Asiair mosaic planning: why do panel rotation angles vary?

ZWO ASIAIR Plus Rotator Acquisition Mosaic Sequencing Beginner
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Benjamin DeHaven avatar
Benjamin DeHaven avatar

Quickish Question. Setting up a plan for a 3×3 panel mosaic of the Sadr region for the future. I’m new to the asiair ecosystem and never done a mosiac before anywhere. I noticed that the rotation needed for each panel is different. I would have expected a uniform camera rotation angle to get everything to line up perfectly. Is this an error? Is this because the sky is a “dome” going up to the zenith, so rotation angle is different for each panel? Just want to make sure… Thanks!

Benjamin

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Tony Gondola avatar
Tony Gondola avatar

That’s about it. If you want the sides of the final mosaic to be square each panel needs to be rotated slightly. I think NINA has the option to rotate or not. It’s logical that the AIR uses rotate as the default as I think that’s what most people want. Th differences in projection won’t matter much unless you have a huge fov or many panels.

Jeramie avatar
Jeramie avatar
There is angular rotation associated with how targets move through the night sky. These rotations can be more or less severe based on the target you are imaging and your location on the planet. 

You can solve this in a couple of ways. 

1. Learn to rotate your camera sensor precisely to match the rotation of your target as it moves across the sky. The ASIAir can help with this, but it is tedious in my opinion.
2. Buy a camera rotator that rotates the camera precisely and automatically to match your intended target framing as your target moves and changes angle. 
3. Use a camera that has a square sensor. (Less important, but this has helped me with framing mosaics)

I like mosaics, and I found that having the large areas of overlap at weird angles induced image artifacts that were difficult for me to remove or solve for. Things like mismatched brightness/gradients, target framing, and other odd issues pushed me to spend the money on a rotator and camera with a square sensor. 

If you're using the ASIAir platform, go buy their CAA. I love mine.

Jeramie
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ItsMeAstro avatar
ItsMeAstro avatar

Indeed, rotations can be more or less severe based on the target you are imaging and your location on the planet.

An example is a mosaic of the Heart&Soul Nebula :

Example without rotation :

📷 image.pngimage.png Example with rotation :

📷 image.pngimage.pngList with position and rotation, copied from Telescopius :

📷 image.pngimage.png I’m using a (large) WandererAstro rotator, as I have heavy equipment Good quality, nice price and three different sizes, see :

https://www.wandererastro.com/en/h-col-126.html

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