I store and carry the scope in a large plastic toolbox with cut foam padding. . The M603 has proven to be an excellent instrument both optically and mechanically. My primary interest is lunar and planetary video imaging and observing for which the scope is well suited. Lunar features are sharp and contrasty, due in part to the heavy baffling of the OTA interior and the interior of the generous size optional dew shield. The scope works quite well on clusters and planetary nebulae, and though I have not done that much observing of 'faint fuzzies' with the M603, it has performed wonderfully on them as well.
Diffraction rings are essentially identical both inside and outside of focus.
Rotation of the focusing knob at the rear of the OTA is smooth, though on this unit there is a bit of lag when reversing focus direction. Annoying, but you tend to get use to it and generally ignore it. I store it in my garage which is not heated, even so, cool down time is usually the better part of an hour or more in cool weather. The tube assembly and dew shield are heavily baffled which adds to the overall diameter and weight of the telescope. Overall I rate the Alter 603 as an excellent instrument both optically and mechanically.