Quote:
Originally Posted by AndrewJ
Gday Bazza
Re
This incorrect if you have properly drift aligned.
Ie If you have correctly drift aligned, the RA axis is pointing at the pole.
Thus, on the first slew, ( of a polar one star), you DO NOT adjust the wedge at all, in any axis.
You just hit enter and centre the second star. PoP.
Also, if you have correctly drift aligned, you dont need to be at perfect HA=0 and DEC = -90 at the start, you can be off by a few degrees either way with utter impunity. As long as you just ignore the eyepiece on the first slew to Sig Oct ( and just hit enter ), then correctly centre the second star,
all will be well 
Andrew
( close yr eyes and trust the force ) |
Hi Andrew
Yes if you have done a full drift alignment you won't need to do any more. The trouble is most only do the first part of a drift alignment on a star near the meridian which will get the azimuth right then try to do an alignment according to the manual that calls for centering Sigma Octans with the wedge which of course will upset the drift alignment. I was just trying to emphasise that you don't need to adjust the wedge again on Sigma Octans which so many try to do. Just accept it and go to the main alignment star.
I always used my own mehod for a polar alignment. I first established that the orthogonality was correct then found the true 90 deg. point of the OTA and used a keyed dec scale with a vernier readout that allowed reseting to about two arc minutes. These items are established before going into the field.
I did an alti/azm two star alignmnent to accurately find a landmark on horizon at true south. I also know the star patterns around the south pole and how they look in a 26mm eyepiece.
I could then put the scope on the wedge and look at the landmark and adjust the wedge azimuth through the OTA and then with the OTA at 90 deg adjust the Altitude till I coud see the star pattern, do a fine adjustment on alt/azm and 90 deg using the known pattern to put the wedge in polar alignment within an arc minute.
Baz
.