Eyepiece and telescope pairing
Explore Scientific 18mm 82 Degree in the Celestron Astro Fi 130: magnification and field
What the Explore Scientific 18mm 82 Degree does in the Celestron Astro Fi 130, worked from the published focal lengths and apparent field.
Field of view
ring = 2.27 degrees true
dot = 3.6 mm exit pupil
- Magnification
- 36x650 mm / 18 mm
- True field
- 2.27 degrees82 deg / 36x
- Exit pupil
- 3.6 mm130 mm / 36x
- Max useful mag
- 307xpublished
Computed optics
- Barrel match
- 1.25 in eyepiece in a 1.25 in focuser
Good fit. In the Celestron Astro Fi 130 the Explore Scientific 18mm 82 Degree gives 36x with a 2.27 degree true field and a 3.6 mm exit pupil, inside the telescope's useful range.
Magnification is the telescope focal length divided by the eyepiece focal length: 650 mm divided by 18 mm is 36x. The true field of view is the eyepiece's 82 degree apparent field divided by that magnification, 2.27 degrees.
The exit pupil, the width of the light beam leaving the eyepiece, is the aperture divided by the magnification, 130 mm over 36x, which is 3.6 mm. That makes this a medium-power general setting.
The eyepiece to buy
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