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Guide scope spec

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3 replies to this topic

#1 DaveySnaps

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Posted 28 January 2020 - 01:52 PM

Hi all.

Its been a while since I was last on here but have just picked up a new (to me) scope and want to match it with a guide scope thats properly sized.

 

Scope is a Willams Optics Zenithstar 2 ED Doublet F6.8 - f:545mm. I'll be using a 0.8x flttener with it and have a QHY5LII guide cam

Mounted on a HEQ5 Pro mount

Expect to use PHD guiding

 

What / how best to calc guide scope focal length given above setup ?

 

Thanks

Dave



#2 SonnyE

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Posted 28 January 2020 - 02:41 PM

Guide scopes do not have to be too big. Remember, they are typically wide-field, and PHD2 only needs to lock onto a single star.

I use an Orion MMAG. But I bought the camera, tried to use an OAG (Off axis Guider) (two, actually) and finally bought the 50 mm guide scope. All problems solved!

If you are using some outrageous SCT, then a more refined (bigger) scope for guiding would be good.

Somewhere I ran across a guide about Guide Scope Vs: Telescopes. But the bottom line is: In reality, the guide scope needs to show you some stars, and PHD2 can Auto-Select a good guide star.



#3 ryanr256

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Posted 28 January 2020 - 04:04 PM

The WO 50mm guide scope has a focal length of 200mm (f/4) if that helps.

-Bob


Edited by ryanr256, 28 January 2020 - 04:11 PM.


#4 t-ara-fan

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Posted 28 January 2020 - 04:38 PM

 

What / how best to calc guide scope focal length given above setup ?

 

Any 50mm-60mm aperture guide scope would be fine. I use a MMAG (50mm aperture, 163mm FL) with my 480mm refractor and they are well matched. 
 




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