How to calculate the step size for auto-focusing
Autofocus method
Data
At
Bin 1x1 and 2x2
Telescope FL 1400
Pixel size 9
Read Noise RMS 10e-
Number of steps 105000
Resolution per steps 0.083 Micros/step
travel 0.35" 8.89mm
CFZ Critical Focus Zone
Ha 3nm 656.39 95
OIII 500.17 72
SII 671.69 97
Red 650.94 94
Green 510.74 74
Blue 475.69 69
Formula
CFZ / Focuser step size Multiple by 1.5 and 2
Step Size 95 / 0.083 x 1.5 = 1716
Step Size
Ha OIII SII Red Green Blue
(CFZ / Focuser step size) x 1.5 = focuser step size 1,716 1301 1753 1698 1337 1246
(CFZ / Focuser step size) x 2 = focuser step size 2,289 1734 2337 2265 1783 1662
So, if you are using SGP for example, in the step size you insert the corresponding step size. The 1.5 figures are the lowest step size and the 2 figure is the highest.
You will need to play round say from 1716 (if you are using Ha filter) to a maximum of 2289. I tried the 1716 and it was good from first time.
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