Off Axis Guiders?

[AlexN]

Agreed Steve, the Lodestar is by far the best autoguiding camera for using with an OAG... I'll be getting one of them as soon as I can afford it..

[Merlin66 (Ken)]

I've used almost every OAG available over the years. Never found the Holy Grail but a couple came close.
For 2" focusers (and or Newtonians etc) the Lumicon Newt OAG is very good. It has a large movable pick-off prism.
For SCT threads, the Celestron Radial guider is hard to beat. Allows almost 120 degree rotation of the prism without moving the camera.
OAG is very different from using a guide scope, but when mastered will give much better results.
BTW I use a QHY5 for guiding, and a Vixen flip mirror system modified to a 70/30 beamsplitter for spectro work.
Hope this helps.

[marki]

Originally Posted by multiweb

Not familiar with the LX200 but I'd assume that if the primary is heavy and designed to move in anyway to get focus bearings or not it would move to some degree. All high end gear seem to have all optical elements linked in a rock solid truss/tube system. The only moving part is the focuser.

The LX 200 has a mirror lock. You adjust coarse focus then lock the mirror via a second knob. I have a crayford behind this so once I am in the ball park the mirror is locked and the rest done on the crayford. If you look closely at where your mirror moves on the baffle you will see a gap stuffed with grease which is used to prevent mirror flop. If this was changed to roller bearings it would reduce much of the slop present in the standard systems.

Mark

[RodM (Rod)]

On the subject of guide cameras - I use a Imaging Source DMK21 USB camera and find it great. I bought it with the intention of also using it as a plantary imaging camera (inspired by IceMan), but haven't as yet gone there. Using a WO ZS66SD as the guide scope I've never failed to find a guide star at 1 second, and generally guide at 0.5-0.7 sec exposures.

I was imaging M104 the other night and could actually make out a blur of the core of M104 itself when guiding at around <1 sec.

[Bassnut (Fred)]

Guide exposures in urban skies less than 2 secs is not a good idea, your then chasing seeing, which no mount can follow without AO. A jumpy star at 0.7 seconds will give erratic guide corrections, 2 secs smooths them out.

[Matty P (Matt)]

Originally Posted by Bassnut

Guide exposures in urban skies less than 2 secs is not a good idea, your then chasing seeing, which no mount can follow without AO. A jumpy star at 0.7 seconds will give erratic guide corrections, 2 secs smooths them out.

I find the shorter exposures I use when guiding, the better results I get. I tend to use 0.5 second exposures and when guiding on a moderately bright star. I get fairly decent results.

I don't think seeing conditions make too much difference in short focal length scopes though.

Back to OAGs, I have looking at the Lumicon GEG and would anyone recommend it over the Orion for any reasons?

[Merlin66 (Ken)]

I used one for many years. I don't think they are currently available from Lumicon.
If you're using, say, a 10" or 12" LX200 the "Eyeopener" adaptor gives an increase in FOV. The built in 3" compressor lens is OK but certainly not as good as a dedicated reducer like an Optec. If you can find one at a good price certainly a nice piece of gear. I replaced mine with the Celestron Radial.
BTW getting the guide camera in focus... usually needs either a 50mm spacer or better a cheap PRISM diagonal between the OAG and the guide camera.
As I mentioned before the Lumicon Newt OAG is good for 2" focusers and it has the same pick off prism adjustments as the GEG.
Hope this helps.

[srchadwi (Steve)]

Originally Posted by Bassnut

Guide exposures in urban skies less than 2 secs is not a good idea, your then chasing seeing, which no mount can follow without AO. A jumpy star at 0.7 seconds will give erratic guide corrections, 2 secs smooths them out.

In general I agree (well, it's about 1 second minimum for me for normal guiding). As it happens I do use AO and that's why I guide at 0.1 seconds. I was just pointing out how sensitive the Lodestar was.

Steve

[Moon (James)]

In general I agree (well, it's about 1 second minimum for me for normal guiding). As it happens I do use AO and that's why I guide at 0.1 seconds. I was just pointing out how sensitive the Lodestar was.

Steve

Steve

I don't want to hijack this thread, but I would be very interested to know a little about your AO setup (perhaps in a new thread?)

[srchadwi (Steve)]

Originally Posted by Moon

Steve

I don't want to hijack this thread, but I would be very interested to know a little about your AO setup (perhaps in a new thread?)

Hi James

I've started a thread "AO"

Steve