Description: Once a target's location has been set (solved) you can then quickly center on that image using the Auto Center routine.

Auto Center Setup

To run auto center you will need to have the following setup an connected to Sequence Generator Pro:

Setting Up the Plate Solver

Setting for proper plate solving of the scope are located in two areas.  First, you must tell SGPro a few things about your current setup.  This is done in the Control Panel in the camera tab.  Here you must specify the camera's angle (for Elbrus only) and your gear's scale (for all plate solvers).  While it is is useful to fill out the remaining information, it is not necessary for plate solving.

After this is complete, you will need to fill out a few things in the Control Panel in the Plate Solve tab.  This assumes your plate solver of choice is installed, setup and ready to go.  If not, please do this first (Elbrus, Pinpoint).  In this tab, you will need to:

  • Choose your plate solver from the dropdown
  • Choose your search method:
    • Elbrus should almost always use "5x5 dual angle" (use 2x2 at any angle if the camera angle is not known)
    • Pinpoint should almost always "Use up to magnitude 20 stars" (wide field imaging may require less)
  • Choose the binning for the plate solve frames.  A binning of 2x2 or less is recommended (more sensitivity and less download time)
  • Choose an exposure time that is sufficient to capture solvable data (this will vary by filter, a good value for broadband filters is about 7-8 sec)

Scope Centering Options

Use these options to ensure that SGPro centers your target according to acceptable tolerances.  More detail on this is here.

The Bin, Angle and Scale for the Scope Frame & Center Here options must be populated before attempting to use Auto Center.  Refer to the Plate Solve area of the control panel for more information.  You should save this information in a profile so you don't have to continually re-enter it.

Running Auto Center

There are three ways to invoke the center here functionality (they all do the same thing... just conveniences depending on where you are operating).  You can invoke auto center from:

The Target Settings dialog:

When running auto center, you have two different behaviors to choose from.

  • SLEW to and then CENTER on location: This behavior will first slew the mount to the target's location.  The slew is imprecise and will just get you in the general area of the target (unless you use external modeling software).  Before the precision centering process starts, auto focus has an opportunity to run (on sequence start).  After the optional auto focus, SGPro will enter an iterative, closed loop process to get you exactly on target (see below for related settings).  This is particularly useful if you are starting the sequence from a parked position and would like to not run auto focus on the side of your house.
  • SLEW to location: This behavior will slew the mount to the target's location.  The slew is imprecise and will just get you in the general area of the target (unless you use external modeling software).

The Target List context menu:

Automatically during sequence execution:

Using the control panel will automatically center on the currently selected target.  You can see the currently selected target in the sequencing dialog.

Number of Attempts and Error Threshold

Anytime Auto Center is invoked, it will attempt to center itself in an iterative fashion.  For instance in the screen shot above, the routine will attempt to center itself up to 3 times until the total error is less than 50 pixels.  If aster the 3rd attempt the error is still greater than 50 pixels, it will quit.

Auto Center FIlter

Because it takes much less time to expose a luminance frame (or any other broadband filter), it can be useful to specify a particular filter to use when running auto center.  FOr instance, if you are imaging with an Ha filter and the sequence automatically invokes a centering routine, it will temporarily change to the luminance filter (or whatever you selected) and then switch back to Ha when the sequence resumes.

Once you have the equipment above connected and your plate solver successfully solving images open up the Plate Solve Control panel:

What you will see during Auto Center

Once everything has been setup and is connected you're ready to begin the Auto Center process.  Simply invoke Auto Center and Sequence Generator Pro will begin the process of Auto Centering on your reference frame; this is also accessible via the Scope Centering Module

You will see the following dialog:

This process is completely automated.  The following steps are performed:

  1. The reference data is solved (if it hasn't been previously solved... this will almost always be pre-solved).
  2. An image is taken and then plate solved.  The coordinates of this solve are then used to sync the telescope.
  3. The telescope is slewed to the reference frame.
  4. Another image is taken and then plate solved.  The coordinates of this solve are used to compute the difference between the expected location and the actual location.  The amount of error (in pixels and Degrees:Minutes:Seconds) is then shown. 

If the error is too high (above your defined threshold), then the routine will automatically attempt to re-center until either the error is under the defined threshold or the maximum number of attempts has been exceeded.

Depending on your imaging setup and scale, different values are more or less permissive for the error amount and it will take some trial and error to find what you feel is acceptable.  In general any error below 100 pixels is usually sufficient depending on focal length, target size and framing.  The error is calculated along the hypotenuse of the RA and DEC error (which is why the total error does not add up to the sum of the two errors).