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Offline Phillyo

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Image calibration in PI
« on: 09:09:19, 09 March, 2015 »
I managed to get some LRGB data last night, even though the moon was out, mostly because I wanted to test the mount again and it was clear so I thought why not.

I gathered 6 x 30min in Lum 1x1 but went with 2x2 binning with the RGB data (6min subs). My issue is that when I'm trying to calibrate it's not letting me calibrate the RGB data, but the lum data it did ok. Is this because it was binned 2x2? Do I need darks, bias and flats binned at 2x2 to match them? (I have flats but not bias or darks at 2x2).

It's coming up with an Incompatible image geometry error?

Thanks,
Phil
Astrotrac | Avalon Linear Fast Reverse with EQmod | WO Star 71 | Astrodon 3nm Ha, 5nm SII and 5nm OIII | Astro-modded Canon 450D | QSI 583wsg | Lodestar X2 Guidecam | Sequence Generator Pro | Pixinsight

Offline chris.bailey

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Re: Image calibration in PI
« Reply #1 on: 09:42:07, 09 March, 2015 »
Phil

Yep, you need calibration frames binned at 2x2. For flats you can get away with doing an integer downsample of the master flat but for bias and darks you SHOULD have specific binned sets though I have at times just upscaled the binned subs and used the unbinned calibration masters.

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 Phillyo

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Re: Image calibration in PI
« Reply #2 on: 09:43:31, 09 March, 2015 »
Thanks Chris, I thought that's what it might be but wanted to check first.

I'll go do that now :)

Phil
Astrotrac | Avalon Linear Fast Reverse with EQmod | WO Star 71 | Astrodon 3nm Ha, 5nm SII and 5nm OIII | Astro-modded Canon 450D | QSI 583wsg | Lodestar X2 Guidecam | Sequence Generator Pro | Pixinsight

Offline Phillyo

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Re: Image calibration in PI
« Reply #3 on: 17:05:03, 09 March, 2015 »
Well after a very frustrating day trying to make my first real RGB galaxy picture I give up. I'm doing something wrong but no matter what tutorial I follow my images never come out close to being the right colour.

See picture.

I've calibrated, corrected, integrated, aligned, cropped, linear fit then channel combined. Then I get this yellow looking mess :/

Where the diddly did I go wrong?

Phil
Astrotrac | Avalon Linear Fast Reverse with EQmod | WO Star 71 | Astrodon 3nm Ha, 5nm SII and 5nm OIII | Astro-modded Canon 450D | QSI 583wsg | Lodestar X2 Guidecam | Sequence Generator Pro | Pixinsight

Offline chris.bailey

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Re: Image calibration in PI
« Reply #4 on: 17:35:58, 09 March, 2015 »
Phil

there is a lot going on in the background in this area so DBE is a bit of a nightmare.

My early RGB workflow these days tends to be RGB Combination > Crop > DBE (manually placed targets) > Background Neturalisation (careful choice of background preview) > Colour Calibration (VERY careful choice of background and white references) > Normal Stretch

Doing a masked stretch to a background target of 0.25 is overstretching to my view. I go to 0.1 and then do noise reduction before using the Histogram or Curves tools to do the rest. Also the preview you used to set the background reference does not look like a good background candidate. You also need to manually adjust the upper limit. 0.05 may be a little on the high side so it starts including some star edges in the calculation.

RGB is a lot harder than Ha. Colour calibration is key. In the Col Cal tool ALWAYS output the masks so you can see what is being used and adjust the limits based on mousing around the background.

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 Phillyo

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Re: Image calibration in PI
« Reply #5 on: 19:03:01, 09 March, 2015 »
Thanks again Chris, I now have an image I'm almost happy with...though it's still very yellow in colour I think this is due to the lack of blue data. Red+green = yellow. I'm thinking there's a way to change the weights so that when you combine them you can make blue come through a bit more?

I'm going to gather a load more blue data next time out, but a question regarding rgb data gathering. I've only really done narrowband, mostly Ha which requires nice long 30min subs. When gathering RGB is it better to keep the subs shorter? Maybe 2-3 min? I've done 6min subs and the stars look very saturated...? What about Lum? Long or short? Or does it all depend on your light pollution levels?

Thanks,
Phil
Astrotrac | Avalon Linear Fast Reverse with EQmod | WO Star 71 | Astrodon 3nm Ha, 5nm SII and 5nm OIII | Astro-modded Canon 450D | QSI 583wsg | Lodestar X2 Guidecam | Sequence Generator Pro | Pixinsight

Offline chris.bailey

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Re: Image calibration in PI
« Reply #6 on: 20:09:43, 09 March, 2015 »
Phil

Colour calibration adjusts the channel weights based on the white reference. so no need to play with the weights before that. One thing to consider is that atmospheric extinction affects blue more than re and green so it sometime pays to gather blue subs when a target is at its highest.

When you say the stars 'look saturated' what are the core values? I often do 8 to 12 minute RGB subs and manage to retain star colour for the most part. Lum subs can go longer. Lp would dictate shorter RGB subs but you would then compensate with more of 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

Offline Phillyo

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Re: Image calibration in PI
« Reply #7 on: 20:24:00, 09 March, 2015 »
This is what I mean about the yellow cast. I've spent all day playing with this data so I think I'm going to have a rest now. Eat something!! It might be clearing up so I'll aim to get more subs tonight if possible to clear up the noise.

Another caveat...I know there's some satellite trails and a huge dust bunny above M81, I'm not too fussed as this was really just an experiment on imaging in LRGB and trying to learn to combine. Another steep learning curve!!

Looking at a single sub from the Red filter, star core is around 0.31?

Thanks,
Phil
Astrotrac | Avalon Linear Fast Reverse with EQmod | WO Star 71 | Astrodon 3nm Ha, 5nm SII and 5nm OIII | Astro-modded Canon 450D | QSI 583wsg | Lodestar X2 Guidecam | Sequence Generator Pro | Pixinsight

Offline chris.bailey

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Re: Image calibration in PI
« Reply #8 on: 22:11:17, 09 March, 2015 »
Phil

Doing RGB with the moon up won't have helped but you should still be able to neutralise the background and colour calibrate to get rid of that overall colour cast. You are doing both prior to stretching?

0.31 at core suggests plenty of headroom for longer subs!

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 Phillyo

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Re: Image calibration in PI
« Reply #9 on: 00:21:01, 10 March, 2015 »
I'm getting some more subs now, but I think I'm doing something wrong. I have around 2 hours of R and G and 1 hour of B plus about 3 hours of Lum here. Might be moon or light pollution I guess :/

Yep, doing both before stretching. It's just yellow. No matter what I do.

Phil
Astrotrac | Avalon Linear Fast Reverse with EQmod | WO Star 71 | Astrodon 3nm Ha, 5nm SII and 5nm OIII | Astro-modded Canon 450D | QSI 583wsg | Lodestar X2 Guidecam | Sequence Generator Pro | Pixinsight

Offline chris.bailey

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Re: Image calibration in PI
« Reply #10 on: 08:46:27, 10 March, 2015 »
Phil

If you want to put the R, G & B stacks up on Dropbox I'll take a butchers. I would not add L to RGB until you get your RGB workflow working well, its an added complication!

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 Phillyo

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Re: Image calibration in PI
« Reply #11 on: 09:43:24, 10 March, 2015 »
Thanks Chris,

They're on dropbox here:

https://www.dropbox.com/s/1rlx6crt5hx58os/Blue_crop.xisf?dl=0
https://www.dropbox.com/s/x4tlqhvu705umgq/Green_crop.xisf?dl=0
https://www.dropbox.com/s/0i3ynbedj6krfm0/Red_crop.xisf?dl=0

I have added another 30 x 6min blue subs plus 5 or 6 green subs from last night, no red as it didn't clear till late and I wanted to get more blue. It's looking much better now, though I'm still struggling!! I'll see how you get on.

Enjoy the gradients ;)

Thanks,
Phil
Astrotrac | Avalon Linear Fast Reverse with EQmod | WO Star 71 | Astrodon 3nm Ha, 5nm SII and 5nm OIII | Astro-modded Canon 450D | QSI 583wsg | Lodestar X2 Guidecam | Sequence Generator Pro | Pixinsight

Offline Phillyo

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Re: Image calibration in PI
« Reply #12 on: 10:10:27, 10 March, 2015 »
This is what I ended up with. Not quite right, but moving in the right direction :)



Phil
Astrotrac | Avalon Linear Fast Reverse with EQmod | WO Star 71 | Astrodon 3nm Ha, 5nm SII and 5nm OIII | Astro-modded Canon 450D | QSI 583wsg | Lodestar X2 Guidecam | Sequence Generator Pro | Pixinsight

Offline chris.bailey

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Re: Image calibration in PI
« Reply #13 on: 10:17:09, 10 March, 2015 »
Phil

Your stacks have some odd registration artefacts as below. Did you use the Batch PRocessing Script?

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 Phillyo

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Re: Image calibration in PI
« Reply #14 on: 10:25:56, 10 March, 2015 »
No I did them individually following your tutorials? Calibrate, cosmetic correction, star align, image integration...?
Astrotrac | Avalon Linear Fast Reverse with EQmod | WO Star 71 | Astrodon 3nm Ha, 5nm SII and 5nm OIII | Astro-modded Canon 450D | QSI 583wsg | Lodestar X2 Guidecam | Sequence Generator Pro | Pixinsight

 

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