SharpCap Forums

Hi Robin,

In SharpCap Settings > Plate Solving tab > Configuring Plate Solving there is a check box to offset the mounts position to center the target. The manual continues “This option is recommended if you use a complex synchronization/pointing model in your ASCOM mount as it avoids sending sync commands,”

I have some questions:

I'm setting up a pointing model in the Celestron CPWI software that will contain 8 points. I don't know if this would be considered complex or not. What are your thoughts?

What would be the impact (if any) of not sending sync commands to the mount? Would there be any negative effects on tracking or subsequent goto commands?

Should I always use the offset the mounts position to center the target or are there situations where I should change to solve and sync?

What would be the best thought process to use to determine which one to use and when?

Would you consider adding this option to the Tools drop down for quicker access?

Thanks
Dave

Hi Dave,

this is one of those questions that can really only be answered by trying it and finding out if the sync approach works nicely or not. Exact details of what happens when you send a sync to the ASCOM driver are drive dependent - the ASCOM standard says ..

The way that Sync is implemented is mount dependent and it should only be relied on to improve pointing for positions close to the position at which the sync is done.

That sounds fine, but there are mounts that may not work that way - for instance EQMOD can be configured to treat a sync as a request to add another point to the pointing model. So, the option to do the offset GOTO is there to help deal with cases where the sync doesn't give good results.

Usually, once you have worked out which you need for your configuration then you can leave the setting alone - no need to change it in normal use once it is set properly.

The disadvantage of the offset GOTO approach is that it changes the co-ordinates of the mount when it makes the adjustment, meaning that the mount co-ordinates no longer read out the correct co-ordinates of the target (instead they read out a nearby set of co-ordinates that gets the target into the center of view). SharpCap tries to keep track of this if you use the button more than once, but there are situations where this might not work properly, so a second attempt to center the target might actually move it out of view since SharpCap would end up trying to center the new offset co-ordinates, thinking they were the true target. This also extends to other applications that are linked to the ASCOM driver (like a planetarium program).

So, in summary - try the sync approach first and if it works then leave it set that way, otherwise change to offset and you can then leave it set that way.

cheers,

Robin