Hi all! I'm trying to figure out what my actual FOV is with my Olympus E-PL3, using a Canon FD 135mm prime lens. I'm going to be using this for astrophotography, so knowing the field of view as precisely as possible will help me plan my photos. An online lens calculator seemed to indicate the effective field of view would be ~9.15 degrees, and some image details on Astrobin seem to agree, indicating a diameter of about 9.4°. My own calculations seemed to indicate something closer to 12°, but I could easily be misunderstanding one or more factors that should figure into that number. I'd like to a) get the FOV calculated right and b) understand the math behind it better. Can anyone give me a better sense of what FOV my 135mm lens should be giving me? Thanks!

This is intriguing . I know only a little about Astro-Photography but love to learn. Can you please explain to us what you are planning with this lens?

Good to see it agrees... heck if I can figure out how to use that page, though. Pretty much just long-exposure shots of the night sky. I've got a Star Adventurer mount, which I've already used a little to take some experimental shots of M33. Being able to know precisely how big the FOV is will help me plan appropriate targets.

For a rectilinear lens, y=f(tan(theta)), where y is the image height, f is the focal length, and theta is the half angle. Everything can be calculated with this simple formula.

That a Star Adventurer mount looks pretty cool. Would love to play around with something like that but Out of my budge right now