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Author Topic: Moon Shots and Atmosphere  (Read 2490 times)
gwarrellow
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« on: February 27, 2005, 08:26:22 AM »
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Indeed, compared to many other full-moon images, this one is at least above average, if not superior. As I thought about it further I began to suspect the fact that the moon was 10-15 degrees above the horizon, no longer orange hued but not super intense in brightness as it is when more overhead in its arc, may have made a significant difference. In effect, I was shooting through more atmosphere with the moon relatively low on the horizon. Anybody know about this?
OK 30 views and no responses so I'll bite!

IMHO I don't think that there is anything special about your lunar image other than to say that you've done everything right

You've an advantage over typical lunar shooters (but not necessarily over astronuts with their quality optics and driven mounts) in that you have used a quality long telephoto on a solid support. You have used mirror lock-up and the timed exposure to prevent vibration. All of this points to great technique.

You have got the exposure about right but if I had to make one comment I would say that the 0.25sec exposure is a little too long for a 500mm + 1.4 extender. I say this because the moon is a moving target and you will undoubtedly have a small amount of motion at this f.l. and exposure combination. My suggestion would be to try it again with a faster speed and a wider aperture. If you look at your image at a larger size you should see this slight blurring effect. I have done a quick calculation taking into account your lens, extender, sensor size, pixel density, moon's motion and exposure time and have come out with a motion of 1.4 pixels during your exposure. Taking the shot at f8 @ 1/125s or even better f5.6 @ 1/250s would have reduced this effect somewhat. I realise that f5.6 would be full aperture but the 500+1.4 combo is stil claimed to be superb.

Added to all this you obviously know what you're doing with processing (I'm guessing that the edge effects are due to jpeg artifacts).

All this preamble is only to say that the height above the horizon has not really helped you to produce this photo. If anything, it will in fact be worse qualitywise to one taken at a much higher elevation above the horizon. This is due to the effects of "seeing" in which you are observing the effect of looking through more of the turbulent atmosphere, pollution etc. at lower elevations than at higher elevation.

Keep shooting the moon!
Regards,
Graham
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QuantumTiger
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« Reply #1 on: March 07, 2005, 06:15:50 PM »
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That's a great shot. Kudos.

On my monitor there is a faint blue line around from about the 11 o'clock position to the 3 o'clock along the circumference. Possibly a result of slightly over sharpening the image.

I'm no expert on moon-shots, but one of my astronomer friends assures me that you get can better contrast if you shoot when the moon is slightly off full. This is because the sun is not directly over head, and as a result you get elongation in the surface shadows. HTH. Keep up the good work!
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Buddy Thomason
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« Reply #2 on: February 26, 2005, 02:58:56 PM »
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I posted this image elsewhere and folks raved about it. I was surprised as I simply went outside, set up my gear, exposed the full moon with a variety of settings, loaded them all into my computer, selected the best one, did the usual post-processing etc.

Indeed, compared to many other full-moon images, this one is at least above average, if not superior. As I thought about it further I began to suspect the fact that the moon was 10-15 degrees above the horizon, no longer orange hued but not super intense in brightness as it is when more overhead in its arc, may have made a significant difference. In effect, I was shooting through more atmosphere with the moon relatively low on the horizon. Anybody know about this?

NOTE: Image is approx 650X632 and 125K - click the thumbnail and it will open in a separate window. I use dial-up and the time to load this image is not a problem for me. If it's too large for others I apologize and that's why I inserted it as a thumbnail - so the viewer can choose to or choose not to open it.



The details:
Canon 1D MKII, EF 500 f4.0 L 'IS' with hood (IS turned off), 1.4 telextender = 910mm
ISO 100, RAW capture, F11, 1/4 sec (approx.), exposure comp minus 3, mirror lock-up, 2 sec delay, evaluative metering, auto WB, single shot mode, Gitzo carbon tripod with Arca Swiss ball head, Wimberley Sidekick and P40 quick release plate. Photoshop CS, lots of sharpening (any of you with the 1D MKII know what I mean by 'lots'), curves to taste, 5% black added, used some blue photo filter (the original had a slight sepia tone) - think that's about it.
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Buddy Thomason
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« Reply #3 on: February 27, 2005, 03:20:12 PM »
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Graham,
Thanks for your thoughtful and informational reply - much appreciated.  I shall experiment with your advice on minimizing the effect of lunar movement (until I one day get one of those fancy motorized gizmos that moves with celestial bodies!).
Your comment about the atmosphere makes sense to me and was what I'd assumed until I began to wonder if actually the increased atmosphere through which the lens must reach acted as a sort of magnifier or 'filter' of some kind that imparted a certain visual quality to the image.  
BTW, I re-worked a number of my moon image files from the other night and edited my initial post to include the 'official' and final best version I could.  It's actually a bit crisper than the other one you saw.  
Thanks again for your response.  I've been looking for a forum that is a step-up from some of the others and this one looks like it might be it.
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