Over the years, I've collected a large bundle of items that accompany me every time I head out stargazing. Starting with astronomy-specific tools and finishing with items that will keep you comfortable, here's a checklist of essentials that will help you optimize your stellar experience.

Excel's AVERAGEIF and AVERAGEIF functions let you find the average of a set of data. However, where they differ from the more straightforward AVERAGE function is in their ability to include or discount certain values within the calculation.