Interface between Cartes du Ciel and PHD2

[Patrick Chevalley]

Hello,

I add a function to Cartes du Ciel planetarium to interface with PHD2.
The main function is to send to PHD2 the offset rates for moving objects such as comets or asteroids.
After the setup and connection between the two software, you can click on a comet on the map, send the displacement rates to PHD2 and enable the displacement.

I am very interested if you can test this functionality and give me your feedback.

A temporary wiki page give all the informations required for testing:
http://www.ap-i.net/skychart/en/documentation/testing_phd2

Patrick

[Andy Galasso]

Hi Patrick,

Nice work on the integration! I tried it with the simulator, and it seems to work great.  I'm looking forward to trying it with a real comet or asteroid when a suitable object becomes visible at my location.

Andy

[Patrick Chevalley]

Hi Andy,

Finally I find some time, telescope access, and clear night to test the comet drift.

The target is C/2014E2 Jacques on October 22 between 19h56UT and 20h56UT.
The drift rate Arcsec/hour computed by CdC was 12 in RA and -37 in Dec.
I take 6 x 10 minutes exposure with my 8" f/d7 Newtonian on a HEQ5 + Eqmod.
The main camera is an Atik 314L+ drived by APT.
The guide scope is a Skywatcher achro 80/400, the guide camera a DMK21.
And sure PHD2 2.3.1j.
All running on Win7, I not wanted to mix Linux problem at this time.
 
The seeing was unfortunately bad and I have normally imaged with a shorter focal length on this night. But I wanted to be sure to show the comet movement so I keep at 0.95"/pixel.

To show the result I make an animated GIF of the six RAW images just stretched and cropped, without any alignment:
http://ap-i.net/tmp/C2014E2_PHD2_1Hour.gif

So it look like it work!
The small residual comet drift is most probably because of field rotation around the guide star because of the quick polar alignment and poor guide scope parallelism.

Patrick

[Patrick Chevalley]

Sorry for the duplicate message, I make a new one because it not appear. And now after three days it is here ??

[Andy Galasso]

Patrick,

That is fantastic! Thanks for sharing it. It's great to see the integration worked. I hope lots of folks will find this feature useful.  Now we are ready for the next great comet.

Andy

(This is my second attempt at a response, my first response appears to have disappeared, sorry if anyone receives this twice.)

[David Billo]

I had a chance to try it out on C/2013 US10 Catalina Saturday morning, however there was some thin cloud, so not a good image, and only had time to get one three-minute exposure.

Unfortunately, it had been some time since I read these instructions, and I got a little confused in the process:

First I brought up the PHD2 toolbox in CdC (PHD2 already running and server enabled)

Clicked the "Connect" button, and saw "Connected"

Clicked on Catalina in CdC, and saw the displacement numbers.

Clicked the "Set rate" button, and another small window popped up with the same offset numbers...

I'm not sure if that window came from CdC or PHD2...there was something there about "Training", and I was asked to centre the comet in the camera (it already was). I'm confused at this point, because I don't know if PHD2 is comet guiding, or just guiding normally on the star.

So I took a three minute exposure, and it looks ok. When I zoom in, the stars are very slightly elongated in NS direction.

I started another exposure, but clouds were covering the comet, so I had to quit.

Anyways, I wasn't sure what to do with the "Training" window, if I click the "Finished" button there, it seems to stop guiding. ???

Also, because of my poor memory, I never did click on the "Off" button in CdC, because I'm thinking "Why would I want to turn if off?"

But, reading the instructions again now, it sounds like that is exactly what I should have done. Am I right?

 

[David Billo]

I looked into this Training window, and apparently it comes from PHD2:

http://openphdguiding.org/man/Tools.htm#Comet_Tracking

From what I can tell, it is for manually setting the tracking rate, but since I'm getting that rate from CdC, my understanding is that I don't need to touch anything in that window, but I just needed to click on the "Off" button on the CdC PHD2 toolbox.

[David Billo]

Well, I now see that "Enable" button in the above linked PHD2 manual, and, subject to my aforementioned lousy memory, I'm must have noticed that button in the window that popped up, and I think I may have pressed it (seems the obvious thing to do), so tell me... does clicking the "Off" button in the CdC toolbox have the same effect as pressing that "Enable" button in the PHD2 comet tracking window?

[Patrick Chevalley]

David,

Yes, the windows described at http://openphdguiding.org/man/Tools.htm#Comet_Tracking is purely from PHD2, it let you do comet tracking without using any other software.

To set the rate from CdC please read the instructions here: https://www.ap-i.net/skychart/en/documentation/toolbox#phd_guiding
When you do the setting from CdC, the PHD2 comet tracking window is not used.

I suggest you make some in-room training with CdC and the PHD2 camera simulator ( make a simulation profile: http://openphdguiding.org/man/Basic_use.htm#Simulators ).

On another point, this comet as an important movement in declination, about 2 arcmin/hour to the north. You must be careful your mount alignment do not require guiding correction to the south, otherwise you may have big problem with the backlash. 

Patrick

[David Billo]

Thanks, Patrick! Yes, I'm not sure what I pressed. Believe it or not, I'm still waiting for a clear morning here to try this again, so maybe the simulator is all I'm going to get for now. Good point about the DEC guiding...I think there is a lot of backlash there, but maybe I can get it so it only needs to nudge in one direction.

[David Billo]

Although it was full moon, I had a chance to test with C/2013 US10 Catalina last night. I did an 8 minute exposure using the comet guiding, and I got star trails (as expected) but also the comet was trailed (not expected). I thought maybe my orbital data in CdC was out of date, it was from December 9th, but updating this morning did not change the Lock Shift numbers by very much, so I'm not sure what is going on.

[Andy Galasso]

Using the tracking rate pulled-in from CdC is a great way to get started.  In some cases you will get more accurate results by using the rate training technique described in the PHD2 help file in the Comet Tracking section.  The rate training method matches the rate to the comet itself and bypasses any uncertainty in errors introduced by camera angle uncertainty, pixel scale uncertainty, non-square pixels, mount tracking rate, polar alignment error, and so forth.

You can practice the rate training method in the daytime using the simulator (as described in the help file.)

Andy

[David Billo]

Oh, ok...I was expecting it to be a lot closer right off the bat. I pushed all the right buttons this time, and although the trailing is in the expected direction (N-S), the comet trail is actually longer than the star trails, which makes no sense at all to me. The guiding was otherwise going very well.

[David Billo]

I got another chance this morning to try out the comet guiding. Initially, I just passed the comet data "as is" from CdC to PHD2, and did an 8 minute exposure. As before, I got the expected trailing stars, and the unexpected trailing comet. I can see the comet trail is about twice as long as the star trails, so I think..."maybe the DEC component needs to be negative." So I edit the value in PHD2 comet tracking tool, do anothe 8 minute exposure, and...waddayknow! It is perfect! Trailing stars, as expected, and stationary comet! So, it appears that the DEC value passed from CdC applies if my OTA had been on the East side of the mount, however for this comet at this time, my OTA was on the West side of the mount, so PHD2 needed the DEC value reversed.

Well, I think I recall seeing a tickbox somewhere about reversing DEC after a Meridian flip, but I don't know if that applies in this case or not. I may just have to remember to manually change the DEC value in situations where the OTA is on the West side.

Now, I wondered whether I should also reverse the RA, but I'm quite sure that RA never changes regardless of which side of the mount the OTA is on...the RA axis is always moving in the same direction.

[Andy Galasso]

David,

The checkbox about reversing DEC after a Meridian flip will not help -- it will just cause runaway guiding.   More likely this is a bug in the comet tracking mode not handling the reversal.  It may be a little tricky for us to fix this since phd2 currently does not have a clear notion of sky directions (N/S/E/W), but only the relative directions determined during calibration (which do not necessarily correspond with actual sky directions).  We do have plans to fix this (#347)

For now your best bet is to reverse the sign like you are doing.

Andy