Aligning R G B images

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Aligning R G B images

#1

Post by Star Dad »


Hi All - I am doing a presentation for some Girl Scouts tomorrow and am in dire straits. The R,G,B images were taken by a NASA telescope and sent to me. I am a complete newb when it comes to RGB frames - I use a standard color camera. But I thought something was suspicious when the Ring Nebula (M57) appeared to be ghosted and indeed after playing around with StarTools I can plainly see that the Red, Green, and Blue frames do not line up - not even close. Frankly, I am rather surprised by this. But how do I get the three color frames aligned? I have both Nebulosity and StarTools. If I align/combine in Nebulosity with translate and rotate I end up with a completely white final image. If I just translate then I get the "ghosting" image. If I do the LRGB Synthesis then I also get the ghosting - and StarTools does as well using the "Combine" feature. That (StarTools) manual says the images must be aligned first - but how? Should I use GIMP to align the frames? I haven't tried that yet, but that is what I will do next - but I have a dozen kids that have images that need to be processed and there isn't time at a meeting to manually align the images.

Any help will be greatly appreciated!
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Re: Aligning R G B images

#2

Post by Micke187 »


Have no experience on nebulosity or startools but try deep sky stacker (DSS) its very easy to align every channel. Just make one of the subs a reference (preferably the best sub) and the program will automatically align every sub in every channel. Just make sure you dont take of the reference on that sub before every channel has been stacked or it will get screwed up.
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Re: Aligning R G B images

#3

Post by UlteriorModem »


The frames have to be registered / star aligned to one another prior to stacking.

Probably the fastest way would be to share the files you have on one drive or drop box and let one of the good folks here throw it together for you.
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Re: Aligning R G B images

#4

Post by Stuart »


Tom is right. One of us can align and combine the images for you really quickly. But you want to do it yourself, there are multiple software packages that can do it for you. Deep Sky Stacker is the cheapest.
Personal equipment: TEC 140 F7 on Astro-Physics Mach 1 mount. Camera QSI 683ws7. Guide with Vario guiding scope
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Re: Aligning R G B images

#5

Post by Star Dad »


Yeah, I'll need to do it myself - I have several images I'm going to have to do. The images I am working on look like they were taken through an Alt/Az telescope centered and tracking on Sheliak. The three colors look like they are rotating, but the stars are so dim they are almost impossible to see. My solution (for what it is worth) is to use Nebulosity to take each image (R G B = 3 total) and individually run them through the "Digital Development" process to stretch them so I can actually see stars for alignment. The Blue image is virtually blank otherwise. I know it over-processed the images, but there is no other way I can see to get the stars to appear so they can be aligned. Then I did a rotate and translate on the 3 colors and then combined the 3 images. The Ring Nebula now looks like it should, but I have many thin blue "horizontal" lines appearing. By dimming down the blue in StarTools I can eliminate them. The lines are not solid but kind of scattered/fuzzy.

It sure looks to me as though the original images were taken not in a row as one would expect but at completely different times. Well, at least I can show them a reasonably processed image. Thanks for bearing with me.
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Re: Aligning R G B images

#6

Post by UlteriorModem »


Sounds a lot like field rotation and is exactly why they have to be star aligned.
The R,G,B images were taken by a NASA telescope and sent to me
&
look like they were taken through an Alt/Az telescope
This confuses me.

Even though the stars seem dim before stretching, trust me the software can 'see' them and register them.

You will probably have ragged edges around the image after the combine. And oh btw its a channel combine, not a simple stacking.
Tom

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Re: Aligning R G B images

#7

Post by Stuart »


I'm as confused as Tom. Maybe you can upload the images and we can take a look at it to see what you're talking about? We can help guide you in processing it better.
Personal equipment: TEC 140 F7 on Astro-Physics Mach 1 mount. Camera QSI 683ws7. Guide with Vario guiding scope
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Re: Aligning R G B images

#8

Post by Star Dad »


UlteriorModem wrote: Mon Jan 06, 2020 10:19 pm Sounds a lot like field rotation and is exactly why they have to be star aligned.
The R,G,B images were taken by a NASA telescope and sent to me
&
look like they were taken through an Alt/Az telescope
This confuses me.

Even though the stars seem dim before stretching, trust me the software can 'see' them and register them.

You will probably have ragged edges around the image after the combine. And oh btw its a channel combine, not a simple stacking.
Ok I will post the images when I get a chance. I'm still working on getting more software references to give to my audience. The problem I have is trying to get the stars aligned before I combine them. There's only one 60 second image in red, blue, and green. I can only see one star that is visible in all three sprectra without stretching the images. If I just combine the three images the result is a total mess with stars of each color in 3 different locations. Ach, let me post the images....
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Re: Aligning R G B images

#9

Post by Star Dad »


"To be good is not enough when you dream of being great"

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Re: Aligning R G B images

#10

Post by UlteriorModem »


I will have a look at these later today.

But could you please explain what you meant by a "NASA telescope" ?
Tom

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Re: Aligning R G B images

#11

Post by Star Dad »


I have no idea what it is.... well actually they did give a link which is since broken. I *think* it was an 8" scope located in Tuscon, AZ but I won't swear to it. You can go here to request an image: https://mo-www.cfa.harvard.edu/OWN/ However, that link is currently down. Girl Scouts USA is promoting the use of this website for the girls to do AP. I'm going to have them do their own AP with a telescope, if the weather ever clears up locally. In the meantime I will show them how to process images.


Oh, and here is the dark file: https://mcleanresearch.com/M57/Dark-B-191125070022.FITS

And quite frankly, I have an image of M-57 I took and it is far better. But the weather.....
"To be good is not enough when you dream of being great"

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Re: Aligning R G B images

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Post by yobbo89 »


I had a go, there seems to be very little dynamic range , the image is about 650 pixel wide,a star has about 4 pixels lol.

there doesn't seem to be any field rotation at all.

I ran it through astrometry

5.18005 arcsec/pix.
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scopes :gso/bintel f4 12"truss tube, bresser messier ar127s /skywatcher 10'' dob,meade 12'' f10 lx200 sct
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Re: Aligning R G B images

#13

Post by yobbo89 »


This is from harvard ?

https://www.harvard.edu/

I don't want to crush peoples dreams of becoming a good astrophotography/digital image processor, but this website functions like it was something from 1990.

there is such little you can do with the data,it seems it really takes the fun out of astronomy .

In the about microobservatory link:

MicroObservatory is a network of automated telescopes that can be controlled over the Internet. The telescopes were developed by scientists and educators at the Harvard-Smithsonian Center for Astrophysics and were designed to enable youth nationwide to investigate the wonders of the deep sky from their classrooms or after-school centers.


(The MicroObservatory remote observing network is composed of several 3-foot-tall reflecting telescopes, each of which has a 6-inch mirror to capture the light from distant objects in space. Instead of an eyepiece, the MicroObservatory telescopes focus the collected light onto a CCD detector (an electronic chip like that in a digital camera) that records the image as a picture file with 650 x 500 pixels.)

did these scientist not consider pixel scale, the camera has to be the cheapest part of the gear.

The detail of saturn below from their telescope.

i just feel that astronomy and imaging processing could of been done in separate parts, ie use hubble's data base and have class room outings in the field.
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Re: Aligning R G B images

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Post by UlteriorModem »


Thanks guys now I dont have to fuss with it. :D I got spiders to vacuum!
Tom

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Re: Aligning R G B images

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Post by yobbo89 »


https://www.researchgate.net/publicatio ... l_Use#pf12

It turns out these telescopes are 19 + years old ?

i've worked out by the scale of m51 given that it has 5''arc/pix , that camera must be 18 um, or a 9 um chip binned 2x2.
scopes :gso/bintel f4 12"truss tube, bresser messier ar127s /skywatcher 10'' dob,meade 12'' f10 lx200 sct
cameras : asi 1600mm-c/asi1600mm-c,asi120mc,prostar lp guidecam, nikkon d60, sony a7,asi 290 mm
mounts : eq6 pro/eq8/mesu 200 v2
filters : 2'' astronomik lp/badder lrgb h-a,sII,oIII,h-b,Baader Solar Continuum, chroma 3nm ha,sii,oiii,nii,rgb,lowglow,uv/ir,Thousand Oaks Solar Filter,1.25'' #47 violet,pro planet 742 ir,pro planet 807 ir,pro planet 642 bp ir.
extras : skywatcher f4 aplanatic cc, Baader MPCC MKIII Coma Corrector,Orion Field Flattener,zwo 1.25''adc.starlight maxi 2" 9x filter wheel,tele vue 2x barlow .

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Re: Aligning R G B images

#16

Post by Star Dad »


Thanks for the info on those scopes. I had a feeling they were pretty c***** - er bad. And the results are pretty bad too. But I did manage to get a better final image. StarTools could not do too much with the images - I basically got a blacker background. Yeah, this is what GSUSA is promoting. Which I why I want my girls to use a real camera, multiple images, and my scope. I KNOW they can do better. But alas, when the clouds roll in. <sigh>

So I guess I'm justified in my disappointment in the image I obtained. I had hoped it was going to be far better than what I can take. Well, you know, you usually get what you paid for - in this case "free". :(

Many thanks for your help. I will explain all the above (your comments) to my girls tonight when we have our meeting.
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Re: Aligning R G B images

#17

Post by Star Dad »


At our meeting I asked if anyone brought their images - no one did. So I used my M-8 Lagoon Nebula image to demonstrate with. About half way through the preprocessing steps one mother asked why we stacked images. I showed her a 1 minute sub which showed some stars - but no Nebula. I then showed her the final result. You could (almost) see and hear her jaw hit the floor and an audible gasp. I think I hooked a whole new bunch of APers. Woo Hoo!

I expect a couple of new members here at theskysearchers in the next couple of days.... :dance:
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Re: Aligning R G B images

#18

Post by yobbo89 »


good job, congrats on the seminar .
scopes :gso/bintel f4 12"truss tube, bresser messier ar127s /skywatcher 10'' dob,meade 12'' f10 lx200 sct
cameras : asi 1600mm-c/asi1600mm-c,asi120mc,prostar lp guidecam, nikkon d60, sony a7,asi 290 mm
mounts : eq6 pro/eq8/mesu 200 v2
filters : 2'' astronomik lp/badder lrgb h-a,sII,oIII,h-b,Baader Solar Continuum, chroma 3nm ha,sii,oiii,nii,rgb,lowglow,uv/ir,Thousand Oaks Solar Filter,1.25'' #47 violet,pro planet 742 ir,pro planet 807 ir,pro planet 642 bp ir.
extras : skywatcher f4 aplanatic cc, Baader MPCC MKIII Coma Corrector,Orion Field Flattener,zwo 1.25''adc.starlight maxi 2" 9x filter wheel,tele vue 2x barlow .

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