Off axis guiding vrs finder guiding

[Robp]

Hi all,

I recently picked up a used Atik one 6.0 with the off axis guide camera.

I have not had a chance to use off axis guiding yet, but wondered if there were any pitfalls to using one?
I have only ever auto guided using a camera/finder setup, currently a QHY5L-ii C camera and evoguide 50ed guide scope combo. I would like to move the least preferable method on to free up some funds for other stuff.

I have three scopes that the current finder setup is swapped between:
WO Star 71
SW 130pds
SW 200p

So which should I keep and why, (or should I keep both?). The off axis guiding seems easier as it moves with the camera, but I'm wary of moving away from something that works well and I'd lose the ability to guide other cameras. The finder guider has been good to me and I can get 15-20 minutes subs with it so I'm torn?

[TheMan]

I don't currently own a guide system, but if you live in horrible skies like me, I don't think off axis guiding will produce enough light to use. But if you live in darker skies it should be pretty good and it would be much easier to use since you don't have to align it with the scope. 

[ollypenrice]

Off axis guiders can be a bit hit and miss with regard to playing nicely or not and they do take more setting up. My feeling is that when you need them (on anything with a mirror which might move or with a long focal length) you should certainly use them. But for small refractors I'd far rather guide with a guidescope. Do you have enough backfocus with your reflectors?

Olly

[Ibbo!]

On a recent test of both with the FS102 @820mm fl I found that the OAG was slightly better although all the clear subs from both FG & OAG went into the mix.

[spillage]

I nearly went down the oag route a while back. I decided that whilst it may help with reducing weight and flex the extra weight hanging off the focuser and the fiddly setup may causing more problems and as long as my guide scope is bolted down its fine. I therefore decided to hang onto my st80's.

If it ain't broke don't fix it.

[Robp]

Cheers all for the quick replies.  I think I'm going to stick with the finder and look into selling the OAG/GP cam. 

The finder guider works fine, can be used with other cameras if I want to, and I didn't think about the balance factor as it is mounted on a dovetail in a way that can be easily moved forward to offset the weight of the camera hanging off the back.

Thanks!

Rob

[kirkster501]

... there are other complexities with OAG as well. If you use autofocus then when the AF runs it can throw the guiding off.  It can be fiddly to get focus right as well.  But when you do get it working it is great.

I am running OAG on both my rigs but, TBH, I find it a PITA, fiddly and temperamental and I am going back to guide-scope I think.  My TEC OAG setup just has a wobble every now and then for absolutely no apparent reason.  The ONE good thing going for OAG is its lack of differential flexure, but, I think that problem is much overstated.  In an obs setup then if you can get everything bolted down thoroughly , cables managed properly then there ain't no differential flexure....

[Jbro1985]

There is a lively discussion on this here:

Ultimately, reading it back, to me the thread indicates that it really comes down to whatever works for you in the situation you're in. 

Since that is so variable, and made up of so many variables (equipment, location, sky quality etc.), there is a broad spectrum of advocates for the OAG and advocates for the Guidescope.

Each can eliminate problems of one sort or another and introduce problems simultaneously.

I use an OAG - it works for me.  I personally think that they are better suited to non-permanent/ non semi-permanent setups, but only if you're not interchanging your main cam regularly.  One day when I get an obsy, etc. I may change over to a guidescope for the reasons that Olly Penrice mentions in the linked thread.