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How to convert a “weak mount” into an appropriate mount by means of TPoint & Star Tracking

Starting point was the available German Mount SP-DX (VIXEN) which is known to be a good one in terms of imaging until aprox.   8 - 10 kg of load.

Since in the worsed case my equipment has a weight of more than 20 kg it was necessary to improve the mount considerably in terms of pointing acuracy as well as perodic error.

The pointing accuracy was improved by TPoint which takes care of bending errors etc. while the genuine total periodic error of 43 arcsec was drastically reduced to 2.7 arcsec (i.e. 6.3%) by the method of “Star Tracking” using a cheap guide scope in conjunction with SBIG’s ST-6 CCD camera. The other beauty of the ST-6 compared with the ST-4 camera is its huge FoV (53’) which takes care of more than enough guide stars in any direction.

Underneath you see the genuine periodic error of the SP-DX German mount with 20 kg load. 27 pixel (Recording camera: MX916 binning 2x2; f=2800 mm) transform into a total error of 27 x 1.6 = 43 arcsec (+/- 21.6):

Underneath you see the residual tracking error in REC&DEC after Star Tracking with ST-6 was switched on.  0.3 pixel (Recording camera: ST-6; f=500 mm) transform into a total average error of 0.3 x 9.2 = 2.7 arcsec (+/- 1.4):

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