simulated finder scope field

Tricked out SkyTools 3 Pro with a "fake" eyepiece, for the Orion finder scope, which offers a 5° field of view, so that I can see the finder FOV circle in the Interactive Atlas chart.

It was a balancing act, playing with two variables, to get the desired effect. The formula I worked with was:

fl_e = fl_t * TFOV / AFOV

where:

• AFOV = apparent field of view - for the "eyepiece"
• fl_e = focal length of the "eyepiece"
• fl_t = focal length of the telescope
• TFOV = true field of view

For my configuration, I used the following numbers:

• AFOV = 180
• fl_t = 2032
• TFOV = 5

In playing with this, I learned that SkyTools does not like an eyepiece focal length of more than 100 mm; but would tolerate very high numbers for the apparent FOV. Crazy high!

The result was that if I used a 57 mm "eyepiece" with a 180° AFOV field, while "hooked up" to the C8 SCT, I'd be able to look through a 5° true field.

This should be handy...

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Of course, another way to do all this is to add a "binoculars" for the finder scope... Ah. OK. The binocular option is better. It presents a more normal view of the sky, not too many stars.