Resetting El and Az Encoders

Modified Version of the Procedure Using Absolute Encoders.Jan 9 2010, David Gonzalez-Huerta

1. Slew the telescope to AZ 120 deg and EL 90 deg

2. Go to the Encoders page on MCSPU,

enc

3. Use the loadfromabs commands to update the motor encoder incremental positions from the absolute encoders.

elloadfromabs

azloadfromabs \xA0

Special modified Elevation procedure from T. Sargent on 15-Jan-2009 (Obsolete)

For the time being, encoder resets should only be done at zenith AND that EL encoder 0 should not be used for the reset operation, but should be used for telescope pointing. So, this changes the reset operation. The T.O. should follow these steps:

• 1- disable EL encoder 0: 'elencdisable 0'

• 2- do the encoder reset with encoders 1 and 3 enabled. That is expected to complete successfully.

• 3- do a elslewtohold to a nice round, nearby number like 85 deg.

• 4- do an 'elload 85' command to set all 4 encoders to 85:00:00.

• 5- All are reading the same now, so encoder 0 can be re-enabled: 'elencenable 0'

Historical Regular procedure using the fiducial markers on the motor encoders

Take the telescope to elevation 3 and azimuth 177 using the elslewtohold and azslewtohold commands on the MCSPU.

Then go to the encoders page typing enc

Type the following commands to start the reset:

azencreset 177 2

elencreset 3 2

If the telescope has lost its position, you will have to load new values to the encoders.

To do this, switch to velocity mode by typing first

elvelmode

Load the new values by typing

elload degrees

or

azload degrees

be careful to be in vel mode and NOT in pos mode before loading values to the encoders.

Go back to position mode by typing

elposmode

or

azposmode

Then type,

elencreset 3 2

This time you should expect the reset process to succeed.

If some of encoders are disabled, like for example

M0 r : 120:00:00 Dis/unk

you will need to enable it by typing,

elencenable 0

In this case encoder 0 is being enabled. If the commands succeeds, the same line will look like this,

M0 r : 120:00:00 En/unk