The documentation and inaccurate information supplied by the manual and in newsgroups across the internet has many people confused when attempting to use the polar finder scope. There have been a few postings in the newsgroups that document how to use the finder but the subject is still confusing. I’ve documented and illustrated the correct way to use the polar finder in an attempt to help LXD55 owners. This procedure is more difficult to perform with the scope and counter weights on the mount. I recommend polar aligning the mount without them, but it’s not absolutely necessary.
At this time if you have not aligned the polar finder scope to the mount itself, it would be a good idea to do so. If it’s not aligned, you be wasting your time performing the procedure I describe below. The manual does not instruct you how to align the polar finder scope to the mount, but fortunately I have written an article on aligning the polar finder scope also.
Find out your longitude and latitude. No precision is necessary at this time. You just need the number in degrees. In my case it is 31N and 97W for Round Rock, TX.
- Level and eyeball the mount to point north at Polaris.
Use the altitude adjustment to raise or lower the altitude to match your
latitude. Move the tripod to align the azimuth. You may move the tripod right
now because it’s easier and faster then turning the knobs.
- Determine the longitude of the meridian in your time zone. To do this, multiply the number of hours you are offset from Universal Time (UT) by 15. For Central Time Zone in the U.S. it is 6 hours. So…. 6 X 15 = 90. The meridian for Central Time Zone is 90 degrees.
- Calculate the difference from the meridian you just
calculated and your longitude In my case, 97 degrees. 90 - 97 = -7
or 7 degrees west. Had my longitude been 87W degrees, the calculation would be
90 - 87 = 3 or 3 degrees east. A positive number means you are
east of the time zone meridian and the negative number means your are west of it.
Now let us deal with the silver dial, and the reticle
pattern. Unlock and rotate the RA axis
until the pattern matches the diagram on
the right and lock the RA axis. Turn the
silver dial so OCT 10 lines up
with 1:20 am. This date and time are specific to the time
which Polaris will best match the reticle pattern as viewed through the polar
finder scope.
Now concentrate on the Meridian scale on the dial.
It has markings E 20 10 0 10 20 W.
Mark the position of 0 on the mount before you do anything else.
I used a white out pen to mark mine. Now adjust the dial to properly set your meridian offset. This is the number we calculated above. In my case it was 7 degrees west. The graphic represents my proper offset with respect to the mark we just made.
Finally, we have performed the proper calibration of the reticle pattern
and the setting circles scales. We are ready to go!I’m polar aligning
my scope on Aug 7 at midnight. Since the finder was calibrated against
UT time, I’ll need to adjust for the difference. There is a six hour offset
from Central Standard Time so midnight is 6am UT. I unlock the RA axis
and rotate the mount until Aug 7 and 6 am UT line up. Then lock the
RA axis.
Now look through the polar finder scope and use the
alignment knobs to place Polaris in the single circle. The Earth’s wobble means that Polaris will not always line up with this reticle pattern. The diagram shows it’s position through the end of the decade.
The image to the right is a screen shot of what Starry
Night Pro shows to be the location of Polaris and the celestial pole on
Aug 7 at midnight Central Standard time (6 am UT). It’s been adjusted to
show the view as seen through the finder scope.
Now that Polaris is lined up in the circle, you should be polar aligned close
enough for short exposure astro photos. I’d estimate you can get two to three minutes at prime focus using film.
