Drift aligning your mount?

I am going to try this out next clear night and will be back to let you know how it went will it make a difference to my images and reduce those star trails in my shots and having to throw out the duff images ruined by them trailing? Will it work we will see in the next post but for now here is the method I will be trying out thanks to Robert Vice.

D.A.R.V. DSLR / CCD Drift Alignment by Robert Vice

Here is what you do:

1. Setup and align your telescope normally.

2. Set your telescope to point due south and at 0 degrees DEC.

3. Find a semi-bright star. A 6th magnitude star works perfectly, but a dimmer star can be used.

4. Insert your CCD or DSLR camera into the eyepiece holder or attach via the t-adapter.

5. Focus the star for the CCD or DSLR. (Use a Batinov Mask and the live view function to do this) NOTE: if you’re having trouble seeing the stars hit the HD function button on backyard eos which will enhance it for you.

 

6. Once focused, move the star to the right hand side of the camera sensor which is the east side.

NOTE: use backyard eos to do this and line up your camera so the star is horizontal with the target line in backyard eos as in this picture so it follows the horizontal line when you move it with your dual axis motor control or mount control.

 

 

 

 

7. Set your telescope to its lowest drive speed. Typically a guide rate mode.

8. Set your camera software to take an exposure of 125 seconds. The first 5 seconds is used to create a point of reference on the image.

9. As soon as the first five seconds have elapsed, then press the W on the telescope keypad to cause the star to move to the opposite side of the sensor.

10. For the first minute continue to move the telescope West. As soon as the first minute has elapsed, immediately reverse the telescope direction.

11. When the second minute has finished, stop moving the telescope.

12. After the image has downloaded, you should have something that looks similar to the image below.

 

This is an initial image taken. What you see is the angle of deviation. What we are trying to do is to make the < a solid line. In order to correct this, we have to make some adjustments to the azimuth on the telescope mount. Notice that the initial star point is lower than where the exposure finished. This tells us that the telescope is pointing too far West. So to fix this, make a correction to the azimuth control to move the telescope east. Turn the screw on the right side forwards as in the picture this will move your mount towards the east. Reverse for procedure for the west. Make notes as you test for best results.

 Now, follow the same steps again. When the image has downloaded, it should show that the angle of deviation has decreased.

 

Here we have the second image taken. Although both images look identical, the angle of deviation has decreased slightly. I need to make further corrections to the azimuth.

Here is a final correction. The star trail is a single solid line. The angle of deviation is now 0.

Once you have the azimuth fixed, you have to fix the altitude. To do this you simply move the telescope to a star along the Eastern or Western horizon and at 0 degrees Dec.

The only difference this time is that we adjust the altitude instead of the azimuth. The images will be identical when adjusting the altitude. However, you will have to adjust the altitude accordingly. Here you will either raise or lower the altitude until the star trail is a single solid line. If done correctly, you will have a very accurately aligned telescope.

Now that you are done with the altitude adjustments go back and double check your azimuth alignment. If everything checks out ok, then you are finished.

The images used are a two minute exposure done for demonstration purposes. You can increase the time exposures to increase the accuracy.

Declination zero means you find a star as close to the horizon as possible about 20 degrees is usually good enough for this.

THIS GUY EXPLAINS IT REALLY WELL TOWARDS THE END OF HIS VIDEO HERE IS THE LINK TO HIS CHANNEL.