Optics are a big part, certainly.<br /><br />The fan is intended to cool the large mirror down to ambient temperature. Once you start observing, the fan should ideally be switched off.<br /><br />If the mirror temp doesn't match the outside temp (ie. reach equalibrium) then the air in the tube will create a minature "weather system". The air will swirl and create unsteady images.<br /><br />Zhumell isn't doing anything that any serious "light bucket) owner hasn't done themselves with a $6 computer case fan for _ever_...<br /><br />Don't downplay the value of a stable mount that's moved easily and smoothly but that requires intentional action to manipulate.<br /><br />You could have the best optics in the world and they'd appear to be junk if the tube so much as vibrates from the flap of a butterflies wings, especially for high-power planetary work. Any vibration is being magnified hundreds if not thousands of times. The mount *must* be rock-solid stable or it's garbage. I can't stress that enough. I'd buy lower quality optics and a higher quality mount any day, but fortunately, Orion seems to have largely addressed that.<br /><br />My experiences with the Zhumell (several, but probably all built on the same line the same day since they were ordered for inventory by the store at the same time) were not favorable with their optics. I found the images (using top-quality Televue Nagler eyepieces that cost nearly as much as the scope) to lack edge sharpness much sooner than the Orion. (Orion uses US-Made Pyrex glass for their mirrors [for the IntelliScope, not sure on the "classic"].) There was definite ghosting out at the edges on the best of the Zhumell's that I tried to like that left much to be desired. (Both scopes laser collimated). I found it was a lot harder to get the Zhumell to collimate, and once it was, it wouldn't hold it for a full session for me (probably the reason you reference lock screws). The focuser, compared to Orion's 2" Crawford focuser (that is <div class="Discussion_UserSignature"> <p>.</p><p><font size="3">bipartisan</font> (<span style="color:blue" class="pointer"><span class="pron"><font face="Lucida Sans Unicode" size="2">bī-pär'tĭ-zən, -sən</font></span></span>) [Adj.] Maintaining the ability to blame republications when your stimulus plan proves to be a devastating failure.</p><p><strong><font color="#ff0000"><font color="#ff0000">IMPE</font><font color="#c0c0c0">ACH</font> <font color="#0000ff"><font color="#c0c0c0">O</font>BAMA</font>!</font></strong></p> </div>