Sat, 21. March 2015
Meade LX-90 Telescope Equatorial Mount - 3
- Level it on the mount.
- Aim it towards the South Celestial Pole by setting the latitude and offsetting in azimuth from magnetic South by the correct angle to arrive at True South.
2. Attach the telescope to the mount.
- Recheck the wedge is level on the mount.
- Align the finderscopes.
- Adjust the tube manually to "Polar Home".
- Use an inclinometer to ensure the tube is exactly the same angle as the forks.
3. Align the Autostar.
- Use "Easy Align" to carry out out a standard two star alignment.
- Make a note of the message which indicates the degree of accuracy.
4. Drift Align Azimuth.
- Slew to a star approximately due South at zero degrees declination.
- Fit the DSLR camera and position the star far right in the monitor field of view.
- Set telescope slew rate to 1x speed.
- Expose for 5 sec with no movement then hold right RA arrow 60 sec then left RA arrow for 60 sec (total exposure: 125 sec).
- Angle of deviation is the amount of adjustment needed.
- If the angle of deviation is raised up, adjust the azimuth controller towards the East. If the angle of deviation is down, adjust towards the West.
- Repeat the routine until accurate in azimuth.
- The final exposure might be extended to two minutes to improve the accuracy.
5. Drift Align Altitude:
- Remain on zero degrees declination and slew in RA to a star above the western horizon.
- Use a similar procedure to expose for 125 sec.
- If star moves up, adjust the altitude controller to a lower altitude. If star moves down, adjust the altitude controller to a higher altitude (latitude).
- Repeat the routine until accurate in altitude.
6. When Finished:
- Tighten all adjuster knobs.
- Do a second Autostar alignment. (ADDED 12th May 2015).
The choice of star magnitude is irrelevant for drift alignment, just change the ISO setting to suit.
The following photo shows an example of a medium-bright yellowish star with some other slightly fainter stars in the background. During this exposure the first five seconds was with normal sideral tracking to achieve the starting marker, followed by about 60 seconds slewing at 1x using the right slew button and almost 60 seconds slewing back with the left hand button.
So the drift aligning technique can replace the tedious search for the magnitude 5 asterism of four stars in Octans and seeking the Celestial Pole offset from Sigma Octans.
It can also commence as soon as the first bright stars become visible, instead of waiting for the dim stars of Octans to appear before starting.
The next night out will be the big test for this procedure!