This blog outlines the differences between the various still and video file formats available with your Altair camera when using AltairCapture or SharpCap.

Still file formats (1 image frame per file)

The .PNG file format:

.PNG Pros: Can be loaded into almost any graphics application. Handles 8 to 16 bit bit depths and mono or colour images.

.PNG Cons: Many imaging applications may discard detail from 16 bit PNG files when loading them. RAW images saved in PNG will appear monochrome with a checkerboard pattern and may need additional manual settings in post-processing to ensure correct debayering. SharpCap can only re-load 8 bits of data from PNG files, even when loading 16 bit saved files.

The .FITS file format:

.FITS Pros: Supports 8 bit and greater bit depths. Supports mono, colour and raw images. Image data such as exposure is stored in the file and some applications will read this data. SharpCap can load 16 bits of data from FITS files.

.FITS Cons: Can only be opened by a limited number of applications. Some applications require additional plugins to open this file type. File format is very complex and flexible, so files may display incorrectly in some applications and correctly in others.

Video file formats – used for solar system imaging, stacking and so-on.

The .AVI file format:

.AVI Pros: Can be viewed in almost any video playback software. Can be uploaded to YouTube, or even better quality, Vimeo.

.AVI Cons: File format is complex and has many sub formats. Correct playback may depend on other software and codecs installed on the machine. Playback and processing errors may be subtle and difficult to solve. 8 bit only. Mono and RAW saved in AVI may appear upside down due to limitations of the file format (but hey this is astronomy, right?). May not stack as well as .SER format due to compression artefacts. (Speaking of which, Altair Cameras do not compress .AVI video, so they are better quality than say, a re-purposed webcam, DSLR or camcorder which compress video reducing the quality).

The .SER file format:

.SER Pros: A simple file format with few variations – applications tend to work correctly with it or not at all. SER file is written with the Bayer pattern of the camera which simplifies post-processing for RAW captures. Supports bit depths of 8 bits per pixel and also up to 16bpp. (More than .AVI!). Each frame in the file is timestamped exactly. Supports Mono, RAW and RGB captures.

. SER Cons: Less post-processing applications support SER format but the ones which are most used, such as AutoStakkert AS2 (for stacking), Registax 5 and 6 (for stacking and wavelet sharpening), and PIPP (for preparing the video files for processing in the above), all accept .SER format. Interpretation of the .SER standard is somewhat different so sometimes you need to help the program to select the correct colour space if it doesn’t auto-recognise it, but it’s usually no big deal.