Really basic question about guide scopes.

[SmokeyJoe]

Current kit is :

SW Ed80 Ds Pro, Eq5 goto, Cannon 450D and an Asiair Pro. 

Next step is to sort guiding, the cheapest way for me to do this is to purchase a Zwo ASI120mm mini, and use my existing SW guide scope.  My question is this....

Given my current setup what difference could I practically expect between the following guidescopes

My current bog standard SW guide scope. 

The Zwo 30mm f4 mini finder/guider. 

The SW Evoguide 50mm f4.8 finder. 

Is it worth spending the extra cash given my current equipment?

[knobby]

Many people use finder guiders successfully so I'd buy the finder guider adaptor and use the 120mm with it.

[SmokeyJoe]

Thanks Knobby, this is my preferred option (the cheapest) just wondering about the others. Luckily I already have the adaptor from a previous equipment path I was going down.  

[Grierson]

21 minutes ago, knobby said:

Many people use finder guiders successfully so I'd buy the finder guider adaptor and use the 120mm with it.

+1 

[rnobleeddy]

Assuming it's a 9x50 finder?

YMMV, but I used a 9x50 finder with a Zwo ASI120 and an EQ5, and the EQ5 was the limiting factor in guiding performance. 

[SmokeyJoe]

1 hour ago, rnobleeddy said:

Assuming it's a 9x50 finder?

YMMV, but I used a 9x50 finder with a Zwo ASI120 and an EQ5, and the EQ5 was the limiting factor in guiding performance. 

Going to be a while before I can upgrade the mount. No point spending extra cash for no gain. Better off putting it in the new mount savings jar. Spent far too much money in this hobby going down the wrong path. 

[symmetal]

I have an AZ-EQ6 rig with a WO 50mm f4 guidescope and ASI120, and an HEQ5 rig with the ZWO 30mm f4 mini-guider and ASI120. Looking at the PHD2 graphs there is no difference between them. Both will guide within +/- 1 arcsec when conditions are good.

I'd recommend the Zwo mini-guider, but if you can adapt your current guide scope I think it would work just as well. Your mount and setup will more likely be the limiting factor in guiding performance, rather than the guide scope. 🙂

Alan

Edited October 1, 2020 by symmetal

[fwm891]

I use a 9x 50 guide scope with an ASi120MM, not with an EQ5 but with a CEM25P it just works. The 50mm aperture will give brighter guide stars than a smaller aperture. Like most things in astronomy - size matters...