Setting up the telescope and alignment

Quick Overview:

  1. Plan what you want to observe in advance, read about celestial coordinates and astrophotography with equatorial mounts.
  2. Charge up the batteries and the laptop.
  3. Set up the mount/telescope with an eyepiece and finder scope.
  4. Balance the telescope in both axis by moving the telescope and moving the counterweights.
  5. Align the small viewfinder scope with the main telescope so they point at the same distant object.
  6. Align the mount with the North Star using the internal telescope.
  7. Connect the mount to the laptop with the usb-to-RS232 serial cable.
  8. Power up the mount by connecting to the 12V battery.
  9. Start the telescope control software, ‘cartes du ciel’ and sync with the zenith or a known star so thethe software knows where the telescope is pointing. Check the sync by moving to a nearby star (clickon star and ‘slew to’).
  10. (If you observe a star whilst the telescope is tracking, and the star drifts, use the ‘drift alignment tool’ within PhD2 for more accurate alignment)
  11. Remove main eyepiece, attach the CCD camera with guide camera. Rebalance the telescope. Connect the CCD camera to the laptop with the USB cable.
  12. Connect the guide camera to the laptop with the USB cable – use the USB triple adapter because laptops do not usually have three USB ports.
  13. Power up the CCD camera by connecting to 12V battery.
  14. For accurate alignment use the drift alignment tool in PhD2.
  15. Focus the CCD camera using the focus tab in SIPS and the Bhatinov mask. (Bin the data in 2×2 or 4×4 pixels if it takes too long for each image to download).
  16. Check the guide camera is also focussed – may need to move it slightly outwards in its holder.
  17. Move telescope to your messier object.
  18. Configure the guide camera, find guide stars and start autoguiding with SIPS or PhD2.
  19. Take exposures in different filters with SIPS.
  20. Careful about ‘meridian flips’ – if the object moves past the meridian the telescope may crash into the tripod.
  21. Take darks, bias frames and flat fields.
  22. Done. Pack up everything and don’t lose lens caps or cables etc in the dark.

 

In more detail……

Setting up the telescope and alignment

The telescopes equatorial mount turns exactly opposite to Earth’s rotation so that you can take along exposure of a fixed point on the celestial sphere. But the mount must be pointed precisely towards Earth’s rotational axis for this to work.

The telescope alignment is made by pointing the rotational axis of the mount at the North Celestial Pole. This is near the ‘North star’ Polaris – over a sidereal day the Polaris rotates completely around this point. Begin before dark so you can see what you are doing and so you can adjust the finder scope to point in the same direction as the telescope. The entire process should take around one hour. That’s ok, it takes about an hour for the telescope to cool down and reach optimumperformance. You may need to refocus as the optical tube settles to the new temperature. For further information read this: http://themcdonalds.net/richard/wp/polar-alignment-of-your-equatorial-mount/

  1. Place the tripod so that with the mount, it points to the North. Use a bubble level to ensure it is roughly level
  2. Fix the mount to the tripod with the screw underneath. Use the metal spreader piece to block the legs open
  3. Do not connect the batteries to anything yet
  4. Fix the tube to the mount using the tube holder. Do not over tighten
  5. Attach or extend the long metal pole for the counterweights
  6. Attached one or two counterweights as necessary
  7. Insert the small finder scope into the holder on the main tube
  8. Attach a wide field eyepiece to the telescope (you may need one or two extension tubes) and take off all the lens caps, extend the tube light protection cover (takahashi scope only).
  9. Balance the telescope on the two axes (right ascension [ra] and declination [dec]): lock the dec lever and open the ra lever. Slide the telescope along its holder until it balances.  Then unlock the dec lever and lock the ra lever, adjust the position of the counterweights to balance the second rotational axis. Note that when you add or remove equipment attached to the telescope it will need to be rebalanced. If the telescope is not accurately balanced then it puts stress on the gears and it will not track accurately and it will wear out the gears.
  10. Align the tube and secondary finder by focussing on a distant object/tree/building/planet through the telescope tube (easiest at twilight) – adjust the position of wide field secondary finder (mounted on the tube) so the same object is in the crosshairs as is visible in the centre of both scopes.

For the Takahashi TSA102 telescope & EM-11 mount:

  • Remove the small covers on the mount (top and bottom that point towards Polaris) so that you can look through the internal telescope at Polaris in the North. you may need to rotate the telescope so the optical pathway is clear
  •  Plug in the remote hand control to the mount
  •  Attach the power cable from the mount to the battery
  • Turn on the mount switch – this will illuminate the internal telescope
  • Turn the RA axis so that the large cross markings are vertical.
  •  Polaris needs to be placed on the 2016 circle at the correct hour angle. 0hr is at the bottom by definition, and the hours run anti-clockwise. Subtract the RA of Polaris (2hr 52mins in 2016) from the local sidereal time. or use an app/software to show you where Polaris should be on this circle
  • Position Polaris at the correct hour by turning the altitude and azimuth knobs. If all is correct, the arrows should point at the constellations Ursa Major and Cassiopeia. (You can also roughly align the mount by turning the telescope mount until these constellations are in the correct place.) Now the mount is roughly aligned.
  • I recommend fine tuning your alignment by using the drift technique below.For the Skywatcher mount with the Williams star optic 71mm small telescope
  • Follow the same steps as above, but read the mount manual for more details

Useful tools:

polarfinder app
http://www.takahashi-europe.com/support/softwares/polarisfinder/polarisfinder-1.5-en.htm
http://myastroimages.com/Polar_FinderScope_by_Jason_Dale/