Hello,

Please forgive me for the detailed description of what I did yesterday night, but I'd like your comments to verify I correctly used PEMProV2.

I use it on my Losmandy G11 Gemini 4 mount fitted with a C11 at F/10 and a SBIG ST2000XCM binned 2x2, giving me very close to 1"/pixel resolution

I set the camera so that RA move is parallel to X axis, and choosed a mag 4.6 star in Aquarius at 1° declination very near to local meridian.

I used the Calibration Wizard to trail the star and get precise image scale and orientation.

First issue: Despite the star was almost the single one visible in the field at 0.1s exposure time, PEMPro was keeping sub framing an empty region, and of course nothing was working. Moon was close, so that background was high, in the range of 1500, maybe this was the issue?

I used the Star Finder mosaic tool, selected in fact the first frame I was originally in where a single star appeared and this time PEMPro was correctly selecting the star.

I then acquired 8 worm cycles with PEC off (see log file), which show altogether a peak to peak PE of -1.86" to 7.86" amplitude.

PEC curve extraction, removing harmonic 3 which is too close of the 76s non-harmonic error of G11 gear train, keeping harmonics 1,2,4,5 shows a computed PE of +2.5/-3.2 and RMS error of 1.19. Is this correct? This seems low for a G11 mount, and pretty much lower than the peak to peak amplitude recorded over the 8 cycles.

I nevertheless fed the mount with the calculated PEC correction table, and re-acquired 3 worm cycles, that were showing an INCREASED PE. I checked "invert", and loaded again the PEC table into the mount. This time, the recorded PE is +/-3" peak to peak, but again calculated PE curve from the acquired curves show much lower numbers: Fundamental has disappeared, and keeping harmonics 2,4,5 show a residual PE of +1.3"/-1.5" with and RMS error of 0.86". Again these numbers look to me too good versus the acquired data.

Did I use correctly PEMPro? Any advice regarding my usage of the software or the gathered results? Is it normal I had to invert calculated PEC table?

Sorry again for the lenghty post.

Antoine

PemPro-2009-09-29-234622.txt (66 KB, 9 downloads) Data PEC OFF

Hi Antoine,

quote:

PEC curve extraction, removing harmonic 3 which is too close of the 76s non-harmonic error of G11 gear train, keeping harmonics 1,2,4,5 shows a computed PE of +2.5/-3.2 and RMS error of 1.19. Is this correct? This seems low for a G11 mount, and pretty much lower than the peak to peak amplitude recorded over the 8 cycles.

Yes, that P-P looks about correct. Because of seeing when you look at the graph it may look worse than it actually is.

quote:

I nevertheless fed the mount with the calculated PEC correction table, and re-acquired 3 worm cycles, that were showing an INCREASED PE. I checked "invert", and loaded again the PEC table into the mount. This time, the recorded PE is +/-3" peak to peak, but again calculated PE curve from the acquired curves show much lower numbers: Fundamental has disappeared, and keeping harmonics 2,4,5 show a residual PE of +1.3"/-1.5" with and RMS error of 0.86". Again these numbers look to me too good versus the acquired data

I don't think that is unreasonable. It certainly looks like you have a very good mount.

-Ray

quote:

Did I use correctly PEMPro? Any advice regarding my usage of the software or the gathered results? Is it normal I had to invert calculated PEC table?

It seems a few people have reported this recently so it's on my "to do" list to track down why this happens sometimes.

-Ray

Thank you so much Ray for your comments.

I'm impressed by your reaction time to my post, and the fact you personally answered. Hope this activity lets you enough free time to further improve this great software.

Clear skies

Antoine

Hi Antoine,

Thanks! I get an email directed to my phone whenever there is a post here so if I'm not in a meeting, asleep, or far from my computer I will usually answer pretty quickly!

Regards,

-Ray