Does Voyager convert J2000 to JNow coordinates?


#1

Hello,

I have an A-P1100GTO mount and the expected EPOCH coordinates for this mount is JNow. I know the coordinates for target DSOs are in J2000 in Voyager but what if the mount expects coordinates to be JNow, does Voyager automatically convert J2000 coordinates to JNow coordinates before sending JNow coordinates to the mount?

The J2000 to JNow conversion can be useful so the first slew to target DSO since the mount was first powered up can be accurate enough that only one or no retry of centering the DSO can be made.

SGPro polls the mount for EPOCH information and if the mount returns JNow, SGPro automatically converts J2000 coordinates to JNow coordinates before sending JNow coordinates to the mount. It works very well with my A-P1100GTO mount and the DSO is pretty much dead center on the first slew since the mount was powered up.

Thanks,
Peter


#2

I did not understand what you want to say …exactly ! Answers is yes.

The accuracy of pointing depends on many factors, the last is what you have indicated. 99% of mounts use JNow and it makes sense. Some use J2000 because set up like this. Whoever says what he uses can be converted … to the other returns epochUnknow … so it’s not all that simple as one believes. In addition, Voyager can directly use the planetarium to control the mount so let’s talk about levels of complexity and homogeneity that go beyond. Voyager uses arcseconds instead of the primes to handle the minimum error, pay attention. If you do not know a prime is 60 arcseconds.

Your mount has an excellent accuracy, could stay below 18" at first pointing unless you move so many degrees between two place in the sky.

All the best
LO


#3

Hi Leo,

Thank you for your prompt reply. To be on the same page as you, when you said “Answers is yes”, do you mean that Voyager converts J2000 to JNow coordinates before sending JNow coordinates to the mount? In the OnTheFly window, all coordinates are in J2000 so do these coordinates get converted to JNow and send them to the mount?

Thanks again,
Peter


#4

DEpends on mount driver if tell what epoch use yes but you can see on the log on monitor. Default for who say unknown is jnow


#5

Thank you very much. What you are doing is what I expected. A-P V2 ASCOM mount driver always returns EPOCH of JNow.

Thanks again.
Peter