RBI?

Discussion in 'STT Series' started by mike m benjamin, May 25, 2020.

  1. mike m benjamin

    mike m benjamin Cyanogen Customer

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    The ghosting effect in the images, is this the RBI effect? I was ready to blame my green and blue filters but then I noticed the effect on my ha astrodon 3nm and became suspicious that it was something else. The camera is a STT-3200me.
     

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  2. Colin Haig

    Colin Haig Staff Member

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    The exposure times listed in the FITS files don't make sense - any idea what was going on there?
    They are really tiny numbers.
    Are you referring to the glow at the left edge?
     
  3. Colin Haig

    Colin Haig Staff Member

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    I just ran an animation, and I think you're referring to something like reflective ghosts running across.
    It does look a bit like a RBI issue; will want @Doug to comment.
    Any chance the filters are in backwards (reflective side should be toward the scope)?
    Do you get them shooting through a blank/clear/luminance as well? If its RBI you would.

    I'd still like to know whats with the exposure length.
     
  4. Doug

    Doug Staff Member

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    RBI would require the previous exposure to have a very bright star at that position. So the question is... what was in the previous exposure?

    The other possibility is some kind of reflection. Possible causes include lack of baffling (anodized tubing can be surprisingly reflective at a glancing angle, and can be very reflective in IR), and any sort of focal reducer or field flattener near the focal plane.
     
  5. mike m benjamin

    mike m benjamin Cyanogen Customer

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    Colin, yes strange about the exposures times, 8.28 seconds. I checked a few other subs from the same night they are correct at 600s. No, not the dim glow in the corner (amp glow) M57 images have a dim blob above and to the left of the nebula. The NGC image has a blob just below to the left of the central bulge. what I noticed afterwards was all the ghost images only occurred in the first in a series, which is right after me adjusting my focus on a bright guide star.
    what I did last night after a focus run my first in a series was a single short (10sec) throwaway image with rbi enabled, then switched to my normal 600s images. No ghosting afterwards.
     
  6. Colin Haig

    Colin Haig Staff Member

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    Mike the exposure time for M57 says:
    8.8281803252460001e-044
    So that's 8.82 x 10-44 seconds.

    4656 green says:
    4.1723293264789997e-008
    So that's 0.00000000417 seconds

    and so on.
    I'm also seeing a HSINKT and INPUTV, and am wondering if those are bleeding across from the DL Imaging driver. Might need @Adam Robichaud to review.
     
  7. mike m benjamin

    mike m benjamin Cyanogen Customer

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    Wow, lol. I don't know what to say other than these were 300s for the NGC target and 600s for M57. I did check a few more and some are messed up but others have the correct duration.
     
  8. mike m benjamin

    mike m benjamin Cyanogen Customer

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    I forgot to upload my best image showing the effect.
     

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  9. Colin Haig

    Colin Haig Staff Member

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  10. Doug

    Doug Staff Member

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    The STT-3200 does have RBI preflash capability. What it does is flood the sensor with IR illumination to fill all the electron traps, and then flush and start the exposure. This produces a pattern of RBI everywhere, but when you subtract a dark frame also taken with RBI preflash turned on it removes the pattern. The only downside is that it adds a little noise to the image.

    The other alternative is to avoid taking images of bright star fields and then immediately do a long exposure of a fainter target. Wait 5-10 minutes for the residual bulk image to fade.
     

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