What is good guiding ?

[Catanonia]

CCD selector tool mentions that under sampling is ok if you have “good guiding”

• What is good guiding?
• is 0.3 RMS on PHD2 considered good guiding ?
• What RMS would be considered good guiding

 

in my case imaging at 1340mm and 2000mm FL if that is relevant 

thanks

Edited March 27, 2022 by Catanonia

[Same old newbie alert]

If you're setup dictates that you need to guide at .3 then you're on the limit

But that's only if you believe those sampling tools are correct

If you're guiding in PhD, if using the ASI air then who knows what scale they use

And if you're talking in pixels or arc sec

Remember it's guiding on your guide cam setup not your imaging camera

In truth, you can't image under your sky conditions, that's the limiting factor

 

Edited March 27, 2022 by Same old newbie alert
Added info

[bottletopburly]

Are you stars round ?    If so 👍that’s good guiding 

[Same old newbie alert]

43 minutes ago, bottletopburly said:

Are you stars round ?    If so 👍that’s good guiding 

Is it thou, errors on both axis cause bloated stars.. they can still be round

Small round stars are

[Catanonia]

2 hours ago, bottletopburly said:

Are you stars round ?    If so 👍that’s good guiding 

 

2 hours ago, Same old newbie alert said:

Is it thou, errors on both axis cause bloated stars.. they can still be round

Small round stars are

Stars are small and round, but the question is really about CCD suitability that says "possible with good guiding" and I wanted to try and quantify this broad statement.

[rnobleeddy]

I don't think there's a simple answer. It depends on your mount and what you're hoping to achieve.

But if you have 0.3" RMS guiding then that's very good - beyond the limit of most EQ6 class mounts, so probably only routinely possible with mounts costing many thousands of pounds. Alternatively, if that's 0.3 pixels and you're using a standard type of guide camera, it's probably not amazing.

 

But mainly came here to say that round stars are not a cast iron guarantee of good guiding. It's entirely possible to have round starts and terrible guiding, as long as both axis are equally terrible. 

 

Much better to measure FWHM of your starts - which is in DSS.

 

 

[Same old newbie alert]

36 minutes ago, Catanonia said:

 

Stars are small and round, but the question is really about CCD suitability that says "possible with good guiding" and I wanted to try and quantify this broad statement.

But what if the suitability calculators are inaccurate ? 

The guiding software is inaccurate

The RMS that you state is in pixels and your guidecam has large pixels... 

 

[The Lazy Astronomer]

Personally, I would class guiding as good if:

1. The total RMS in arc seconds is less than or equal to 0.5x the imaging scale of the main camera

2. RA and DEC have approximately equal error

3. There are no or minimal large spikes in either axis

[SamAndrew]

Depends what part of the sky you're looking at; you'll get great numbers tracking Polaris, worse numbers at the equator; better numbers at the Zenith, worse numbers at the horizon. For those reason it's pretty meaningless to compare numbers without qualification.