What to image tonight with a Seestar S50?
The Seestar S50 has a tight field for a smart telescope: roughly 1.29° by 0.73°. That single figure shapes everything else. Where a wide-field instrument captures a celestial landscape, the S50 takes portraits. It goes for the core of an object and brings out its detail.
That is a genuine advantage across much of the deep sky. Globular clusters like M13 fill the frame nicely. Medium galaxies — M51, the M81/M82 pair, M104 — sit comfortably. Planetary nebulae such as M27 or M57 benefit from the longer focal length, where a wide-field scope would reduce them to a small disc lost among the stars.
What you should know
250 mm focal length, 50 mm aperture, f/5. The built-in dual-band filter is a decisive asset on emission nebulae: it passes the H-alpha and OIII lines, which makes decent results possible even from a light-polluted sky. Galaxies gain nothing from it and benefit strongly from darker skies.
Mosaic mode widens the frame by stitching several captures automatically.
Worth keeping in mind
Large objects overflow the field. M31 will not fit in a single frame: you will get the central bulge and part of the arms, but not the whole galaxy with its companions. The Veil Nebula, NGC 7000 and the Rosette need a mosaic to be shown in full.
That is not a flaw, it is a framing choice. Many people prefer a detailed close-up of Andromeda's core to a wider but fainter overview.
Finally, the S50 is not a planetary instrument. Its focal length is too short, as with most smart telescopes.
NightAstro and the S50
NightAstro knows these characteristics. It uses the field of view to flag when a mosaic is needed, and the filter to adapt its advice to the target's emission type.
It then adds what no spec sheet can tell you: tonight's weather, the position of the Moon, the actual altitude of each object above your horizon, and the obstacles around you.