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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: |
AstroLAB
IRIS MPT68 |
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| Aperture
(Diameter) |
D = |
680.00 |
millimeters |
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| Focal Length |
F = |
3,000.00 |
millimeters |
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| Aperture D = |
26.77 |
" |
inches |
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| Focal Ratio N = |
4.41 |
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| Maximum magnification = |
1,360.00 |
X |
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| Eye-piece for max.
magnification: |
2.21 |
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 = |
9,436.77 |
X |
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| Faintest Star (visually) = |
15.94 |
m |
magnitude |
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| Faintest Star
(photographically) = |
17.94 |
m |
magnitude |
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| Barlows: |
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Effective F (mm) |
Focal Ratio N |
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| Barlow 1 = |
1.80 |
X |
5,400 |
7.9 |
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| Barlow 2 = |
2.00 |
X |
6,000 |
8.8 |
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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 |
625 |
1.09 |
1125 |
1250 |
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| 7 |
429 |
1.59 |
771 |
857 |
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| 9 |
333 |
2.04 |
600 |
667 |
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| 13 |
231 |
2.95 |
415 |
462 |
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| 17 |
176 |
3.85 |
318 |
353 |
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| 20 |
150 |
4.53 |
270 |
300 |
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| 25 |
120 |
5.67 |
216 |
240 |
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| 27 |
111 |
6.12 |
200 |
222 |
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| 58 |
52 |
13.15 |
93 |
103 |
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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: |
0.47 |
" |
arc seconds |
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| Green Light: |
0.41 |
" |
arc seconds |
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| Blue Light: |
0.36 |
" |
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: |
0.19 |
" |
arc seconds |
2.84 |
353 |
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| Green Light: |
0.17 |
" |
arc seconds |
2.48 |
404 |
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| Blue Light: |
0.15 |
" |
arc seconds |
2.16 |
463 |
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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: |
0.20 |
" |
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: |
0.17 |
" |
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: |
0.10 |
" |
arc seconds |
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| 2. DETECTOR |
Type: |
CANON
EOS-10D |
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| Width: |
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22.70 |
millimeters |
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3,072.00 |
pixels |
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| Height: |
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15.10 |
millimeters |
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2,048.00 |
pixels |
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| Number of Pixels: |
6,291,456 |
pixels |
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| Diagonal: |
27.26 |
mm |
millimeters |
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| Magnification factor: |
1.58 |
X |
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| Pixel Heigth: |
7.39 |
µm |
micrometers |
Comparison Objects |
Size |
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Width |
Height |
| Pixel Width: |
7.37 |
µm |
micrometers |
Moon/Sun |
31 |
' |
119.2 |
179.1 |
| Field
of View (FOV) of the detector on this telescope: |
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Jupiter |
40 |
" |
2.6 |
3.9 |
| Width: |
26.01 |
' |
minutes of arc |
Mars |
25 |
" |
1.6 |
2.4 |
| Height: |
17.30 |
' |
minutes of arc |
Saturnus |
20 |
" |
1.3 |
1.9 |
| Resolution: |
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M51 |
11 |
' |
42.3 |
63.6 |
| Resolution in height: |
135.63 |
lpm |
lines per mm |
M13 |
17 |
' |
65.3 |
98.2 |
| Resolution in width: |
135.33 |
lpm |
lines per mm |
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in % |
in % |
| Angular Size of a Pixel: |
Zonder Barlow |
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Barlow 1 |
Barlow 2 |
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| Width: |
0.51 |
" per pixel |
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0.28 |
0.25 |
"
per pixel |
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| Height: |
0.51 |
" per pixel |
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0.28 |
0.25 |
"
per pixel |
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| Rescalings: |
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Scale: |
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| 2048 |
0.76 |
" per pixel |
66.67% |
0.42 |
0.38 |
"
per pixel |
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| 1536 |
1.02 |
" per pixel |
50.00% |
0.56 |
0.51 |
"
per pixel |
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| 1024 |
1.52 |
" per pixel |
33.33% |
0.85 |
0.76 |
"
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: |
23.00 |
Barlow: |
5.21 |
X |
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| Green Light: |
26.34 |
Barlow: |
5.97 |
X |
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| Blue Light: |
30.19 |
Barlow: |
6.84 |
X |
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Average: |
6.01 |
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: |
0.067 |
mm |
millimeters |
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| Diffraction DOF: |
0.043 |
mm |
millimeters |
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| DOF: |
0.067 |
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 |
0.00000 |
############ |
6.90 |
5.56 |
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11.0 |
10.9 |
| Typical Seeing |
25.00 |
0.00000 |
############ |
5.52 |
4.45 |
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8.8 |
8.8 |
| Typical Seeing |
30.00 |
0.00000 |
############ |
4.60 |
3.71 |
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7.3 |
7.3 |
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40.00 |
0.00000 |
############ |
3.45 |
2.78 |
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5.5 |
5.5 |
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50.00 |
0.00000 |
############ |
2.76 |
2.22 |
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4.4 |
4.4 |
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60.00 |
0.00000 |
86,532,740 |
2.30 |
1.85 |
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3.7 |
3.6 |
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70.00 |
0.00023 |
429,437 |
1.97 |
1.59 |
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3.1 |
3.1 |
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80.00 |
0.00729 |
13,719 |
1.73 |
1.39 |
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2.7 |
2.7 |
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90.00 |
0.07727 |
1,294 |
1.53 |
1.24 |
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2.4 |
2.4 |
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100.00 |
0.41827 |
239 |
1.38 |
1.11 |
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2.2 |
2.2 |
| WHT 4.2m (La Palma) |
150.00 |
22.83122 |
4 |
0.92 |
0.74 |
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1.5 |
1.5 |
| ESO 3.6m EFOSC2 |
200.00 |
92.57738 |
1 |
0.69 |
0.56 |
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1.1 |
1.1 |
| ESO (Paranal Site) |
300.00 |
251.63630 |
1 |
0.46 |
0.37 |
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0.7 |
0.7 |
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400.00 |
357.08141 |
1 |
0.35 |
0.28 |
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0.5 |
0.5 |
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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: |
5 |
7 |
9 |
13 |
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
= |
59,500 |
39,857 |
30,333 |
20,077 |
mm |
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| Effective focal ratio f = |
88 |
59 |
45 |
30 |
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| Source: |
http://www.licha.de/AstroWeb/articles_fullsize.php3?iHowTo=2 |
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