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Old 19-03-2011, 10:14 AM
dmb
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Bit of help with Maxim autoguiding ?

Just trying out the demo version to see if my scope will autoguide, but I can't get it to work after hours of trying :-(

As you can see from the screenshot below it rapidly jumps and then just gets worse in both directions. Increasing the X-aggressiveness doesn't make huge differences e.g. from 0.1 to 1.0 or higher. Increasing the Y-aggressiveness makes it go through the roof - the plot goes almost vertical at 1.0. I can't see what else to tweak to flatten the curves out at a near zero constant

http://images.yellowbell.net/public/guiderrs.JPG
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Old 19-03-2011, 10:23 AM
adman (Adam)
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I haven't used Maxim for guiding - but that looks like there are no corrections getting through to the mount. The top graph looks like it could be normal PE of the RA axis, and the bottom graph looks like DEC drift due slight polar misalignment....

I see you are using camera relays to provide output to the mount - have you tried it with using Maxim DL?

Adam
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Old 19-03-2011, 10:58 AM
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I agree with Adam, looks like PE and dec drift. I suggest you might want to think about tweeking your polar alignment a bit before trying again. That's a pretty strong drift
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Old 19-03-2011, 11:46 AM
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Did it make a nice L shape when you calibrated?
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Old 19-03-2011, 12:14 PM
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Agree with all comments above. Aggresiveness of 4 is 40% from memory, so you really want to have 3 or 5 in there to get corrections. Maxim doesn't show corrections on the graph so you need to check the tracking log file too to see if it is trying to correct. Also min and max moves - it may be making corrections that are very small and not making any difference.

Critical piece of info has already been asked for - did you see it cal properly with a decent L shaped red line for the star it was cal'ing on. You can do an exposure, pick your star, then it will cal on that chosen star - usually best option rather than auto selection.
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Old 19-03-2011, 12:21 PM
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Rob could you explain
Quote:
Maxim doesn't show corrections on the graph so you need to check the tracking log file too to see if it is trying to correct.
I haven't been using Maxim to autoguide as it doesn't appear to be correcting in the graph so I've been sticking with PhD
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Old 19-03-2011, 12:47 PM
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if increasing aggressivenes makes it drift away faster, then its correcting the wrong way.Also less than 1 agressiveness usually dosent do anything, 4-8 is typical. Whats the FL of your guide scope?, if its less than say 500mm then the cal time should be about 15 seconds for x and y.

As mentioned, a nice large red L is required in cal, if you dont get cal right guiding wont work.
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Old 19-03-2011, 04:21 PM
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Quote:
Originally Posted by [1ponders] View Post
Rob could you explain
I haven't been using Maxim to autoguide as it doesn't appear to be correcting in the graph so I've been sticking with PhD
It seems to be a bit of a quirk that the "error" values you see appearing are distance the guidestar has moved since tracking began, not adjustments the software is making as it tracks. Its fine to be able to see this on the graph, but you don't get any graphical indication of a correction. You have to load up the tracking log (text file). You can turn that on and set where it is saved from the Options dialogue on the Guiding Tab.

More on it here - doesn't seem to be a priority to include graphical indication at this point....
http://tech.groups.yahoo.com/group/M.../message/44234

You usually have a pretty good idea if the software has made an agressive correction from the graph when you see it jump back towards zero, but of course that's not too ideal from a tracking/photography point of view.
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Old 19-03-2011, 04:28 PM
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thanks Rob I'll check it out next time its clear at night
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Old 19-03-2011, 06:35 PM
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Thanks all for so many responses so quickly !

Yes it makes a nice L shape, with the cal times shown I get 30 pixels in the X direction and 15 in the Y consistently.

I started with aggressiveness of 6 in each, but the corrections were pretty wild, about 3 pixels at a time ! However now you've all got me thinking. I don't remember the exposure time I was using on the guidescope, but I think it may have been as high as 10 seconds. That may have allowed the guide star to drift too far to be corrected 'gently'. When I reduced the aggressiveness that seemed to calm things down but then over the course of the night I reduced the exposure to a final 2 seconds. Maybe with shorter exposure I should have gone back up to higher aggressiveness ?

The polar alignment I did was pretty basic, I'll spend a bit more time checking the drift next time. Could I use the graph to help, making the appropriate adjustments in RA/DEC with my wedge adjusters ?

FWIW I'm using a 10" Meade with SX guider/SXV-H9 camera, hence the camera relays mode - the guidecam plugs into the camera which sends ST4 to the mount. I'm using both through an off-axis guider, so FL 2032mm.
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Old 19-03-2011, 06:41 PM
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Interesting I'm using almost the same guider/camera setup and have the similar problem, only difference is I'm using and ap900 and guidescope
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Old 19-03-2011, 06:52 PM
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Quote:
Originally Posted by dmb View Post
The polar alignment I did was pretty basic, I'll spend a bit more time checking the drift next time
yep polar alignment is pretty important - always pays to get that close before trying any guiding. It just takes one more variable out of the equation. So many of my problems have come down to polar alignment or balance.

Adam
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Old 19-03-2011, 07:27 PM
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Quote:
Originally Posted by dmb View Post
The polar alignment I did was pretty basic, I'll spend a bit more time checking the drift next time. Could I use the graph to help, making the appropriate adjustments in RA/DEC with my wedge adjusters ?
Certainly no reason not with caveats below. This is a no fuss way to home in on good alignment in fact without dismantling your camera config. Need to ensure:
- Camera aligned with RA and Dec axes (or guiding graph options chosen to show mount/drive axes, not camera)
- corrections turned off (in DEC axis at least - might help to have RA tracking if you're way off to start with)
- Pointing at overhead meridian star, or zero Dec horizon star as per normal polar alignment routines (to adjust azimuth and altitude respectively)

Remember you can change the pixel scale on the graph as you zoom in on alignment. Another trick is to select your main camera as the "guide camera" on the guide tab as you get closer to good PA. Gives you an additional resolution boost if the FL of your main OTA is significantly greater than guidescope. You could save a camera configuration like this to re-use. In fact its sometimes handy to have the cameras reversed from their normal roles when you're first finding an object using the Camera Exposure tab too....
(again however, of most use when your guidescope FOV much wider than main OTA setup)

Maxim may not be the best place to start if you're just learning autoguiding though? PHD gets you going quick. Maxim allows much more control and tweaking, but would suggest you have to be prepared to invest hours thinking why you've get each and every setting where it is.
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Old 21-03-2011, 08:53 AM
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Thanks Rob, I'll give that a try. Appreciate what you say about Maxim/PHD, there certainly are a huge number of variable settings to think about in Maxim. I plan to try PHD as I already own Nebulosity for processing. My problem is that my camera and guidecam are effectively one physical unit so it's tricky to get two programs accessing them at the same time. However I found an ASCOM driver that apparently presents them as two devices to Windows so have to get that working first.
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