Heterodyne: The aspect of the MSB (Minimum Schedulable Block) you most want to think about is its length. If you have been allocated e.g. eight hours for a single source, you could submit a single 8-hour MSB if you wanted. But that would be a very silly thing to do. If your source is not up for more than eight hours, it would never be scheduled as our software would detect that it would set before the MSB could be completed. But even if your source were observable for 8 hours solid, the observer won’t choose to undertake it except near the very beginning of the night, which vastly decreases your scheduling opportunities.
On the other hand, if many short observations are all scheduled one after the other they would have to be sent to the queue one by one, thus driving the TSS and observer insane.
If your sources are well separated across the sky a pointing will be required between them (even if they are only separated in time by ten minutes). However if they are close by each other they can be done consecutively. If you are including multiple sources in an MSB try to pair or group them so they are all are all close together. If this is not the case then include an note highlighting this to the operator.
The golden mean? A 30-to-90 minute MSB. If you have any questions about the best way to distribute your sources please consult your Friend of Project for ideas.
SCUBA-2: We have a 40 minute limit on SCUBA-2 observing blocks. This upper limit usually concerns large pong maps while small daisies fall at the other end of the scale being potentially only a few minutes each. Having short MSBs for SCUBA-2 does not incur the same overheads as heterodyne. Like heterodyne observation consecutive sources that include a large slew will likely require a pointing between them, however SCUBA-2 has the additional factor or requiring the arrays to be setup again after a move between sources.