Capturing images with a tracking mount—advanced Geoff Smith

Overview of this talk Polar alignment of an equatorial mount revisited Guide camera setup Software for guiding

Polar Alignment Refresher Approximate polar alignment Use the south polar region https://www.assa.org.au/resources/e quipment-reviews/polar-alignment/

Polar Alignment Refresher Approximate polar alignment Point the eyepiece at Polaris, or more precisely, at the NCP https://www.skyandtelescope.com/ob serving/daylight-polar-alignment/ Can be done in daylight

Tuning Polar Alignment Near the meridian Errors in azimuth dominate Near the horizon Errors in altitude dominate

Tuning Polar Alignment Point telescope at a star near the meridian Tweak azimuth Point telescope at a star (30° altitude) near the horizon Tweak altitude Repeat as necessary

Tuning Polar Alignment Do it manually. Slow but works well. See https://www.assa.org.au/resources/equipment- reviews/polar-alignment/ Numerous free/cheap software programs. Just Google “Polar alignment software” I suggest using PHD for tuning your polar alignment. See a tutorial here https://openphdguiding.org/tutorial-drift-alignment-with-phd2/

Guiding In the old days guiding was done by looking through the guidescope and keeping the guide star centred on the cross hairs for hours at a time, using the hand paddle. Digital makes it easier—do 10 min, take a break, do another 10 min, take a break, do another 10 min, take a break, … … … Then stack the pictures.

Manually guided images with a DSLR 4 x 5 min, 10 x 30 sec 5 x 5 min 3 x 10 min

Autoguiding You will need A computer A guide camera A guidescope or an off axis guider (See Session 4 for details) A USB connexion from your computer to your camera A connexion from the guide camera to the autoguider port on your mount and/or Preferably a connexion from computer to mount (usually a serial connexion, or typically a USB/serial connexion) which enables the computer to control mount movements Guiding software

The ASCOM Platform It is a highly desirable minimum to install the ASCOM platform https://ascom-standards.org/Downloads/Index.htm and the ASCOM drivers for your mount. This enables your computer to control the telescope movements.

Autoguiding software I recommend PHD2 (Push Here Dummy) to begin with, unless you already have another package https://openphdguiding.org/ It is free and easy to understand. Loads of tutorials on YouTube Make sure you look at PHD2, not V1

Autoguiding setup—Camera connexions Connect the guide camera to computer usually via USB Two options Option 1: Connect the guide camera to the autoguider port on your mount using the supplied ST-4 cable. Option 2 (Preferred): Connect your mount to your computer using a serial cable (or USB to serial adapter)

Autoguiding setup—Connect equipment with PHD2 Select “On Camera” if using autoguider port. Otherwise select your mount

Autoguiding setup—Select a guidestar

Autoguiding setup—Guider Calibration The exact orientation of the autoguider, the focal length of the guide telescope optics, and the speed of the motor drive all affect the movement of the guidestar on the camera chip. The software moves the telescope East-West and North-South and notes the effect on the star position. This is guider calibration

Autoguiding—When to calibrate If you are using the autoguider port on the mount and no computer connexion to the mount Every time you change declination Every time you change the guide camera or its orientation You will have to tell the software if you do a meridian flip If you are using a computer connexion to the mount Once near the celestial equator—good for multiple sessions Every time you change the camera or its orientation

Autoguiding setup—start tracking

Successful Autoguiding Autoguiding is not as simple as sellers of software and guide cameras make out. Here is an in-depth article on autoguiding http://acp.dc3.com/McMillanAutoguiding11-2005.pdf Don’t spend too much time on this article at this stage. As you get more experience with the vagaries of autoguiding there will come a time when it will be useful.