If you plan on opening a file again in CCDOPS for further processing, be sure to save the file as an SBIG file type (either compressed or uncompressed).  CCDOPS can only open SBIG, FITS, and TIFF files.  You can, however, save a file as any of a number of other formats for use with another program such as JPEG.

File Formats

• FITS - Flexible Image Transport System.  FITS files are probably the best way to save CCD files, but they can only be read by CCD processing programs like MaxIm DL and CCDOPS.  There is an available Photoshop plug-in for reading FITS with that software.  FITS have file headers which contain information such as exposure time, date, telescope, temperature, etc.  All of the information contained in the original exposure is retained with FITS files, whereas other formats can sacrifice some of this information.

• TIFF - Tagged Image File Format.  TIFF files are the best way to save color image files or any file you plan on transferring to Photoshop or a similar program.  Many image-processing programs cannot read 16-bit TIFFs (Photoshop version 6.0 or later being an exception) and 8-bit TIFFs must be used instead.  This requires you to sacrifice some image data, but this is almost never a problem (see below).

• JPEG - Joint Photographic Experts Group.  These are the most common image files; most web images are JPEGs.  JPEG is a lossy image format, meaning detail within the image is lost each time it is saved.  For this reason it is not recommended that you save an image more than once as a JPEG.  JPEGs are highly compressed (and different levels of compression can be selected before saving the file) allowing faster download times when being viewed over the Internet or when emailing your latest pictures to a friend.

Saving FITS Files

If you plan on transferring an image to another CCD processing program for further enhancement, it is probably best to save it as a FITS (although most packages will also read SBIG files, since these are the default format from the most popular cameras).  FITS files are saved with a "header" which contains much information about the image.  Time, date, exposure, camera temperature, etc. are all saved in the FITS header.  Also, user-defined information can be stored.  Saving a file as FITS in CCDOPS brings up the FITS Setup window where you may enter data about the image and select settings for the file.

Above:  FITS Setup window for an image of M42.  Info such as observer name can be entered here.

Saving TIFF Files

TIFFs are the best way to save files which will be used in image processing programs such as Photoshop which typically cannot read FITS files.  Saving as a TIFF file in CCDOPS brings up the TIFF Setup window, which, like the FITS Setup, allows you to enter short notes as well as select settings for the file.

Above:  TIFF Setup window.

There are a few settings which can be changed when saving a TIFF file. 

Bits Per Pixel

Bits per pixel should probably be left at 8.  Newer versions of Photoshop (6.0 and later) can read 16-bit TIFFs, so if you plan on processing the image in Photoshop, 16 bits is recommended.

Back/Range

These are only used for 8-bit files.  All pixels below the Back value will be recorded as 0 in the TIFF image, and everything above the Back + Range value will be 255, the maximum value of an 8-bit file.  The values in between will be scaled linearly.

Strips

There is a choice of Multiple Strips or Single Strips (sorry, no chicken strips).  Multiple is the best setting for most purposes.  There are some programs which will not read Multiple Strip format TIFFs, but this should not normally be a problem.

Single Shot Color Options

This setting will retain the proper single shot color offsets.  Each camera requires a different X and Y offset to create the proper color image.  (See the Imaging Basics section on Color Imaging for more details.)

Saving JPEG Files

JPEGs are compressed files, ideal for emailing to friends or posting on a website.  The amount of compression is somewhat adjustable in CCDOPS, but it is hard to know exactly what will happen.  For ideal results you should save a file as a TIFF and transfer it to a program such as Photoshop which gives you more control over saving a JPEG.  CCDOPS does not give any indication as to how much compression is applied but comparisons of the file size with Photoshop suggest the choices are similar to the Maximum, High, and Medium JPEG quality settings in Photoshop.

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