Quick star drift - azimuth adjustment


Pierre Henrotay
 

Hello,

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
buttons.

Thanks in advance for your hints,
Pierre

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