Equinox 80ED problem.

[Daddystu]

Hi all,

I've just had my equinox 80ED delivered and i noticed that it is very short physically. In fact its just 400mm. My question is how can it possibly have a 500mm focal length?

[dmahon]

The focus tube extends, and you need to stick a diagonal in too to achieve focus.

[Daddystu]

Yes that was my first thought. However on their product details page skywatcher state that the tube length is 540mm. Problem solved though. It seems as though they give tube length as measured with focuser fully extended and dewshield fully extended.

[laser_jock99]

The tubes tend to be a lot shorter than the stated focal lengths these days. Because imaging is so popular now a lot of back focus head room is designed into scopes to allow for field flateners, filter wheels and other goodies to be hung from the focuser. The problem arises when you just want put in a plain eyepiece for observing- it inevitably means using an extension tube or diagonal.