[marki]

I have used quite a few guiding options over the years and will try to list some with my own insights of their effectiveness. All of these were used bar the last with a QHY5 (same as the orion guider).

A meade series 5000 80mm F6 apo.

This gave good results but was a little heavy for the task. The FOV was great and I never had difficulty finding a guide star. It did show signs of flexure unless I bolted it down in a fixed position (no adjustable guide scope rings). To overcome the inability to point the scope I used the orion XY guide star finder. I liked this alot but again weight is a killer and the setup was over the top.

William optics ZS 66mm F5.3 doublet.

This also worked well giving a wide FOV and finding guide stars was never a problem. Again this needed to be nailed to the main rig to avoid flexure so I also used the XY star finder on this. Problem was the focuser had a bad habit of coming loose sometimes delivering interesting guiding corrections. Again over kill.

Stellarview F60M3 finder scope.

I liked this setup as the finder had an adjustable focuser to which meant easy focusing and it only weighed about 380g. Wide FOV meant guide stars were easy to find. Only problem was the mounting system allowed lots of flex to creep in and if fixed solidly to the main rig, it did not have enough back focus for me to use my XY guide star finder. Still a good option.

Orion off axis guider

Not good as it had way too much slop in it and I put it aside quickly.

TS Optics OAG9

This is a great little unit as it only takes 9mm of back focus out. I got my roundest stars using this unit but it does have some flaws. The prism is very small meaning the QHY5 was not really sensitive enough unless the guide star was bright and it only offers a very limited FOV. This is compounded by the very restricted movement of the prism which means you have to re-orient your framing to suit a good guide star, not ideal. As I said this unit delivered my best guiding results to date but is a bit of a pain to use and can be very frustrating if your imaging time is limited and you do not have a permenent setup.

SBIG ST-i with lens kit.

Although I have used the ST-i with the OAG and stellar view (excellent sensitive guider) I am yet to use it with the lens kit due to weather and time restraints. It is a small compact unit with the kit fitted offering a wide FOV (about 1 brick wide by two deep (pointed it at a wall)) so I don't expect finding a guide star will be a problem. It is easy to focus and comes with a very rigid mounting system so hopefully no flex. Best of all it is very light and compact so will be easy to mount any where on the rig to aid in balancing.

The ability of software to precisely calculate the centroid means a fast scope is best as the mount will still correct and you get the widest FOV to find a guide star. Most guide camera's use tiny little pixels so you are unlikely to loose much with a fast scope. I have used the above to guide up to F8.


Mark