Pointing accurately

[Guest]

I have trouble getting the scope to point exactly where I want automatically.

I use APT, cartes due ciel and eqmod. The mount is an heq5.  I use cdc to drive the scope to the object I want. It gets pretty close but sometimes the object is not in the field. Then I take a picture and do a plate solve through APT and it usually gets a result in a few seconds. Then I click on synch (in apt) to set the scope coordinates  to the plate solve result. Then I go to cdc, click on the object I want again and then click on slew in cdc. The scope moves. This is always a very small movement.  But when I take another picture the object is in the field of view but still quite a way off from centre. I've tried changing the coordinate system in cdc but it doesn't make much difference.  There's also a thing called 'intelligent' but that didn't work either.

Is there a sure way to get the scope to the right direction? I know there is a system in APT and other programmes which will iteratively take a picture, plate solve, make an adjustment until it's bang on target. However I'm sure it's something to do with the coordinate system. I think the plate solving works in J2000 coordinates so no matter how many times I go around the loop the object is still off.

Cheers

Steve

 

[andrew s]

Try centering a star sync on it. Do a slew away then back if it's not centred then you have backlash or other hysteresis which needs to be removed before you can get accurate pointing.

Try different directions for the slew.

I don't  know your system / software so can't be more specific. 

Regards Andrew 

Edited January 23, 2021 by andrew s

[Merlin66]

I don’t use APT but use CdC and EQMod on the NEQ6PRO.

Just make 100% sure all the programs are using the same EPOCH.

Either Jnow or J2000.

Andrew’s suggestion of sync and slew is worth trying.

 

[smashing]

I use point craft in APT and it works a treat...you can always make a custom target with the co-ordinates from the planetarium software and it will put it bang on center

[newbie alert]

Unless both programs are sync'd then they're they're not going to agree.. you don't need CDC or stellarium to point, you can't do it all in APT,  within a few pixels accuracy,  fantastic software

[Guest]

Thanks, Yes I will definitely check the backlash.  I did adjust it a while ago but I didn't want to overtighten it so maybe I left it too slack.