Overheads in the estimator are adjusted to regular OTF observing blocks. the overhead estimates might not be accurate, please consider the following guidelines to estimate the overhead of your observation:

• Telescope must be pointed every 0.5 - 1.5 hours (depending on frequency) which takes around 5 minutes
• Focus should be checked every 3 - 4 hours. It takes about 10 minutes.
• A hot-cold-sky calibration takes about 2 minutes and should be done every 10-15 minutes at lower frequency and more often at higher frequency or under unstable weather conditions.
• For every scan, about 20-40 seconds overhead are needed (depending on receiver) for the telescope slew and the software and hardware setups (including tuning).
• APEX observations are in service mode. Depending on LST pressure for your sources and the observing strategy within the pool of projects, scheduling might require to observe a given program in several dates or different timeslots. These can introduce additional overheads difficult to predict in advance. It is possibly a good practice to consider an additional 10 percent of your total time (including all other overheads) to account for this.