ACP PinPoint settings question

[David Sun]

Hi

I am trying ACP out and broadly making good progress - documentation and this forum have been very helpful.

One specific area i am struggling to understand are two of the pinpoint settings on the preferences tab, so can you elaborate more specifically what the following two settings do:

Maximum pointing error (arc mins)
Maximum slew without pointing update (degrees)

My pinpoint solves seem to be working fine but I havent been able to work out specifically what these settings do. Also do the entries have to be whole numbers or not ?

Thanks

[Jim McMillan]

Hi David,

Max point error - if the error for the final plate-solve is greater than this number, ACP will recenter the target. If you are stacking lots of images, you probably want this number to be pretty low. If your mount is of high quality, a number like 0.125 is reasonable (my setting).

Max slew without pointing update - if the slew between targets is greater than this number, ACP will do a pointing update. (Mine is 10 degrees.)

Both of these settings affect how many pointing updates take place. And, you can use decimal #'s.

Hope that helps.

Jim

[David Sun]

Hi Jim

That seems to make sense. Thanks for this - ill give it a try out next clear night

David

[Chris Houghton]

Hello,

Jim McMillan said: "Max slew without pointing update - if the slew between targets is greater than this number, ACP will do a pointing update."

So, if the slew distance is less than that number it won't do a pointing update?

Or, it will always do a pointing update if the pointing error exceeds "Max pointing err."? If yes then the "Max slew without pointing update" would seem redundant so I'm not sure I'm understanding this... is there a help file description of this (I cannot find it).

Thanks,
Chris

[Jim McMillan]

Hi Chris,

So, if the slew distance is less than that number it won't do a pointing update?

Yes, this is correct.

Or, it will always do a pointing update if the pointing error exceeds "Max pointing err."?

This is correct also.

When this is not redundant is when the relatively small slew between targets (max slew without pointing update) is within the max pointing error.

For SN searching or photometry, exact pointing isn't required as long as the target is in the FOV. Therefore, you can have a fairly relaxed settings for both of these parameters. However, for pretty picture imaging where you are lining up lots of exposures, you want these parameters quite tight. In my case, my max pointing error is only 0.15, so the Max slew without pointing update parameter is basically irrelevant for me. But for some, it does improve efficiency as it can reduce the number of pointing updates required - an important factor if doing hundreds of targets per night.

FWIW.

Jim

[Chris Houghton]

Hi Jim,

Thanks for the reply!

I think then that we can just set "Max pointing err." to say 0.5 (arc)min and be assured that pointing will never be any worse than 0.5 arcmin independent of the "Max slew" setting?

Our scope is usually within 15 arcsec pointing so it should not do many updates anyhow.

Thanks,
Chris