Finder FOV for Mr Lazy

[vaztr]

So I'm trying to setup Cartes du Ciel with my equipment and doing FOV for my eyepieces is a breeze (cause I know the formula), but I have no idea if there is similar for an 8x50 or 9x50 or 6x40 etc. finderscope.

I could just go outside and by using the finder 'guess' at the FOV for the finder, but I'm sure one of youse guys will be able to tell me how this is worked out mathamatically.

Thanx in advance

Mr Lazy :)
VAZ

[Scorpius51]

Hi Andrew

Here are a few suggestions.

http://stargazerslounge.com/topic/61380-finderscope-field-of-view/

Your method of going outside and estimating is probably going to give you a reasonable result.

Cheers
John

[mikerr]

Vaz, on the site linked below it seems that the 8x50 scopes are 5 degree FOV and the 6x30 are 7.5 degree FOV. This might get you started.

http://www.optcorp.com/productList.aspx?uid=105-109-166-168

Michael.

[alocky]

Here's how we used to do it in the good old days.
Centre a star in the finder with no tracking operational. Time how long it takes the star to reach the edge of the field of view. Double it. Multiply the answer (in minutes) by 15. That is your fov in minutes of arc.
Cheers.
Andrew.

[vaztr]

Thanx All, Great sites and suggestions.

When I'm back at my scope I'll give them all a go.

By the by I also found a formula that roughly translates to
FOV = 57.3 x Small lense diameter / Focal Length

So an 8 x 50 with a FL of 150mm gives approx 3 Degrees FOV

VAZ