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Solar Gravity 2018

Author Topic: Horsehead gone weird  (Read 807 times)

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Offline Ian Straton

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Horsehead gone weird
« on: 16:24:50, 10 February, 2018 »
Anyone know what has gone wrong here?

This is a stack of 20x5 minute exposures at iso 400.  The processing has been done in pixinsight.  I ran the sub frames through the blink comparator to get rid of gross aberrations,  then through the subframe selector script to check for good quality frames and basically selected the 20 best frames in terms of star shape eccentricity and fwhm having done that I ran the remaining frames through star alignment and image integration and this is the result. 

The stars are these odd bow tie shapes... now each sub frame is pretty good in terms of tracking but there is overall quite a bit of movement between the first and last frames which if you traced it out would be pretty similar to this shape but I would have expected the star alignment to have removed this?

Online chris.bailey

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Re: Horsehead gone weird
« Reply #1 on: 16:34:50, 10 February, 2018 »
Ian

Did you do any calibration (Darks/Flats/Bias)? Whats settings did you have for Interpolation in Star Alignment and what rejection method did you use in Image Integration and what Sigma settings?

Chris
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Offline Ian Straton

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Re: Horsehead gone weird
« Reply #2 on: 17:14:11, 10 February, 2018 »
No calibration just the light files. Interpolation was left at the default settings of Auto / 0.30 clamping threshold.  Rejection method was Winsorized Sigma Clipping sigma low was 4.0 high 3.0 (again default settings)

Online chris.bailey

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Re: Horsehead gone weird
« Reply #3 on: 17:38:50, 10 February, 2018 »
Mmm very strange then Ian. Not sure what has happened I'm afraid.

Chris
LX200|ZS70|FSQ85|FLT110|Altair DF250RC|EQ6 Pro(Rowan Belt Mod)|ParamountMX
ATIK383L+/EFW2/OAG|Lodestar|Baader 36mm LRGBHaSIIOIII
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Starlight Express SXVRH814/ONAG/FW|LodestarX2|Baader 2" Filters
Lunt LS60PTBF1200|DMK41|Quark Chromo
Samyang 135mm f1.8

Offline Ian Straton

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Re: Horsehead gone weird
« Reply #4 on: 17:59:38, 10 February, 2018 »
And here is m101 basically done through the same process...

I'd swear that the stacking hasn't translated the positions of sub frames...

Offline PaulB

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Re: Horsehead gone weird
« Reply #5 on: 21:54:47, 10 February, 2018 »
Try re-setting Registax back to default. Try again.

BTW. You don't have comet stack, ticked to you?
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Offline Ian Straton

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Re: Horsehead gone weird
« Reply #6 on: 22:12:09, 10 February, 2018 »
Paul, this was stacked in Pixinsight not registax... But the comet alignment was a good suggestion... unfortunately that is a separate function in pixinsight so no cigar on this occasion :(

Offline PaulB

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Re: Horsehead gone weird
« Reply #7 on: 22:29:53, 10 February, 2018 »
Sorry. I ment to say Deep Sky Stacker.
Paul.
"Whirlpool Observatory"
Losmandy G11-Gemini L4.
Celestron C9.25.
Megrez 80 ED II Triplet.
Orion OMC 140
Altair 115ED F7
Coronado PST
Atik 428EX
Atik EFW 2
QHY5L-II.
Modded Canon 1000D.
IOptron Mini Tower II
CCD Images
http://www.flickr.com/photos/paulabrierley/

Online chris.bailey

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Re: Horsehead gone weird
« Reply #8 on: 08:41:39, 11 February, 2018 »
Ian

That M101 is more illuminating. During Star Alignment are you getting any Ransac errors popping up in the console window? If so try try increasing the RANSAC tolerance to 3. If not try reducing Log (sensitivity) in the Star Detection to -2.00. It can also help to use the frame with the highest S/N ratio reported in SubFrame Selector as the reference image.

Chris
LX200|ZS70|FSQ85|FLT110|Altair DF250RC|EQ6 Pro(Rowan Belt Mod)|ParamountMX
ATIK383L+/EFW2/OAG|Lodestar|Baader 36mm LRGBHaSIIOIII
Starlight Express SXVRH16/ONAG/FW|Lodestar X2|Baader 2" Filters
Starlight Express SXVRH814/ONAG/FW|LodestarX2|Baader 2" Filters
Lunt LS60PTBF1200|DMK41|Quark Chromo
Samyang 135mm f1.8

Offline Ian Straton

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Re: Horsehead gone weird
« Reply #9 on: 13:43:42, 11 February, 2018 »
No there were no errors at all.  Someone on the pixinsight forums suggested that since the images are uncalibrated the star align might be picking up noise and dead pixels as stars... So I am going to start again and calibrate with some darks from my library and see what happens..

Online chris.bailey

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Re: Horsehead gone weird
« Reply #10 on: 16:18:25, 11 February, 2018 »
Ian

Yes I saw Robs comment. Worth try calibration first and if not fiddle with the settings I listed.

Chris
LX200|ZS70|FSQ85|FLT110|Altair DF250RC|EQ6 Pro(Rowan Belt Mod)|ParamountMX
ATIK383L+/EFW2/OAG|Lodestar|Baader 36mm LRGBHaSIIOIII
Starlight Express SXVRH16/ONAG/FW|Lodestar X2|Baader 2" Filters
Starlight Express SXVRH814/ONAG/FW|LodestarX2|Baader 2" Filters
Lunt LS60PTBF1200|DMK41|Quark Chromo
Samyang 135mm f1.8

Offline Ian Straton

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Re: Horsehead gone weird
« Reply #11 on: 19:56:46, 08 March, 2018 »
I am really starting to despair here so it looks like the original problem was indeed that the alignment routine wasn't detecting stars properly I have calibrated my original lights with flat and dark images following the tutorial here: http://www.lightvortexastronomy.com/tutorial-pre-processing-calibrating-and-stacking-images-in-pixinsight.html and at the end of the process got a stacked output that was clearly mosaicked as I would expect and the stars were nicely lined up.

The problem is that the calibration and debayer process appear to have completely wiped out all the detail except for a few of the brightest stars.  The attached image show the same frame, the top one was calibrated then debayered, the lower one debayered direct from the camera raw.  Both were then stretched with the screen transfer function to make them visible... as you can see the only colour left in the calibrated image is blue and all the detail is gone.

This is really frustrating as I have a lot of data, over 80 subframes at 5 minutes each but I just can't get anything out of the data :(

Online chris.bailey

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Re: Horsehead gone weird
« Reply #12 on: 20:09:28, 08 March, 2018 »
Ian

Any chance of Dropboxing a handful of image and I'll take a look.

Chris
LX200|ZS70|FSQ85|FLT110|Altair DF250RC|EQ6 Pro(Rowan Belt Mod)|ParamountMX
ATIK383L+/EFW2/OAG|Lodestar|Baader 36mm LRGBHaSIIOIII
Starlight Express SXVRH16/ONAG/FW|Lodestar X2|Baader 2" Filters
Starlight Express SXVRH814/ONAG/FW|LodestarX2|Baader 2" Filters
Lunt LS60PTBF1200|DMK41|Quark Chromo
Samyang 135mm f1.8

Offline Ian Straton

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Re: Horsehead gone weird
« Reply #13 on: 20:59:35, 08 March, 2018 »
Thanks Chris, I have put a selection of the lights, darks and flats here: https://drive.google.com/open?id=1UJQX1qU0wRvETFXjaO8JQgC0pEvBzKm3 along with the master dark and flat I produced.

Online chris.bailey

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Re: Horsehead gone weird
« Reply #14 on: 22:40:08, 08 March, 2018 »
Ian

A couple of things. Your Master Dark has 14 bit ADU readings higher than your lights so light-masterdark will result in negative values which will be rounded to zero. Could there have been some light leak in taking the darks. Second you dont seem to have any bias frames. Flats won't work correctly without them

Chris
LX200|ZS70|FSQ85|FLT110|Altair DF250RC|EQ6 Pro(Rowan Belt Mod)|ParamountMX
ATIK383L+/EFW2/OAG|Lodestar|Baader 36mm LRGBHaSIIOIII
Starlight Express SXVRH16/ONAG/FW|Lodestar X2|Baader 2" Filters
Starlight Express SXVRH814/ONAG/FW|LodestarX2|Baader 2" Filters
Lunt LS60PTBF1200|DMK41|Quark Chromo
Samyang 135mm f1.8

 

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