Changes
/* Making a pointing model using SHOC */
== Making a pointing model using SHOC ==
Open all the usual SiTech software and ready the telescope for observing, then in /home/observer/bin, then also openthe programme that connects to SHOC and run astrometry:
sudo mono SiTechCamera.exe
sudo ./RunAstrometry
The SHOC browser should be closed, but there's no need to turn the camera off. In the SiTechCamera GUI, select the Latest Image tab, enter an exposure time and click "TakeImage". Check that the image loads (the image scaling can't be adjusted, so if you can't see any stars, make sure you're pointing at stars and tracking, and that the exposure time is sensible).
Make sure that SHOC's rotator is tracking, and is set to "Track PA" and "If PA is out of range, Track PA+-180" on "Config Page 1" of the rotator GUI. On the "Tertiary mirror" tab of the SiTech TCP Focuser GUI, ensure that the tertiary mirror is at the correct angle ("Current Position" = "Final Position (Right Fork)".
In SiTechExe GUI:
On Scope tab, click SkyView. In the window that opens, turn off most things in the Objects dropdown menu, but turn on calibration points and future calibration points.
On Scope tab, right-click on the large, central "PointXP...Calpoints" button, and select "Yes" in the blue pop-up window that asks "Do you want to clear all PXP calibration points?".
On Feature tab, click Run Script. Two windows open: Astrometry and Script.
In the Script window:
Select the Plate Solve Stuff tab, and enter the number of calibration points you want to include in the model (100-150), the exposure time (depends on sky conditions, but typically ≤8s), SHOC binning (1) and the delay between the telescope settling and the image being taken (7s is reasonable - note that the dome needs to settle in this time) and make sure "Wait for rotator" is ticked to stop the image being taken while the rotator is getting into position.
Click "Make PointXP Run". The model will start gathering points with the telescope pointing South, so you can either rotate the dome to the South before running the script, or press "Play", then "Pause" while the dome catches up with the telescope. This is the only time during the script that you would need to pause on account of the dome. Note that the way to resume the script is to click "Unpause", not "Play".
The script then move the telescope from calibration point to calibration point in numerical order, taking an image with SHOC, using Astrometry.net to match the image to a catalogue, determining the position of the telescope, then moving on the telescope to the next point. Things to watch (lots!):
- The Script window, Plate Solve Stuff tab gives a running commentary of events, showing how far it has progressed through the script displayed on the right-hand side, and what is happening (slewing, waiting, counting down the preset delay, saving image, etc).
- The Astrometry window has a dialogue box showing whether it is currently idle or busy trying to match coordinates to an image. It then gives the results for each successful calibration (plate scale, rotation angle, number of extracted and matched stars, and how long it took to crunch). If the rotation angle is more that a few arcminutes, check that parallacting tracking is ticked on the rotator tab.
- On Skyview: for each successful calibration, a yellow mark will appear inside each red (numbered) calibration point. Click "Refresh" periodically to keep the two aligned as time passes.
- On SiTechExe: the central "PointXP" button keeps a count of the number of successful calibration points, and the RMS and Peak of the model as it builds.
- The SiTechCamera GUI displays each image. If points are failing to calibrate, check whether there are stars in the images.
If an image fails to calibrate, you can return to that point when the script has finished running...
The model
- Left-click on the SiTechExe GUI "PointXP" button to open the PointXP window, where you can edit the parameters of the pointing model. Note that this does not update while the model is running, so you'll need to close and reopen the window to register new points.
== Troubleshooting ==
