Moving the telescope after polar alignment

[meterman_56]

Ok. I've polar aligned..my scope is pointing at polaris in the north..if I want to see the orion nebula in the south east I just move the scope not the mount..have I got it??

[CaptainShiznit]

Imagine the sky and your mount are both clocks.

Polaris is the sky's midnight and your mount's polar axis is the mount's midnight.

Polar alignment aligns your mount's clock with the sky's clock.

Once your mount and the sky are both pointing at the same midnight, you can slew the telescope to, for example, 3 o'clock and it will point at the part of the sky that you were expecting (using both RA and Dec if necessary)

The mount will also be able to track to 3:01, 3:02, 3:03 in perfect sync with the sky and keep your object centered in view (using only RA).

[CaptainShiznit]

This sort of image also helped me to get to grips with polar alignment. Your polar axis points at the celestial pole in the top right of the image. Slewing the scope in Dec moves the scope along the top right to bottom left diagonal blue lines, while slewing in RA moves the scope along the top left to bottom right diagonal blue lines. Automatic tracking also follows the target as it moves in RA across the sky. If your alignment is slightly off, the slewing and tracking will not perfectly follow those lines and so the target you are observing or imaging will drift in your field of view. If it's a lot off, your targets will not be at all where your mount thinks they are.

Edited February 25, 2020 by CaptainShiznit

[Merlin66]

Hmmm

the diagram seems to show Hour Angle ( the difference between the RA on the Meridian and the RA of the object)

Ever wondered why the RA circle on the mount is movable and can be rotated and locked, whereas the Dec circle is permanently locked?????

Ths is to allow you to set the RA at the Meridian to the local Sidereal time, lock the circle. then move the RA axis to the target RA. Then move the Dec axis to the target Dec. (This is how we did GOTO in the ol' days  )

 

Edited February 25, 2020 by Merlin66

[joe aguiar]

I made a video few months ago cause I have heard new people ask and not understand  

I will PM u a link

joejaguar 

[carastro]

Quote

I've polar aligned..my scope is pointing at polaris in the north..if I want to see the orion nebula in the south east I just move the scope not the mount..have I got it??

Correct.  The polar aligned mount will then track the target.

Carole 

 

[Cornelius Varley]

13 hours ago, meterman_56 said:

Ok. I've polar aligned..my scope is pointing at polaris in the north..if I want to see the orion nebula in the south east I just move the scope not the mount..have I got it??

Correct. This link shows how the telescope is pointed in different directions.

[Astro-Geek]

On 24/02/2020 at 23:42, meterman_56 said:

Ok. I've polar aligned..my scope is pointing at polaris in the north..if I want to see the orion nebula in the south east I just move the scope not the mount..have I got it??

As an alternative to the concise answers given already to this question, I'm thinking about maybe why it has been asked.

When someone tries to use an equatorial mount for the first time it can seem an unwieldy beast compared to the more logical alt az mounts.

When properly aligned to the North polar axis, the act of then slewing the scope round to view objects to the South results in the telescope going through apparently strange acrobatics (to newcomers), so they could be tempted to swing the whole mount round so that at least it still resembles an alt az mount, with the telescope on top and well clear of the tripod legs.

Once the principles of Polar alignment are understood, we understand the need to keep that RA axis constant and get used to things like "Meridian Flip" 🤓

[Bryan_D]

On 25/02/2020 at 13:30, Cornelius Varley said:

Correct. This link shows how the telescope is pointed in different directions.

Thanks Cornelius, your video link really helped the penny drop for me. I had been struggling to understand the concept of PA and then observing to the south. Cheers! 😊