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I am guiding at from 2 Hz to 0.5 Hz, depending upon how bright the guide star is. At my focal length, guide stars can cometimes be few and far between.

I am focusing using a Robofocus unit and the builtin focusing algorithm in Maxim. I could use FocusMax, but haven't.

My best guiding has been at the fastest refreshrate. But, I can't always achieve that.

Thanks.

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Since the guiding error is measured by your guider camera is may have a different scale than your main camera.

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I am guiding at from 2 Hz to 0.5 Hz, depending upon how bright the guide star is. At my focal length, guide stars can cometimes be few and far between.

I am focusing using a Robofocus unit and the builtin focusing algorithm in Maxim. I could use FocusMax, but haven't.

My best guiding has been at the fastest refreshrate. But, I can't always achieve that.

Thanks.

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Is anyone trying to do what I am doing with a fork and AO unit? I'd be curious how well they guide as a comparison.

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3.) Keep what I got until Jared gives me his Mach1 GOTO. Ha, ha.

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Miguel -- I take it you think I should keep my setup? The AO is definitely a miracle for fork-mount-imaging.

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...
3.) Keep what I got until Jared gives me his Mach1 GOTO. Ha, ha.

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Thanks for the replies. From memory (I'm still figuring all this stuff out -- ha, ha) I think my FWHM's are about 4 to 5 arcseconds. What does that mean? Is that an indication of seing?

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If seeing is decent and guiding is good, I think fwhm's should be down around 2.5". If you have AO and a brightish guidestar, it should go to 2.0" and below.

I don't know of a fundamental difference between GEM and fork - I would think it mainly depends on the quality of the bearings and gears.

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I think there are too many variables, which are unknown to give 2" as an expected outcome.

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The problem is not your mout, it is the scope.
If you want smaller stars get a Refractor...

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This is what I was looking at...

OP " I wonder if my stars could be made smaller by better guiding?"

1)Find a mountain top and still dry air
2)Faster f/ ratio scope
3)___________

Fill in the blank..

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Forgot to add this:
a color camera allways has worst FWHM than a mono. Not only because of lack of resolution but also because you need more time to get the same quantity of photons...

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Forgot to add this:
a color camera allways has worst FWHM than a mono. Not only because of lack of resolution but also because you need more time to get the same quantity of photons...

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A OSC camera produces a MONO image until it is debayered so how does this increase the FWHM? Wouldn't pixel size play a larger role than the fact your using a OSC camera.

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Well, FWHM, as the name says, is the full width at half maximum of a star bell-shape. Due to resolution loss from the debayering (compared to a mono camera), the star will have a smaller SNR, the peak value will be minor, therefore the FWHM will be higher.

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But for arguments sake most stars are composed of mainly "White" light. in other words, they are an RGB object. That being true, am I not using all of the pixels in the image of my OSC to compute my FWHM? You would be correct if we were shooting through a single color filter but we're not. Correct me if I'm wrong but a 6 MP mono camera and a 6 MP OSC camera should have the same resolution if the pixels are the same size and we're shooting an RGB object no?

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But for arguments sake most stars are composed of mainly "White" light. in other words, they are an RGB object. That being true, am I not using all of the pixels in the image of my OSC to compute my FWHM? You would be correct if we were shooting through a single color filter but we're not. Correct me if I'm wrong but a 6 MP mono camera and a 6 MP OSC camera should have the same resolution if the pixels are the same size and we're shooting an RGB object no?

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They would, if you were looking at the raw data from the chip instead of the interpolated data that is actually used.

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IMO the problem is not in the debayering, it's just because you have less resolution. Interpolation tries to compensate that.
You are right, for a pure white star, if the FWHM algorithm only looks at luminance data, it should be very similar.
But then when we look at the small details, it is not the same.
For example, a mono camera without IR block will be very sensitive in the IR, which is less affected by turbulence.
Also, as you can take a sub frame in 1/3 of the time, the PSF will be smaller.

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Can METAGUIDE be made to work with an Orion Starshoot? It looks incredibly promising for guiding and was curious.

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On the topic of fwhm - in order to get the smallest fwhm in the image, all errors will contribute - and I find there is enough error in the guide star centroiding that there is benefit in doing things differently. So focus, guide tuning, latency, etc. all need to be addressed - and even then the centroiding algorithm can be improved, which is why I wrote MetaGuide.

Thanks,
Frank

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On the topic of fwhm - in order to get the smallest fwhm in the image, all errors will contribute - and I find there is enough error in the guide star centroiding that there is benefit in doing things differently. So focus, guide tuning, latency, etc. all need to be addressed - and even then the centroiding algorithm can be improved, which is why I wrote MetaGuide.

Thanks,
Frank

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Which brings us back to the mount accuracy. Since the purpose of guiding is to correct tracking errors AFTER the errors are made, good mounts will produce less errors that won't need to be corrected and so the centroid produced by an average mount, even in perfect focus and seing conditions, cannot be as small as a good mount with small PE.

If I understand well however, Permanent Periodic Error Correction, such as implemented in the new CGEM or CGE-pro, is supposed to prevent tracking errors before they happen and so the pictures obtain with these mount should show an improved resolution...But, in practice, I suspect that the correction made under PPEC, being automatic, can be also inaccurate and to a certain point it remains to be seen how a middle range mount like a CGEM really needs PPEC when it is also autoguiding.

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+/- true. If you SBIG examples, they do make a test on a Paramount and there is a slight improvement...

Also... Paramount = 14.000€, AO = 850€ - 1800€

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lthough PEC can and does help, depending on the situation and the mount there is still as you say an error to it. Wether by eye or by camera, the errors will be corrected for either as they happen or after they happen. In the case of my G11, until I get the new worm block I have an issue with the 76 sec error. This makes using PEC a non issue as the error occurs at a different point in each worm cycle.

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Some more info to throw into the stew! A friend of mine images at a site 50 miles from my house. He is a bit higher and darker. Anyway, he reports that he usually sees FWHM of 1.5 to 2.5 on a "steady night", but 2 - 3 is more typical. His opinion is that the atmosphere around here is too unstable for anything over 1500mm focal length. I'm imaging at around 1440mm or so.

I don't have CCDInspector, but when focusing Maxim reports around 4 or 5 as my FWHM (if I remember correctly). So, my guess is that the best I can achieve is 3 to 4 and thus I have some room for improvement.

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