How do I determine size of Saturn on my sensor if I know all optical & sensor info?

[ivanrostas (Ivan)]

Hello all.

I have accumulated a mixed bag of gear, Vixen VMC110l, Sony A7 and A6000 cameras, a Samyang 800mm/F8 mirror lens (and 2x extender), a 2x barlow.

I also have a Skywatcher All-View mount, and last night mounted the A6000 body straight to the back of the VMC110l (prime focus?) rather than to a Baader Hyperion Eyepiece (eyepiece projection?) which I have (it all gets a bit wobbly the setup is so long).

I ran a time lapse app on the phone to fire of shots at the rate of one per second, and about 1/50s. I intend to stack in Lynkeos (I am on a Mac) this evening and see how it went.

The question I have this morning is what the calculations would be to determine which is the choice setup for taking a picture of Saturn with my gear? Given that setting up mount, scope or lens etc is time consuming enough, it would be great to just calculate what setup would make Saturn, my choice target for the coming weeks, as large as possible or alternatively, covering as many pixels as possible on my sensor.

These calculations I presume would be by finding all the optical properties of the lens or scope, knowing the sensor size of the camera I choose. Also a question is Photo or Video? Should I preserve the mechanics of the camera and just take 1920x1080 video (which I think is simply scaled-down and cropped from the 6000x4000 24Mp native sensor size, taking in to account the aspect ratio change from 3:2 to 16:9 - there is no crop mode I don't believe so no 1:1 pixels in video recording mode on this camera).

Anyway, I wonder if anyone more experienced in AP might point me in the direction of a site that might explore this, or have some quick and dirty advice?

Cheers and thanks in advance!

Ivan

[hobbit]

Try this site
http://www.skyatnightmagazine.com/field-view-calculator

[ivanrostas (Ivan)]

Thanks I'll give it a look!

[ivanrostas (Ivan)]

Thanks. The Sony SLT-A77 in the list is the same sensor and pixel pitch!

[ivanrostas (Ivan)]

If I could pose again to someone whether recording video is better than stacking stills?

Cheers

[Amaranthus (Barry)]

For bright objects, video is better, because you get more frames and so the ability to peek between the seeing (a kind of adaptive optics). Far superior for the planets out to Saturn, for instance. For DSOs, they're just too faint to benefit from this method, and so stacking long-exposure frames works best.

[ivanrostas (Ivan)]

Thanks Barry, clearly explained.

[OzEclipse (Joe Cali)]

Ivan

Size of Saturn (planet disk) = focal length ÷ 10000

Size of Saturns rings = focal length ÷ 4400

This gives the size in mm.

Then
no pixels across image = size(mm) x 1000 ÷ sensor pixel size(micron)
tells you how many of your cameras pixel are contributing to the image.
Joe