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21. Specifications
Except where stated, the following specifications apply to all SDLs.
Telescope
Length
260 mm
Objective aperture:
SDL30: Ø45mm
SDL50: Ø36mm
Magnification:
SDL30: 32x
SDL50: 28x
Image:
Erect
Resolving power:
SDL30: 3
″
SDL50: 3.5
″
Field of view:
1°20
′
Minimum focus:
1.5m (5.0 ft)
Stadia ratio:
1:100
Stadia additive constant: 0
Staffs
Invar staff
BIS20:
85mm (W) x 40mm (D) x 2000mm (H)
{3.4in. (W) x 1.6in. (D) x 6.6ft (H)}
4.3kg (9.5lb.) (one staff) 17.1kg (37.7lb.)
(two staffs and case)
BIS30:
85mm (W) x 40mm (D) x 3038mm (H)
{3.4in. (W) x 1.6in. (D) x 10.0ft (H)}
5.5kg (12.2lb.) (a staff) 23.4kg (51.6lb.)
(two staffs and case)
The coefficient of linear expansion:
α
=1 x 10
-6
/
°
C
Glass fiber staff
BGS40:
58mm (W) x 28mm (D) x 4080mm (H)
(3 sections)
{2.3in. (W) x 1.1in. (D) x 13.3ft (H)}
2.4kg (5.3lb.) (one staff) 3.0kg (6.6lb.)
(a staff and case)
BGS50/50G: 58mm (W) x 28mm (D) x 5090mm (H)
(4 sections)
{2.3in. (W) x 1.1in. (D) x 16.7ft (H)}
3.0kg (6.6lb.) (one staff) 3.6kg (8.0lb.)
(one staff and case)