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Posts posted by rotatux

  1. Basically : far too short exposures.

    1/ use longer "subs" luke ! ISO between 800 and 3200 (varies with camera models, I'm not a specialist of Canons), and longest duration you can with no or moderate trailing (do some test shots)... This depends on focal length (lens) and pixel size (camera) : the longer focal, the shorter possible duration => start with a wide field, such as your Tokina, and 5-15s subs, to get something at least (take many subs and stack them !). Then move on progressively to a longer focal and shorter subs until you don't get enough signal to stack any more => that will be your untracked limit.

    2/ for a starter until you know better, use a remote in continuous shooting mode (an intervalometer will also do it usually, but is not required)

    • Like 1
  2. On 02/02/2021 at 14:05, vlaiv said:

    There has to be some rationale behind using RGGB instead of say RLGB.

    It may have something to do with color management : the cheapest for cams is to output images with a color model similar, if not identical, to our display devices, which are near exclusively RGB. Using alternative color models at capture time such as LRGB, (L)LRB, (L)Lab, Cmyk, Yuv etc would incur an in-camera processing cost which means more complex embedded code, more power consumption, more latency to display image, and so on.

    Now we start to have S-log light curves and the like used at capture time in some devices, which has a non null processing cost too, so lines are starting to move. Maybe a few years from now we could hope for other color models to appear.

  3. On 29/10/2020 at 15:45, kaelig said:

    have two filters: IDAS LPS P2 filter & Baader Neodynium

    With your experiences, are they sufficient with the 130PDS tube?

    In your opinion, what is the best for:

    - galaxy

    - nebula

    Ok I don't have much experience but I can relate on what I've read so far.

    About matching with 130PDS : I don't think there such a thing as matching filters per instrument, photographically speaking, since they will darken the sky background more or less, and hence allow more or less long exposures. Visually that's another story : their filtering intensity should match your instrument diameter, roughly small or big, e.g. you're probably not going to add a dark-colored filter to a low (<=80) diameter tube.

    On matching targets : galaxies are more wide-band so you should not use nebula filters (usually more narrow-band) on them. So on nebulas go for the IDAS (though it's still wide-band, just somewhat less than Neodymium), and for galaxies check visually the Neodymium first then swap with the IDAS to see the difference.

    • Like 1
  4. 3 hours ago, kaelig said:

    I am a beginner with 130PDS & I want to improve my setup

    Hello Kaelig and welcome here. I'm sure you'll find a cheerful hand to help here, just as I got a few years ago.

    Not answering directly, but just a few remarks...

    1) I am afraid CEM25P production has stopped, if I understood correctly, so it's getting difficult to get anywhere.

    2) CLS ≠ neodymium; neodymium or "moon and skyglow" are a very wide band, glass-tinted kind of filter, which efficiency I found has dropped these past years with new generation led-based lighting (but is still good depending on your conditions); while CLS is a kind of interferometric filter, between wide and narrow band, much like UHC but more dedicated to cameras rather than visual.

    (won't comment on others)

    • Like 2
  5. 3 hours ago, Space_Plane said:

    gif above was at ~ F/3.6 using step-down rings infront of the lens

    IMO You should instead really try stopping down with the lens' own diaphragm : I have tried step-down rings too, surely they cut down on light (affect aperture geometrically, if I can say like this) but mostly don't enhance optical properties as much as the native diaphragm (I was still having coma and CA in sides and corners, shooting RGB on OSC camera)

    • Thanks 1
  6. Threads are different between T2 (×0.75mm) and M42 (×1mm);

    I can screw my T2 adapter in full only on half of my M42 lenses, others only screw half or third of the "bayonet". I have the Vivitar equivalent of your lens and like you can only screw part of a T2 adapter on it (but I'm using this as lens2scope to put oculars, not for camera)

    In doubt you would buy a specific M42 adapter for your camera.

  7. 17 hours ago, Maho said:

    Any idea where I can get a t ring for Olympus EM10 m2 t ring? 

    I advise in favor of the Baader adapter : https://www.teleskop-express.de/shop/product_info.php/info/p3676_TS-Optics-Optics-T2-Adaptor-Ring-for-Cameras-with-Micro-Four-Thirds-bayonet--Panasonic--Olympus-.html

    (This one is from TS as I can't find the Baader page for it atm.)

    Without the extension it allows to rack the focuser out a bit more to reach focus, avoiding much of the known problem of focus tube protuberance in the fov.

    Also with the SW ComaCorr it allows for several reduction factors (w/ or w/o ext, w/ or w/o M48 filter).

    BTW you could find this useful too : https://www.teleskop-express.de/shop/product_info.php/info/p3504_TS-Optics-Adaptor-from-M48x0-75-to-T2---low-profile.html

  8. Only my 2nd attempt at Perseus Double Cluster with that tube.
    I had this in stock since last year but didn't put online. Now the more time passes the more I like it, and no good night since, so here it is.


    Gear: Olympus E-PL6 with Skywatcher 130PDS and SWCC at 600mm/4.62 and dydimium filter on Omegon EQ-300 tracking RA
    Capture: 22 lights × 20s × 2000 ISO, master bias, at 1.28"/px
    Site: deep country 26km from Limoges, France
    Processing: Regim 3.4, Fotoxx 12.01+

    • Like 7
  9. Difference is far from obvious to me... Depth looks the same, as well as colors. But they are not the same scale so there may be much more details in the second one.

    Both good shots given the respective exposures, maybe too large a framing (reduce 25-30% ?), but be proud of them :)

    • Thanks 1
  10. On 22/02/2020 at 23:01, Bishkek said:

    I am aware that nothing can be done to fix the absolutely abysmal sky conditions

    Only partly true: did you try a light pollution filter ? I think of the so-called moon & skyglow kind, aka didymium / neodymium; It is cheap, and filters out enough that color balance is a bit better; And you can mount a astro-2" one on a lens with an adapter. For mounting directly on-lens, search for a used or new redhancer / red enhancer model (same filter material, usually for capturing autumn colors).

    Just a detail about "histogram clearing the left edge" technique, it works but you need to account for the fact that on many cameras the histogram is an average of 3 channels, so you need to make enough space on the left that all 3 channels are (heuristically) cleared at the same time.

    Edit: and of course the most efficient against LP is Narrow Band imaging but you have to deal with much longer exposures (and hardware setup to achieve it).

  11. On 10/11/2019 at 16:31, martin070 said:

    when I use this scope with SW coma corrector to do high contrast DSO imaging such as M42, I will get some ghosting. (I use APS-C DSLR)

    Yes I have seen this being reported too. But in my own experience I didn't encounter this problem.

    Or, I may have found ghosts around "Navi" (see here) but these were really intended 😉

    Maybe there's one detail that keeps me away from ghosting: I usually mount my LP filter after the SWCC in the imaging train, i.e. between the CC and the camera. So that's glass which could also filter out reflections from the CC after all. YMMV.

  12. Yes fantastic lens, not only for AP, it's also a killer for portraits :)

    I have "lab" tested that Samy and there's a bit of CA and coma wide open at f1.8 in sides and corners, but it's not a lot, rather like what remains after closing 1 or 2 stops most old manual lenses. It's just that for 1st light I didn't want to waste the shot and closed to F/2.8, which is enough to control it as you see.

  13. I have been suffering too long from bad weather, so I'm a bit rusty at AP. Any way this challenge is an excuse to post the only nice something I could get recently (taken on 2019-08-29).

    I like that region, it's rich with emission and reflection nebulas, open and globular clusters, and even a planetary nebula (though you can't guess it in the photo). It's also about the lowest I could shoot at the milky way this season, without getting too much light pollution.

    From middle left to upright through center: Kaus Borealis (star), M28 (glob), M8 (laguna), M20 (trifid), M21, M23 (open). Also some minor globulars SW of laguna can be guessed as fuzzy stars.


    Gear: Olympus E-PL6 with Christmas' Samyang 85mm/1.8 first light at f/2.8 and dydimium filter on Omegon EQ-300 tracking RA
    Capture: 16 lights × 60s × 1000 ISO, master bias
    Site: deep country 26km from Limoges, France
    Sky: average to good
    Processing: Regim 3.4, Fotoxx 12.01+

    • Like 5
  14. On 30/07/2019 at 18:16, Tomatobro said:

    I am still to decide what the best editor to use in Ubuntu, any suggestions?

    "Best" would be highly subjective. But I can add a suggestion.

    Most of my dev work is done in a lightweight vi clone called vile (having used it for nearly 30 years).
    However I found in recent years that Python work is more easily done in IdleX, which is an extension of the Idle editor (which comes with stock Python). It has builtin shell, editor, both with completion, documentation viewer linked to them, and ability to execute fragments of files being edited. Its editor lacks the much-loved vi feel (for me), and is instead a rather neutral notepad-like more suited to anyone.

  15. As always it depends on your choices of desired targets and interpretation of "portability":

    * Do you want deep-sky objects ? moon / planetary ? globulars ? A MAK would be good for moon, planetary and globulars, but rather not deep-sky (at least visually). A short-focal-ratio refractor or reflector (such as your 130PDS) would be better for deep-sky.

    * On which criteria do you judge your current setup not portable enough ? Is it size : a Mak or small frac would be shorter, at the expense of luminosity; Is it weight : the 130PDS is ~4 kg and my Celestron MAK 127 is ~7 kg, so if you want lighter it must be a smaller MAK (such as 90/1250), a medium fast wide-angle refractor, or a long narrow refractor.

    * You want to keep your current mount : fine, a manual alt-az is probably the lightest mount your could find, except for table-top dobson or EQ(1) mounts. Depending on your choice of instrument (i.e. if it's enough small and lighweight), you could also examine the possibility of solid tripod + small dobson (such as orion sky scanner series).

    • Thanks 1
  16. On 29/05/2019 at 22:15, happy-kat said:

    @rotatux(if I have the member right) did just this a 130pds on an altaz mount for their journey in imaging.

    Yes I'm often (wheather permitting) using a 130PDS on a Nexstar SLT mount, an alt-az one just to be clear. It's perfectly usable for visual, and a bit limited for astrophoto: My copy of this mount is a bit erratic and only allows 20s subs most of the time, 30s up to 40s when lucky. Other copies or mounts may be better, YMMV :)

    You can turn the tube in the rings to place the focuser straight upside, to line up the field of view to be more natural (up/down and left/right wise) for Alt-Az and frac/cass users.

    Only drawback is the vixen plate screws forbid the direct insertion of the plate in the mount: the plate must slide in the mount so one of the screws blocks the operation. I simply unscrew the front side of the plate and gently insert it (with the tube weight on my hand) before re-screwing it, trying not to change the plate alignment.

    If you need more info about this config just ask (I thought a few others would be using the same, but apparently not the case).

    EDIT: after reading the whole thread you (OP) appear to not have the same mount (and potential problems) as me; Your mount problably has better tracking than mine, so keep hope. However keep in mind the tube length of a 130PDS will prevent going to zenith or high altitudes, just like me, unless you use a long vixen plate and use it to offset the tube in the mount (with additional counterweights to compensate).

    • Like 1
  17. On 17/05/2019 at 17:50, Stub Mandrel said:

    Most folks switch this off so they stay put and use flat frames instead.

    My camera can't disable that auto-clean feature. And, the dust on my sensor as I checked it seems totally opaque, so I don't think flats would take care of it (or badly); "Capture dithering" in my setup would be more complicated than just a power cycle every now and then. I'm half surprised that flats work so well with others, but seeing some flats shown here I saw most dust is transparent contrary to mine (because of my smaller pixels ?).

    That moving dust might also explain why I failed to make working flats so far :-/ but living well without them as you see :)

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