New PHD2 static polar alignment tool

[kens (Ken)]

It's been 18 months since I first started working on this.
http://www.iceinspace.com.au/forum/s...d.php?t=143297

Now it's a tool within PHD2 and available in the latest dev release. Documentation will follow shortly.
Why static alignment? No reason other than to distinguish from the various forms of drift alignment.
This tool lets you polar align by pointing at the pole rather than the equator and in my testing so far is pretty quick. It works particularly well in the Southern Hemisphere due the availability of several identifiable stars near the pole.
Feedback welcome.

[RobF (Rob)]

Looking forward to docs Ken. Congrats on your efforts to get this far.
What are the hardware requirements? (sounds like you need a WDM capable camera and modified polar scope from your other thread?)

[kens (Ken)]

Nothing special is needed. You can use your guidescope and camera or imaging scope and camera - anything that PHD2 can connect to.
Just connect as usual in PHD2, point at the pole and select Tools>Static Polar Alignment from the menu.
Attached is a screen shot of what you get
There are instructions on-screen (help file is on its way) and the process is mostly automated

[glend (Glen)]

That seems very similiar to Sharpcap's PA tool. Its great to see another tool that negates the need for additional equipment and expense (like Polemaster etc). While I have PHD2 for guiding, I use Sharpcap for PA now (when required), and it is very fast, can you give me some idea of the amount of time required for PHD2's version? Does it require internet connection for plate solving or does it carry the sky map internally? What field of view is required?

[Merlin66 (Ken)]

Glen,
I'm sure the other Ken will reply more fully..
No internet required, no external plate solving required.
The thing that interested me was the limited rotation required to generate the correction arcs and hence the Alt/Az corrections.

[glend (Glen)]

Originally Posted by Merlin66

Glen,
I'm sure the other Ken will reply more fully..
No internet required, no external plate solving required.
The thing that interested me was the limited rotation required to generate the correction arcs and hence the Alt/Az corrections.

OK thanks for that. I guess when I see the Rotation button in the photo it tends to make me think Rotation is still required. I will wait for his clarification. If Rotation requirement is reduced, then that is a good thing, but I have found that Sharpcap will work with rotation of less than 90 degrees. I find Sharpcap's instruction set lacking in some areas and I hope PHD2's version can provide and easier to understand interface.

[kens (Ken)]

I've been getting good results with rotations in the order of 10-12 degrees.
The main limitations are seeing and the mechanics of the mount- the same things that are limitations with the PHD2 centroid calculations used in guiding.
In automated mode the rotation is done automatically. The slewing takes place in calculated steps so that PHD2 can track the star. Plus the graphic overlay shows the direction of the adjustments you need to make.

ETA: If you look at the attachment I posted a little earlier you can see the "Ref Star" in a small blue circle and another small blue circle just nearby on the magenta arc. That is how far the tool slewed to get a result.

[Camelopardalis (Dunk)]

Looks neat Ken

Anything that speeds up polar alignment is a Good Thing(tm) IMO.

[lazjen (Chris)]

Ken - is there any limitation on the scope fov for this to work? Sharpcap has some limitations in this regard - I can get it to work with my scope at about 400mm focal length but at 700mm it appears to be too narrow a fov.

[kens (Ken)]

Well I've been using it with my RC8 at 1600mm but I'm also using my ASI1600MM as the camera so my FOV is about 38'x28'
The main issue for small FOV is being able to identify a reference star - but plate solving could help there.

[peter_4059 (Peter)]

Hi Ken. Does the wizard display show the expected orientation of the stars around the SCP? What happens if the initial alignment is out such that those stars are not in the camera fov?

[kens (Ken)]

In automated mode it shows the stars in the correct orientation within the limitations of your mount reporting its correct RA and your calibration indicating the correct camera angle. In manual mode it makes a guess based on LST and assuming the mount is at 18h Hour Angle.
In both cases it assumes your declination is +/-90.
If the stars are not in your FOV you need to move in declination until at least one can be identified. For that you need a reasonably good star alignment or you need to plate solve or star hop.
Once you are pointing at one of the stars your polar alignment can be up to 5 degrees out and it will show you the correction needed. In that case the correction may well take you outside the FOV. In that stuation I'd recommend to move the star in the required direction to the edge of the FOV, correct in declination to recentre the star then rerun the alignment. process.
I'm interested to know what sorts of FOV people have. At present the outermost star I show is sigma Octans but I can easily add more if the demand is there.

[RobF (Rob)]

Originally Posted by kens

Well I've been using it with my RC8 at 1600mm but I'm also using my ASI1600MM as the camera so my FOV is about 38'x28'
The main issue for small FOV is being able to identify a reference star - but plate solving could help there.

Excellent - I was expecting problems here, but if I can get PHD2 to read the QHY9 ASCOM driver then hopefully FOV won't be a problem for my setup.

[kens (Ken)]

You'll see some nice new features in dev4 that help both manual and auto users:

- The JNOW algorithm will hopefully result in more accurate placement of the reference stars based on their J2000.0 coordinates which in turn should make the corrective moves more accurate
- You have the option to turn off the reference star orbits to make the corrections easier to see
- Auto mode users can now adjust the rotation (hour angle)* of the reference stars. It is*meant for small adjustments but the full 360 degrees is available. The idea behind this is that you adjust the rotation so that the corrections to move, say, three reference stars to their correct positions is the same for all three. That provides greater accuracy as it accounts for any pointing error in the mount.
- The calculated PA error in arc minutes is now displayed on the status line for bragging rights and for comparison with drift alignment. In truth, it should be used so you know when you are "near enough"
- Slightly brighter colors for alt and az corrections should hopefully make it easier to see them in the dark
- A "Clear" button is provided to clear the display completely so you don't need to close and reopen the tool
- A "Flip Camera" option is provided for those situations where the displayed star positions are inverted from their true positions. Other changes in the code hopefully make this redundant but for now its worth having