814 polar alignment finder question

[Roadblock]

I've lost my instructions (and the little card calculator "thingy") that goes with my 814 polar alignment finder.  Anyone out there have one they could make a copy of, or maybe just give me some ideas/advice about how to use it without the thing?  It's been a few years since I set up my scope, and I don't really remember exactly how to do it.  Thanks!

[Mark Sibole]

What mount is this on?

Mark

[Roadblock]

It's on an LXD750.

[Mark Sibole]

OK now the LXD 75 and LX750 are 2 different mounts all together. There was no LXD 750
If you need info on the LX 750 here is a PDF file on it.

http://www.manualsonline.com/manuals/mfg/meade_instruments/lxd_750.html

If you need the manual for the LXD 75 go the Meade site in customer support then users manuals.

Mark

[Roadblock]

Thanks Mark.  I actually have the manual for the mount still.  I lost the "Polar Alignment Circle" (I think it's called), that came with the polar alignment finder that I bought seperately (probably .. 7-8 years ago).   I have a rough idea how to use the thing, I just miss having the little card calculator gadget that tells you where to put polaris in the little ring when looking through the alignment scope.

For what it's worth:  my mount is labelled LXD750, it came with my 152ED Refractor.  I don't remember exactly when I bought it, somewhere around 8-9 years ago.

Sorry for the confusion.

[jrcrilly]

For what it's worth:  my mount is labelled LXD750, it came with my 152ED Refractor. 

The several LXD750 mounts I've owned were also (correctly) labeled LXD750 - as is the manual linked to above. There was never an LX750.

John C.

[Mark Sibole]

I stand corrected.
I got my numbers mixed up
Sorry about that.
Its the LXD 75 and LXD 750
Mark

[Mark Sibole]

try this.

Polar alignment (done at night; northern hemisphere instructions only, sorry):
Wait until you can see Polaris by eye before doing this. If you can't see Polaris, then the polar finder won't help much: it's not got much aperture.

Level the tripod. Aim it approximately north by eye. Attach the mount. Again, don't attach the ota or counterweight shaft. Set the mount to polar home position and then rotate DEC 90 degrees, so the DEC motor is north of the mount. Remove the cover over the scope and the plug opposite it to expose the optical path for the finder scope.

Set your latitude on the latitude adjustment and center the azimuth adjustment (for now).

Calculate the meridian of your time zone. This will be 15 times the offset between GMT and your STANDARD time. Subtract your longitude from this. Now look at (not through) the finder: there's a white line on the finder and a silver scale with black markings. The innermost graduations of the silver scale run from 20E to 20W, near the zero mark on the outer graduations. Move the silver scale so that the white line is opposite the difference between your zone's meridian and your longitude (negative being west).

Unlock and move the RA setting circle (the black scale with white marks) until the zero on this scale and the pointer on the RA casting line up. Lock the RA setting circle. Now it's worthwhile to turn on the illuminator of the finder and adjust the brightness until you can see it easilly.

Using the outer markings on the silver scale and the markings on the RA setting circle, line up today's date (The outer scale has long and short marks. The longest marks represent the beginning and end of each month and the month number is in the gap in between; the short marks are for days.) with the current local time in 24-hour format.

(A sanity-check: in the evening during the month of April, that puts the mount such that the OTA would be BELOW the mount -- which is why you don't want to do this with the telescope on the mount!)

The above procedure has put the little circle in the correct spot relative to the actual celestial north pole for the current date and time. Use the azimuth adjusters (and the latitude adjusters if you must) until Polaris is in the circle. That completes the polar alignment.

Polar alignment took me about fifteen minutes the first time I did it. Now I just check that the silver scale hasn't drifted off the white mark somehow and I leave the RA setting circle locked at zero, since with the Autostar you really don't need an RA setting circle.

Another tip: If you always set up in the same spot, it's handy to mark where the tripod legs go -- then your latitude and azimuth adjustments will only be a turn or two if you've leveled the tripod properly. Since I started doing that, I've been able to get perfect polar alignment in about five minutes.


Mark

[Roadblock]

Thanks Mark! I will give that a shot and let you know how it turns out.

Apparently, unpacking your telescope for the first time in a few years seems to create the same sort of cloud cover as buying a new scope .

[Roadblock]

Finally had a semi-clear night to set up the scope, although clouds to the north made it impossible to see any constellations.  I was able to barely see Polaris in my polar scope, but I must have a different model than the one you're referring to, as mine doesn't illuminate, or have any markings on the "crosshair".  Mine is just a crosshair with a circle (all in black lines).  If I recall correctly, the little gadget I'm missing just tells you roughly where to put Polaris on the circle, depending on the date.  Maybe I can figure out a good way to use a star charting program to calculate something similar and at least get me close.

Thanks again for all of the help, guys!