Today’s Question: I want to take a series of photographs of the lunar eclipse and stitch them together to show the phases. Most specifically I want to know if cropped photos can be successfully stitched.
Tim’s Quick Answer: Yes, you can assemble these images, including if they are cropped, into a composite image. However, you will need to assemble the images manually rather than through an automated approach such as that used to assemble a composite panorama.
More Detail: The weather in my location did not cooperate for the recent total lunar eclipse, so I’m glad that some readers were able to get out and photograph this event. For those who captured images at various times throughout the progress of the eclipse, you can assemble a composite image showing those phases together.
Because of the nature of the images, however, you won’t be able to assemble them the way you could assemble a composite panorama. Instead, you’ll need to take a more manual approach to assemble these images, for which I recommend using Photoshop.
You would start off by opening the images as layers in Photoshop. If you’re using Lightroom Classic you can select the images and then from the menu choose Photo > Edit In > Open as Layers in Photoshop. If you’re not using Lightroom Classic you could select the photos in Adobe Bridge and then from the menu choose Tools > Photoshop > Load Files into Photoshop Layers.
The result will be a layered image in Photoshop, and you can then go about assembling those layers into a blended composite. This would involve selecting individual layers and using the Move tool to move each layer into the appropriate position. Along the way you will need to drag an image outside of the existing canvas area to put it into the right position, essentially dragging that layer out of view. You can expand the canvas after each of these moves by choosing Image > Reveal All from the menu.
With the layers arranged in the right positions, you can add a black (or very dark) background. I would add a Solid Color adjustment layer for this purpose. Click on the “Add Adjustment Layer” button (the half-black/half-white circle icon) at the bottom of the Layers panel and choose Solid Color from the popup. Select the color you want to use that will best blend in with the sky around the moon and click OK in the Color Picker dialog. You can then drag the thumbnail for this adjustment layer to the bottom of the order on the Layers panel.
Finally, you’ll need to mask the individual moon photos so they will better blend into the background. I would use the Elliptical Marquee selection tool to create a loose selection around the moon one layer at a time. With a selection for a given frame of the moon make sure the appropriate layer is active on the Layers panel and click the “Add Layer Mask” button (the circle-inside-a-rectangle icon) at the bottom of the Layers panel. On the Properties panel go to the Masks tab and increase the value for the Feather slider so that the masked moon image blends smoothly into the background.
With this basic approach you can adjust the position of each image, blend each of those images into a background, and otherwise refine the result. You could even use the Free Transform command found on the Edit menu to resize individual frames of the composite as needed. The result can be a nice composite showing the transition of the total lunar eclipse.