combining images from different sized scopes

[andy274]

Hi guys,
not really sure how to phrase the question title, but effectively im asking if there is a way to take OSC images from a Canon 450D camera on a small 3inch APO refractor (for chrominance) and the same target through a Canon 450D with Ha filter (luminence) on an 8inch Ritchey Chretien?
Im sure that there's a way to do this using Pixinsight but im not sure how i'd go about it - can anyone tell me if im dreaming or not!
Cheers
Andy

[Alejandro Tombolini]

Hi Andy,

StarAlignment does the job. Add all the images and set the smallest as reference and the image will be rescaled and registered on that.

Saludos, Alejandro. 

[TobiasLindemann]

If the distortion differs much, use "2-D Splines" as RegistrationModel and activate "distortion correction"

[andy274]

thanks guys - i knew it could be done & its helped massively!
Cheers
Andy

[alcol]

Follow up question.

Having successfully registered the red stacked image from my 8SE scope with the red stacked image from my ED80 scope I then tried to use ImageIntegration to combine the 2 red images but Pixinsight gave me an error message saying it needed at least 3 images.

What do I use to combine the 2 red images. The intention was to combine the 2 reds, 2 blues, 2 greens before combining them into an RGB image

[pfile]

you can actually add the same image more than once to ImageIntegration. having said that, at least one user reported that on windows, this does not work anymore because PI thinks the file is busy after opening it the first time. if that happens you can just duplicate one of the images on disk and then add those 3 unique files to the II process. you might also experiment with adding each image twice to see if there is any difference in how the input images are weighted.

rob

[alcol]

Thanks Rob

I will give that a try and come back.

Regards

Alec

[alcol]

All worked fine for the 2 Luminance images. I registered the 2 images and then duplicated them and used ImageIntegration to combine what was now 4 images. Hey presto a combined image came out of the process.

However, not so with the Red and Blue images (I haven't tried the Green images yet). I couldn't register them with each other. I got and error message at the end of the registration process saying: Unable to find an initial set of putative star pair matches.

It is true to say that there are not a great number of stars on the 8SE scope image of M51, so presumably this might be the cause of the problem? However, it did register the 2 luminance images.

Any views?

[pfile]

it could be. usually when this happens it's because the stars are either kind of soft, or they are not round enough. there are a couple of things you can fiddle with in StarAlignment. first is to set the mode to "Detected Stars" and apply SA to one of your problem images open on the desktop. it will create an image showing where it thinks the stars in the image are. if you see a lot of hot pixels or noise being detected as stars, you can change the "Noise Scales" or "Hot Pixel Removal" under the "Star detection" dropdown of SA. if you simply see too few stars recognized, you can change the Peak Response to allow it to detect less "peaky" stars. you can change "Maximum Distortion" to try to get it to detect more oval stars. if you hover your mouse over the sliders you can see tooltips which will guide you on which way to move the sliders.

rob

[alcol]

Hi Rob

How can I thank enough. Followed your instructions and could see there were lots of hot pixels round the edges of the image where different sessions had let to images not always perfectly aligned. Adjusted the noise setting and the hot pixel removal and Staralignment found enough stars to register the 2 images. Copied each image and put them into ImageIntergration and I now have a merged blue channel image of the images from the 2 scopes.


Magic - How do you guys know all this stuff?

Thanks again

Alec

[pfile]

cool, you are welcome. i guess another thing to do is just crop off the bad edges.

i've been using this software for a long time and have run into a lot of different situations... so it's just experience. now you know how to fix SA problems too

rob

[alcol]

Thanks Rob, much appreciated

Alec