Polar Alignment Tool for Celestron TripodPosted By Joe Ulowetz |
Hi all,
I've posted several photos over in the CCD forum, but this is my first post here. I have a Celestron Nexstar 5i and have been having great fun with it doing planetary photography over the last user using a ToUCam. One thing I've done is take a series of photos of a planet such as Mars or Jupiter over a series of hours and animate them to show its rotation; I also find the animation helps the eye pick out features better such as Olympus Mons because of the motion. (I am only using a 5 inch after all.)
If the NexStar (or any telescope) is set up in altazimuth mode, then there is field rotation of the image over time. The solution is to set up the mount in equatorial mode. However for my scope that requires an initial 2-star alignment, followed by the special wedge aligment, followed by repeating another 2-star alignment.
To speed up setup, I tried lining up the mount toward the pole by eye (I have the advantage of a moderately bright pole star in this hemisphere), but there is nothing on the Nexstar to help identify the polar axis, and any misalignment on the pole results in a drift in declination during observing. As I'm sure many of you know, it is a real pain to lose your target object at f/30 when the only other tool you have is a red dot finder.
To help with polar alignment, I built the tool shown below. My Celestron tripod has a right-angle featur in its mostly circular outline. A rectangle of wood fits very securely there, as long as the corner is trimmed off to accommodate the rounded corner on the tripod (see the upper right photo, the nearest corner of the wood block). I chose a finder that stood out from its base (Rygel Systems in this case) to be sure it could see past the telescope. I screwed the finder to the wood block, and glued 2 extra pieces of wood to prevent the finder from wobbling.
At first I meant to permanently hot-glue the assembly to the bottom of my NexStar, but the 2nd cold night I took it outside it fell off. The ridge of remaining hot-glue is visible in the photos, and this may actually help with my alignment.
I've found that this tool works very well to repeatedly set up the telescope in polar alignment. Using one hand to hold the finder block against the tripod and mount, it's easy to use my other hand to move the mount around and center Polaris within a fraction of a degree.
Since Polaris isn't exactly at the pole, I should probably recalibrate the finder alignment every few months, but since I observe about the same time each evening it is sufficient to repeat my set up on Polaris.
My astrophoto sessions are now much nicer since I don't have to keep fighting drift in declination from misalignment, and it lets me get set fast.
Comments welcome; I'm interested to see what others have done who have similar types of scopes.
Thanks,
-Joe
I've posted several photos over in the CCD forum, but this is my first post here. I have a Celestron Nexstar 5i and have been having great fun with it doing planetary photography over the last user using a ToUCam. One thing I've done is take a series of photos of a planet such as Mars or Jupiter over a series of hours and animate them to show its rotation; I also find the animation helps the eye pick out features better such as Olympus Mons because of the motion. (I am only using a 5 inch after all.)
If the NexStar (or any telescope) is set up in altazimuth mode, then there is field rotation of the image over time. The solution is to set up the mount in equatorial mode. However for my scope that requires an initial 2-star alignment, followed by the special wedge aligment, followed by repeating another 2-star alignment.
To speed up setup, I tried lining up the mount toward the pole by eye (I have the advantage of a moderately bright pole star in this hemisphere), but there is nothing on the Nexstar to help identify the polar axis, and any misalignment on the pole results in a drift in declination during observing. As I'm sure many of you know, it is a real pain to lose your target object at f/30 when the only other tool you have is a red dot finder.
To help with polar alignment, I built the tool shown below. My Celestron tripod has a right-angle featur in its mostly circular outline. A rectangle of wood fits very securely there, as long as the corner is trimmed off to accommodate the rounded corner on the tripod (see the upper right photo, the nearest corner of the wood block). I chose a finder that stood out from its base (Rygel Systems in this case) to be sure it could see past the telescope. I screwed the finder to the wood block, and glued 2 extra pieces of wood to prevent the finder from wobbling.
At first I meant to permanently hot-glue the assembly to the bottom of my NexStar, but the 2nd cold night I took it outside it fell off. The ridge of remaining hot-glue is visible in the photos, and this may actually help with my alignment.
I've found that this tool works very well to repeatedly set up the telescope in polar alignment. Using one hand to hold the finder block against the tripod and mount, it's easy to use my other hand to move the mount around and center Polaris within a fraction of a degree.
Since Polaris isn't exactly at the pole, I should probably recalibrate the finder alignment every few months, but since I observe about the same time each evening it is sufficient to repeat my set up on Polaris.
My astrophoto sessions are now much nicer since I don't have to keep fighting drift in declination from misalignment, and it lets me get set fast.
Comments welcome; I'm interested to see what others have done who have similar types of scopes.
Thanks,
-Joe
