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AP1100 polar alignment with RAPAS
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O'Neal, Michael
I recently acquired a RAPAS for my AP1100 mount. Setting up the mount where I can view the pole, and using APCC and the RAPAS module, placed Polaris at the indicated position on the reticle. Then, using PemPro, I did a drift run to get an idea of the accuracy of the process. To my amazement, PemPro indicated a pointing error of 42 minutes. Thinking there was something wrong with my settings in that program, I tried drift scans with SharpCap and PHD2. Both programs also indicated an error range of 40+ minutes. Going back to PemPro, I did a new drift run, correcting the mount position in azimuth and altitude, finally getting an error of around 0.1 minutes. A check with PHD2 confirmed the PemPro results. At this point I looked to see where Polaris was now positioned on the reticle and found it was completely off the reticle in the 4:00 direction. I have checked the fitting of the RAPAS to the rear plate of the mount and find no apparent problem with how it fits and no play is noted, even as only two of the three mounting screws provided on the finder attach the unit to the rear plate. Also have reviewed the computer's time and local GPS position. I am hesitant to adjust the rear plate as indicated in the instruction documentation, as this seems to be a large error considering the quality of the equipment, and seeking advice from other users, to see if I am missing something in the setup.
Mike O. |
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Roland Christen
The whole idea is to do a drift alignment FIRST. Then adjust the rear plate to put Polaris into the RAPAS reticle to the place where it shows in the app. This essentially calibrates the RAPAS to your mount. From then on you can use it without having to do drift alignments again. Yes, do adjust the 3 alignment screws on the back plate - that is what you need to do first. 42 arc minutes is not a huge adjustment.
Roland
-----Original Message-----
From: O'Neal, Michael <starman43@...> To: main@ap-gto.groups.io Sent: Fri, Feb 11, 2022 12:45 pm Subject: [ap-gto] AP1100 polar alignment with RAPAS I recently acquired a RAPAS for my AP1100 mount. Setting up the mount where I can view the pole, and using APCC and the RAPAS module, placed Polaris at the indicated position on the reticle. Then, using PemPro, I did a drift run to get an idea of the accuracy of the process. To my amazement, PemPro indicated a pointing error of 42 minutes. Thinking there was something wrong with my settings in that program, I tried drift scans with SharpCap and PHD2. Both programs also indicated an error range of 40+ minutes. Going back to PemPro, I did a new drift run, correcting the mount position in azimuth and altitude, finally getting an error of around 0.1 minutes. A check with PHD2 confirmed the PemPro results. At this point I looked to see where Polaris was now positioned on the reticle and found it was completely off the reticle in the 4:00 direction. I have checked the fitting of the RAPAS to the rear plate of the mount and find no apparent problem with how it fits and no play is noted, even as only two of the three mounting screws provided on the finder attach the unit to the rear plate. Also have reviewed the computer's time and local GPS position. I am hesitant to adjust the rear plate as indicated in the instruction documentation, as this seems to be a large error considering the quality of the equipment, and seeking advice from other users, to see if I am missing something in the setup.
Mike O. -- Roland Christen Astro-Physics |
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Well, Thank you Roland. That is incredibly helpful. I should have known. My new old mount came with a RAPAS and I also noted an issue and was scratching the bald spots on may head. Many to choose from. Thank you very much for the information. Yes, I did not read the instructions. I apologize for that. I looked up the meaning of the capitalized word FIRST in the urban dictionary and it says, read the directions first clown. I do read them some times, but when things seem intuitive I don't. I should have known that a calibration of the position of the RAPAS is required for the first use. |
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Roland Christen
The adjustment should come right in with perhaps 10 thou of screw adjustment. We provide that since we don't know how exactly square each of the rear housings is with respect to the RA centerline. Also, you can easily check that the prism in the RAPAS is properly seated by removing the back cover and taking a look. It should be square up against the front of the housing.
Roland
-----Original Message-----
From: Emilio J. Robau, P.E. <ejr@...> To: main@ap-gto.groups.io Sent: Fri, Feb 11, 2022 2:39 pm Subject: Re: [ap-gto] AP1100 polar alignment with RAPAS Well,
Thank you Roland. That is incredibly helpful. I should have known. My new old mount came with a RAPAS and I also noted an issue and was scratching the bald spots on may head. Many to choose from. Thank you very much for the information. Yes, I did not read the instructions. I apologize for that. I looked up the meaning of the capitalized word FIRST in the urban dictionary and it says, read the directions first clown. I do read them some times, but when things seem intuitive I don't. I should have known that a calibration of the position of the RAPAS is required for the first use.
Thanks again. -- Roland Christen Astro-Physics |
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Hi Michael
It is also worth checking a couple of simple things as well. I have made all of these mistakes before with obvious effects.
Mike AP Polar Align v2.7 - Incorrect position for Polaris  Polar Scope Align Pro Watch - Correct location of Polaris 
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O'Neal, Michael
Thanks Roland, the instructions with the RAPAS said to position the mount as indicated on the reticle without any adjustment. The drifting was done to see how close the pointing was. The reticle did appear to be positioned properly but will look at the prism. I don't have an Apple watch or phone but is interesting to see the error as noted by Mr. Hambrick. Now that I have done a drift polar alignment, I would assume that error will not be an issue once the rear plate is adjusted as indicated in APCC.
Mike O. |
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