Speed correction of the platform Speed of the platform depends, for example, on telescope weight so it is good idea to check and eventually correct it at the start of using with particular telescope. Speed correction should be done after platform was setup on Polar Star.
Correction should use objects laying on local meridian and ecliptic. So rotate telescope to south direction and try to find star on ecliptic. To make correction use finder or eyepiece with small magnification. Fullfill next steps:
1. Power off the platform and select object laying close to meridian and ecliptic
2. Set finder crosshair in position when object will slide on crosshair line during telescope rotating over azimuth ax (horizontal line).
3. Check visible area by measure time object need to travel from one side of area to another along longest diameter. Visible area has 15.041arcsec/sec x measured time. For example, if time when object travel from one side to another along diameter is 120 sec then visible area has 15.041 x 120 =1805 arcsec or about 30.1 arcminutes.
4. Power on platform and set it on 1/3 or 2/3 way. Next set object at central point of visible area and watch it about 10-15 minutes. Notice drift object will do from the central point along horizontal crossline. Drift in vertical direction is meaningless. If object will drift to the edge faster than 10 or 15 minutes notice this shorter time. Check also what sign has drift. Usually drifting to right side means platform is slower than sky and drifting to left means platform is faster than sky.
5. Knowing difference D between sky and platform way during measure time calculate rate k = (platform way) / (sky way) and next multiply actually platform sequence by k. Set new sequence and reapeted measure or/and eventuallly corrected sequence again.
6. For example lets assume that actual sequence is 028331 (or 0 28331) and measure time has 10 minutes (600sec). During this time object drifted from center to right side 12 arcminutes (12*60=720 arcsec). In means that platform is slower than sky. During measure time (600 sec) sky rotated 600*15.041=9024.6 arcsec and platform did only 9024.6-720=8304.6 arcsec. Correction rate k = 8304.6arcsec / 9024.6arcsec = 0.92. This value is used to correct sequence but only second part (digits 2-6) so count 0.92 * 28331 = 26065 (round to nearest integer). New sequence will be now 026065 and this sequence should be establish in EQ Tracker.
Usually is enough to make one or two sequence correction as described upper to adopt to current environment. After correction enjoy stable beauty of dark sky ;-) |
setting horizontal crosshair  finding visible area (power is off)  test start (power is on)  drift measure |
