How to chose a guiding setup?

[hjw]

Hi,

I have started to look into guiding for my SW 80ED. How would I go about choosing a guide scope/camera to match what I've got.

The pentax has a pixel size of 4.8µm. I am thinking to get a SW Startravel 80 (80x400mm f/5) as a guide scope and a ZWO ASI120MM guide camera (3.75x3.75µm pixel size). If a star travels 1 pixel (3.75µm) on the guide sensor it will travel 5.6µm on the Pentax sensor which is more than one pixel.

My question does it actually matter? Do I need a longer focal length guide scope? Or more basically, are there any guidelines on how to match the different pieces together?

Thanks in advance

HJ

[Marky1973]

Hi HJ

I'm not really sure about pixel sizes etc etc, but I use an ST80 on top of my ED70 with an ASI120mm and it works fine - not had any major issues finding a guide star until recently - but I think that is more to do with light pollution, not very dark summer nights and the encroaching full moon.... I struggle to get it working with PHD and PHD2, but found it worked okay with Metaguide. I have managed 10 minute subs with the set-up....not sure I'd actually ever need them with this current set-up, but it was nice to know I could! :-) Normally around 4-6 minutes and it works a treat (in my eyes).....

[DaveS]

PHD and PHD2 (Possibly all software) guides to sub-pixel resolution. My own set-up has the ubiquitous ST80 coupled with a QHY 5 II with 5.4 micron pixels guiding either a Megrez 90 or 130P-DS (621 or 650 mm) and SX694 camera with 4.5 micron pixels with no problems apart from me.

My understanding is that the arc sec per pixel of the guide camera should be less than 4 times that of the imaging camera for good guiding.

[hjw]

Thanks, so my view was a bit simplistic then and and it turned out to be much ado about nothing. Now I will see whether I can work out the FOV per pixel  . Since it seems to be a common combination it should be fine however I like working things out to gain a deeper understanding.

Much appreciated!

HJ