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05-08-2012, 10:23 PM   #1
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Focusing on the Moon

So I spent 2 hours driving around shooting the supermoon from various angles and with different objects in the foreground, and ended up with about 50 shots altogether. Out of all those shots, only 1 was in focus, and that one just barely. I have such a hard time getting the moon in focus, no matter what lens I am using, and I can't for the life of me figure out why. Do others have this problem? Seeing all the shots others have posted with a nice crisp in focus moon is just driving me nuts! I have the K-r, and mostly use the 55-300mm kit lens. Autofocus doesn't work, and I would think that in manual focus I should just be able to turn the ring all the way to the right, to "infinity" and get the right focus, but that doesn't work either. The moon doesn't get big enough in the viewfinder for me to focus by eye, so I end up using live view, turning on spot metering and centering the moon in the view so it's not all washed out, then hitting the info button a few times for digital zoom, and tinkering with the focus ring while watching the screen, but this is very hit or miss.

HELP! I love photographing the moon and stars but without being able to get things in focus it's kind of pointless.

05-08-2012, 10:33 PM   #2
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QuoteOriginally posted by pdxfive Quote
Autofocus doesn't work, and I would think that in manual focus I should just be able to turn the ring all the way to the right, to "infinity" and get the right focus
When you're dealing with the moon, infinity as marked on the lens isn't always going to actually be infinity. Typically, you have to turn the focusing ring a little bit past (or before, depending on the ambient temperature) infinity, and look through the viewfinder to verify that the moon is in focus. While it is difficult to achieve perfect focus, it can definitely be done by looking at the edges of the moon, even when all you've got is a 300mm. Getting a 2x eyepiece magnifier might help, though For this particular application, properly focusing is especially important, as your aperture setting has no effect on the DOF at infinity (but you still need to stop down a few stops in order for the lens to deliver its best IQ).

Also, remember that you need to shoot at a fast shutter speed (I recommend 1/250s or higher), as the moon is constantly moving relative to the Earth.

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05-08-2012, 10:35 PM   #3
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definitely switch to MF and use live view zoom to verify you are capturing moon detail. when you zoom in tight, the LCD image darkens enough to see more of the moon (rather than the blown out white blob otherwise).

never trust the infinity marking on a lens to be set to infinity. also, if you have foreground objects you want in focus, you may need to stop down enough to get them in focus along with the moon.
05-09-2012, 12:17 AM   #4
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My K7 with the 55-300 and AF-S set to center point focus will easily focus on a single bright star such as Sirius or Regulus centered in the view. Moon should be no problem what so ever because it's really bright.
Maybe try center point focus?

My guess is that the moon IS in focus, but you may underestimate just how fast the moon moves in the frame at 300mm - so if your exposure is 1/100 it will be smeared noticeably, which could look like an out of focus image.

For correct exposure on the moon, set the exposure mode to manual and try 1/250th, f8 and iso 100. If too dark, try either iso 200 or increase aperture.

05-09-2012, 03:37 AM   #5
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QuoteOriginally posted by pdxfive Quote
So I spent 2 hours driving around shooting the supermoon from various angles and with different objects in the foreground, and ended up with about 50 shots altogether. Out of all those shots, only 1 was in focus, and that one just barely.

--------

HELP! I love photographing the moon and stars but without being able to get things in focus it's kind of pointless.

QuoteOriginally posted by calsan Quote
--------
My guess is that the moon IS in focus, but you may underestimate just how fast the moon moves in the frame at 300mm - so if your exposure is 1/100 it will be smeared noticeably, which could look like an out of focus image.

For correct exposure on the moon, set the exposure mode to manual and try 1/250th, f8 and iso 100. If too dark, try either iso 200 or increase aperture.
I would also guess that the Moon was indeed in focus in many/some of the 50 exposures. However, it is not true that there will be motion blur at 300mm and a 1/100s exposure. It's a widespread myth - but only a myth anyway. The Moon moves approximately 350 degrees and always near the celestial equator during 24 hours. That is 0.004 arc seconds in one second of time. And at 300mm FL this produces a trail of 0.02mm - in one, full second. At a 1/100s the blur/trail will only be 0.0002 mm - which is a mere four percent of the pixel width of a K-5 sensor, (0.005mm pixel width).

The culprit is most likely poor seeing = turbulence in the air which tends to smear out fine detail. Add to that that at 300mm FL the moon diameter will only be 2.6 mm long on your sensor which corresponds to some 525 pixels on a K-5. So, to capture fine detail on the Moon 300mm just barely is enough to produce what may LOOK as a sharp picture.

The solution is finding an observing site with clean and CALM air + stacking and (preferrably) more focal length.

I may - somewhat immodestly - refer to my own experiences which I have described here:

Camera Settings for Astrophotography

Here's about what you may expect with a single shot (with a K-5 and a 350mm lens) and a bit of post-processing involving sharpening and contrast enhancement. Often, lack of contrast may be misinterpreted as "unsharp":



Stacking would have been better, but this is about what you could expect with a 300mm lens. Note that this image was taken with an 1/80s exposure time at ISO 80.

Don't give up! Lunar photography with a DSLR is a bit of a challenge but it is not impossible.
05-09-2012, 08:12 AM   #6
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Thank you all for the help, I very much appreciate it!
Stone, what is stacking?
05-09-2012, 08:35 AM   #7
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stone, good info here. i have also found in practice that when framing moon and city lights in a single exposure, I can get away with longer exposures if necessary without significant motion blur from the moon in order to reasonably(not optimally) expose both.

this was a 2sec exposure at 280mm and I recognize some blur vs the shorter snaps, but not enough to detract greatly from the image.

05-10-2012, 12:38 AM   #8
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QuoteOriginally posted by pdxfive Quote
Thank you all for the help, I very much appreciate it!
Stone, what is stacking?
Stacking (in astro photography) is a process where one combines several pictures of the same subject (e.g. the Moon) pictures into one, single resulting image. You may regard this as a kind of advanced averaging and there are three major benefits:

- improved signal-to-noise ratio
- enhanced clarity in fine detail
- improved high dynamic range
- (all of which meaning also that post-processing such as sharpening and contrast enhancement will work much better)


Astrostacking is made in dedicated software, and I think most of us have started out with the freeware, Registax:

RegiStax- Free image processing software

If you want to try this with fixed tripod photos, do note that here the movement of the Moon does matter! So, you will need to work fast and be prepared to do some manual alignment in an ordinary photo editing software. That may be a bit tedious, but the good news is that with the Moon you can get a remarkable improvement with just about 5-10 images stacked.

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