Section 4 – Camera Hardware
Page 50
From the telescope's point of view, the different models offer differing fields of view for a given
focal length, or turned around, to achieve the same field of view the different models require
differing focal lengths. Tables 4.4 and 4.5 below compare the fields of view for the cameras at
several focal lengths, and vice versa.
C8, 8" f/10
LX200, 10" f/3
4
14" f/11
Camera
Field of
View
(arcmins)
Pixel Size
(arcsecs)
Field of View
(arcmins)
Pixel Size
(arcsecs)
Field of
View
(arcmins)
Pixel Size
(arcsecs)
TC211 Tracking CCD 4.2x4.2 1.3x1.5 11.7x11.7 3.7x4.3 2.3x2.3 0.7x0.8
TC237 Tracking CCD 8.2x6.2 0.75x0.75 21.9x16.5 2.0x2.0 4.3x3.2 0.39x0.39
ST-5C 5.4x4.1 1.0x1.0 14.4x10.8 2.7x2.7 2.8x2.1 0.5x0.5
ST-237A 8.2x6.2 0.75x0.75 21.9x16.5 2.0x2.0 4.3x3.2 0.39x0.39
STV 8.0x5.0 1.5x1.5 21.6x13.5 4.0x4.0 4.0x2.5 0.75x0.75
ST-7XE 11.9x7.9 0.9x0.9 31.2x20.8 2.4x2.4 6.1x4.1 0.5x0.5
ST-8XE 23.8x15.8 0.9x0.9 62.4x41.6 2.4x2.4 12.2x8.2 0.5x0.5
ST-9XE 17.6x17.6 2.0x2.0 46.2x46.2 5.3x5.3 9.1x9.1 1.1x1.1
ST-10XE 25.1x16.9 0.7x0.7 67.0x45.2 1.8x1.8 13.0x8.8 0.36x0.36
ST-1001E 41.6x41.6 2.4x2.4 111x111 6.5x6.5 21.6x21.6 1.27x1.27
ST-2000XM 20.0x15.0 0.75x0.74 53.4x40.1 2.0x2.0 10.4x7.8 0.39x0.39
Table 4.4 - Field of View
Object
Size
Focal Length to fill 211
Tracking CCD
Focal Length
to fill ST-7XE
Moon 0.5° 275mm = 11 inches 760mm = 30 inches
Jupiter 40 arcseconds 13000mm = 510 inches 34000mm = 1350 inches
M51-Whirlpool Galaxy 8x5 arcminutes 1040mm = 41 inches 3700mm = 145 inches
M27-Dumbell Nebula 8.5 x 5.5 arcminutes 1040mm = 41 inches 3700mm = 145 inches
M57-Ring Nebula 1.3 x 1 arcminutes 6400mm = 250 inches 23000mm = 900 inches
Table 4.5 - Focal Length Required
From these numbers you can deduce that the popular C8, an 8" f/10 telescope will nicely frame
many popular objects with the ST-7XE whereas a much shorter system (f/3, perhaps achieved
with a focal reducer) will frame the same objects for the tracking CCD. Another point to bear in
mind is that, except for planetary images, you'll rarely take images where the pixel size in
seconds of arc is down near the seeing limit. Most objects are relatively large, where the field of
view is more important than whether the individual pixels are less than half the seeing.
4.6 Connecting accessories to the Camera
There are two 9 pin accessory ports on the ST-X series of cameras. The first is labeled “AO7 /
CFW8/ SCOPE.” This is the port that supports our AO-7 Adaptive optics device, CFW8A color
4
f/6.3 telescope with an f/6.3 focal reducer and star diagonal.
To Next Page
Loading...
