To OAG or guidescope, that is the question.

[HarryD]

Hi All

I know this has all been gone over many times, but.......

I have a William Optics FLT 132 f7 refractor on a EQ6 pro mount all driven by EQMOD. Works well. Now want to change the EOS 5DII to a cooled CCD and will require guiding.

I am a bit concerned with OAG and would rather go down the guide scope route.

Andrews Comms has a Long Perng carbon fibre 66mm f6 refractor that I was considering for a guide scope. Should be light and stiff. If I get some decent rings maybe flexure won't be a problem.
I'll use a QHY-5LII as a guider.

Any thoughts?

[graham.hobart]

Hi!
If you could afford a QSI you could get one with the OAG fitted.
Or an SBIG with integral guiding on the filter wheel?
Depends on the money for your new CCD.
I have been quite happy for about four or five years with the guide scope route- having all varieties and combinations in the past. But everybody seems to agree that to take that next step needs either OAG or self guiding.
I bought the SBIG STT with guiding filter wheel but it is a really heavy camera and have yet to get first light due to my new focuser being stuck at customs still!!
Anything that minimises flexion will help.
Have fun
Graham

[Amaranthus]

Interesting topic -- I'm tempted (read likely) to get the QSI 690 wsg-8 with built-in OAG for my next CCD (maybe next year...), and have been musing on what sort of a guidecam I should get to fit in the OAG port.

One option is to use my current Orion SS G3 CCD - it is quite sensitive, albeit perhaps a little heavy for an OAG port?. Another is to get a lightweight and sensitive CMOS camera like the QHY-5LII, but I'm not sure if it will be sufficiently sensitive for use in an OAG. Ahhh, decisions.

I currently guide with a NexImage 5 planetary cam using Metaguide and a guidescope - works well enough, but risks issues with flexure etc. at longer exposures.

[rogerg]

Self-guiding with my ST8-XME is a breeze, until the blue filter gets involved. Brightness of guide stars then becomes a significant issue, to the point that it's only about 50% the time I can guide blue exposures.

Guide scopes have potential for all sorts of flexure issues and other issues stemming from not guiding through the exact same telescope as imaging. I like the idea of OAG where the OAG is in front of or beside the filters.

[Amaranthus]

Yes, the OAG port on the new QSI is in front of the filters -- that problem you mention about the blue (and even worse, NB) filter was what put me off considering an integrated guide chip on the SBIG.

[HarryD]

Is the size (small) of the Sony chip in the QSI a concern?

[Amaranthus]

Well, you can always get the KAF chipped version, or a short FL scope! Me me the 690 will give an excellent sampling and avoid any vignetting on my scopes.

[gregbradley]

OAG all the way. Guide scopes are often problematic. They are OK up to about 800mm focal length then they start to become a bit weak.

OAG is a reliable way of getting round stars. Guide scopes may or may not.

Greg.