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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: |
Astro-Physics
155 f/7 EDFS |
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| Aperture
(Diameter) |
D = |
155,00 |
millimeters |
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| Focal Length |
F = |
1.085,00 |
millimeters |
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| Aperture D = |
6,10 |
" |
inches |
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| Focal Ratio N = |
7,00 |
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| Maximum magnification = |
310,00 |
X |
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| Eye-piece for max.
magnification: |
3,50 |
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 = |
490,31 |
X |
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| Faintest Star (visually) = |
12,73 |
m |
magnitude |
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| Faintest Star
(photographically) = |
14,73 |
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 |
814 |
5,3 |
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| Barlow 2X |
2,00 |
X |
2.170 |
14,0 |
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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 |
226 |
0,69 |
170 |
452 |
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| 7,0 |
155 |
1,00 |
116 |
310 |
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| 9,0 |
121 |
1,29 |
90 |
241 |
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| 13,0 |
83 |
1,86 |
63 |
167 |
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| 17,0 |
64 |
2,43 |
48 |
128 |
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| 20,0 |
54 |
2,86 |
41 |
109 |
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| 25,0 |
43 |
3,57 |
33 |
87 |
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| 27,0 |
40 |
3,86 |
30 |
80 |
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| 58,0 |
19 |
8,29 |
14 |
37 |
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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: |
2,05 |
" |
arc seconds |
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| Green Light: |
1,79 |
" |
arc seconds |
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| Blue Light: |
1,56 |
" |
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: |
0,86 |
" |
arc seconds |
4,50 |
222 |
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| Green Light: |
0,75 |
" |
arc seconds |
3,93 |
255 |
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| Blue Light: |
0,65 |
" |
arc seconds |
3,43 |
292 |
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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: |
0,89 |
" |
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: |
0,75 |
" |
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: |
0,45 |
" |
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 |
' |
34,5 |
51,9 |
1531 |
574 |
| Field
of View (FOV) of the detector on this telescope: |
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Jupiter |
40 |
" |
0,7 |
1,1 |
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| Width: |
90,94 |
' |
minutes of arc |
Mars |
25 |
" |
0,5 |
0,7 |
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| Height: |
60,52 |
' |
minutes of arc |
Saturnus |
20 |
" |
0,4 |
0,6 |
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| Resolution: |
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M51 |
11 |
' |
12,1 |
18,2 |
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| Resolution in height: |
122,30 |
lpm |
lines per mm |
M13 |
17 |
' |
18,7 |
28,1 |
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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: |
1,55 |
" per pixel |
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2,07 |
0,78 |
"
per pixel |
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| Height: |
1,56 |
" per pixel |
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2,08 |
0,78 |
"
per pixel |
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| Rescalings: |
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Scale: |
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| 2336 |
2,34 |
" per pixel |
66,67% |
3,11 |
1,17 |
"
per pixel |
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| 1752 |
3,11 |
" per pixel |
50,00% |
4,15 |
1,56 |
"
per pixel |
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| 1168 |
4,67 |
" per pixel |
33,33% |
6,23 |
2,34 |
"
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: |
3,64 |
X |
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| Green Light: |
29,20 |
Barlow: |
4,17 |
X |
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| Blue Light: |
33,46 |
Barlow: |
4,78 |
X |
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Average: |
4,20 |
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: |
0,134 |
mm |
millimeters |
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| Diffraction DOF: |
0,108 |
mm |
millimeters |
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| DOF: |
0,134 |
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 |
0,04862 |
2.057 |
6,90 |
5,56 |
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3,6 |
3,6 |
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| Typical Seeing |
25,00 |
1,40893 |
71 |
5,52 |
4,45 |
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2,9 |
2,9 |
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| Typical Seeing |
30,00 |
8,77241 |
11 |
4,60 |
3,71 |
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2,4 |
2,4 |
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40,00 |
54,05510 |
2 |
3,45 |
2,78 |
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1,8 |
1,8 |
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50,00 |
125,41896 |
1 |
2,76 |
2,22 |
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1,4 |
1,4 |
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60,00 |
198,11656 |
1 |
2,30 |
1,85 |
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1,2 |
1,2 |
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70,00 |
261,00254 |
1 |
1,97 |
1,59 |
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1,0 |
1,0 |
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80,00 |
312,14055 |
1 |
1,73 |
1,39 |
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0,9 |
0,9 |
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90,00 |
352,87818 |
1 |
1,53 |
1,24 |
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0,8 |
0,8 |
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100,00 |
385,24039 |
1 |
1,38 |
1,11 |
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0,7 |
0,7 |
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| WHT 4.2m (La Palma) |
150,00 |
474,22590 |
1 |
0,92 |
0,74 |
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0,5 |
0,5 |
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| ESO 3.6m EFOSC2 |
200,00 |
510,00446 |
1 |
0,69 |
0,56 |
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0,4 |
0,4 |
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| ESO (Paranal Site) |
300,00 |
537,20165 |
1 |
0,46 |
0,37 |
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0,2 |
0,2 |
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400,00 |
547,05944 |
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
= |
21.519 |
14.415 |
10.971 |
7.261 |
mm |
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| Effective focal ratio f = |
139 |
93 |
71 |
47 |
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| Source: |
http://www.licha.de/AstroWeb/articles_fullsize.php3?iHowTo=2 |
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