Quote:
Originally Posted by Jonathan Farmer
Sassan,
I understand your set up, but what shutter speed were you using? The surface of the moon would have mooved past quickly in your view finder; this must have been your bigest challange or did you have a tracking device as used on some telescopes?
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No Jonathan I didn't use any tracking device. As you mentioned the moon does move extremely quick at this magnification. To give you an estimate, for every 4 fast shots I take, a repositioning is a must (Moon has moved out of view finder).
The effective diaphragm, considering I started with wide open 600mm's of F/4.5 would be 1/3 higher for FD to EOS adapter, 2x2x3 for the 3 extenders, and 1.6 for digital factor, so something like 27 lower F which is translated to something like F/107.
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How I reach to this F number? Well
Fstop = Focal length / maximum diameter of lens
so my magnification is:
(600 + 33%) x 1.6 x 2 x 2 x 3
or
14285mm lens
Now apply formula:
F = 14285mm / 133mm
F = 107
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My main secrete or rather luck is the good sensor of Canon that can take a reasonable (Within the limitations) picture at ISO 1600.
If you check the EXIF, I had ISO 1600 for 1/15 seconds. This is at F/67 (If my calculation is right). I have tried lower shutter speed even close to 1 second with various degree of success to not show motion artifact. Also I tried one or two F stop lower from lens but not much to speak about. Well all I can say is I am personally impressed and had a fun in this trial. By the way now that we got to this discussion, let me just talk little like Archimedes:
"Give me a level point and with adding few more billions extender, I may let you walk to the moon literary with my tele tube..." 
Ahhh not felt good like this in a long time.
Well truly speaking after learning about the problems builder had to erect the London's Eye in the side of Thames river, I really start to appreciate Archimedes' wisdom even more...