Dave Grennans new scope

:lol: :lol:

Scuse my ignorance :oops: , but the ST4 is the scope piggybacking on the new & impressive Celestron, right?
What exactly is it's purpose?
Will it allow two different procedures to run simultaneously?
It's a little too big just to be a finderscope... :

The scope piggybacking is indeed a 5" mak skywatcher guide scope.

The ST-4, which is actually behind Dave on the table is a SBIG autoguider.

You plug it into the guide scope and the mount, centre a star, and it automatically and very acuratly guides the scope for you.

Makes astrophotography so much easier

Later,

Jed.

PS you should see it now, being held by a pair of very business like Losmandy 6" rings.

As Jed mentioned, the scope on top is a 5" maksutov cassegrain which is primarily used for guiding photographs, but is also a great little scope itself. The SBIG ST4 autoguider (belongs to jed) is effectively a CCD camera which is plugged into the guidescope and has a stand-along box of electronics which looks at frequent images (of a star) coming from the guidescope and sends tiny corrections to the mount when the mount encounters small tracking errors (and the guidestar moves( which would otherwise make the stars in a photography look elongated or even like little lines.

The problem I had was the guidescope weighs 7lbs and was mounted on what is effectively a camera bracket which allowed both telescopes to flex a small bit with respect to each other during photographs, effectively negating all the good work the ST4 does, also it restriced where the guidescope could be pointed making it extremely hard to find a decent guidestar. The solution arrived on my doorstep yesterday. Its a set of losmandy guidescope rings and a mounting plate which now bolts to the main scope and is extremely rigid. The guidescope rings have three adjustment thumbwheels allowing my to offset the guidescope a couple of degrees in any direction making the process of acquiring a decent guidestar a whole lot easier and eliminating flexure at the same time!

The SBIG ST4 autoguider (belongs to jed) is effectively a CCD camera which is plugged into the guidescope and has a stand-along box of electronics which looks at frequent images (of a star) coming from the guidescope and sends tiny corrections to the mount when the mount encounters small tracking errors (and the guidestar moves( which would otherwise make the stars in a photography look elongated or even like little lines.

OK. Does this system bypass the built in scope guiding software all the time, or just when needed?
And if so, is the scope software not good enough to provide accurate tracking to begin with?

OK. Does this system bypass the built in scope guiding software all the time, or just when needed?
And if so, is the scope software not good enough to provide accurate tracking to begin with?

Hi Paul,

The average mount tracks OK for visual needs however if you are photographing you need the tracking to be much more accurate.

So the ST-4 guides out the errors inherent in the mount, the main error is usually periodic error in the RA worm gear, and sometimes DEC errors due to less than perfect polar alignment.

Later,

Jed.