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What is the correct The imaging / guiding ratio?


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Hi,  i am just about to make the move into guiding.

I am hoping someone might be able to advise me if my current selection is a good match.

My main scope is a Skywatcher Evostar 150ED,  Focal Length 1200mm

Imaging camera is a ZWO ASI224MC

Guide scope is a Orion 60mm Guide scope,  Focal Length 240mm

The guide camera that i was looking at is a ZWO ASI120mm MC Mini

Using the astronomy.tools calculator,  it gives me a Imaging/ guiding ratio of 1:5

The other option was the ZWO ASI290mm MC Mini

This gives a Imaging / guiding ratio of 1:3.87

 

I am also planing to use the Orion 60mm guide scope and either camera for ShapCap when doing a polar align

So the field of view with the ZWO ASI120mm MC Mini comes out at 1.14° x 0.86°

and with the ZWO ASI290mm MC Mini it comes out as 1.34° x 0.76°

 

The SharpCap manual suggests a field of view in the camera of between 0.5 degrees and about 2.5 degrees

 

Any advice would be greatly appreciated.

 

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With today’s sub pixel guiding software it’s not as important, but anything up to 1:4 is good.....but you could go up a bit more without issue, so your 1:5 would probably be fine...just tighten the settings down a bit in PhD2  👍😀

Edited by Stuart1971
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Thanks for the advice,  yet to use PhD2 yet,  just been watching some youtube videos on it actually.

But i take it the other option,   the ZWO ASI290mm MC Mini,   This gives a Imaging / guiding ratio of 1:3.87

This would be a better pick of the two for my setup?

 

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17 minutes ago, bluesilver said:

Thanks for the advice,  yet to use PhD2 yet,  just been watching some youtube videos on it actually.

But i take it the other option,   the ZWO ASI290mm MC Mini,   This gives a Imaging / guiding ratio of 1:3.87

This would be a better pick of the two for my setup?

 

Yes, but like I say with modern sub pixel software it’s not as important.... 👍😀

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