Eyepiece and telescope pairing
Explore Scientific 18mm 82 Degree in the Sky-Watcher Classic 150P (6-inch Dobsonian): magnification and field
What the Explore Scientific 18mm 82 Degree does in the Sky-Watcher Classic 150P (6-inch Dobsonian), worked from the published focal lengths and apparent field.
Field of view
ring = 1.23 degrees true
dot = 2.3 mm exit pupil
- Magnification
- 67x1200 mm / 18 mm
- True field
- 1.23 degrees82 deg / 67x
- Exit pupil
- 2.3 mm152 mm / 67x
- Max useful mag
- about 304x2x aperture
Computed optics
- Barrel match
- 1.25 in eyepiece in a 2 in focuser
Good fit. In the Sky-Watcher Classic 150P (6-inch Dobsonian) the Explore Scientific 18mm 82 Degree gives 67x with a 1.23 degree true field and a 2.3 mm exit pupil, inside the telescope's useful range.
Magnification is the telescope focal length divided by the eyepiece focal length: 1200 mm divided by 18 mm is 67x. The true field of view is the eyepiece's 82 degree apparent field divided by that magnification, 1.23 degrees.
The exit pupil, the width of the light beam leaving the eyepiece, is the aperture divided by the magnification, 152 mm over 67x, which is 2.3 mm. That makes this a medium-power general setting.
The eyepiece to buy
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