Partial Lunar Eclipse Astrophotography: Camera and Telescope Imaging Settings

Check the timing and the Moon's height first

Start with the eclipse times for your location, and confirm that the Moon is above your horizon during the part of the event you want to image. The Moon's height changes with time and latitude. At 35° N, 50° N and 35° S, the Moon can sit at very different heights at the same moment. A low Moon passes through more atmosphere, which brings haze, colour shift and a softer image. Use a planetarium program set to your coordinates to see the Moon's altitude through the eclipse, and plan your setup for the period when it is highest.

Rehearse at least one night earlier. Confirm the camera, mount and focus routine, check the capture software or shutter release, and test a short sequence on the Moon, even when it is not in eclipse. This shows you how the Moon moves across your frame and how your equipment responds.

Framing and focal length

The Moon is a small target in most frames, so choose a focal length that fills a useful part of the image without cropping the disk.

• Camera with a lens: 200 mm to 600 mm is a practical range. Longer focal lengths enlarge the disk but demand steadier tracking.
• Telescope with a camera: 1000 mm to 2000 mm focal length gives a disk that fills much of the frame on a typical sensor.
• Smart telescope: use the framing the device provides. A typical setup shows the whole disk with the shadow edge in each frame.

Leave a margin around the disk. The shadow edge moves across the lunar surface during the event, and you want the full disk in every frame so the edge can be followed through the sequence. Check framing with a field-of-view calculator before the night, and note the sensor size and focal length you used so the framing can be reproduced.

At long focal lengths, the Moon crosses the frame within minutes. Use a tracking mount, or re-center the Moon between sets. Drift that is visible in the live preview will show as elongated or blurred limbs in the stack.

Exposure and gain

The lit part of the Moon is bright, so its exposures should be short. The shadowed part is much dimmer, and a single exposure rarely records both the bright limb and the umbra with good detail. Capture a bracketed set at each time step, with one exposure for the bright limb and one or two longer exposures for the shadow.

Starting ranges for a camera at f/8 and ISO 100:

• Bright, lit part: about 1/250 s to 1/60 s. Shorten the exposure if the lit surface looks white with no surface detail.
• Shadow edge and dark disk: about 1/15 s to 2 s, depending on how dark the umbra looks at the time of capture.

Use the lowest ISO or gain that gives a usable bright exposure. Noise is rarely the limiting factor on a bright Moon, so high ISO adds grain without helping the shadow. Raise gain only if you need a shorter exposure to freeze the Moon's motion.

With a dedicated astronomy camera, set gain in the low to middle part of its range for the bright exposure, and use longer exposures to record the umbra. Write down the gain and exposure for each set so you can match frames during processing.

With a smart telescope, let the device handle exposure, but check the first frames. If the lit limb is clipped to white, reduce the exposure or choose a shorter capture mode if the device offers one.

Filters and focus

No solar filter is needed for this event. A lunar eclipse is safe to view with the naked eye and with any instrument, and the Moon does not need the heavy attenuation that the Sun does.

A neutral density filter can reduce the brightness of the lit limb if you use a telescope and find the bright exposure clips even at short times. It is optional, and most setups do not need one. Keep the camera's infrared-cut filter in place for colour imaging. Avoid narrowband filters, because they remove most of the shadow's light and its reddish tone.

Focus on the bright limb rather than the dark disk. Switch to live view at maximum magnification, then adjust until the lunar edge is sharpest. A focus mask can make the adjustment repeatable. Refocus after large temperature changes, and recheck focus after any change of lens, eyepiece or camera.

Frame count and integration time

Frame count matters more than any single setting. For a partial eclipse, a useful target is 100 to 300 bright exposures and 50 to 150 shadow exposures across the event. The shadow exposures add up to a few minutes of integration time, while the bright exposures add many frames without much time.

A shorter sequence still gives a usable image. If clouds, haze or a low Moon interrupt the capture, a smaller set of well-focused frames can be stacked into a clean result. Stop capturing when the Moon drops too low or the sky degrades, and keep the images you have.

Stacking

Stacking reduces random noise and averages out small errors. Use a stacking program that aligns frames on the Moon's disk and can reject poor frames. Remove frames with blurred limbs, cloud, passing aircraft or tracking errors before stacking, because even a few bad frames can soften the shadow edge.

Stack the bright exposures and the shadow exposures in separate groups. Each group needs its own alignment and rejection, since the two sets have very different brightness.

Processing the frames

Process the bright and shadow stacks separately, then combine them.

1. Stack the bright exposures and the shadow exposures in their own groups.
2. Align each group on the disk, and reject frames with poor tracking.
3. Stretch the shadow stack until the umbra edge and the dark disk show texture, without letting the bright limb clip.
4. Blend the two stacks with a mask that follows the shadow edge. The lit part keeps its surface detail, and the shadow shows the dark disk.
5. Apply light sharpening or deconvolution to the combined image. Then reduce noise in the dark area only, so the lit surface keeps its detail.

Keep the colour natural. The umbra often looks reddish, and that tone is part of the event. Avoid heavy saturation, which makes the shadow look artificial and hides the gradient at the edge.

Save an unprocessed copy of each stack. If the blend looks wrong after you adjust the mask, you can return to the stacks and redo the step without recapturing.

Setting up on the night

Set up before the eclipse starts, so the mount and optics can reach the outside temperature. Choose a spot where the Moon clears nearby buildings and trees, and where the Moon's altitude is highest during the part of the event you want. Polar alignment and focus are easier to get right before the Moon is in the shadow.

Keep a short log of the time, focal length, exposure, gain and ISO for each set. The log lets you match frames if the conditions change partway through, and it helps you plan a better setup for the next eclipse.

Suburban sky and realistic expectations

From a suburban sky, the lit part of the Moon is bright enough that light pollution has little effect on it. The umbra is much dimmer, though, and nearby lights can reduce its contrast, especially in short exposures and in the naked eye. The naked-eye limit here is about magnitude 5, so the shadowed area may be difficult to see by eye, even though it stays clear in a photograph.

Expect the shadow edge to be visible in your images. Expect the dark disk to need careful stretching and blending to show texture, and do not expect it to match long-exposure photographs of the Moon taken from a dark site.