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My home viewing site prevented access from anything to the East, South or West up to an altitude of nearly 70+ degrees - 30-40m tall trees surrounding the back lawn !
Making Polar star alignment impossible for most of the time
After a couple of drift aligning sessions when switching between reflectors and refractors and wasting too many hours, I wondered if there was a better way
I already used the broom stick/compass (adjusted for magnetic North) method when aligning the tripod and a digital inclinometer for Alt on the NJP for visual use and that got me really close
But given I was mostly imaging this meant by the time I took off the scope counter weight added the camera system and rebalanced the scope by sliding it up the rings - any polar alignment I had during the visual phase was lost in the imaging phase
Plus it was just time wasting and laborious and ultimately inaccurate
I had Tpoint and TheSky so I could generate a Polar Alignment report by mapping 6+ stars in under 10 minutes with my imaging rig.
So the method I developed was to make myself a pier where the mount adapter plate was able to rotate. I machined up an accurate rotational mechanism, this was lubricated, the bearing surfaces were brass on brass and smooth as silk, but nicely firm.
By using a toolmakers digital inclinometer I could firstly align the top of the pier to be dead flat (so that when I rotated it later it didnt change any of the angles) , then align the scope and mount in Alt to within 0.1 degree of my GPS Latitude for wherever I was imaging from.
I would then setup my imaging system, focus the OTA, slew the mount using TheSky to a bright star high in the sky in the early evening even before dusk
The bright object could even be the moon/planet through the clouds !
I would then rotate my scope and mount manually to align it with the bright object (I could do this because I had rotation built into my customised portable pier)
I had a RDF that always located accurately and although I also had a finder scope, I rarely ever used the finder because it needed to be aligned to the main scope.
So I would manually align and take an image - if it was the moon or a planet I was using they are so bright that even if they werent in the cameras field - the bright gradient glow off to one side or corner would indicate where it was and I could nudge the mount to put it into the centre of the field.
Maxim has a cool feature which allows you to click on a star or any position of a just taken image and then slew the mount to that position
This allows you to accurately position any object to exact centre of the screen.
I would then map that object using Tpoint and slew to a new star and repeat this process 6-8 times.
The mount was already very close to aligned to start with, so this process wasnt accurate but the star you slew to was always in the field of view and usually within less than an arc minute of the screen centre and a quick move using MaxIm with the screen magnified by 400% would see the object dead centre of the screen and then accurately mapped using Tpoint.
Once I had 6 or more points mapped, Tpoint can then generate a Polar alignment report and you make the necessary physical adjustments on the Mounts Alt and Az knobs - so many turns, so many knob ticks and the mount is polar aligned. Takes about 10-15 minutes first time around
If my camera didnt take so long to download you could do it quicker !
I would delete the Tpoint model and repeat the mapping process again for 6-8 points using the same stars all high in the sky and close to one another
This confirms your Polar alignment is spot on and if you want you can fine tweak it the last few arc seconds for Alt and Az
If I made a physical mount adjustment I would delete the model again.
I would then run a fully automated mapping run of 20-40 points while I had some nibbles and drinks
15-25 minutes later I have my mount perfectly polar aligned with a full sky model to correct for all the usual physical pointing errors and enable Protrack if I could be bothered, so my real time tracking was also being corrected by the Tpoint model
The benefit of this is the whole process from setting up out of the back of the car to full alignment including an all sky Tpoint model could be achieved in under 2 hours - even 1.5 hours
But what was really handy is that this can be achieved before astronomical twilight. The camera can see all the stars that the eye cannot.
Also its a mechanical process, doesnt require any special skills, you just follow it and its always accurate and works.
Using this same method I once aligned my buddy's new Paramount when the sky was 99% clouded out. Under 5 arc seconds in both Alt and Az
We used the moon through the clouds as the first point to get a rough alignment in Az (Alt was done with the digital inclinometer) and every few minutes a sucker hole would pass through and we used that gap in the clouds to grab and map another star by using the planetarium package and some guesswork as to which one would be visible - it worked !
This method obviously doesnt work for visual systems but solves all the problems for imaging systems
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