Currently objects with "unknown" magnitude are only displayed when they are selected. The problem is that one could be looking thru the EP at an an obvious open cluster but have a difficult time identifying it using SkySafari 6. Currently one would have to perform a search on OCs within a certain RA/Dec range.
Let me use NGC381 as an example. One could very well be observing it and noticing two other OCs within a 1 degree FOV. But NGC366 and NGC358 are not labeled on the SkySafari display because their magnitudes are "unknown". On the other hand, given that they are NGC OCs, their actual magnitudes are probably brighter than 9 or so. On a catalog-by-catalog basis, it is possible to make certain reasonable assumptions about "unknown" magnitudes.
