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Posts posted by Shibby

  1. Hi Mark,

    I hope this doesn't sound funny, but I can't help but wonder why you have bought all these filters if you're not sure what they're for?? They all have different purposes in different situations. I suppose the first question is : What camera are you using?

    • Like 1

  2. 58 minutes ago, Peter_A said:

    Are we going to see cheaper CMOS sensors overtaking CCDs maybe? Will automatic polar alignment happen (if it hasn't already)?

    Both probably, yes. Mounts are improving, cameras and good quality optics are (slowly... in some respects) getting more affordable and I expect that trend to continue.

    Also, I think collaborative imaging and data analysis will become more popular as online services and software become better and easier to use.

    The quality of our skies, however.................

  3. I hate to be "that person", but I recommend checking what arcsec/pixel you're aiming for and consider the diffraction-limited maximum resolution of your scope, which is roughly 1.9 arcsec. Maybe you already have, but I just don't want you to waste money on an expensive barlow.

  4. Pretty much, yep. (There's read noise too).

    19 minutes ago, astrosatch said:

    Then how to reduce that residual noise which was left from removing LP?

    Your choices are:

    • Light Pollution filters, which are becoming less effective with new LED streetlights
    • Shooting with narrow-band filters.
    • More sub-exposures. This follows the law of diminishing returns.
    • Software noise reduction, although you'll always lose at least some detail. Generally, we'll apply it only to the fainter areas, where the noise has more effect.
    • Thanks 1

  5. 3 hours ago, David_L said:

    I'm impressed with this, excellent detail and colour management on an easily smeared object - really well done.

    It would be improved only by somehow toning down the stars visible in the area of the remnant itself?

    Thanks! I'll have a go at that. More importantly, perhaps, I've noticed on my desktop monitor that the background is a bit of a mess, so I should sort that out with the fore-mentioned "long, careful" version.

  6. Here's an attempt at a target that needs no description - the Crab Nebula, in bi-colour. For this one I decided to go for 300s subs, although I can't specifically remember why... :)

    I did a "rough and ready" process, followed by a long, careful one. In the end, I preferred the first version so here it is! I didn't bother with a star layer as they're not particularly bright.

    Any feedback/ suggestions appreciated, thanks.

    • Hα: 31x300s (R)
    • Oiii: 17x300s (G+B)
    • Atik 460ex
    • SW MN190
    • Orion 50mm guidescope + QHY5L-ii
    • Stacking: DeepSkyStacker
    • Processing: Photoshop


    • Like 12

  7. As you say, it's unwanted signal. So it's not really treated as noise - procedures like stacking/calibration and noise reduction don't have any affect on it. Think about a pixel in your image - some of the signal in that pixel comes from light pollution, some from the target. By "removing" the light pollution aspect with whichever tool you use to do so, you're left with the signal from the target. So in theory, you're not removing that signal from the DSO as the sky brightness adds to the signal, rather than replaces it.

    The real problem is the magnitude limiting - when part of your target is so faint that the difference between sky and target is so small it falls within the read noise of your camera, there's not much you can do to recover it. With a really dark sky, you can just expose for longer. I must admit, I don't know much about the theory of all this, so I'm sure someone wiser will be along soon...

    • Thanks 1

  8. Here's my image of the Cat's Eye Nebula in Bi-Colour Hα/Oiii

    The central nebula, very bright, was formed ~1000 years ago. The other nebulosity, much fainter was apparently ejected from the star previously every 1,500 years or so. The different age material then interacts to form the various shock waves & knots you can see.

    To capture that bright, inner nebula, I took a series of just 10s exposures. The rest of the nebula required 10 minute exposures, so that gives an idea of the difference in brightness!

    I struggled a bit with this one, as you can probably tell. Partly down to my lack of processing skills, partly down to the fact I was constantly chasing this into my light-polluted horizon for a few nights.

    • Hα: 17x600s (R)
    • Oiii: 17x600s (G+B)
    • Atik 460ex
    • SW MN190
    • Orion 50mm guidescope + QHY5L-ii
    • Stacking: DeepSkyStacker
    • Processing: Photoshop


    • Like 9

  9. Yeah it's a tough call, especially difficult bearing in mind that our images look different on every monitor!

    20 minutes ago, carastro said:

    Thanks Shibby, did you get your EFW sorted out?

    Well, it's working fine, just not in Artemis still. My filters aren't parfocal anyway, so I'm happy to manually change them for now...

  10. A very impressive swath of sky you've captured! Perhaps there's a way to combine Ha as red with some creative processing? Some of the stars look right, perhaps due to the longer exposures of Ha.

    On my monitor, I can clearly see the 6 panels, so I think it'd be worthwhile having another go at combining/tweaking the mosaic.

  11. It seems the film was very divisive! Personally, I thought it was great and had a very good, authentic feel to it. To me, the characters were far more real than those portrayed in Apollo 13. In fact, Neil Armstrong's sons have defended the portrayal of their father so it can't be that far off can it?

    I'm not sure why it's such a problem that the actual flag planting was missed out; there wasn't that much screen time devoted to the lunar surface anyway. The film was about Neil Armstrong, not specifically about the lunar landing. Besides, there was plenty of pro-American content such as JFK's speech.

  12. Hi all, I know it's been a long time coming but just wanted to let you know that I've finally released an update for Astro Panel. It's not perfect yet by any means, so I do plan to release some more updates in the near future! An important improvement is the great reliability of the new server provided by @ecuador 

    Release notes:

    • New darkness screen.
    • Finally added a (basic) widget!
    • Improved reliability of clear sky alerts.
    • Now defaults to new 7Timer server; old server for backup.
    • Fixed a bug in lunar altitude and another couple of small bugs.

    It may be a couple of hours before the update is visible to all users. Please do let me know if you encounter any issues with the update. Thanks :)

    • Thanks 2

  13. On 23/10/2018 at 17:53, michael8554 said:

    The results don't show any sign of a dip as far as I can tell.

    Precise measurements can be very difficult. What magnitude of star were you imaging, and how deep is the dip you're looking for? For a mag 12 star, I settled on 120s exposures, so 5s seems a bit short if you're hoping for a good star profile? Also, how many reference stars are you using? The more the better, but it's best if they have similar colour profiles to your target.

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