Dithering with ASIair Pro and a Skyguider?

[Mike73]

I'm hoping someone can shed some light on a problem I ran into last night......

I'm using a Skyguider Pro with ASIair and a Redcat 51.

Last night the guiding calibration went fine and I had great looking stars with 5 minute exposures so I set up my Autorun. 

The Skyguider only tracks in RA so in app and in Dither settings I turned RA Only on, interval was set to dither every image and Pixels was set to 2. Everything worked great for the first 6 images then the guider wouldn't settle enough to continue. Just looking at my Guide Stability settings, Stability was set to 3", with hindsight I should of raised this to the max 4" but I dont think that would of helped very much.

What I dont understand is that my RA was pretty consistent at around 1" but my Dec which I have no control over was nearly always at or above 4". It looks like the total RMS is averaged which is why my guiding wouldn't settle enough to take the next image. Is that right? Can anyone see where I'm going wrong or how to fix this?

 

Thank you

Mike

 

[michael8554]

I don't have ASIAir, but from your image, looks like it did a Dec Dither (red graph) ?

Michael

[Mike73]

Thanks Michael and yes it does look that way, you've got me second guessing myself as whether I told it to track RA only, won't find out until next time I get out I suppose?

[michael8554]

Realise now you only have a RA drive mount, so even if you'd not selected RA only, there shouldn't be any signal on the Dec axis.

Post the ASIAir GuideLog, although it will be vague compared to PHD2, there may be a clue.

Michael

[Richard_]

From the image you posted, if you tap on the chart you will go into the guiding settings. The guiding chart will now show across the bottom of the screen (if not, tap "Graph" on the left side of the screen). If you look to the left side of the screen you may see one of the following options shown for "DEC Mode": <Auto> / <North> / <South> / <OFF>. If anything other than <OFF> is shown, tap it until it shows <OFF>. Your chart should now only show RA. Your guiding thus far, has taken into account the DEC axis so you will need to reset the calibration settings for your guiding. Follow the below to do this:

1. Tap the rotating arrows icon on the right
2. Tap the "i" icon and tap "clear to clear any previous calibration settings already set
3. Now tap the rotating arrows icon again followed by the circular crosshair to calibrate using just the RA

Whilst you're at it, you may as well ensure that "Auto Restore Calibration" settings are disabled. On the top of the screen, tap the circular cross-hair icon to enter the guide scope settings. Scroll down and ensure "Auto Restore Calibration" is shown as grey and not green. This option allows you to use calibration data from the last session which is great if you have a pier or don't take your mount down, but with portable mounts like the Skyguider Pro and Star Adventurer, you will likely be taking the mount down after each session so you will need to re-calibrate each time.

This worked for me with my Star Adventurer, hope this helps!

[david_taurus83]

Looks to me like it has dithered in Dec but obviously the mount has no way to recover in that direction. Not familiar with Air software but PHD2 gives the option to turn off Dec commands and dither in RA only.

[michael8554]

After further thought, I think that ASIAir is reporting Dec movement of the guide star.

Since you have Dec guiding off, that movement in Dec is due to sudden Dec movement of the mount, maybe a cable snagging, tripod leg sinking, Alt adjustment loose etc etc.

Michael

[Mike73]

Michael, David and Richard thank you all for your replies!

Richard that's lots of great info and from memory that's pretty much exactly what I did, I had maybe 10 minutes of cloud with a few spots of rain so I covered the scope and sat it out for 10 minutes then restarted my guide calibration from scratch but then this error cropped up. Maybe I did miss something when I reset the settings?

David, yes the ASIair Pro is very similar to PHD2 but dumbed down a little.

I've though that too Michael. I'm using a w/o wedge under the sky guider which is far better than the standard Ioptron base  but if there was a sudden movement to the mount I would have thought it would show in both Dec and Ra?

Looking like clear skies tomorrow so hopefully I will get to the bottom of this.