All input images must be either RAW files from supported cameras, or TIFF files. TIFF files should be 16-bit with a profile that supports a large color gamut, e.g., ROMM RGB. Images must be RGB (not grayscale). Note that the list of supported cameras varies depending on the version of the operating system in use. The fastest way to find out if the version of macOS that you are using supports RAW files from your camera is to attempt to open a RAW file with the built-in app Preview. JPEG files are supported for input but are strongly discouraged because of the low image quality. FITS files are not supported.
The camera must be absolutely motionless during capture.
Light frames should not have alpha channels. Some RAW converters cannot generate TIFF files without alpha channels (e.g., ON1, Photos). As long as all your light frames have alpha channels and you do not want to use an externally generated mask that marks the entire image sky or the entire image ground, then your light frames can have alpha channels. (If all of your light frames have alpha channels and you want have an externally generated mask that marks the entire image as sky, use a grayscale tiff without alpha for the mask).
All light frames and dark frames should have identical exposure settings (duration, aperture, ISO, focus). (Aperture and focus are irrelevant to dark frames and are ignored for dark frames).
The maximum time from capturing the first frame to capturing the last frame is 120 minutes. Less than 30 minutes is strongly recommended.
EXIF information should include capture time and lens information. Otherwise alignment might not work and is likely to be very slow.
The maximum output image size with 16-bit samples is about 500 M pixels. The maximum output image size with float samples is about 200 M pixels. Both of these limits are due to limits on the maximum size of a TIF file.
macOS 11 or later is required for SLS version 1.10. There is no iPad, Windows or Linux version.
SLS should work on any Intel Mac supporting macOS 11 and any Mac using Apple Silicon.
Lightroom and Adobe Camera Raw (ACR) users with mirrorless cameras--as of spring 2020 Lightroom and ACR automatically apply lens distortion correction for many mirrorless cameras. There is no way to turn this off other than to manually strip the metadata from the RAW files. Lens distortion correction, as implemented in Lightroom and ACR (as well as many other RAW converters) adds artifacts that are enhanced by stacking. This means that neither Lightroom nor ACR can be used as a RAW converter before stacking if you have one of the affected cameras. There are other RAW converters that allow lens distortion correction to be turned off for all cameras. Alternatively (and perhaps better), let Starry Landscape Stacker handle the RAW conversion.
Capture One users--if you are exporting very large TIFF files, e.g., 100M pixel, then specify "Tile 128" in the export format, probably "Uncompressed - Tile 128", see https://captureintegration.com/tech-tip-mitigating-black-tiffs-in-el-capitan-10-11-6/.
Luminar users--as of the spring of 2020, Luminar would occasionally change the size of images during RAW conversion. This makes Luminar unsuitable for use as a RAW converter.