Hi!

Thanks for you reply! I understand that the polar alignment involves plate solving and a mathematical algorithm. But what I do not quite get is why the mount should rotate by a defined angle? That information is already right there and can be retrieved by plate solving too. In fact, that's what software like SharpCap does. I can get a decent polar alignment within five minutes on a non-goto mount. But that's on windows and does not run on Rpi3. I'd prefer Ekos

Clear skies
Stephan

It can be done, but currently not supported by Ekos. Maybe in a future version.

Just for info. I also want to use a polar alignment algorithm on a StarAdventurer. I have done that using SharpCap under Windows but want to centralise my system around a Pi running Astroberry. Thus this facility would get another vote from me. For a use of a mount such as this I would not really want to go through a drift alignment process.

Thanks for all the work that is done to make this such an excellent suite of applications.

David

Just use the polar scope for rough alignment and then PHD2 to drift align and fine tune. It is almost as fast as the rotational alignment.

You can use Telescope Simulator for a mount and then do the rotation manually. Once you have done the two rotations manually you can proceed normally with the polar alignment.


Wouter

Use PHD2 Polar Drift Alignment tool. You just select a star near the pole, make sure tracking is on , then start the tool. It shows you where you need to move the star to for a pretty good polar alignment. Not as precise as other methods but very simple and quick. No need to rotate the mount or anything like that. Can be done without PHD2 being calibrated also.
If there's enough interest, maybe the tool could be incorporated into EKOS?

Having that tool incorporated into Ekos would be fantastic, Ken! It is not a big deal starting PHD2 for PA and then shut it down again and start Kstars, but having it all in one would very convenient.
Jo

Ekos already has two PA tools, one of which is at least similar to the drift method that PHD2 uses.

I don't understand this desire to put everything in one big bucket, the whole point of modern multitasking operating systems is to be able to use multiple things at the same time.

Not a problem if someone has a third camera just for PA, but if one wants to use the guide cam or main cam for drift alignment, one would have to first start PHD2, then drift align, then quit PHD2, then start KStars to avoid a conflict with the camera being recognized by two systems (provided one wants to use the internal guider with the guide cam). By integrating a drift align option into Ekos, that (small) hassle is averted.

Anyway, if I understood that correctly, Ken was just wondering whether there was interest and in principle, I think there is. I would not need this much, since I use the PA tool in Ekos already and that works great with the polemaster, but for others it might be useful.

I have a SkyGuider Pro and I too would like to see a non-critical placement manual adjustment in Ekos, so you can manually rotate to roughly 30° positions and the program triangulates from there. PHD2 needs a better alignment tool as well. I do not find the concept of regular drift alignment remotely attractive, and I would like to see a more accurate Polar Drift Alignment tool in PHD2, essentially one go to, one-shot alignment procedure. Having to jump to multiple alignment routines in PHD2 seems unnecessary.

The current three image PA method in Ekos doesn't need critical movement of the mount, just that the movement is large enough that there is a signficant change to the images. Any movement over about 15 degrees should be enough. There must be no movement of the dec axis, that's not difficult to achieve.

The only one goto, one shot polar alignment I know of is Celestron's ASPA and this uses the previously done mount alignment to get the polar alignment error.

The nature of drift alignment means that it can only see the error in one direction so it hs to be done in two positions.

Part of the problem with polar alignment is that people are too fussy. A small amount of PA error can be guided out and may help because the declination corrections are all in the same direction. What is left is field rotation and if you do the sums this will be insignificant.

A PA error of less than 10 arc minutes should be fine. If you have a permament mount then it may be worth the effort to get closer but even then less than an arc minute won't achieve anything useful.

Polar Drift Alignment is close to being one-shot. It operates near the pole and relies on the fact that PA drift is perpendicular to the PA error so it detects the error on both axes. It also does not need any calibration for camera rotation nor any slewing. All it needs is a guide star within about 5 degrees of the pole. On the down side its accuracy is limited by PE and seeing as it uses very small drift amounts that get smaller as PA error reduces. It can also give wrong results when tracking is disabled as the resulting RA drift is indistinguishable from PA drift. But used correctly, it should however be able to get within 10 arcminutes quite readily and in good conditions even less.
The theory is described at canburytech.net/DriftAlign/DriftAlign_4.html
I developed the module in PHD2 so it would not be a stretch to implement in Ekos.