OAG, ZWO or OVL?

[wimvb]

I'm considering going off axis and need advice on which oag you think will suit me best. My current setup consists of an AZ-EQ6 with a SkyWatcher MN190 and at the moment a SW ST80 with ZWO ASI120MM for guiding on top. The imaging camera is a ZWO ASI174MM-Cool.

I find the dual scope solution a bit cumbersome. The mount handles the weight without problem, but the whole setup behaves like a frigate on the high seas. With an oag, I can also manage all the cables a bit better, I think.

I've reduced the number of candidates to two (TS oags are eliminated because of possible stability issues. I don't want to deal with flexure in a system that is to be used to avoid flexure in the first place.)

ZWO:

https://www.firstlightoptics.com/zwo-accessories/zwo-off-axis-guider-oag.html

OVL:

https://www.firstlightoptics.com/off-axis-guiders-oag/off-axis-guider.html

Steve Richards ( @steppenwolf ) has given a very usefull review of the OVL oag (https://www.firstlightoptics.com/blog/blog-53.html), and there are several reviews of the ZWO oag online.

Both Steve and several ZWO reviewers report that the guider turret may wobble slightly, and that it is best fixed in place with some sort of wedge or tape (to thicken the turret). The ZWO guider has the slight advantage that it should attach to my imaging camera and guide camera without the need for further adapters.

So, which one should I get?

[steppenwolf]

Hi Wim, I still use the OVL OAG and it works very well for me with my SXVF-M25C and Lodestar guide camera but I have shimmed the turret with kitchen foil to stabilise it! This is easy to do and, of course, the foil cannot be compressed easily as it is metal.

I hope that helps.

[wimvb]

8 minutes ago, steppenwolf said:

I hope that helps.

Thanks, Steve. It certainly does. But if the ZWO is as stable, then it has a slight advantage as it fits my cameras. Let's see what others have to say.

[Laurin Dave]

Hi Wim

I've used the ZWO oag successfully with my ASI1600 and ASI120, the version I have has the stabilising thumbscrew and allen screw opposite each other on the turret so like Steve I had to shim it for stability. The current picture of the OAG on their website has them perpendicular so I would expect that to be a more stable arrangement.

HTH

Dave

[AKB]

1 minute ago, Laurin Dave said:

The current picture of the OAG on their website has them perpendicular so I would expect that to be a more stable arrangement.

 

Oh, that’s annoying. I recently got a ZWO one with opposing screws, and it wobbles. To me the obvious solution was to make them perpendicular.  Didn’t know they’d actually done that. 

Still, a foil shim works OK. 

Tony

[wimvb]

10 minutes ago, Laurin Dave said:

The current picture of the OAG on their website has them perpendicular so I would expect that to be a more stable arrangement.

 

5 minutes ago, AKB said:

I recently got a ZWO one with opposing screws, and it wobbles. 

So, I guess I should wait until @FLO replenish their stock. 

Thanks for the replies. What about the quality and size of the prism? The sensor of my camera is about the same size as the one Steve used while testing the OVL. Have any of you had problems with suitable guide stars?

[Laurin Dave]

Hi Wim

It was on my Esprit 150 (1070mm focal length) /AZEQ6 with ASI120, I used 1 second exposures (PE awful) and never failed to find a guide star, although away from the Milky Way it did at times require a high gain. 

Dave

[gorann]

44 minutes ago, Laurin Dave said:

Hi Wim

It was on my Esprit 150 (1070mm focal length) /AZEQ6 with ASI120, I used 1 second exposures (PE awful) and never failed to find a guide star, although away from the Milky Way it did at times require a high gain. 

Dave

Inetesting. Why is it no longer on your Esprit 150?

[Laurin Dave]

 

4 minutes ago, gorann said:

Inetesting. Why is it no longer on your Esprit 150?

Hi Goran…  Because it has been replaced by an SX-46.. plus OAG...…  the ASI1600 will go on a newly arrived (and to be piggybacked) Esprit 100...

[gorann]

7 minutes ago, Laurin Dave said:

 

Hi Goran…  Because it has been replaced by an SX-46.. plus OAG...…  the ASI1600 will go on a newly arrived (and to be piggybacked) Esprit 100...

Good to know Dave as I plan to start to use an OAG on my E150  for the autumn?

[Zayvin]

Hi Wim,

I got a ZWO OAG from FLO on Tuesday and it was the newer variant. No stalk wobble issues and it seem to be a well engineered piece of kit. I have yet to test it out on my rig, maybe tomorrow.

Cheers,

Andy

[wimvb]

1 hour ago, Zayvin said:

Hi Wim,

I got a ZWO OAG from FLO on Tuesday and it was the newer variant. No stalk wobble issues and it seem to be a well engineered piece of kit. I have yet to test it out on my rig, maybe tomorrow.

Cheers,

Andy

Excellent. What a great community this is. I got exactly the kind of response, and confirmation, I was hoping for.

[wimvb]

ZWO oag ordered from our trusted supplier.

[gorann]

7 hours ago, wimvb said:

ZWO oag ordered from our trusted supplier.

Looks like it also comes with all the adapters you need - that was not the case with the TS one I bought......

[wimvb]

5 minutes ago, gorann said:

Looks like it also comes with all the adapters you need - that was not the case with the TS one I bought......

That, and the repositioned grub screw (= probably more stable design) were the deciding factors. Hopefully I can still test it this season. Nights are getting awfully short up here. One more month and it's bye bye astrodarkness.

[gorann]

Now I know that I should always consult with SGL before I buy something.

EDIT: I just checked my TS one (that I have yet to use) and it does not feel wobbly so I may be fine.