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Author Topic: Horsehead gone weird  (Read 1041 times)

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Online chris.bailey

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Re: Horsehead gone weird
« Reply #30 on: 08:44:03, 11 March, 2018 »
That is very strange then Ian as I ran your data through PI Star Alignment on default settings and it stacked fine. You are doing Calibration - Debayer - Star Align - Integration?

Chris
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Offline Ian Straton

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Re: Horsehead gone weird
« Reply #31 on: 22:06:57, 11 March, 2018 »
Hi chris, yes, calibrated (dark, flat and bias), debayer, star align then integrate... I did notice that although the alignment never errorred the report offsets were very low, subpixel low... I have no idea what it is aligning on but it isn't stars...

The pictures I uploaded were the middle 20 of the first nights run, the full set of 80 was captured over 2 different nights and a meridian flip so framing is slightly different.  The gross rotation of the meridian flip has been handled fine but the x - y translation seems entirely absent..

Online chris.bailey

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Re: Horsehead gone weird
« Reply #32 on: 22:16:55, 11 March, 2018 »
Ian

I think therefore that the frame chosen as the reference may be the issue, as may some of the frames have a very low S/N ratio. I am in the habit of running all frames through the SubFrameSelector tool and assigning the quality from that as a keyword and then use that as a weighting in stacking. The SFS tool will also give information about what is the best frame to use as a reference.

Chris
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Offline Ian Straton

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Re: Horsehead gone weird
« Reply #33 on: 22:41:27, 11 March, 2018 »
I did the same thing, used the subframe selector and used the frame with the highest weighting as the reference... :(

Online chris.bailey

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Re: Horsehead gone weird
« Reply #34 on: 07:50:45, 12 March, 2018 »
Ian

VERY strange then. Without seeing all the sub-frames, I don't know what else to suggest.

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 #35 on: 10:09:23, 12 March, 2018 »
Chris, I have uploaded the full set of lights and the bias files I created to the same google drive folder I linked to earlier.

For me the subframe selector showed img_5043 as having the highest snr, lowest eccentricity and lowest fwhm so this is the frame I used as reference.

I was thinking about what I changed in between stacking attempts and came up with the following: When I got the blue frame I had run the cosmetic correction applet to remove hot and cold pixels, given the pervasive H-alpha in the region its possible that I set the tolerance to a point where it simply removed every red pixel?  However of course this was the run where registration and integration produced the expected outcome, so it does suggest that without the hot pixel removal the registration process is still picking up on hot pixels or noise instead of actual stars despite the improved calibration of the subs...

Online chris.bailey

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Re: Horsehead gone weird
« Reply #36 on: 16:00:50, 12 March, 2018 »
Ian

I re ran all 80 light frames and got them to properly register in Star Alignment with Detection Scales of 6 and Log Sensitivity of -1.5. Stars are quite big and lots of them are very faint but these setting did the trick.

If you ran cosmetic correction, be sure to tick the CFA button. I ran it with a Hot Sigma of 5.0 and a Cold Sigma of 4.0 and it did clean the frames up nicely.

Given the very low S/N of the individual subs, the stack ended up pretty good I think. This is just with the default unlinked screen stretch applied.

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 #37 on: 22:56:32, 12 March, 2018 »
Chris, that's amazing, thank you for your efforts, I'll check my settings and see if I can replicate what you got :) fingers crossed!

Offline Ian Straton

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Re: Horsehead gone weird
« Reply #38 on: 18:34:22, 14 March, 2018 »
Great news!  I have got a decent result out of them at last!  Thank you so much for the help and advice :)
just one question, the tweaks to the image registration settings, did those make the algorithm more selective or less selective regarding the detection stars?

Online chris.bailey

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Re: Horsehead gone weird
« Reply #39 on: 19:51:19, 14 March, 2018 »
Great news Ian! Detection Scales 6 = bigger stars. Log Sensitivity  -1.5 = more stars. These are the two settings I play with when things dont register.

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 #40 on: 11:07:30, 15 March, 2018 »
good to know,  the bigger stars thing might be a common issue for me, the Vixon scope has really thick spider vanes which generate big diffraction spikes which make the stars big and square instead of small and round...

 

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