Abstract: Alignment to the celestial poles is crucial to clear images in astro-photography. The ways in which to obtain alignment are varied in method. Most of these methods, however, are for alignment to the North Pole. The Mark IV is pointed towards the south, so a new method had to be devised. This is method is discussed, along with the results found.
Discussion: The alignment of the Mark IV was done through the use of visual observation. When properly aligned south, and with the right assention drive off, the images taken with a long exposure should have the trails lying along a vertical line. If the trail were to be angled (shifted), the Mark IV would be moved to compensate. The cooling system of the Mark IV was not used for alignment.
Marking the original position of the Mark IV started the process. This was done using four (4) pieces of duct tape at right angles to one another. The front legs of the Mark IV sat in the inside corners of the tape
This tape also allowed for a place to mark each subsequent position the Mark IV was moved to (as shown in the close-up of the tape below):
From this start position, an object image was taken for 60 seconds. The left leg was then moved from the start position an amount toward the back of housing to position A, while the right leg remained fixed. Another 60-second exposure was taken from this point. The left leg was moved once again, the same amount and direction as previously, to position B. From position B, another 60-second exposure was taken
Note that the images shown here are rotated 90 degrees, so that the north south directions are along the horizontal axis. After viewing these three (3) images, it was decided that there was not enough trail to determine a significant shift. To rectify this problem, all exposures after were taken for 240 seconds. These longer images produced trails long enough to produce noticeable shifts
An example of the angular shift can be seen in
A table of measurements and angular shifts at different locations is shown below.
After the image at position D was taken, the Right Ascension drive was turned on and fast-forwarded through about an hour. Again, an image was taken. This image showed an angular shift 0.00 pixels, meaning that the Mark IV was perfectly aligned to the south.