Sunday, March 01, 2009

Periodic error of a NJP JP-Z mount

Do you know PEMPro? You can measure the quality of the worm inside your mount with it. Although PEMPro offers much more functionality than worm measurement I will stay on that, since I measured the worm of a Takahashi JPZ mount with it.
Note: The peaks on the quasi sinus curve are due to bad local seeing conditions. The periodic error (PE) of this mount seems to be +2.8 to 3.5 arcseconds. Wow!

Example 1: This is the area around the Horse Head nebula in Orion (530mm focal length, color camera with 7.8mu pixels). The JPZ mount was totally unguided for 15 minutes!

Example 2: This is the area around the star Deneb in Cygnus at a resolution of 3.26 arcsec per pixel (560mm focal length, 9 mu pixels. The JPZ mount was totally unguided for 20 minutes!

Please find attached the guiding curve (in fact this is a guiding ... line!) of this Takahashi NJP JPZ. The mount was guided by a binned 2x2 Starlight Lodestar camera on a Takahashi FS-60C (f/5.9) scope with the software MaximDL

What does such a guiding line really mean at night under the stars? The following astrophoto has been taken at 530mm focal length with an unmodified Canon 7D camera.

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