Question

If have a custom made telescope with these specifications then what's the focal length of my telescope? (refractor telescope only please)

_Specifications:_
*Objective diameter*: 90mm
*Distance between lenses*: 230mm
*Eyepiece focal length*: 4mm
*Eyepiece size*: 31.7mm

Please respond fast. Also please give a simplified answer for a brainliest answer tag. Thanks!​

Answer 1

Answer:

i don't know sorry

i know a good website that may help you

it's called https://skyandtelescope.org/observing/telescope-calculator/

Explanation: