Home made focal reducers that work for the lx90 !

[5ash (Philip)]

I have made two focal reducers from lenses i have collected. The first
was made from a 4cm focal length lens that i attached to the nose of
the lpi. Below can see a photo of the jupiter graze taken using it.
The second one was made using an 18cm focal
length objective lens that i obtained from an old spectoscope
telescope. This i force fitted into the opening in an old rubber
eyepiece guard from a microscope. this when trimmed is a push fit
into the back of the opening in the back of the lx90 . I made this one
up and tested it on the moon by taking a pictures of copernicus with and witout the reducer. No perceptible chromatic abberation. I estimate the apparent focal length to be about 1000mm, F5. You might get a similar lens from a pair of binoculars or small finder scope. What do you think of the results of the second setup i only wish i had it for the jupiter graze.
regards philip

[ballaratdragons (Ken)]

Excuse my dumbness but what is a focal reducer and what does it do. I've heard the term a couple of times now.

[5ash (Philip)]

A focal reducer acts in the opposite way to a barlow lens. It reduces the apparent focal length of a telescopes objective giving lower magnification and hence a wider field of view. This is useful in photography when you are using a large focal length telescope like a schmidt cassegrain and wish to get a larger field of view .
regards philip

[[1ponders] (Paul)]

Not too shabby at all 5ash. Pretty damn good infact. Very clever.

[ballaratdragons (Ken)]

Thanks Ash,

In other words, I don't need one.

[iceman (Mike)]

That's right Ken.. us f/5 dob owners have a wide field of view when compared with thost SCT guys, that usually have double the focal length of equivalent aperture.

We want more image scale for planetary stuff, whereas they usually want less for DSO stuff!