Quick star drift - azimuth adjustment

Pierre Henrotay


It seems that the clouds are going away tonight, which will allow me -
hopefully - to try the quick star drift method again.
This will be my second or third try only: the weather has been
terrible since the acquisition of my Mach1 last December.

To prepare for this, I looked back at the manual, using the recently
updated version.

While I expect no particular trouble for altitude adjustement (and I
do not remember any), I still am somewhat puzzled by the azimuth
adjustment part.

I refer here to steps 6c and 6d, p30 of the updated manual.

6c is the centering correction step with the azimuth adjuster; from
the description, the movement with the azimuth adjuster is
expected to be (at least roughly) parallel to the RA (E-W) axis -
and this is indeed shown as such in the new companion graphics.

This is where I am in trouble: is it really that simple, as the
azimuth adjustment will cause a movement both in RA and in DEC, and
not just in RA.

As an example, take Alioth + psi Vir (2 stars suggested in appendix
I): using SkyMap for my location and at about 21TU, the Alt/Az axis
are rotated about 45 degrees wrt the RA/DEC axis; so a significant
move in DEC will also take place.

So, I remain a bit confused - unless I am wrong or misunderstand
something: what is the best strategy as the text says to make half of
the centering correction using the adjuster and half using the EW

Thanks in advance for your hints,

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