G11 users - do you use PEC?

[JohnH]

Hi,

I am curious - as ever I would like to get crisper images so - do you find PEC improves your guiding with a G11G or not?

I autoguide and use PHD with both RA and DEC traces staying within the 1st division on the graph - in other words +/- 1 pixel and typically less than half that, the guidecam imager is a QHY5 and a WO66SD which is 2.75"/pixel. So my guiding is to +/- 2" typically.

I am not sure if it is a good measure of seeing (I am in suburbia north of Sydney) and AA4 shows FWHM of 2-3" typically when focused with 0.5s exposures.

If I train PEC using the native Gemini routines it seems to make things worse - I have tried averaging multiple runs, smoothing and adding an offset but even at its best with PEC on my tracking looks no better than without it. I have also tried PEMPRO but again I could not achieve significant improvement - I guess that PEC may be reducing the size and frequency of the guide corrections which is better in theory but it did not show in the images...

I typically use 2 or 3s guide exposure. I also use an OAG sometime but I find no measurable impeovement with that (imaging scope is 127ED at f7.5 vs guide at f5.9).

I measured my native PE at about +/- 9".

So am I at the limit here with guiding/seeing - if not what can I do to get a sharper image? My imaging scale is 1.4" / pixel and I use 300 and 600s subs typically.

Any tips? Is PEC going to help or is seeing always going to limit me at my current location?

[Barrykgerdes]

I have never thought much about PEC in a G11 but without any PEC the drive will follow the "worm" without a software correction which is in effect adding a further error to correct an error.

This action could most certainly interfere with the direct correction to the movement caused by an autoguider, particularly if the corrections are in opposite directions.

For this reason I would not make any PEC corrections if I intended to autoguide.

Barry

[SkyViking]

I don't autoguide, but I don't use the PEC either. I find it rather annoying that I have to train it every time I power up the mount, and the few times I've done it I didn't see much improvement. Could be my particular mount though.

[JohnH]

AFAIK you do not have to re-train each time but if you do not you must use the offset option to remove any residual drift from your PE data. If you are not guiding then I guess you are not imaging (or use short exposures) so it is all a little irrelevant anyway....

[multiweb]

I did use PEC in the past. The data uploaded is still valid as long as you don't remove the worm. Yes it does improve your tracking significantly. No it doesn't make autoguiding worse to have it on.

[Alchemy]

No don't use PEC I did at one time but found no improvement over my regular guiding.

Note I use phd BUT set the guiding to about 10% aggressiveness and 1-2 sec updates I did use a program that mapped the error and thought the mount was pretty good... G11 mounts can be a bit of a lucky dip according to reports, but happy wih mine.

Deconvolution can sharpen your images somewhat if you are up against the wall.

I found seeing to be noticable at 1500 mm but 1000 seems to be reasonably forgiving.

You don't specify mono or color camera, mono will significantly be sharper due to the bayer array averaging.

[SkyViking]

My mount does not have Gemini, so maybe that's the difference?
When I power on the mount it seems the PEC is never on, so if I want to use it I'll have to train it again. I also cannot find anything in the Losmandy manual about this, only the instructions for how to record the PEC in the first place.
I do imaging but yes only at relatively short exposures. I longest I've tried was around 4 minutes. Normally under a minute because I really need guiding to go any longer than that.

[TrevorW]

Don't use it as don't have permanent set-up

[[1ponders]]

Yep that's standard for the Digital Drive. Re-record each time you turn the power off.

Like others I've never had an improvement with my G11/Gemini/Digital Drive using PEC. Often the outcome has been worse. So I don't use it.

[JohnH]

I use a mono camera, an Opticstar 145m which has a Sony ICX285AL sensor.

[JohnH]

Here is a crop from a 300s exposure from last night, no processing at all - just saved to jpeg. It is a LUM frame, would value any comments as to how I might do better or if this might be about the limit for the scope and location.