Indicate that only channels between the First and Last defined by Min Max and Type should be considered to produce the image. Type can be CHANNEL, VELOCITY or FREQUENCY.
For type CHANNEL, Min and Max indicate offsets from Channel 1 and Channel Nchan (the number of channels in the data set). Thus Max can be negative: it then indicates Last = Nchan-Max. Also Min=0 and Max=0 implies all the channels.
This is a more convenient replacement of the deprecated MCOL variable.