Field Rotation example

[carastro]

I am doing a talk soon to the local Astro society members on "How imaging is done", for the benefit of those who don't image and I was looking for a good example of field rotation, does anyone have a good example of this I might use please?

Thanks

Carole 

[michael.h.f.wilkinson]

You could perhaps demo this effect in Stellarium: select an object to view, and select the camera FOV view, and then simulate the motion with and without EQ mount option switched on.

[symmetal]

Carole,

This detailed article gives a good description, and the animation half way down the page, and below, shows the difference between an eq and alt-az mount. An interesting point is that if you're pointing exactly East or West there is no field rotation as that's where it stops and reverses direction, and it's at a maximum when pointing North or South.

From the article:

The stars rotate around the central aiming point, but over 24 hours they WOULD NOT make a complete circle.
Orion does not "flip upside down" as it progresses from the western horizon, under the Earth, and back to the Eastern horizon.
The following animation shows what would really happen if you or your camera had X-ray vision and could see Orion as it passes under the Earth (shown in green).
Note that the Celestial Equator (shown in dark red) as well as the frame as seen from an Equatorially mounted camera (yellow) stay with the figure constantly. The Alt-Azimuth view (always level with the ground) is shown in red.

Alan

Edited March 4, 2022 by symmetal

[carastro]

@symmetal

Thanks so much for that animation, it's a great example. 

Thanks Michael, I have taken the 2nd option offered as it saves me having to work out how to do thatin Stellarium.    

Carole 

 

 

[malc-c]

Carole, not sure if this is helpful, but someone posted their images as they were having issues stacking.  They were taken on an AZ mount.  I've just taken the first and last image and overlaid them as two layers in Photoshop, and then rotated one layer until the stars overlap (as good as I could ) to show the angle the image has rotated between the two.  It's not perfect, but hope that helps