Apparent Field And Actualfield - Meade 8" LX100 Series Instruction Manual

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4.
Apparent
Field and
Actual
Field
Two terms that are
often
confused and
misunderstood
are "Apparent
Field'and 'Actual
Field'. 'Apparent
Field'
is
a
function
of the
eyepiece design and
is
built into the
eyepiece. While
not totally accurate (but
a
very
good approximation),
'Apparent Field'
is
usually thought
of as the
angle your eye sees when looking through
an
eyepiece. 'Actual Field'
is the amount of the sky that
you
actually see and is
a
function of the eyepiece
being used and the telescope.
The
'Actual Field'
of
view
of a
telescope can
be
calculated by knowing the "Apparent Field' and power
of an
eyepiece with
a
given telescope. The "Actual
Field" of
a
telescope
is
calculated
by
taking
the'Apparent Field'
of
the eyepiece and dividing by the power.
The following table lists the most common optional eyepieces available and
the'Apparent
Field" for each
eyepiece. The power and 'Actual Field" of view that each eyepiece yields is listed for each
basic telescope
opticaldesign.
8" t/6.3 10' l/6.3 81/10
10"
l/10
Eyepiece/Apparent
Field
Power/Actual
Field
Power/Actual
Field
Power/Actual
Field
Power/Actual
Field
Serles
2
Modlfled Achrornatlc
Eyepleces
(}elemenb;
1-114" O.D.)
40mml360 321113()
40/0.90' 50/o.72' 63/0.57'
Serles
2
Orthoscoplc Eyepleces
(4+lements;
1-1/4"
O.D.)
4mm/45o
6mm/45o
9mm/45o
12.5mm/450
18mm/45o
25mm/45o
320t0140
211tO.210
142/O320
102/O.440
71l0.630
51i0.880
4oo/0.1
10
267/O.fio
17$tO.25()
128/0.350
89/0.510
64tO.700
500/0.09'
333/0.14'
222tO.20'
160/0.28'
111/0.41'
80/0.56'
625tO.O7'
417tO.1't'
27BtO-16'
200to.8'
139/0.32'
100/0.45'
Super Plossl Eyepleces
(5+lernents;
1-1/4" O.D., except as
noted)
6.4mm/52o
9.7mm/52o
12.4mm152o
15mm/52o
2Omm/5f
26mmtlf
32mmt5*
40mm/44o
56mm/52o (2" O.D.)
200to.260
132/0.39(,
1
o3/O.5oo
85/0.61(,
64/0.810
49/1.060
4ol1.30(,
32/1.69()
23t2.270
250to.210
165/0.320
129/O.4oo
107to.490
8o/0.65(,
62tO.Uo
5o/1.040
4ol1.350
29t1.820
31
3/0.17'
206to.25'
161tO.32'
't
33/0.39'
100/0.52'
77tO.68'
63/0.83'
50/0.88'
36/1.46'
391/0.13'
25UO.n'
20a0.26'
167/0.31'
125tO.42'
96/0.54'
78t0.67'
63/0.70'
4V1.16'
Super
Wde
Angle Eyepleces
(6-elernents;1-1/4"
O.D.,
ercept
as
noted)
13.8mm/6f
18mm/67o
245mml6f
32mmt6f
(2" O.D.)
40mm/6f
(2"
O.D.)
93tO.720
71tO.940
52t1.280
40t1.670
32t2.O90
1
1
6/0.580
89/0.750
65/1.030
so/'t.340
4011.670
145tO.46'
111/0.60'
8AO.82'
63t1.O7'
50/1.34'
181tO.37'
139/0.48'
1020.66'
78/0.86'
63/1.07'
Ultra Wide Angle Eyepieces
(8-elernents;1-1/4" O.D, ercept
as
noted)
4.7mm/84o
6.7mm/84o
8.8mm/84o (1-1t4" -
2',O.D.)
14mm/84o (1-1t4" - 2" O.D.)
272/0310
't91to.44()
1
45/0.580
91tO.920
340t0.250
239/0.350
182/O.460
114t0.730
426t0.20'
299tO.28'
227tO.37'
1430.59'
5320.16'
37UO.23'
284/0.30'
179t0.47'