I do a lot of panoramas at night, and frequently people ask me about problems they are having stitching panoramas together. This is the single most common question I hear. I almost never have any problems stitching panoramas together unless there are moving clouds or I attempt double row panoramas. I’ve even done panoramas with fisheye lens without many issues. There are a lot of factors involved so I thought I would write down how I do it.
A panorama is the stitching together on multiple images, frequently vertical images, to create a wider image than the camera and lens can usually manage. These can be as wide as you desire. Many panoramas at night are around 180 degrees, but you can make panoramas up to 360 degrees.
So how to go about it? Adequate equipment is essential. It does not need to be expensive.
First you need a sturdy tripod and a tripod head. You need a tripod that is steady and prevents shake and vibrations. There are many choices. A bad tripod or can drive you crazy. It may fall over and break your camera or lens (all too common), and a bad tripod head can move between images.
I use an Acratech Ballhead that I like a lot an works for me. I also use an Acratech Leveling Head which I love. The leveling head makes it much easier to get all the images in a horizontal plane. If there is one additional piece of equipment that I would recommend, then this is it. I use it for every night photo. There are lots of leveling heads out there. As long as it works the brand does not matter. At first I only used it for panoramas, but then I started using it for every night photo and life got a lot easier. Once you level the camera and take that first long exposure photo, it is so much easier to recompose the shot, even if you are not making a panorama. If the camera is level then you can just swivel it from side to side, or up/down (a little trickier) and the camera remains level. I can usually get the composition right in 2 shots with the leveling head, rather than taking multiple shots without it.. Sometimes it takes more, but it is a lot faster to get the composition right with the leveling head. Also you can switch the camera from horizontal to vertical and not have to change the tripod.
I also use an Acratech “L” Bracket on the camera. There are again many “L” brackets on the market, and the brand does not matter as long as it works. I just keep the L bracket on the camera for all night photos. It is really helpful for quick switching of the camera from horizontal to vertical, Also it helps to balance the weight of the camera over the center of the tripod. Additionally, having the camera balanced over the center of the tripod and over the center of rotation really helps to prevent or decrease parallax problems.
I obtain multiple vertical images with a lot of overlap, usually greater than 50%. I just wing it on overlap, and overlap a lot. I also sometimes use a Acratech Nodal Rail to position the focal plane over the point of rotation. This prevents parallax and the computer can reconstruct it better. In reality though, I only use the nodal rail when there is something in the foreground that is very close, and parallax might be an issue. If everything is moderately far away then I just use the L bracket and it all works out just fine.
My favorite lens for panoramas is the Rokinon 24 mm f/1.4 lens, but if I need more vertical coverage I use a zoom lens such as a 14-24 mm f/2.8 or a 16-35 mm f/2.8. For a really high Milky Way the Rokinon 14 mm f/2.8 would be a good choice. Some people get double row panoramas when they are trying to capture a really high arching Milky Way. I have found it easier to use a fisheye lens such as the Sigma 15 mm f/2.8 lens. I do a lot of overlap with this lens and do moderate lens correction in Lightroom of Photoshop RAW, and it works out just fine.
Another issue that you can encounter with really wide angle lens is distortion. The more you angle upwards, the more distortion you get. I may angle upwards to some degree, but I try to limit it as much as I can. It is better to use a wider focal length lens (such as 16-20 mm rather than 24 mm), capture more vertical territory, and keep the lens relatively more horizontal. This may mean that you capture more ground on your image than desired. The images will stitch together better, and then jus crop off the extra ground later.
Another problem I hear often is seeing dark bands in the panoramas after stitching. I have not encountered this, but I suspect it is due to widely spaced images with a lot of vignetting. Vignetting is the darkening of the image around the sides and corners, especially in the corners. It is especially a problem with wide angle lens, and these are exactly the lens we are using for night photography. The degree of vignetting is different for every make of lens. If you can choose a lens with less vignetting, then do it. Unfortunately this is not always a choice. Here are things you can do. Take off all filters! They will typically not do you any good at night, and really increase vignetting on wider lens. Also use the lens correction function in Lightroom or Photoshop RAW to make the exposure even across the frame. Use this before stitching the images together. This function decreases distortion and lightens the corners. Adjust properly for your frame.
I then stitch the images together in Lightroom or Photoshop, usually Lightroom. If you take these precautions, then stitching together the images is rarely a problem.
I am learning double row panos, and using special software for that like PTGui pano software. If you want double rows think about this software. For the really high MWs I use the widest lens I have and do them vertically. I have had decent luck with my 15 mm Sigma fisheye lens vertically. I do some lens correction on each image in Lightroom or Adobe RAW and then stitch them together and it works out OK. Just do lots of overlap.
