on APS) about noise (grain) : 17 subs is probably quite low, depending on the ISO used; I see your stars are saturated so it may be your processing (learn and practice the art of stretching !) or too high exposure; If the latter I can suggest a higher number of shorter subs (with same other settings). How many darks did you use ? I read from many DSLR users that a too low number can actually degrade your subs before stacking, hence more noise. Try processing without any darks or bias to check the resulting noise Also, unless you want to scale a master dark, or calibrate flats, bias are redundant with darks and one of the two is useless IIRC, so eliminate one and use the other; For me I kept darks to handle thermal noise, but I have read most other DSLR users rather keep and use bias (because of thermal instability of DSLR sensors leading to uneffective darks) and eliminate the thermal gradient later with image processing software as a 'background removal' step. PS: please upload jpeg images unless you're sure it deserves an uncompressed version, detail- and quality-wise, it will save our and sgl's network bandwidth
  7. rotatux

    Imaging with the 130pds

    Speaking of results, here's what I could catch during my last september holidays in 3 nights — Yes I'm the multi-subject-per-night kind of man :-P. Kind of tribute to this marvelous photon hoover (details on separate pages in my gallery) Night 1: details M31 Night 2: details M8 Laguna details M20 Trifid details M17 Omega details M16 Eagle details M33 Triangulum Night 3: details M45 Pleiades details Gamma Cas Unfortunately no clear night during christmas holidays -- apart the one before I leaved PS: sorry if layout is messy, editor/preview was a bit hard on me...
  8. rotatux

    M1 - Crab nebula wip

    I like the color version very much, it is splendid !
  9. rotatux

    Hello from north of France (Lille suburb)

    Bienvenue!
  10. rotatux

    The "No EQ" DSO Challenge!

    In fact I have seen that cropping also zooms in the remainging image, and so magnifies inner star trails to the point the whole image is mostly unusable. So you may be better off keeping exposure limited to a smaller value and take+process more subs. It's actually a combination of altitude and azimuth, but yes globally more alt = faster alt-az-relative rotation = less exposure. Rotation starts at a given speed low on horizon then raises to a common maximum speed (lowest possible exposures) at zenith. Azimuths East and West give the lowest rotation speed on horizon, while South and North are higher. There's a PDF with graphs depending on your latitude somewhere in the thread... PS: I don't have it at hand, but it should be pinned somewhere as the question comes in frequently.
  11. Hi! Slow zooming in the video was a really good idea, it gives some dynamic while the comet moves, and doesn't feel overdone. Thx and good capture.
  12. rotatux

    My Grand Tour of the Solar System 2018

    Very nice ! Damn, where is Earth
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