Points List And Pointing Accuracy

Points List And Pointing Accuracy

If you create a list of alignment stars using an eyepiece and later create alignments with a CCD you should probably keep the alignments in separate lists. Generally speaking CCD centered stars have an accuracy higher than those manually centered using an eyepiece. It is OK to mix them but the ones centered by the eyepiece (depending on the way it was centered) would slightly 'degrade' the overall accuracy.

If you are planning to populate the list using a CCD camera as a centering tool, make sure the camera is not moved during the entire alignment process.

  • If you are planning to keep the list for a long period of time, the following points must be considered.
  • The list is heavily “time-accurate” dependent. There is a small amount of variance with regards to the PC Time (where all timing data is based) over a specific time period. Any timing “skew” on the PC clock would degrade the accuracy of the entire list after some time period. To overcome this, your PC has to be synchronized always with a more accurate clock prior to populating the Star list. This is where the GPS will come in. With a GPS device on EQMOD, the time data is “normalized” based on a common reference time (the atomic clock). Now assuming you have already a list of stars centered/populated on a GPS-Synchronized PC, the accuracy of the list will still degrade over a time period from the last GPS synchronization, to regain back the accuracy, simply re-synch the PC again using the GPS.
  • The accuracy of the points list is also dependent on the mechanical configuration and inherent flexure of the mount (specially the heavy ones). You lose the accuracy of the list if you;
  • moved the mount to some other location.
  • you loosened the RA and DEC clutches.
  • you removed or replaced the scope.
  • something in the scope has moved such as re-collimating your optics (mirror shifts), or changing the focuser tube, etc.
  • added or removed an accessory to the entire assembly (the added weight would contribute to flexure).
/home/welshdra/public_html/eqmod/data/pages/points_list_and_pointing_accuracy.txt · Last modified: 2009/05/21 23:54 (external edit)
 
Recent changes RSS feed Donate Powered by PHP Valid XHTML 1.0 Valid CSS Driven by DokuWiki