For an investment of approximately $ 400 Canadian, it is possible to align the mount on the Celestial North Pole (PNC) with an accuracy of up to 30 arc seconds (30 ″ arc). She asks to use a German equatorial mount. The PoleMaster software is used with the CCD camera dedicated to him. This precision will allow exposure times of 10 minutes or more per photo. Usually, polar alignment can be achieved within 2-3 minutes after starting the software. This is the revolutionary method to align the mount on the axis of rotation of the Earth in record time!

Here is the procedure I produced for using the software Pole Master. It includes certain details for using the application properly.

Installing the camera, driver and software

  • Install the camera driver by following the on-screen instructions
  • Install the software by following the on-screen instructions
  • Install the camera Pole Master on the frame

View user's Guide of the PoleMaster for all the details.

User manual

  • Roughly position the equatorial mount toward the Celestial North Pole (PNC). To do this, put the axis of the latitude in conformity with the observation site (for example for the region of Montreal the latitude is 45,5o) and make sure the telescope is pointing near the North Star by following the mount's instructions. Do not start the mount.
  • Connect the camera Pole Master to a USB port on the computer using the cable supplied with the device.
  • Position the camera's USB cable on the left side (when facing the camera).
  • Start the mount without initializing it.
  • Start the software Pole Master.
  • Menu Language : To select French
  • Click on the Menu Connecter.
  • The following image will appear:

  • Select region : To select North part for the northern hemisphere.
  • If the cabin crew is at a latitude of 30o or less, a correction must be introduced to take account of atmospheric refraction (for further explanation, see note 1 at the end of the procedure):
    1. Tools | Astronomical refraction : Enter the latitude and longitude of the observation site and select Activate astronomical refraction correction.

    1. If at your observation site, the Cabin Crew Member is at a latitude of more than 30o, it is necessary to deactivate Activate astronomical refraction correction.
  • Close the window Astronomical Refraction.
  • Parameters : Adjust Exp (ms) et Gain until you can see several stars in the field of vision on the right of the screen.
  • Click on the button Completed after adjusting the exposure and gain.
  • Locate the North Star on the screen by referring to the following image:

Use the Zoom menu to display the entire image.

  • Double click on the North Star.
  • Align the calibration stars with the round white circles. To match the stars in the circles, there are two possibilities:
    1. By dragging the cursor over the marked tool Rotation.
    2. With the arrow keys on the keyboard.
  • At the end, there should be a star visible in each of the white circles as shown on the following screen:

  • When the match is good, click on the button Yes.

AD adjustment (right ascension)

  • Choose a bright star adjacent to the North Star by double clicking on it. To make the process more precise, it is best to use a star that is not too close to the North Star. The instruction screen prompts you to rotate the mount. You have to remember the chosen star, because you will have to select it two more times. Use the mount control lever to perform an AD rotation of at least 30o. Do not manually rotate by loosening the AD axle from the mount. This will cause a large alignment error.

  • For the rest, follow the instructions on the screen. Indeed, from this moment, it is faster to follow the procedure which is described in French directly on the screen.
  • At the end of the procedure, close Pole Master and initialize the mount.

GoTo mounts 

Considering that the MES on the Cabin Crew Member with Pole Master is very precise, going up to 30 '' of arc, an alignment (or calibration) of the mount on a single star is sufficient. No need to align (calibrate) the frame on two or three stars and even more. Thus, the frame calibration procedure will be much faster. Referring to the owner's manual for your GoTo equatorial mount, choose the single star alignment. Personally, with my CGEM mount, after MES using Pole Master and the calibration of the mount on a single star, I succeeded in displaying the object to be imaged directly on the screen of my imaging camera!

In summary, MES is carried out in 3 stages:

  1. Adjustment of the AD axis on the PNC.
  2.  Approximate adjustment on PNC (DEC and AD).
  3. Precise adjustment on the PNC. See note 2.


Although the procedure described above seems long and complex, with getting used to and memorizing the various steps, it only takes a few minutes to complete. If you ever hang your mount by accident resulting in loss of MES, you will greatly appreciate this quick MES procedure on the Cabin Crew Member.

Note 1: Correction to take account of atmospheric refraction (step 10 above)

Atmospheric refraction is an optical phenomenon which consists of a non-rectilinear path of light crossing the atmosphere and which is due to the variation of the density of the air with altitude. The following graph shows the importance of the deflection of light when approaching the horizon:

The graph shows that at the horizon (0) the atmospheric refraction is about 34 minutes (') of arc! At an altitude of 25o, it is about 2,5 'of arc. At 40o, it is 1 'of arc. The application Pole Master recommends activating atmospheric refraction correction when the PNC is at a latitude of 25o and less.

Here are examples of corrections made by Pole Master depending on the cabin's latitude (1 pixel = 0,5 'of arc or 30' 'of arc):

25o 2 pixel correction (1 'of arc)
20o 3 pixel correction (1,5 'of arc)
15o 4 pixel correction (2 'of arc)

Note 2: Precise adjustment on the PNC

If the green target moves randomly in several directions preventing it from aligning in the red circle (which represents the PNC very accurately up to 30 '' of arc), it means that the stationing (MES) on the PNC is not good. MES must be restarted from the beginning. Before starting over, pay attention to the following points:

  • If the altitude of the cabin crew at your observation site is 30o and less, it is necessary to activate a correction to take account of the atmospheric refraction. See step 10 above. For more details, see note 1 above.
  • Make sure to position the USB cable of the camera Pole Master on the left side (when facing the camera), as described in step 3 above.
  • When rotating in AD, use the mount control lever. Do not make manual rotations when loosening the AD axis from the mount. This will cause an alignment error, the importance of which varies depending on the mount used.
  • Before using the app Pole Master, make sure that the mount is positioned towards the cabin crew. Follow steps 1 to 14 for setting up the telescope by clicking on the following link: put_en_stat.htm.
  • During MES, if there have been clouds that have passed in front of the PNC, this affects the accuracy of the MES by introducing atmospheric refraction. Choose a night without clouds or with very few clouds. Never carry out an MES when the sky is foggy, the atmospheric refraction will be too great, regardless of the cabin's latitude.

Richard Beauregard
Sky Astro - CCD

Revised 2021/11/05