CCD question - when is an autoguider an autoguider

[Gem]

A CCD camera, like say the ATIK 16ic, is both an autoguider and a CCD camera. Does this mean it does both at the same time? Or do you need two to have one guiding and one taking the image? Does it do one for a few seconds, then the other for a few seconds?
Sorry for all the newbie questions over the past few days... you are all just TOO helpful and make me want to know more!!!

[tlgerdes]

Autoguiders will have a CCD or some other image capturing device. An autoguider is a camera device that has a direct output for connecting to and autoguider port on a telescope mount. The most common of the ports conforms to SBIGs ST4 format.

You can use other methods for autoguiding a telescope though. These will often involve using a computer with software as a proxy interface between a camera and a telescope control port. Camera detect picture, computer processes picture and computer issues dorectional corrections via another hardware interface to the telescope mount.

A lot of modern astronimical CCD camera have an autoguider output on then as well. and can be used by a computer as the control interface to issue movement commands to a telescope mount via the output port.

A true "Autoguider" is a camera that is self contained and can select stars and issue guiding commands to a telescope in one unit. Most "autoguiders" though nowadays are a hybrid of software/hardware with a camera capturing images, a PC software control interface for selecting stars and the issuing guide commands is done via a PC through a dedicated port in the guide camera.

[dannat]

I think the atik is a ccd, that can be used as a camera & for guiding, but not at same time unless you have off axis guiding setup

[Gem]

Thanks Daniel. That clears it up. So you would need two units to both autoguide and take a photo at the same time?

[higginsdj]

The starlight xpress ccds are the only self guiding single chip ccds that I am aware of. Sbigs range has an additional ccd built is (as do the sbig clones).

In this modern age, true autoguiding can be done in software, such as ACP controlling Maxim so any camera setup will usually suffice, but in the case of the Atik, you will either use the camera as the main camera or as the guider, not both.

Note that off axis guiding is a means of 'extracting' part of what the telescope sees and making it available for a second camera or ccd chip.

Cheers