help

TJD (Trevor) · #1 21-02-2009, 11:15 PM

i would like to find the field of view of my 9-50 finder scope i dont know anything else about it

i would also nlike to know how to work out the apparent field of view of my eyepieces i dont know anything about them to.

please help me

jkrah · #2 22-02-2009, 12:52 AM

Do your eyepieces (EPs) have nothing written on then ?
.. otherwise this might help..

If you know your EP Field of View (FOV) and EP Focal length (FL)
and you know the scopes Focal length .. then I think..

Magnification = Scope FL / EP FL
Apparent FOV = EP FOV / Magnification

alexch (Alex) · #3 22-02-2009, 01:33 AM

Hi Trevor,

You could check with the well known stars. The angular distance between Alpha and Gamma Crucis is 5 deg 45 min, Alpha and Beta Centauri are 4 deg 8 min apart. I measured the angular distance in Stellarium computer program.

If I remember correctly I could just get the Alpha and Gamma Crucis in the field of view of 9/50 Skywatcher finder.

With the eyepieces it is easier to claculate the FOV, I find this online calculator quite useful:
http://www.davidpaulgreen.com/tec.html

Cheers,
Alex

bmitchell82 (Brendan) · #4 22-02-2009, 01:36 AM

your 9x50 is 5 deg fov. as for your sw ep's they are generally 52 deg afov

PaulM (Paul) · #5 22-02-2009, 10:51 AM

Hi Trevor,
A few years ago I wrote a short article about figuring out the field of view. See here.

Cheers,
Paul.

TJD (Trevor) · #6 23-02-2009, 08:47 PM

i can see what bmitchell is saying as the ep's that can with my new dob were 52'

thanks for the finder fov

TJD (Trevor) · #7 23-02-2009, 10:59 PM

thanks my ep's are 52' and i think the finder is 300 arc mins thanks