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Posted (edited)

Hi Guys

Recently started using a used EQ5 Pro after upgrading from an AZGti. 

I aligned the polar scope with the adjustment screws on a TV aerial in all axis following a tutorial I found online, so i'm sure that's correct now. It was way out and the crosshairs didnt line up when rotating 90deg.

I have a 72ED with a Canon550d attached to the EQ5. It is attached with 2 tube rings to a dovetail bar then clamped into the EQ5.  I polar align with the built in polar scope and get it spot on as best I can. However, When looking through the Canon viewfinder polaris is nearer the bottom of the screen.  Should this not be near the middle similar to the polar scope?  ie: should I be aligning the telescope with where the polar scope is pointing? Or does it not matter? Because when I come to doing a 3 star alignment on the mount i'm centering the alignment stars in the Canon window.

Regards

Ray

 

Edited by TerraC
Posted

I dont know about astrophotography but if you have aligned the polar scope up with the mount like you said on a TV aerial to check put the end of the aerial on the ring in the polar scope either you or someone else rotate the weight bar and make sure the end of the aerial stays on the circle all the way around.

if you use android download Synscaniit from here https://synscaninit-2.soft112.com/    that will show you everything to put in the handset and Polaris position once you have done that do your 2 or 3 star alignment and it should be accurate.

Paul

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Posted

It doesn't matter. As long as its RA axis points to the NCP, the mount will be able to track objects regardless where the telescope is pointing at.

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Posted

As long as the polar scope is well aligned with Polaris that’s the important part for accurate tracking. The view not lining up with Polaris in your telescope is due to cone error in the telescope mount.

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Posted

Thanks guys.  

I've heard it said to align the mount rather than the scope. I've also seen people using sharpcap to polar align. If this is used will that not be out compared to the axis and polar scope on the mount? Or am I missing something here? If you sharpcap align do you need to make sure you are guiding?

Planning to add guide scope and astroberry over the summer - ready for next season.

thank you

Ray

 

Posted

Don't forget that when you polar align you are not centering polaris in the eyepiece. Just to prove this you could center polaris in your polar scope and it should ideally be centered in your eyepiece. Then go on to polar align using your polar scope and you will see polaris shift in your eyepiece to the PA clock position.

Posted

Ray, don't get hung up on polar alignment using the polar scope.  Its design is still open to error (the circle in which Polaris is placed is so large you could be a few arc minutes off depending where in the ring Polaris is placed).  In an ideal setup you would have the polarscope centred in the mount and then once the mount is polar aligned ensure that any cone error is removed so the scope and RA axis are as for all purposes parallel.  The if using a guidescope it is then set so it's axis is also parallel to the main scope.

The reason I said don't get hung up on getting the polarscope perfect is because of you go down the imaging road you end up plate solving to get the PA set and then for any imperfections between the mount and scope (or guidescope) you use something like PHD2 to guide on a target star.

If you still want to get the polarscope set, then the tip above about placing the tip of a landmark on the large circle and rotate the mount, making adjustments as you rotate the mount so the ring remains on the landmark will ensure the polarscope and mount axis are parallel.  Taking this a stage further, remove any cone error by swinging the mount with scope attached until a star (ideally polaris) remains in the centre of the field of view when the mount gets rotated back and forth through 180 degrees, adjusting the small set screws in the cradle to tilt and angle the scope.  Finally, align the finder / guide scope so that it too has the target star central when the mount is flipped through 180 degrees.    You could then use the excellent plate solving PA tool in sharpcap to ensure the RA axis is perfectly aligned with the Earths axis, which should then mean that PHD2 shouldn't have to work hard tracking a target star. 

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