Filter wheel back focus question?

[emadmoussa]

While I'm planning on getting a filter wheel for the sake of not screwing and unscrewing filters into the eyepiece, I hear that with certain scopes such a device makes it very difficult to achieve focus due to insufficient back focus.

Any thoughts on that?

[emadmoussa]

Forgot to mention, visual use only.

[ollypenrice]

You need to check the physical dimensions of such a wheel to see how much back focus they add and then see if your focus travel will allow it. I can think of plenty of scopes on which it wouldn't work. Basically if the wheel adds x mm to the light path, can you rack your focuser in by x mm?

Olly

[emadmoussa]

You need to check the physical dimensions of such a wheel to see how much back focus they add and then see if your focus travel will allow it. I can think of plenty of scopes on which it wouldn't work. Basically if the wheel adds x mm to the light path, can you rack your focuser in by x mm?

Olly

I've had a talk with Bern from Modern Astronomy and he asked the same. For the sake of saving all this hassle and not being sure of the result I decided to give it a miss this time and just use filters as usual - which I don't necessarily like.

[Tinker1947]

I've had a talk with Bern from Modern Astronomy and he asked the same. For the sake of saving all this hassle and not being sure of the result I decided to give it a miss this time and just use filters as usual - which I don't necessarily like.

If you measure the amount of back focus when your viewing and its more than the thickness of the filter wheel, i suppose it should be ok....