Contents - Index

Plate solve exposure

Plate solving consists of using star pattern matching against a given stellar catalog to calculate the coordinates of the center of a given image.  In order for many of the features and functions of CCDAutoPilot to be successful, plate solving is required.  And in order for plate solving to be successful, proper setup is mandatory.



Plate Solve Exposure
  • Sub-frame: For most imagers, this setting can be left at Full.  However, if you have a large chip imager and/or a wide field scope, you may need to set that to a lower fraction.  Choices go down to 1/16.  The fraction is a percentage of the chip size by which the imager is sub-framed, while keeping the sub-frame in the center of the chip.  This has to be determined experimentally for your given system.  PinPoint seems to be more tolerant of wide fields and CCDSoft/TheSky6 is limited to 1 square degree.  In the latter case, it is best to use a sub-frame.  There is no loss of accuracy.
  • Filter: This selects the filter that will be used for plate solving.  For maximum sensitivity and performance, the most transparent filter is generally used.  In the above example, a clear filter is specified.
  • Exp. Time: This is the exposure time for the plate solve exposure.  Usually 5 - 10 sec. exposures are sufficient.
  • Bin: This is the binning that will be used for the guide exposure.  Increasing the binning gives better sensitivity and should be used with long focal length systems.  For my 3315 mm system, a bin of 2x2 is used.

    PinPoint
  • Catalog: Select the catalog appropriate for your system.  I generally use the GSC ACT catalog with excellent results.
  • Path: Using the '...' button, navigate to the folder that contains the catalog you wish to use.  Note that catalogs from TheSky6 can not be used with PinPoint.
  • Expansion: This parameter determines how much error can be accommodated during the plate solve operation, at the expense of solve time.  Consult PinPoint documentation for details.

    CCDSoft/TheSky6
    There is no explicit setup in CCDAutoPilot.  TheSky6 can be configured to use a number of optional reference stellar databases.  In general, the Guide Star Catalog (alone) has proved effective for my applications.  If you have a particularly narrow FOV system, you may need to use the UCAC/USNO B sub-set selection with appropriately longer plate solve exposures.  CCDSoft has the ability to customize the detection threshold.  See CCDSoft documentation for details.  In general, the detection threshold should be around 1.5 to 2.  If you are imaging an area with bright nebulosity, a higher detection threshold of 3 - 4 may give better results.