Computing angular scale

[Robert Siska]

Hello,

I have a problem - I need to know the max. angular scale spanned by the image. (the larger value from 'Size' field of Calibration)

The nova API only sends radius and pixscale. Is there a way to compute the value from these?

I found that it's approximately 1.6 times the radius, but I'd rather know what's exactly going on in here :)

Thanks!

[Dustin Lang]

Hi,

pixscale is in arcseconds per pixel.

The radius computed by the API is simply the hypot(W,H)/2 of the image size in pixels, times the pixscale.

Assuming you know the maximum of the width and height of the image, you can just do pixscale * max(W,H)

cheers,
--dustin

[Robert Siska]

Thanks! Quite obvious after you point it out :D

Regards,

Robert