Kit №II
The Long Refractor
ACHROMATIC DOUBLET · 4-INCH · f/11
LUNAR & PLANETARY DETAIL
A slim, long-focus lens tube — high-contrast on the Moon, planets, and tight double stars, with almost nothing to maintain.
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- 1Objective lens
- 2Star diagonal
Instrument record
- Optical design
- Achromatic doublet
- Aperture
- 4 in (102 mm)
- Focal ratio
- f/11 · 1100 mm
- Mount
- Equatorial, slow-motion
At the eyepiece
The long focal ratio keeps the achromatic doublet’s residual false colour faint and delivers the tack-sharp, high-contrast planetary and double-star views that refractors are prized for. There is no central obstruction to scatter the light and nothing to collimate — you uncap it, let the glass cool to the night air, and observe.
Pairs with · ✦
The Eyepiece
A long focal ratio rewards a good high-power eyepiece; a short Plössl splits the tight doubles it was built for.
Take it further
Read the deeper observing guides, size up gear in the field kit, or carry the notation as original merch in the shop.