Re: RAPAS on Mach2
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I have found the RAPAS to be quite accurate.
It is suggested to have the mount level because if it’s not level in the east/west direction, it means that the reticule would be rotated clockwise or counter-clockwise, depending on which direction the mount is unlevel. If you stop and think about it, you would need to have a significant unlevel situation for it to be a problem. Certainly if the mount “looks” level, then it should be fine.
When I set up in the field, my general workflow is to set up the mount during the day and go through the daytime polar alignment routine. Then, at dusk I use the RAPAS to do a final tweak to the polar alignment. If I do this, and then blink a stack of a whole night’s imaging, there is no noticeable field rotation between the first and last images of the session. The daytime alignment takes me two to three minutes while the sun is up, and the tweak with the RAPAS takes about 30 seconds.
If you are going to image unguided, my suggestion is to do an APPM run before it gets dark enough that you are wasting productive imaging time, so that you can use a tracking model. You should be easily able to get a 100 point, or so, run before it gets really dark. The tracking model will compensate for any residual polar alignment error (which, from my experience with the RAPAS, will be really small, if noticeable at all).
I did do one really good PEMPro polar alignment to check the RAPAS calibration. This is a one time exercise per mount (I have two mounts, so I’ve done it once for each). To be honest, though, I found that just as shipped (without the one-time calibration), the accuracy of the RAPAS is pretty good.
From: firstname.lastname@example.org <email@example.com> On Behalf Of Terri Zittritsch
On Thu, Apr 16, 2020 at 11:17 AM, uncarollo2 <chris1011@...> wrote:
Roland, I didn't expect you to respond. The RAPAS feels like the rest of the kit I have from AP, solid and built like a tank! Being an engineer, I can appreciate it all.