Allego un interessante documento che illustra le due diverse modalità di guida: via ST-4 e via Pulseguide (Ascom); la modalità Pulseguide consente un maggior controllo dei parametri di guida. Il documento fa parte delle istruzioni del driver EQmod, e lo si trova nella sua forma integrale qui:
http://www.welshdragoncomputing.ca/eqmod/EQMOD_Doc_2008.pdfCita:
Guiding
Guiding control of the mount can be accomplished in 2 different ways. The guiding signals can be sent
to the dedicated ST-4 port on the mount or they can be sent to the regular control port on the mount.
ST-4 Port and ST-4 Autoguider port rate
For the ST-4 port, the signal could come directly from the guide camera (if the camera supports that
option) or the signal could come from a separate port on the computer using a relay or electronic switch
box.
If user intends to use the ST4 based Autoguider port found at the faceplate of the mount's stepper
controller, the "Autoguider Port Rate" sets the correction applied on the RA and DEC motors if any of
the four ST4 lines (RA+ RA- DEC+ DEC-) are activated. Possible values are x1.0, x0.75, x0.50, x0.25
of the Sidereal rate.
ASCOM pulse guide settings
For guiding through the regular control port of the mount, the guiding signal uses the same cabling as
the signals used for slewing and GOTO's. The ASCOM POTH (plain old telescope hub) software
allows 2 or more programs to send signals over the same port without conflicts.
Other than ST4 type of autoguiding, EQMOD also provides the "PulseGuide" Method where the
correction commands are fed directly through ASCOM. A pulseguide message contains two
parameters, the direction and the duration. The Pulseguide message currently does not contain any
Guide Rate settings. The correction rate has to be provided by the user by means of two "slider bars" at
the EQMOD setup window. Each bar specifies the speed of the RA and Dec motor during the course of
the pulseguide correction. The Duration parameter (specified in terms of milliseconds) determines the
duration to which the correction speed is applied. Once the duration of the correction expires, the RA
speed is restored to the sidereal rate speed (or in DEC where the motor is stopped )
The pulseguide speed rate can be set between x0.1 to x0.9 of the sidereal rate at increments of 0.1
independently on each motor (RA or Dec).
The "Duration Override" option allows the user instead of the autoguiding application to dictate a fixed
duration correction.
See further information about EQDIR and pulseguiding in the miscellaneous facts section.
Personalmente utilizzo la seguente combinazione: camera di guida Magzero MZ5-m su C8 a f@6, che controlla direttamente la EQ6 attraverso il software PHD Guiding e la porta ST-4 sulla montatura, ottenendo ottime riprese autoguidate (utilizzo subframes da 300 secondi ciascuno con una 350D su ED80 @f/480mm).
Ma non ho alcun dubbio che attraverso il protocollo Ascom Pulseguide, si possa ottenere un controllo ancora più raffinato dei parametri di autoguida............
Saluti da Roberto
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