Polar Alignment technique

[PKay]

Hi Brains trust

A few days ago I took possession of a new EQ6-R Mount with SynScan (wahoo!).
I know a few ways of gaining good polar alignment (drift align, polar scope, good luck), however I cant see the pole (badly placed mountain), so that narrows down my options.
I also only have a narrow FOV (badly placed trees).

I have theorised about another way of doing it. Maybe I have re-invented the wheel, or I am deluded. Here is the technique:

1: Point the mount south and level using compass and levels
2: Scope is in home position - Use levels
3: Initialize the mount.
4: Start a 1 star alignment and pick one of the few stars I can see.
4.5: Wait for the scope to stop slewing.
5: When SynScan asks to centre the star using the slew controls...
6: Instead of using the slew controls, I use the ALT/AZI bolts.
7: Once the star is centred, I turn OFF the power.

8: Manually return the scope to home and repeat the above.
9: Is the star any closer (in step 4.5 above??)

In any case I will try this tonight.
And my case (since I will be using a guide scope and PHD), I believe that I don't have to have spot on alignment anyway.

RIGHT! There it is. Any thoughts appreciated.

[xelasnave]

Sounds good.
I have been trying to get perfect align in similar circumstances.
You mention luck.
My luck was I inadvertently moved the tripod trying to do something and when I looked I think I had nailed South.
I am getting a unusual drift which may be balance.
But I am here to tell you it may not come easy...the longer you are at it the more confused one gets, well I do.
Keep at it and hide the axe.
Good luck.
Alex

[jimmyh1555]

Hi Peter!
Your method seems too good to be true. I think that the mount knows where it is pointing when it starts from home. When you alter the screws instead of using the controller, the computer will not realise that the scope has moved and will assume it is still pointing at where IT thinks the star is at. Confusing, I know! I will try your method though!
I have tried a different method for visual work. . I do the star alignment, and keep the scope on, and do not touch the screws. I then tell it to slew to Alpha Crux (say), When it has finished pointing, I manually then de-clutch the RA and Dec levers, manually centre the scope on to the star and then tighten the levers. Then I tell it to go to the next star. I am not convinced though this works, because it still does not stop exactly on the next star!
Remember that when you use your compass, to take into account the magnetic variation for your area - ie if it is 14 degrees East (published on web sites and good charts) then in the Southern hemisphere, you get compass needle to point to 180-14 = 166 degrees, then the south mark on the compass will point to 180 degrees True. Remember the adage "Variation East, steer least, Variation West, steer best.";)

[Steffen]

The method works to get a good initial approximation, but it is not very accurate. There is no easy way to set the mount at exactly the home position, and the initial slew may be affected by other stuff the SynScan controller remembers (like cone error and NPE). I use this method to gauge how far I'm out after initial setup, and bring things closer to home before starting alignment.

[doppler]

The one star align and manual move works for me. Because the alt is aligned for your latitude it shouldn't change between setups as long as you level the tripod. I pick a star low in the east or west and use that for my first star. Then manually go to park and do a 2 star alignment. This method is good for visual use but your guide scope will be working hard if the alignment is too far out. Best to use the "DARV" method with your camera to tweak alignment.

[jimmyh1555]

What's DARV??:shrug:

[PKay]

I tried 'my' new alignment technique last night and guess what...it worked!

I guess that when you place the scope in the home position, and turn on the power, the SynScan must assume that it is aligned with the pole, otherwise how would it locate the first star?

So...after the scope skewed to the first alignment star, it was off by a mile.
At this point I turned off the power & used the Alt/Azi bolts to centre the star.

Then returned the scope manually to the home position. For accuracy here, I used the RA and DEC. dials turning them to a small texta dot! The dials don't need to be calibrated since this is a relative measure.

I then repeated the 1 star align, and this time the star was in the field of view. Repeated again and the star was in the middle!!

Also I guess the reason I had to perform this a few times is during the time you take to move the scope, the star has moved.

The auto guider was very happy.

Tonight I will try and get details on the POLAR alignment accuracy.

For proof, I was able to get my first EVER image. Will post it in the images section when processing done:):):):)

[xelasnave]

https://www.cloudynights.com/articles/cat/articles/darv-drift-alignment-by-robert-vice-r2760

Alex

[xelasnave]

I spent more time last night and its getting there but still small trailing.
Another week should fix it:D

Alex

[Lognic04]

PHD has a very useful polar alignment tool based on DARV, probably worth a shot

[Atmos]

I use this method to get me ballpark close to polar alignment. It isn't perfect as there are a number of errors that get in the way.

If you do a 2 star alignment with your hand controller, after the alignment is successful it tells you how far you're out from an accurate PA. Although a 1 star alignment can help you get close to begin with, 2 star alignment will help you narrow it in that bit more.

[xelasnave]

After near one week with only 15 x 25 degrees of sky my mount is tracking near perfect, I didn't train it even...could it remember its training from years ago?
Just completed a 11 minute unguided run and the stars are real good.
I used a six inch scope 750 mm fl from recollection with iso set at 100 so it did not white out.
So happy.
Bought a lap top waiting to connect to net and download deed sky stacker and see what I can do.
Didn't have my reticle working so all done by examining captures...
The harder you work the more good luck you have.
Hot for a new scope to go with the new Nikon.
Alex