Exposing the Moon

[Andy Tejral]

This is turning out to be trickier than I thought. There is an eclipse coming up later this month that I'm going to try to capture.

I bought a tracking telescope and have mounted the HV20 to it. I'm still working out the details of that.

But getting the exposure right has me baffled. Now, the moon is extremely bright. Except, of course, during the eclipse (go figure!).

I'd really like this to be a set and forget rig. Touching the camera at all will introduce shaking--I'll probably leave steady shot on too. (Is it just me or is the lens range skewed too far toward the telephoto side?)

Any ideas?

[Eugenia Loli-Queru]

I am afraid I can't help you with that, but maybe Massimo can:
http://www.vimeo.com/454522/
You can message him if you register on Vimeo.

[Daniel Browning]

Originally Posted by Andy Tejral

I bought a tracking telescope and have mounted the HV20 to it. I'm still working out the details of that.

Eyepiece projection or piggy-back? (Just curious.)

Originally Posted by Andy Tejral

But getting the exposure right has me baffled. Now, the moon is extremely bright. Except, of course, during the eclipse (go figure!).

I recommend 24p, 0db gain, and f/4.0. Then use the shutter speed to get your exposure just right. The shutter speed will probably not matter unless you have terrestrial subjects (like clouds) in the frame. For inky black space, overexpose to the point where the highlights are almost clipped, then back off about two-thirds of a stop. That should be plenty of room for the red channel to capture the earth glow and not blow out. Then darken in post for a noise-less black.

Originally Posted by Andy Tejral

I'd really like this to be a set and forget rig. Touching the camera at all will introduce shaking--I'll probably leave steady shot on too.

Tracking telescopes compensate for the rotation of the earth, but not usually for the motion of the moon. Be aware that the moon's proper motion will cause it to drift over long periods of time (such as if you want to get the entire eclipse and both penumbral shadows).

Originally Posted by Andy Tejral

(Is it just me or is the lens range skewed too far toward the telephoto side?)
Any ideas?

Most consumer lenses are, because it's cheaper than making a 10X that starts at wide or ultra-wide. That's part of the reason why ultra-wide is automatically associated with professionals.

I wish you clear skies.

[Andy Tejral]

Well, I mounted the camcorder in place of the OTA. I found a hunk of metal that will mount to the dovetail mount. I mounted the camera to it.
So kinda like piggyback but not really. Perhaps the axis of the scope/camcorder is more critical than I thought.

I think I need to have some level of auto exposure--I've been warned the difference between full moon and eclipsed moon is dramatic. I wanted to set a fixed aperture (probably wide open) and use the shutter to vary the exposure.

I'm going to try the program setting 'night' next--trying it in the house with bright and dark objects it seemed to work OK. Perhaps it is setup the way I want to work.

This scope (Celestron NexStar 60) does have three tracking speeds: sidereal, lunar and solar. That is one of my problems at the moment. I forgot to change it so my first attempt was on sidereal and the moon traveled out of frame in 10 minutes. However, on lunar, it still moved out of frame but took 35 minutes. I guess the alignment method I used wasn't accurate enough. Or the scope itself isn't.

[Daniel Browning]

Originally Posted by Andy Tejral

I think I need to have some level of auto exposure--I've been warned the difference between full moon and eclipsed moon is dramatic. I wanted to set a fixed aperture (probably wide open) and use the shutter to vary the exposure.

You're right.

The HV20 does not have enough telephoto reach to fill the frame with the moon, and I doubt that the AE is intelligent enough to weight the exposure correctly for something that only takes up a tenth of the image (even with, say, -2 EV).

If you could mount it with eyepiece projection, fill the frame, then AE would have enough of an image to analyze and compensate for with -2, if you're lucky.

[Zack Birlew]

Yeah, the HV20 couldn't have the moon fill the frame unless you catch it while the moon is at its biggest and you happen to be in the right spot at the right time with the camera turned on and set up just right for it. Unless you have those circumstances, it's just not possible.

However, I have successfully captured the moon twice now at very beautiful moments for some filmmaking purposes. The first time was just the moon by itself against black sky and it was rather large looking at the time so I thought it was worth it to get it while the getting was good. The moon came out to be about the size of a nickel in the LCD but I later played with it in post and, thanks to the wonder that is HD, I could blow that moon up to giant proportions without adverse effect in the image. The second time involved clouds and the moon. The moonlight was reflecting off the clouds just so perfectly and I grabbed the camera and got a few minutes of it, perfect for a title sequence or stock footage.

How did I do it? Well, as has already been said, the auto exposure isn't going to help, so you need to do the manual exposure trick with a white picture on a cell phone or Sony PSP or something with the brightness set properly (it differs from device to device). Then you hold it in front of your camera lens, turn it on, lock the exposure and adjust as needed. Be aware that when you zoom in, the exposure will change as well, so if you do the manual exposure trick, you have to be at full wide to get the proper range of exposures, the most being F1.8 with 1/24 shutter or higher, then you can zoom in and adjust as needed when it changes. I film in the HDV 24p mode using the Cine mode so I don't know if it will be different with 60i mode or not, I would guess it wouldn't matter. If doing 24p, I think you're supposed to go into Shutter Priority mode and select the shutter as 1/48 and then switch over to Cine mode if you want. You'll also need to have a memory card for your camera so that you can monitor the exposure range by halfway pressing the photo button to display your exposure and shutter.