Tulips anyone?

[RobertM]

Not fussy, thats what you need. +/- half a pixel may show on fainter stars and dimishes their brightness substantially.  BTW 0.0133 sounds like an excellent result.

[Fay]

Stop showing off Chris!

[MarkS]

.0133 at 600mm is an absolutely astonishing result!  But how does that translate into a third of a pixel at 2 meters?

With my C11 on the EQ6 I've got my guiding down to approx 1.3 pixels at 1800mm.  Still got a long way to go ...

[Rocket Pooch]

The pixels on the guide camera are 13microns at 400mm the ones on the imaging camera are 6.45 at 2000mm and the .0133 is the adv of guiding with .025 being the max at 400mm, just work out therefore what the movement at 400mm at .025 is against the smaller pixels at 2000mm and you will get the image scale drift, easy, and no I can't do it in my head so you can work it out for yourself.

[MarkS]

O.K. then.  Working it out for myself I get this:

guide camera pixels are almost exactly twice the size of the  imaging camera pixels.  The imaging camera has 5x the focal length of the guide camera.  Therefore a 1 shift on the guide camera would result in a 10 pixel shift on the imaging camera.

So if .025 pixel is the max error on your guide then on the image you will see 10x this i.e. 0.25 pixel.  Since this is a tiny fraction of the blur caused by the seeing when using 2000mm, I can't believe it would ever be noticeable.

[Rocket Pooch]

It does a little have a look at this, http://farm3.static.flickr.com/2249/2483192672_10d463c6a2_o.jpg

You will see a little elongation.

Chris

P.S. You probably right though, I'm being fussy.