[gregbradley]

I thought I'd start a thread about autoguiding to get some ideas going on that may be helpful.

One question I have is time delay. I noticed Martin Pugh mentioned once he uses a 1 second delay after corrections in his autoguiding. I don't know if he does that all the time or just some of the time.

Anyone noticed any improvement in guiding from doing that? I have done that when using shorter guide exposures and if its windy or bad seeing.

I guess it would help more on a mount that had a bit of backlash or was struggling a tad as it would give the mount a chance to settle.

I often see the guide corrections start off a bit high drift down a bit and when its nicely aligned, balanced it just pops down into a lower range. I think this is a similar thing as the bounces and momentum of the mount wears down gradually.

The first thing I learnt about autoguiding is its not a solution to bad polar alignment. It tends to be as good as your polar alignment and balance.
So I spend a fair bit of time on getting the polar alignment as good as possible.

I thought of a potential good accessory someone could make. That would be a polar alignment scope with a CCD camera in it so you could plate solve the image when its pointing at the SCTParea and adjust until the reticle matches exactly. Just like you do manually but without the crouching down and the dim SCP Octans stars.

I'd like to hear some opinions about Min/Max move and what aggressiveness you use under what conditions.

A few points I use are if the seeing is not so good it makes sense to use longer exposure times for less often corrections. It would also make sense to set the max move lower so you are not trying to correct the seeing variability.

If the minimum move were too low then the mount would be correcting mostly for seeing and the correction would be meaningless as we only want to correct for drift and periodic error of the mount.

I use CCDSoft and about to switch over to the Sky X. It all works in Sky X now but haven't used it as clear nights are not common and I don't want to find out I did not know something and I got no data overnight!

Here is a quick summary of what I do:

1. Concentrate on polar alignment and Balance.
2. I calibrate the autoguider often. At a meridian flip or if I move too far away from the last location imaged.
3. I find the selection of the guide star makes a huge difference to the guide errors. I am often surprised at how much guide errors can drop if I simply select another star. I usually pick a guide star that is not too bright and is very round and no double stars and without another similarly bright star too close by that could confuse the autoguider about which is the guide star. I often use the auto button in CCDSoft to select the star and use that for calibrating. I add a 1 second delay when calibrating otherwise on SB mounts which move fast I can get a streaky star whilst it does the calibration and I don't want that.
4. I vary the exposure length but the better mounts when best setup I tend to go a bit longer. Currently I am using 3 seconds on the PMX and the Honders and 4-6 seconds on the PME with the CDK17.
5. Off axis guiders have been the best autoguider solution I have used so far.
6. I am looking to achieve guide errors that range from .02 to .5 that will give round stars. Errors greater than .5 on average will give elongated stars. Errors averaging over 1 are a waste of time and the stars will be unacceptably elongated.
7. The most accurate polar alignment tool I have used is T-Point and its polar model feature. The Sky X has added a feature recently called accurate polar alignment with T-Point where you adjust the mount until the bright star is centred in the image. It seems good. Pempro polar alignment wizard is another good tool I have used if I have trouble using T-Point (T-Point can be a bit fussy and hard to get going sometimes at least for me).
8. Sometimes elongated stars are not guiding related and its tilt of the camera, sag in the imaging train, wrong spacing to reducers and flatteners. Of course autoguiding is no solution to heavy wind.
9. Make sure everything is tight, all adapters are seated properly, the scope is mounted securely and balanced well, the counterweights are tight and try not to use counterweight shaft extensions and keep the counterweights up as high on the shaft as you can. There could be a discussion here about is it better to increase the number of counterweights and have them higher up the shaft or less and have them lower down the shaft.
10. Refocus often as it affects the OAG stars as well. I haven't found tight OAG focus to be vital but it does help.
11. As far as autoguiding software goes I'd like to hear opinions about which ones work best. CCDSoft has been my goto software and its very familiar to me.
12. I don't have any backlash settings on my autoguiding, I use direct guide (for SB mounts) and I use 50-75 as the setting for the calibration. That could be increased if its a wide field scope like an FSQ. I currently am using aggressiveness at 3. I find when PA is perfect, balance is perfect then you are only doing gentle corrections and don't want to overcorrect.
13. It pays to watch the correction errors and if you start seeing + to - too often then its just correcting the last correction so turn down the aggressiveness or increase the guide star exposure time.
14. I use auto darks on my SBIG STi guider ( a fabulous guider and my favourite of alltime, SBIG really got that little sucker right). If not hot pixels can throw off the software and are often brighter than any guide stars and you can get crazy large corrections all of a sudden.
15. Once I have autoguiding working well as above I add Protrack to the corrections as it corrects for slow flexes whilst the autoguider corrects for PE. With my CDK17 that takes stars to the final roundness I am after.
16. I sometimes use a .6X (I think its .6 it may be .5X) reducer that attaches to the end of the STi. This makes guide stars brighter and more guide stars so that is a worthwhile accessory.
17. I have also used a 750nm IR filter attached to the end of the guide camera to see if guiding in infrared cuts through the seeing better. I find it dims the stars quite a bit but still useable on many occasions but the improvement to guiding was not always seen. So I tend not to use it. Perhaps a better IR filter that allows everything above 750nmto go through is the go. This one is an Edmunds Optics one and they have several. Its worth experimenting as a simple way to incorporate the IR cutting through the seeing effect.
18. I have no experience with AOs at this time but am about to use one.
19. Don't overload your mount and keep it in good condition. Keep screws that tighten in good condition and stripped heads or missing screws need to get replaced.
20.. As far as minimum/maximum move is concerned I use .1 and 3.0. I sometimes lower that to .2. If its windy I would lower that as the larger numbers are simply wind caused and once the gust is past the mount should settle. Too low and actual PE corrections needing to be done get missed. Too high and non PE errors are being corrected like wind gusts.

Greg.