[Kokatha man]

Hi again Gary - forgive me for being a "dog at a bone" here, but as previously indicated I think my clarity of articulation is the main problem!?!

Just to clarify - when I say that "I realize a dob hasn't the sophistication of an EQ..." I am merely acknowledging that to track/maintain an object in the FOV an EQM requires only RA inertia (once the object is centred) to do so... Going back to basics this is a function of the telescope's longitudinal axis (the optical axis you refer to) being parallel to the RA axis of the mount, which is of course aligned to point at the south celestial pole - directly related to the latitude as you point out. (Pardon the pun!)

A pedant like me would have to add that although these 2 axis are actually parallel to each other all objects they are targetting are at such great distances that parallax deems them to be one and the same point.

Perhaps the confusion in my diatribe centres on this: when I speak of the levelled mount having the optical axis pointing geo south (not SCP) I am referring to a scribed line on the revolving baseboard of the dob mount that is directly below and aligned with the optical axis of the scope - and the Hour Angles (RA) marked on this baseboard referenced from this scribed point.

This is also to state that regardless of whether the polar axis is set at whatever angle the observer's latitudinal position is; 35, 60 or 90 degrees, all of the RA gradations will correspond exactly to each other: which is why I included the bit about positioning a dob mounted scope at exactly the south pole where the latitude is 90 degrees - if the turntable is level the dob mount assumes EQ status insofar as once an object is centred in the FOV only azimuth/RA inertia would be required to keep the object in the FOV - no adjustment of altitude/declination would be necessary.

Another way of stating this is to visualize RA motion as a circle around its' latitude corrected axis pointing at the SCP. Changing the tilt of this axis to 90 degrees the RA motion then describes a circle parallel or "level" with the ground - ie it takes on properties of a dob mount albeit one where tracking is not facilitated because the declination axis is not fixed at right angles to the RA axis.

However, notwithstanding the lack of any tracking benefits that an EQ affords with single motion inertia - when using tables to view the RA of an object at 0 hours UT and converting to local time, these (proposed) Hour Circles would allow the observer to roughly set the dob mount to the given/calculated RA figure and "sweep" using the Altitude motion of the dob mount to (hopefully!?!) target the object.

Which goes back to my real and basic question - why mark setting circles in degrees rather than RA's Hours etc if you wish to gradate the azimuth motion of your dob when you can scribe an optical axis on the azimuth board and reference your setting circle from this, geo align this scribed line with south (also levelling the whole thing) and have a more specific gauge.

Having ploughed through all this Gary; I assure you that your Argo Narvis system, which is next in line on my impoverished income, is likely to make me just wait until I can afford said!!!

Regards, Darryl.