Default grid sizes

[shashankdholakia]

One of the nice features of CANDID is that it can automatically set defaults for the grid sizes based on the maximum resolution of the instrument. Although this is just a heuristic, I think this could be a useful feature in drpangloss to make it quick to do ra/dec grid fits to data.

[benjaminpope]

Sounds good. The grid size should be a decent factor smaller than λ/(B_Max), and the field of view should be no larger than the coherent field of view or, if very narrowband, much larger than λ/B_min.