Mini guider scope

[Veloman]

I'm looking at mini guider scopes and notice that a lot don't have the means to align themselves with the main scope. Is this a thing that is compensated for by the software and if so to what kind of alignment error is tolerable?

ATB

Rob

[Albir phil]

I have found as long as the guide scope is mounted parallel with the main scope all works ok I use 50mm WO guide scope with mgn stand alone system,no problems

[bomberbaz]

Can you elaborate on what you mean please, what scope are you referring to and mount, plus is this for visual scope or imaging ?

Edited October 29, 2023 by bomberbaz

[StevieDvd]

A guider scope, unlike a finder scope, needs to be in a fixed alignment with the main imaging scope.  When guiding the target being imaged is not necessarily used as the guide star.  The star chosen for guiding will move the same as the target so essentially no adjustments are needed for the guide scope.

 

[900SL]

The guide scope does not need to be precisely aligned with the main scope. It should be approximately in the same area however.

What is important is ensuring there is no relative movement between both scopes during guiding. The connections should be rigid. If there is relative movement between scope and focuser/camera, or scope to scope, the image will show the drift

With long focal lengths and catadioptric/mirror systems, many choose an off axis guider,  although this can bring its own issues

Edited October 30, 2023 by 900SL

[Veloman]

On 29/10/2023 at 00:59, bomberbaz said:

Can you elaborate on what you mean please, what scope are you referring to and mount, plus is this for visual scope or imaging ?

Hi, the scope is a WO Megrez 80 II, cradled in Skywatcher tube rings and mounted on a CG5 AS GT. The reason that I posed the question is because when I  set the tube rings on my surface plate & measured the machined heights there is a difference of 3 thou". I'm not able to accurately measure the screw hole's but they seem to be OK.

At the moment I'm using the scope  for visual but I've treated myself to an ZWO ASI air plus and a ZWO ASI220 guide- camera with a view to starting imaging.

Many thanks for the replies.

Rob

Edited October 30, 2023 by Veloman
AI predictive text!

[bomberbaz]

56 minutes ago, Veloman said:

Hi, the scope is a WO Megrez 80 II, cradled in Skywatcher tube rings and mounted on a CG5 AS GT. The reason that I posed the question is because when I put set the tube rings on my surface plate & measured the machined heights there is a difference of 3 thou". I'm not able to accurately measure the screw hole's but they seem to be OK.

At the moment I'm the scope is being used for visual but I've treated myself to an ZWO ASI air plus and a ZWO ASI220 guide- camera with a view to starting imaging.

Many thanks for the replies.

Rob

Thanks for clarifying, it wasn't exactly clear. However both @StevieDvd & @900SL have answered in the manner I would have. Basically it's fine. 

[Albir phil]

On 28/10/2023 at 23:55, Veloman said:

I'm looking at mini guider scopes and notice that a lot don't have the means to align themselves with the main scope. Is this a thing that is compensated for by the software and if so to what kind of alignment error is tolerable?

ATB

Rob

As I have said it only needs to be in line with the main scope and you will have no problems .hope this helps🤗

[ollypenrice]

On 28/10/2023 at 23:55, Veloman said:

I'm looking at mini guider scopes and notice that a lot don't have the means to align themselves with the main scope. Is this a thing that is compensated for by the software and if so to what kind of alignment error is tolerable?

ATB

Rob

None of them does. The alignment adjusters you'll have seen were invented for the opposite reason: They allow the guide scope to be moved off axis in search of a guide star. In the past, this was necessary for guiding on a star by eye or when using early and insensitive guide cameras which only picked up brighter stars. They are now redundant and I would far rather have a guidescope bolted down hard than carried in potentially flex-prone adjusters.

Guiding on an off-axis star has one side effect.  If polar alignment is out, the imaging scope will describe an arc around the guidestar. If you guide on a dead central star the chip will rotate on its centre point.  If it's off axis it will describe an arc.  If shooting in old-school 30 minute subs, polar alignment is critical. Since CMOS cameras use only short exposures, and since stacking software will easily align slightly rotated subs, polar alignment is less of an issue.

Nutshell: guidescopes don't need to be precisely aligned, as everyone has said. They do need to be rigidly mounted.

Olly