Telephoto lens or short refractor?
Posted: Sun Jul 02, 2017 1:37 am
Now that it's getting close, I am considering my options. Flying from Europe suggests travelling light. I did a dry run today with a Canon EF 300mm F4 IS camera lens vs an APM 480mm F6 telescope. The camera was a Canon EOS 100D. In terms of solar image size, I can see that the wider field of view of 300mm might be handy (I'm trying to imagine what the corona would look like). The 480mm is pretty nice also and would give better resolution of fine structure, I assume.
The camera lens is much smaller and lighter of course. But the big disadvantage I see with it is focusing. Auto-focus didn't seem to work well at all and manual focus was quite fiddly and my guess is would not stay put for long periods. The telescope was much easier to focus and images were much sharper. The Feathertouch focuser can be locked and then not worried about again.
I have attached jpeg files taken with 300mm camera lens and the 480mm telescope. These were taken with Baader film and are as they came from the camera. It's not so obvious the difference in sharpness unless you view the photos at 1:1 (which I don't think you can do on this webpage).
The camera lens is much smaller and lighter of course. But the big disadvantage I see with it is focusing. Auto-focus didn't seem to work well at all and manual focus was quite fiddly and my guess is would not stay put for long periods. The telescope was much easier to focus and images were much sharper. The Feathertouch focuser can be locked and then not worried about again.
I have attached jpeg files taken with 300mm camera lens and the 480mm telescope. These were taken with Baader film and are as they came from the camera. It's not so obvious the difference in sharpness unless you view the photos at 1:1 (which I don't think you can do on this webpage).