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					Astrophotographic exposure program by Han Kleijn. Internet adres: Han_kleijn@compuserve.com
Version 2.02 1998-6-8                                            The red cells are the input of the spreadsheet.                                                   Blue is output
                                                                d1c654a0-d044-4aee-9cf8-42b591d0f624.xls
Direct focus:                                                                                                                Eyepc projection:

Focal ratio telescope:       (ETX=14,6)       4
Telescope focal length:                  1250 mm                                                                             Project distance:                              80            mm
Film speed:                                100 asa                                                                           Focal length_eyepc:                            12            mm
Filter factor:                                1                                                  3)
Schwarzschild exponent film:                0.8                                                  1)                          Equivalent focal length      7083                            mm
Object altitude [degrees], (above horizon) 45 °   ==>                                              2)         90%            New focal ratio (projection)  23
1) Schwarzschild factor of typical fast film (e.g., Tri-X) = 0.65, Schwarzschild of typical slow film (e.g., 2415) = 0.8, No correction (hypersensitized or spectroscopic film) =0,9
Slide film: Kodak chrome 64 = 0,9, Kodak chrome 200, 400 =0,85         Fujichrome provia 1600 slide film = 0,83, CCD = 1,0
2) At lower altitude more atmospheric absorption. A good night can add 0,3 or 0,4 magnitude at zenith
3) Typical visual sun filter type A or B has a factor of 0,001 % = 0,00001. Type C for photographic use only 0.0001

                                                                <-----------Direct focus----------->                         <--------Eyepc projection------->
                                                   Mag pro sq
                                                                                                      Size on 35                                                   Size on 35
                  Object:                          arc sec      Exposure time                         mm film                Exposure time                         mm film
                                                                                                      resolution film 0.1%                                         resolution film 0.1%

Moon (thin crescent, 2-3 days)...                       6.7              0.020      sec.              49.0%                          0.676       sec.              277.7%
Moon (wide crescent, 4-5 days)...                        6               0.010      sec.              49.0%                          0.346       sec.              277.7%
Moon (quarter, 7 days).........                         5.2              0.005      sec.              49.0%                          0.163       sec.              277.7%
Moon (gibbous, 10 days).........                        4.5              0.003      sec.              49.0%                          0.085       sec.              277.7%
Moon (full, 14 days)............                        3.5              0.001      sec.              49.0%                          0.034       sec.              277.7%
Mercury................                                  4               0.002      sec.              0.2%                           0.053       sec.              1.0%
Venus..................                                 2.7              0.001      sec.              0.7%                           0.016       sec.              3.7%
Mars...................                                 4.7              0.003      sec.              0.6%                           0.102       sec.              3.1%
Jupiter................                                 5.9              0.010      sec.              1.1%                           0.315       sec.              6.4%
Saturn................                                  7.1              0.029      sec.              0.4%                           0.998       sec.              2.5%
Sun                                                    -10.8             0.000      sec.              0.4%                           0.000       sec.              2.5%
Sun, total eclipse prominences. 6)                      3.5              0.001      sec.              0.4%                           0.034       sec.              2.5%
Sun, total eclipse inner corona.                        4.3              0.002      sec.              0.4%                           0.071       sec.              2.5%
Sun, total eclipse middle corona.                       7.2              0.032      sec.              0.4%                           1.101       sec.              2.5%
Sun, total eclipse outer corona.                        9.4              0.245      sec.              0.4%                          10.693       sec.              2.5%
Sun, total eclipse extreme corona.                     11.3              1.531      sec.              0.4%                          88.384       sec.              2.5%

Height of 35 mm film [arcmin]                                                                         63.25 '                                                      11.16 '

Bright centre of M31, M42                               18                42.2 min. 5)
Minimum most deep sky                                   19               133.4 min. 5)                23.7%
                                                                                                                             m31=20, m51=22, m81=21.
              [Magn. / square arcsec]:                 19                133.4 min.                          <=====          m1=20, m8= 22, m42=20, m57=18
                                                                                                                             m15= 20, m13=21, m46=22
          Sky fog limit close to a city                 20               421.5 minutes max

Stars till Magnitude                                    5                    0.0    min               4)
Stars till Magnitude                                    6                    0.0    min
Stars till Magnitude                                    7                    0.0    min
Stars till Magnitude                                    8                    0.0    min
Stars till Magnitude                                    9                    0.0    min
Stars till Magnitude                                    10                   0.0    min
Stars till Magnitude                                    11                   0.1    min
Stars till Magnitude                                    12                   0.4    min
Stars till Magnitude                                    13                   1.3    min
Stars till Magnitude                                    14                   4.0    min

4) The surface brightness of a point-source image is very dependent on lens aberrrations and focusing accuracy.

   Empirische point source factor (D^ 2/F^ 0,4) from: Astro-photographie by Patrick Martinez, German translation
5) Minum value to see brightest centre.
6) Sun eclipse exposure data based on Astronomy 1978 Page 44. Brightness corona dependent on distance ( could be factor 1000 !).
   Inner corona is 1.02 till 1.3 Sun radius. Middle corona is 1.3 till 2.3 Sun radius.
  Outer corona more then 2.3 Sun radius. At sea level till maximum 5 Sun radius visible due to background level sky.
  The brightness of the corona is dependent on sun spot cycles and sun-moon distance.


Note: Brightness is given in magnitude pro square arcsec. This can be easily calculated from total the brightness
                                                                                             Seite 1
Example, full moon has a brightness of -12,6. In lux is that 10^(-0,4*-12,6)*2.06E-6 is 0,24 lux. (Note 10^0,4 = 2,51)
The total brightness dived by the surface should be equal in the brightness pro square arcsec.
10^(-0,4*m)/ (pi*r^2) = 10^(-0,4*b) ==> b - m = 2,5 log( pi * r^2) For moon m= -12,6 results in b=3,5 pro square arcsec.
                                                  d1c654a0-d044-4aee-9cf8-42b591d0f624.xls
For the Sun with a magnitude of -27 and 1860 arcsec diameter results in brightness of -10,9 pro square arcsec.
For Jupiter with a magnitude of -2,2 and 48 arcsec diameter results in brightness of 5,9 pro square arcsec.
Galaxies have a brightness between 18 and 22 pro square arcsec
To convert from brightness pro arcsec to brightness pro arcmin, subtract 8,9.



Prime focus, Optimum CCD pixelsize deepsky [microns]:                             15 (result in 2,5 arcsec/pixel)
Prime focus, Optimum CCD pixelsize planets [microns]:                              2 (result in 0,4 arcsec/pixel)
Eyepc project., Optimum CCD pixelsize deepsky [microns]:                          86 (result in 2,5 arcsec/pixel)
Eyepc project., Optimum CCD pixelsize planets [microns]:                          14 (result in 0,4 arcsec/pixel)


Resolving power (Dawes limit):                                                   0.6 arcsec
(pratical minimum 2 arcsecs, for very short exposures 1 arcsec)




The ETX has a focal ratio of 1250/90=13,9, however due to the aluminium spot a more practical value is 14,6


                         CCD pixel size: TC 211                   15 microns
                                           TC 215                 12 microns
                                           TC 241                 25 microns
                                           TC 245                 23 microns
                                           TC 255                 10 microns
                                           KAF 400/KAF 1600        9 microns, (binned 18 microns)


Pixel size of photographic film:                                  17 microns




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posted:2/20/2012
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