How to use AstroArt 5 for guiding?

[Gina]

Sky's cleared and pointing at Heart Nebula - guiding with AA5 working well   It's much quicker at calibrating than PHD

Working better tonight - maybe better guide star.  Second & third charts are for the Drift set to < 0.8 which seems better.

[Earl]

LOL Olly

I have had AA for ages as i used to use it before the PI calibration script was finalized, its just sat on the PC now doing nothing, Guiding with a dual Chip SBIG is not supported by many applications, abd im seriosuly of a mind to guide with it as ill be doing it at the longest focal lenght in the rig.

bow of course someone is going to release a good multi scope dithering app that wont be compatible........ LOL

[Gina]

Here is an Ha sub of the Heart Nebula with one image resized and the other cropped 1:1 pixel ratio.

[ollypenrice]

The results are good but I'm surprized by the wild guide trace. I use a binned Lodestar at 400mm FL so should we mulitply my guide error by about 2.3 to be comparable with your guiding FL? (I never trust my maths!)* If so, I worry if I dont reach an error of 0.07 in AstroArt. (This covers all the mounts I've used. NEQ6, iOptorn 45, Mesu, Avalon.) Multiply that by 2.3 and we get O.16. You are currently on a bit over 0.5. This seems odd to me. On the other hand your subs look fine.

Olly

*We really need to convert the guide error into arcseconds to get a proper comparison.

[Gina]

I presume the figures relate to pixels of the guide camera.

From this I gather the error I'm getting is up to 0.5 x 1.69 = 0.85 arc seconds which is significantly less than the seeing and hence has no noticeable affect on the DSO image.

[Merlin66]

Gina,

I would have thought you'd be using the Lodestar at 2 x 2 binning?

[Gina]

Could the scatter be due to poor PA?  Or is electrical interference a more likely cause?  I have not yet built my new power distribution box with interferenc suppression.

[Gina]

Gina,

I would have thought you'd be using the Lodestar at 2 x 2 binning?

Somehow I missed that so I've changed it to 2x2 binning.  This is the result.

[Merlin66]

Gina,

I have to assume that the guide frame is not exactly orientated to the RA-Dec...

It looks like it could be sitting at around 45 deg

Your "patches" of guiding - there seems to be a series of guiding - gap - guiding etc. This could be due to the guiding trying to control both axis and some slop in the Dec?

[Merlin66]

Looking at your screen dump....

I'd change the "do not guide" setting in RA/ Dec to around <0.2 and tick the "Dual axis" guide option....

[Gina]

Gina,

I have to assume that the guide frame is not exactly orientated to the RA-Dec...

It looks like it could be sitting at around 45 deg

Your "patches" of guiding - there seems to be a series of guiding - gap - guiding etc. This could be due to the guiding trying to control both axis and some slop in the Dec?

I didn't think of orientating the guide camera with RA or Dec.  The calibration indicated that it is indeed at around 45 degrees.  So would it be better to turn the Lodestar 45 degrees so that it aligns with RA or Dec?

[Gina]

Looking at your screen dump....

I'd change the "do not guide" setting in RA/ Dec to around <0.2 and tick the "Dual axis" guide option....

OK I'll do that.

[Merlin66]

Gina,

AA5 will guide at almost any orientation, but then needs to issue both RA/ Dec with corrections....

If the PA is good and the guider is sitting in RA/Dec it makes it much easier to guide with the majority of corrections only in the RA and the occasional correction in Dec...

[Gina]

Latest results.

[ollypenrice]

Ah, the fact that you were at 45 degrees might have explained the simultaneous spikes in RA and Dec. Like Ken I'd always have the guide camera orthogonal. Apart from reducing the number of corrections (which themselves can introduce errors) it allows you to make more sense of the guide trace by uncoupling the axes.

If you try an orthogonal guide cam the simultaeous over-corrections may stop.

Interesting thread. Sorry I forgot to run through the defaults I use, including Dual Axis Guiding.

Olly

[harry page]

Hi

Why don't you use the automatic calibration to get the correct setting inc camera rotation etc ?

Harry

[ollypenrice]

Hi

Why don't you use the automatic calibration to get the correct setting inc camera rotation etc ?

Harry

I don't find it works very well, Harry, and passed this finding on to Gina. I find it is considerably too aggressive after auto calibration on most of the mounts I've used. I increase the value for mount speed to slow the inputs down.

It is all very well using the auto angle finder but as discussed above this means both axes need corrections. Keeping them to a minimum is surely the best thing? It also allows you to see what's going on.

Olly

[Gina]

Thank you for your posts Harry and Olly

I shall turn the Lodestar to align with the mount/scope axes so that RA and Dec corrections are separated.  Unfortunately, the weather forecast shows no clear night skies for at least the next 5 days so I won't be testing this any time soon   Instead I shall use the time to improve my power feeds and try to eliminate that cause of problems.  I was getting interference stripes on the guiding image display again last night (though not earlier with AA5) so I'm convinced I have electrical interference which needs fixing.

I'm considering moving the PSUs to the pier head and feeding mains through the cable pipe from warm room rather than DC.  I know many people do this but I was concerned about mains born interference getting into the USB.  I guess the best answer would be to feed the mains through proper metal conduit.  I don't think I'll say any more about the technical issues in this thread as it's somewhat off-topic but I will report the results when I get guiding again.

[Earl]

Right im plugged in, camera working fne in nebulosity, but i have no option in the ccd plugin other than simulator?

[chrisshillito]

Gina,

AA5 will guide at almost any orientation, but then needs to issue both RA/ Dec with corrections....

If the PA is good and the guider is sitting in RA/Dec it makes it much easier to guide with the majority of corrections only in the RA and the occasional correction in Dec...

If I understand you right, that sounds to me like a rather odd way for an autoguider to function. If the star moves in RA only then any correction should be in RA only. It shouldn't matter at all what the camera orientation is. The autoguider will calibrate, measure the camera angle and adjust any pixel X/Y movements it measures accordingly to the measured RA/DEC axis - so if you put your camera at 45 degrees then a star movement at 45 degrees will result in the guider seeing a RA star  movement and only a RA correction should be issued. I can't see why placing the camera at 45 degree would result in any more RA+DEC mountc orrections than if it were orthogonal.

Howerver, you are relying on the calibration routine to measure the camera angle accurately and this is certainly one possible source of error that might be minimised (particularly if your guide cam has non square pixesl) by setting everything up orthogonally in the first place. As is generally the case with these things it generally pays to try to minimise the opertunities for the software to mess up!

Chris

[Earl]

Ah seperate download for SBIG, that is sorted... now to get the filter wheel configured.

[Earl]

Now I dont seem to be abel to get the guide to work at the same time as the main ccd... humms

[ollypenrice]

If I understand you right, that sounds to me like a rather odd way for an autoguider to function. If the star moves in RA only then any correction should be in RA only. It shouldn't matter at all what the camera orientation is. The autoguider will calibrate, measure the camera angle and adjust any pixel X/Y movements it measures accordingly to the measured RA/DEC axis - so if you put your camera at 45 degrees then a star movement at 45 degrees will result in the guider seeing a RA star  movement and only a RA correction should be issued. I can't see why placing the camera at 45 degree would result in any more RA+DEC mountc orrections than if it were orthogonal.

Howerver, you are relying on the calibration routine to measure the camera angle accurately and this is certainly one possible source of error that might be minimised (particularly if your guide cam has non square pixesl) by setting everything up orthogonally in the first place. As is generally the case with these things it generally pays to try to minimise the opertunities for the software to mess up!

Chris

Interesting point about error in the measurement of the angle. I have seen AA give inconsistent measurements of angle when I've recalibrated from scratch without changing the guider. In fact on one of my rigs, where I have carefully set the guide cam orthogonally, AA5 insists on finding a considerable angle. I'm not sure how this happens. I set the camera to orthogonality by exposing while slewing in one axis. The angle of the star trails reveals the camera's relationship with RA and Dec. I've only seen this on one of the rigs here. It happens to be the Avalon running EQ6 electronics/electrics but I think that's unlikely to be relevant.

Olly

[Gina]

There appears to be an option for changing the angle but I haven't tried it.  It's been giving an angle of -138 degrees.  I was thinking of setting the Lodestar to orthogonality and seeing what the angle box says.  Then I'm wondering if it could be set manually to the nearest of 0, 90, 180 or -90 degrees if it isn't already on one of these.

[Gina]

Regarding power problems, I have posted a new thread in the DIY Astronomy forum here.