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POLAR ALIGNMENT QUESTION

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#1 drexelpbp

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Posted 08 August 2009 - 10:29 AM

This may be a stupid question, but .... Is there any way to polar align an equatorial mount if Polaris is blocked by a building or tree?

I am asking because I just received my Mallincam and an Orion Sirius mount, however my backyard does not have a view of Polaris. Obviously when I get a chance to go to a darker location this won't be a problem but at my location it is.

Is there any way to do this with enough accuracy to use the MallinCam?

Thanks for any help with this.

Gary

#2 jim molinari

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Posted 08 August 2009 - 11:13 AM

Gary ...
I would recommend purchasing a reasonably good compass. I assume your mount has a bubble level that can be used for reference? If not, use a small flat level and level in 2 directions. Take your mount/telescope to a place where you can polar align using Polaris that is nearby your backyard. Level the mount and accurately polar align. Then use the compass to determine magnetic North and observe the offset between the compass needle at N and the direction your telescope is pointing (true North is slightly to the left). Maybe you can mark this offset (black marker) on the compass? Also record (or mark ... pencil mark or tape?) the declination setting on your mount ... this scale is adjacent to the Sirius label. Once this is done, you can set-up the mount/telescope in your yard using the compass to point the direction (mount/telescope pointing slightly to the left of magnetic North). And, if the mount is leveled as before move and the Declination scale reading the same, you should be very close to polar aligned. I would think you should have no problem with Mallincam exposures in the 14 second or longer range.
Even though I am always able to use Polaris, When traveling to my observing sites, I use this method just to place my mount during the daytime hours before observing. I find it puts Polaris well in the field of my polar scope when it is dark enough to see for a more accurate alignment.
Jim Molinari

#3 tommyhawk13  Happy Birthday!

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Posted 08 August 2009 - 11:22 AM

Yeah, the drift method, if you have a reasonable clear view of the East, or west.

It would take some time, considering how far off you might be in the beginning, so I'd suggest setting up in the same spot every night, and mark the ground where the tripod legs go once you have it figured out.
Start off with Jim's method, and go from there.

#4 EricLashley

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Posted 08 August 2009 - 11:27 AM

I've used this crude method to get a close enough alignment to do some short exposure pics. I've since cut a few trees down. I took my mount (minus counter weights and OTA) to a location close to home where Polaris was visible. I assume your skyview came with a polar alignment scope. Center Polaris as best you can. Unlock the clutch so that the counter weight bar moves freely. Rotate until you make a line between Kocab and Polaris. Take a marker and place a mark on your counter weight bar to match the position of Kocab then mark Polaris location.
When you set up in your yard point your scope as due north as you can. Unlock clutch and rotate your counter weight bar until your mark get near Kocab ( hopefully it will be high enough in the sky to clear the tree). Make adjustments to your fine Azimuth Knob until you your mark is aligned with Kocab You should have a halfway dissent alignment. Its better than aimming north anyway. When doing this myself I could get 30 sec exposures before star trails became evident. Good luck!

#5 drexelpbp

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Posted 08 August 2009 - 11:52 AM

Wow - Thanks for all the great advice.

I'll try these methods and let you know how it works.

Thanks again

Gary






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