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Philippe's Telescope / Detector
Calculator |
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Red Light: |
630 |
nm |
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Input Parameters: |
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Green Light: |
550 |
nm |
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Derived Parameters: |
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Blue Light: |
480 |
nm |
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| 1. TELESCOPE |
Type: |
175 f8 TMB |
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| Aperture
(Diameter) |
D = |
175,00 |
millimeters |
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| Focal Length |
F = |
1.400,00 |
millimeters |
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| Aperture D = |
6,89 |
" |
inches |
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| Focal Ratio N = |
8,00 |
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| Maximum magnification = |
350,00 |
X |
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| Eye-piece for max.
magnification: |
4,00 |
mm |
millimeters |
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| Light Power: |
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| Calculations
based on a 7 mm pupil size and 6th magnitude for the naked eye |
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| Gain = |
625,00 |
X |
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| Faintest Star (visually) = |
12,99 |
m |
magnitude |
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| Faintest Star
(photographically) = |
14,99 |
m |
magnitude |
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| Barlows: |
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Effective F (mm) |
Focal Ratio N |
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| Reducer 0,75X |
0,75 |
X |
1.050 |
6,0 |
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| Barlow 2X |
2,00 |
X |
2.800 |
16,0 |
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| Eye-pieces: |
Magnification |
Exit |
Magnification |
Magnification |
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| Eye-piece focal lengths in
millimeters: |
without barlow: |
Pupil: |
with Barlow 1: |
with Barlow 2: |
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| 4,8 |
292 |
0,60 |
219 |
583 |
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| 7,0 |
200 |
0,88 |
150 |
400 |
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| 9,0 |
156 |
1,13 |
117 |
311 |
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| 13,0 |
108 |
1,63 |
81 |
215 |
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| 17,0 |
82 |
2,13 |
62 |
165 |
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| 20,0 |
70 |
2,50 |
53 |
140 |
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| 25,0 |
56 |
3,13 |
42 |
112 |
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| 27,0 |
52 |
3,38 |
39 |
104 |
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| 58,0 |
24 |
7,25 |
18 |
48 |
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| Size of the Airy Disk: |
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| Linear
diameter of the disk out to the first dark diffraction ring |
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| Red Light: |
1,81 |
" |
arc seconds |
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| Green Light: |
1,58 |
" |
arc seconds |
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| Blue Light: |
1,38 |
" |
arc seconds |
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| Full-Width
at Half-Maximum (FWHM) of the Airy Disk: |
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Size of the Airy |
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| 50
% of all incoming light is concentrated in this central core |
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Disk at focal plane |
Resolution |
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| is
a realistic measure for the smallest detail in an astronomical image |
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in µm |
in lpm |
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| Red Light: |
0,76 |
" |
arc seconds |
5,14 |
195 |
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| Green Light: |
0,66 |
" |
arc seconds |
4,49 |
223 |
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| Blue Light: |
0,58 |
" |
arc seconds |
3,92 |
255 |
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| Rayleigh's resolution limit |
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Resolution |
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| resolution:
the center of one Airy Disk is just one radius away of the other one |
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comparisons: |
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| Green Light: |
0,79 |
" |
arc seconds |
Cassini Division |
0,50 |
" |
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| Dawes's resolution limit |
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Encke Division |
0.0n |
" |
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| resolution:
empirical method based on the separation of binary stars |
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Rille in Alpine Valley |
0,27 |
" |
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| Green Light: |
0,66 |
" |
arc seconds |
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| Optimistic Sparrow's
resolution limit |
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| resolution:
2 PSFs (Point Spread Function) are separated by 1/2 radius of the airy disk |
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| Green Light: |
0,40 |
" |
arc seconds |
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| 2. DETECTOR |
Type: |
CANON
EOS-1D Mark II |
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| Width: |
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28,70 |
millimeters |
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3.504,00 |
pixels |
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| Height: |
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19,10 |
millimeters |
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2.336,00 |
pixels |
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| Number of Pixels: |
8.185.344 |
pixels |
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| Diagonal: |
34,47 |
mm |
millimeters |
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| Magnification factor: |
1,25 |
X |
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1 pixel = … km |
| Pixel Heigth: |
8,19 |
µm |
micrometers |
Comparison Objects |
Size |
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Width |
Height |
Barlow 1 |
Barlow 2 |
| Pixel Width: |
8,18 |
µm |
micrometers |
Moon/Sun |
31,4 |
' |
44,6 |
66,9 |
1187 |
445 |
| Field
of View (FOV) of the detector on this telescope: |
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Jupiter |
40 |
" |
0,9 |
1,4 |
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| Width: |
70,48 |
' |
minutes of arc |
Mars |
25 |
" |
0,6 |
0,9 |
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| Height: |
46,90 |
' |
minutes of arc |
Saturnus |
20 |
" |
0,5 |
0,7 |
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| Resolution: |
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M51 |
11 |
' |
15,6 |
23,5 |
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| Resolution in height: |
122,30 |
lpm |
lines per mm |
M13 |
17 |
' |
24,1 |
36,2 |
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| Resolution in width: |
122,09 |
lpm |
lines per mm |
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in % |
in % |
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| Angular Size of a Pixel: |
Zonder Barlow |
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Reducer 0,75X |
Barlow 2X |
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| Width: |
1,20 |
" per pixel |
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1,61 |
0,60 |
"
per pixel |
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| Height: |
1,21 |
" per pixel |
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1,61 |
0,60 |
"
per pixel |
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| Rescalings: |
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Scale: |
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| 2336 |
1,81 |
" per pixel |
66,67% |
2,41 |
0,91 |
"
per pixel |
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| 1752 |
2,41 |
" per pixel |
50,00% |
3,22 |
1,21 |
"
per pixel |
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| 1168 |
3,62 |
" per pixel |
33,33% |
4,83 |
1,81 |
"
per pixel |
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| Maximum
focal ratio to obtain diffraction limited images: |
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| When the seeing is perfect ! |
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| Red Light: |
25,49 |
Barlow: |
3,19 |
X |
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| Green Light: |
29,20 |
Barlow: |
3,65 |
X |
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| Blue Light: |
33,46 |
Barlow: |
4,18 |
X |
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Average: |
3,67 |
X |
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| Depth of focus (DOF): |
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| this
tells you how accurately you must be able to focus the detector to have a
sharp field |
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| Geometrical DOF: |
0,153 |
mm |
millimeters |
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| Diffraction DOF: |
0,141 |
mm |
millimeters |
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| DOF: |
0,153 |
mm |
millimeters |
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| Diffraction limited images
(DLI) |
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P = chance to obtain a
diffraction limited image |
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FWHM = long exposure
image width |
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| Example |
r0 in mm |
P (in %) |
1 DLI per |
Resolution |
FWHM |
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W |
H |
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… images |
in " |
in " |
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pixels |
pixels |
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20,00 |
0,00372 |
26.850 |
6,90 |
5,56 |
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4,6 |
4,6 |
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| Typical Seeing |
25,00 |
0,27216 |
367 |
5,52 |
4,45 |
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3,7 |
3,7 |
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| Typical Seeing |
30,00 |
2,80054 |
36 |
4,60 |
3,71 |
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3,1 |
3,1 |
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40,00 |
28,43843 |
4 |
3,45 |
2,78 |
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2,3 |
2,3 |
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50,00 |
83,14714 |
1 |
2,76 |
2,22 |
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1,8 |
1,8 |
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60,00 |
148,91945 |
1 |
2,30 |
1,85 |
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1,5 |
1,5 |
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70,00 |
211,62414 |
1 |
1,97 |
1,59 |
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1,3 |
1,3 |
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80,00 |
265,83823 |
1 |
1,73 |
1,39 |
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1,2 |
1,2 |
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90,00 |
310,83314 |
1 |
1,53 |
1,24 |
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1,0 |
1,0 |
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100,00 |
347,61847 |
1 |
1,38 |
1,11 |
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0,9 |
0,9 |
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| WHT 4.2m (La Palma) |
150,00 |
453,05421 |
1 |
0,92 |
0,74 |
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0,6 |
0,6 |
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| ESO 3.6m EFOSC2 |
200,00 |
497,06906 |
1 |
0,69 |
0,56 |
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0,5 |
0,5 |
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| ESO (Paranal Site) |
300,00 |
531,10277 |
1 |
0,46 |
0,37 |
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0,3 |
0,3 |
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400,00 |
543,55714 |
1 |
0,35 |
0,28 |
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0,2 |
0,2 |
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| Eyepiece Projection
Photography |
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| A |
The amplification factor
also called magnification factor. |
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| S |
The distance from the
eyepiece to the film plane or CCD chip. |
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| F2 |
The focal length of the
eyepiece, i.e. 20 mm |
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| F total |
Effective focal length
for the whole system including primary of the telescope. |
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| F1 |
The focal length of telescope
itself. |
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| f |
The
effective focal ratio of the whole system, i.e. f/20 |
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| D |
The
diameter of the primary objective or mirror of the telescope, i.e. 200 mm or
8 inch |
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| Distance eyepiece - detector
S: |
100 |
100 |
100 |
100 |
mm |
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| Focal length of the eyepiece
F2: |
4,8 |
7,0 |
9,0 |
13,0 |
mm |
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| Magnification A = |
19,83 |
13,29 |
10,11 |
6,69 |
X |
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| Effective focal length F total
= |
27.767 |
18.600 |
14.156 |
9.369 |
mm |
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| Effective focal ratio f = |
159 |
106 |
81 |
54 |
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| Source: |
http://www.licha.de/AstroWeb/articles_fullsize.php3?iHowTo=2 |
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