Plate solving with PHD2...

[rsf...@rsfotografia.com]

Hi,

As a spectrographer I would like to ask if it would be possible to Plate Solve using the image of PHD2.

Why? 

When doing spectroscopy we have the main camera behind a slit and what we see there is an image with a line = the spectrum of a star or whatever we want to do spectrogrphy on it. So we can not plate solve with the main camera.

Now for getting a star into the slit and for this we need to first plate solve the image of the guide camera in another software like maybe SharpCap and then switch the camera to PHD2.

Is it feasible to integrate plate solving into PHD2 or is it already there and I have not found it?

Thanks for your comments

Rainer

[Bruce Waddington]

Plate solving isn't part of PHD2 for a number of reasons.  First, the guide camera frames often have a pretty small field of view, and more importantly, they reference a different part of the sky from your main camera.  If you're using an off-axis-guider, the pick-off prism will be outside the main field of view so the guide camera image will normally be offset by at least the radius of the main camera image.  If you're using a separate guide scope, it's usually not practical or even necessary to get the two telescopes precisely co-axial.  For these reasons, I don't think a plate-solved image through the guider is very useful and isn't appropriate for synching the mount.  If you feel the need to pursue this, you can acquire guide camera image frames through the PHD2 event server and then do the plate-solving yourself.  A different question though is whether you need to do any of this.  Plate-solvers aren't necessarily thrown off by central obstructions or non-stellar bright areas - have you tried plate-solving an image through the main camera?  I'm attaching an example of a field with a large black rectangle in the center of the frame and it can be plate-solved very quickly.

Beyond all that, adding plate-solving to PHD2 would involve a lot of configuration, installation, and support headaches that we don't really want to deal with given the limited value of the end-result.  We have a substantial number of PHD2 users who do spectroscopy so I assume they've found workable solutions without the need for any new features in PHD2.

Regards,

Bruce

[NHSA]

Thanks Bruce.  I understand the amount of work.

Most spectrogrpahs do have the guider integrated imaging the image of the mirror with the slit and that is why I asked. I ahve no problem solving on the image delivered by the guide cam so far.

I at least have to first Plate Solve using let me say SharpCap and Plate Solve on the image delivered by my ASI 174MM mounted on the guider of the Spectrograph. After solving I go back to PHD2, center the star in the slit and start guiding be it on the star in the slit or any other visible star around the main star.

I have not yet found a video or paper explaining how they remotely center the star in the slit?

Thanks again and was just a curiosity question.

Rainer

[NHSA]

quote: "... you can acquire guide camera image frames through the PHD2 event server and then do the plate-solving yourself. "

How does this work and so far I understan I can share the PHD2 image with another program at the same time without disconnecting the camera from PHD2?

Thanks Rainer

[Bruce Waddington]

PHD2 has a server interface that is used by session manager apps or any other script/app that needs to interact with it.  The server interface is documented here:

https://github.com/OpenPHDGuiding/phd2/wiki/EventMonitoring

So you would probably use the capture_single_frame method followed by the save_image method to get an image and save it for subsequent plate-solving by whatever software you want to use.  There is no need for shared access to the camera.

Bruce

[NHSA]

Thanks, will take a look at that.

Rainer