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EQAlign - Drift Alignment

PostPosted: Sat Aug 13, 2011 12:39 pm
by martin_h
Drift Align using EQAlign

If you have Eqmod controlling your mount a lot of the commands will be done automatically for you, if you don’t have it you will have to slew to stars and start/stop tracking through the handset.

You will also need to be reasonably Polar aligned and goto aligned

After downloading and installing EQAlign a setup wizzard will run, you will be asked to input some basic data, ie your Log and Lat, scope , mount, and camera information.(the scope and camera you are going to use for the alignment)
Once this is entered correctly you are ready to begin.
With other methods of drift aligning you need to ensure that when you move the mount in RA the star moves across the screen/EP in a horizontal fashion, with EQAlign there is no need for this, it wil calculate the ‘roll angle’ of the camera and add/subtract this from all readings, so the first thing we need to do is calibrate the camera.
You can use the built in planetarium to do this…click on a star and click the goto button (bottom right of screen) . Or slew to it using the hand control, the RA and DEC cordinates are given in a bos bottom right of screen.
Click the Calibrate tab on the left of the screen and a new window will open with a cross hair, bullseye and your star, use the controlls to centre the star close to the center of the bullseye, Click the Process button the calibration will start and EQAlign will turn off the tracking of your mount (or turn it off yourself), leave it to calibrate, it doesn’t take long, when its done a window will popup telling you its calibrated and to turn on thr tracking if it hasn’t already done so.

Now to Polar Align, click the Align tab on the left side of the screen, a similar window will open as before, select which axis you want to correct (Altitude or Azimuth) and EQAlign will help you to select a satisfactory star near the east/west horizon (for altitude axis) or near local meridian (for azimuth axis).

Altitude Error measurement and correction.

Click the East or West radio button and click the select star button, you will be presented with the planetarium window with a zone marked out on it, select a star in that zone (the closer to the centre line the better) when you have chosen a star the mount will slew to the star (or use your controll to move to it) and center it up in the screen. Click on the star (a circle will enclose it) Click the process button and let it run for at least 10 minutes, click the process button again to stop measurement.A message will appear in the upper right corner of the screen….“Please place the star with the control pad into the init correction point (little red circle). If you have a compatible computerised mount, you can push the ‘autoguide to init point’ button. Then turn the Azimuth axis screw until the star fall into little green circle or near the perimeter of the larger white circle.”

If measured error is larger than maximum screen possible displacement, correction must be
done in several steps and the following message will be shown in the help window:
“The measured error is larger than the window dimensions. You must repeat the axis correction
n times. The last correction you must carry the star from initial correction point (red circle) to the
perimeter of the smallest white circle.”

Now repeat for the Meridian and do the same as above but adjusting the Azimuth screws of the mount.

Finished? Well not yet, its best to go back and do it again, by adjusting one axis you disturb the other so by repeating a couple of times you narrow the error.

EQAlign and instructions can be found here - http://eqalign.sourceforge.net/index-en.html

A quickstart PDF for alignment can be found here-http://www.eqalign.net/projects/EQAlign2PAen.pdf

Re: EQAlign - Drift Alignment

PostPosted: Sat Aug 13, 2011 3:50 pm
by martin_h
Just an additional note for the above.....When you get to the select a star for drift align, the program shows you a wedge where the best stars are....there will not always be a bright star in that area so people using webcams might struggle to find one...there is a camera controll panel on screen you might have to play with the settings...gain - framerate etc to get the best image, If you can't get a star go back and select another from the area and try again.