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SUPER BIG moon with refractor ED120 last night, 10 feb 2011


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re. "What sort of exposure time does it need for photos like that? Or is this on a tracking mount."

no need to track the moon Steve, it's just a normal sunny day up there so exposure times are really short. :-)

It is an amazing pic

Edited by geordieskies
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Hi everybody, and thanks for all the coments.

Today I saw some questions, so I´ll respond.

Yes neilm, like in the other moon photo, I used a 2x barlow to get bigger moon, because 900mm is not much, and with 2x, I get 1800mm.

And the BAADER IR/UV 1.25" was between the barlow and the DSLR.

As said by BeyondVision and geordieskies, normally and in most DSLR shoots on the moon, there´s no need to track the moon, because of the "normal sunny day up there ", but if using barlow and depending the moon phase, motorized mount for low exposure can be needed.

StevieDvd, with the barlow 2x, it reduces alot the F, from 7.5 to 15, that complicated keeping fast exposure time, so I used a motorized mount CG5 to take 1/8 sec.

I prefer refractors to get a fast shoot on the moon, because it has no need to cooldown or colimate to get a high performance. But if I had time, I could try a SCT, that gives high quality on the moon.

Thanks all astropeople,

Luis Beja

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You have to remember the moon is basically reflecting sunlight, and is approximately the same distance from the Sun as we are (give or take 250K miles). It's also grey. This is how the meter in your camera works anyway. It takes the scene in front of it, and averages all the light reflecting off it, and averages them out at a mid grey level and decides on an exposure to render the average of all the tones grey.

As the average scene during the day, at noon, will be approximately 125th/sec at ISO 100 and F8 to f11 (assuming you are not shooting into the light), then this is almost exactly the same for the moon, as all it's doing is reflecting sunlight directly.. just as the ground, buildings, people and your Aunt Mable do when you take a snapshot, and hence the exposures are broadly similar. You may have to factor in what the aperture is, as you are not using a camera lens, but shooting through a scope, but basically, a good starting point would be 125th @ ISO 100.... or to mitigate camera shake, 500th @ ISO400. If you have a fast scope, you may need a faster shutter speed.

It's also easy to work out, as aperture and shutter speed are reciprocally linked, so .

125th @f11 ISO100 is the same exposure as:










If you shoot at ISO400, then everything is shifted up that scale by 2 "stops". The slower the lens, or scope, the slower the shutter speed needs to be to allow the same amount of light in, as there is only one correct exposure.

ISO, aperture and shutter speed are reciprocally linked, so change one of the three, and the others have to change to compensate.

Edited by pook
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