Re: Need help with issue in RA guiding and Synchronous Pulseguide


Dear Parijat,

Howard will contact you with an return authorization to send your RA axis for evaluation. That will be the best way to determine the source of the spike.

Clear Skies!

Marj Christen
Vice President
Astro-Physics, Inc
11250 Forest Hills Road
Machesney Park, IL 61115
Phone: 815-282-1513
Fax: 815-282-9847
Please include this e-mail with your response.

From: ap-gto@... [mailto:ap-gto@...] On Behalf Of photonphisher
Sent: Saturday, May 05, 2012 11:30 PM
To: ap-gto@...
Subject: [ap-gto] Re: Need help with issue in RA guiding and Synchronous Pulseguide

Hi Rolando,

I cleared the PEC by using keypad to record with no inputs. Later verified by reading from mount in PemPRO and got flat line. So far so good.
Then made sure keypad PEM state was set to "none". Disabled PEC in AP driver.

Well, I am still seeing spikes in RA guiding with period of worm.

The above shows 3 graphs, totaling in 4-periods of the worm (marked with numbers in red). The spikes are circled on the graph representing RA.


--- In ap-gto@...<>, chris1011@... wrote:

In a message dated 5/4/2012 3:03:43 AM Central Daylight Time,
parijat_singh@... writes:

And just completed running several hours of tests in PEMPro, imaging and
guiding. So far, the issue has not come back. So either there was something
in the gear teeth (which I could not see) or old grease, or the act of
taking the gears out and assembling back with the pinions. Not sure but the
issue seems to be gone now! :)
It is quite possible that one of your various programs turned PEM on even
though you had it off in PEMPro. It could be the keypad sending the command
to turn it on. You should check the setting there. You may have thought that
the problem was a piece of dirt or grit, and after cleaning the problem
disappeared, but it could also be that you actually turned off PEM properly, and
that stopped the problem temporarily (but it will come back once your
software turns PEM on again).

I am still betting that you have a set of data in your PEM memory that
turns the sidereal rate to zero during one of the 2 second data slots. It is not
an uncommon thing to happen. Then every cycle this command will stop the
rotation of your motor for the time period saved in that memory slot. This
random error can occur in the PEM memory even if you did not actually program
it (lightning strike nearby, cosmic ray hit, severe power supply spikes
during startup, etc).

The best way to make sure that the PEM is not causing a problem during
trouble shooting is to set the Keypad to PEM - OFF. Second best way, which I
recommend for you to do, is to set the Keypad PEM to "RECORD", but do not send
any guide commands during the 7 minute record cycle. This will "clean house"
in the memory and replace all data with zeros, so that even if it is
accidentally turned on by one of your various programs, it will not affect the
sidereal rate. Once that is done, and you have established that the periodic
error is normal with no sudden departures, you can do a PEMPro run and record
the new data.


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