Please check For Guiding Error Or Backfocus distance Error.

[ollypenrice]

I think so. The mount is responding in the right direction but too slowly and by too much. It is not just going mad, though. Basically the guiding needs tuning - or so I believe by looking at the traces.

Olly

[Singlin]

I'm busy in the Hotel but manage to skive off every now and then to try and sort this problem out.

We have had warm weather and the ground is thawing out fast.

I started a drift alignment this evening and the alignment is out. I only managed to do half a drift alignment . I will go back later and finish it off as soon as everyone is in bed.

This must be the cause of the problem, or at least I hope it is.

[ollypenrice]

Your guests go to bed? Consider yourself lucky!

lly

[Singlin]

We dont all have a siesta during the day        

[Singlin]

Bingo!!

After a drift alignment my software is responding to the mount.

Attached is my PHD graph in pixels.

I need to sort out the RA trend.

[Thalestris24]

Hi

Qhat's your graph like in arc secs? Your error values seem similar to before... I'm struggling to improve my guiding at the moment (on my Heq5 syntrek) which obviously doesn't compare to a Mesu even under the best of circumstance! But anyway, have been following your thread with interest.

Louise

[steppenwolf]

Well that looks a heck of a lot better!! A bit of fine tuning and you'll get even better results. My only observation is that I am surprised that a slight PA error would have such devastating effects before. Is there nothing else that you have changed at the same time?

Sent from my iPhone from somewhere dark .....

[Singlin]

No, I only did another drift alignment.

[Thalestris24]

Hi

Oops! Apologies! Ignore what I said before about your error values! I think my eye-brain co-ordination leaves a lot to be desired! However, I'd still like to see another guide graph in arcsecs when you can

Thanks

Louise

[Singlin]

I have not managed to get phd2 to work.

I can't get descent results with my St80 either.

Only with my finder guider.

I have installed Astroart demo but have yet to fine tune the settings.

Here is my guide graph with Phd 1 and my finder guider (can't get my st80 to guide accurately either)

Here is a link to  a zip file with 1 x 20s, 1x 300s and 1 x 900 sub with this setup.

https://www.dropbox.com/s/6307d72kumpcl01/PHD%201%20subs.zip?dl=0

Conditions were windy.

Regards,

Simon

[Thalestris24]

Hi

I wonder why it is that sometimes PHD1 works and PHD2 doesn't! It's a bit of a mystery! I'm thinking of mounting my ST80 in place of the 60mm guider I've been using but don't know if it will guide better. I suppose the longer focal length of the ST80 might be advantageous. The only way is to try, I suppose

Cheers

Louise

[ollypenrice]

I have not managed to get phd2 to work.

I can't get descent results with my St80 either.

Only with my finder guider.

I have installed Astroart demo but have yet to fine tune the settings.

Here is my guide graph with Phd 1 and my finder guider (can't get my st80 to guide accurately either)

phd 1.jpg

Here is a link to  a zip file with 1 x 20s, 1x 300s and 1 x 900 sub with this setup.

https://www.dropbox.com/s/6307d72kumpcl01/PHD%201%20subs.zip?dl=0

Conditions were windy.

Regards,

Simon

Then I'd just go with that. As I may have said, I got nowhere with PHD2 when I tried it.

You're dead sure that the ST80 isn't flexing anywhere? Focuser rear end in steel tube is a good one. Drawtube. Be brutal with the lock screw. The lens cell couldn't be loose? Check everyting from end to end. 

The other variable might be the angle of the camera. Whatever  the software instructions say, it can do no harm to be orthogonal with RA and Dec. Simple beats complicated.

Light at the end of the tunnel?

Olly

[Thalestris24]

I have not managed to get phd2 to work.

I can't get descent results with my St80 either.

Only with my finder guider.

I have installed Astroart demo but have yet to fine tune the settings.

Here is my guide graph with Phd 1 and my finder guider (can't get my st80 to guide accurately either)

phd 1.jpg

Here is a link to  a zip file with 1 x 20s, 1x 300s and 1 x 900 sub with this setup.

https://www.dropbox.com/s/6307d72kumpcl01/PHD%201%20subs.zip?dl=0

Conditions were windy.

Regards,

Simon

Hi

I think maybe PHD2 tries to be too clever by calculating arc second errors. That calculation depends on the user entering accurate guide scope data and when calculating the calibration step size. I don't know how you set your guide speed but for my heq5 it's set in eqmod whereas with AVX it's set in the hand controller. The latest PHD2 build handles the nudge south better, I think. I suppose calibration relies on having reasonably good PA. Whenever I've had calibration problems in PHD2 similar to yours, it has been because PA has been too far out! I find it useful to examine guide logs in PHDLab. I'm still working on improving my PHD2 guiding, though I think the atmosphere above Glasgow city will always be limiting...

Louise

[Singlin]

Hi Louise,

Here is a dropbox link to my PHD1 log file.

https://www.dropbox.com/s/afhb1snilp7m8ik/PHD_log_11Mar15.txt?dl=0

Could you run it in PHD Lab and tell mo how my Pa is.

I am not technically minded like yourself and would appreciate the help.

Regards,

Simon

[Thalestris24]

Hi Simon

I had a quick look for you. Here are PHDLab outputs for the two main guiding sessions:

They look quite good to me - you appear to be achieving sub-pixel guiding. Better than I can do! The PA looks fine too though PHDLab isn't necessarily accurate as it samples only when corrections aren't being sent but I think you can be confident that you only have a small error

Here is output in arc secs (based on the guide scope data you've entered):

It's saying your PA error is 0.22 arc min which is very good! You should be getting nice, tight stars

Louise

Edit: I don't understand where it says at the top RA rate = 0.0009?

[Singlin]

Cool!

Thanks Louise-

I drift align with a x2 barlowed 10mm crosshaired ezepiece so was quite confident on the outcome.

[Singlin]

I seem to remember  inputing 180 as my focal legnth for my guide scope.

Does Phd Labs calculate it via the software?

[Thalestris24]

Hi

Ahhh... sorry - no, it's something you enter on PHDLab's screen....

Here's the first one re-done:

It's probably better to play with PHDLab yourself, that way you can change things and check it has the right data!

http://countingoldphotons.com/phdlab-intro/

I don't know if you have a reducer? That would affect the imager px - in this one I've assumed 1000mm?

Cheers

Louise

[Singlin]

I have a coma corrector that does not reduce.

[chrisshillito]

The other variable might be the angle of the camera. Whatever  the software instructions say, it can do no harm to be orthogonal with RA and Dec. Simple beats complicated.

The other variable might be the angle of the camera. Whatever  the software instructions say, it can do no harm to be orthogonal with RA and Dec. Simple beats complicated.

You'd think so wouldn't you, but the problem is 'smart' software has the habit of making the simple complicated. I doubt many can get their camera perfectly orthogonal and if they don't then PHD is going to be measuring, and subsequently correcting, its data by a very small angle. A small error in measurment (or varying guide star image quality) can therefore have a big effect.  I guess that for orthogonal use you need an option not to measure RA angle during calibration and instead accept  a manually entered value of 0 degrees. Perhaps this exists on PHD2 I don't know.  If this isn't possible then an angle of 45 degrees will at least give generate the maxium xy deflection for the autocalibration to work with and any errors in the angle measurment process will hopefully have proportionally less effect.

Chris.

[Thalestris24]

The other variable might be the angle of the camera. Whatever  the software instructions say, it can do no harm to be orthogonal with RA and Dec. Simple beats complicated.

The other variable might be the angle of the camera. Whatever  the software instructions say, it can do no harm to be orthogonal with RA and Dec. Simple beats complicated.

You'd think so wouldn't you, but the problem is 'smart' software has the habit of making the simple complicated. I doubt many can get their camera perfectly orthogonal and if they don't then PHD is going to be measuring, and subsequently correcting, its data by a very small angle. A small error in measurment (or varying guide star image quality) can therefore have a big effect.  I guess that for orthogonal use you need an option not to measure RA angle during calibration and instead accept  a manually entered value of 0 degrees. Perhaps this exists on PHD2 I don't know.  If this isn't possible then an angle of 45 degrees will at least give generate the maxium xy deflection for the autocalibration to work with and any errors in the angle measurment process will hopefully have proportionally less effect.

Chris.

Hi Chris

Yes, PHD2 has an option to assume orthoganality between RA and DEC. In their help file they say the default is ok but in cases of very bad seeing, or high periodic error, you can force RA and DEC to be perpendicular. It then computes the camera angle in RA and asserts a DEC angle that's orthogonal to it. Anyway, that's what they say...

Louise

[chrisshillito]

Hi Chris

Yes, PHD2 has an option to assume orthoganality between RA and DEC. In their help file they say the default is ok but in cases of very bad seeing, or high periodic error, you can force RA and DEC to be perpendicular. It then computes the camera angle in RA and asserts a DEC angle that's orthogonal to it. Anyway, that's what they say...

Louise

Thats not quite what I meant. I was thinking that if you mount your guide camera orthogonally to the mount you should be able to tell the autoguider not to measure the ra angle at all but rather take it as read that it is 0. It is certainly true that the periodic error inherent in the worm drives could act to compromise small angle measurement especially with higher magnification guiders.

Bad seeing or not I would always expect the dec angle to always be 90 degrees offset with respect to the ra. If phd measures and applies corrections on any other basis then the guiding corrections aren't going to be optimal.

Chris.

[Singlin]

THe bad weather has rolled in and we are set for cloudy nights until next weekend.

I would like to thank everyone for the help on this topic.

My conclusion is that my Telescope will always be difficult to guide well without using an OAG.

I have also concluded that PHD2 in my case is not as reliable as PHD 1 and every now and again when it is playing up I need to uninstall and delete log files and re-install.

I also underestimated the amount my 1 cubic meter of concrete moves with major temperature changes-I will do drift align check more often.

Thanks for the patience.

Simon

[ollypenrice]

I also underestimated the amount my 1 cubic meter of concrete moves with major temperature changes-I will do drift align check more often.

Thanks for the patience.

Simon

Wow. Probably your altitude and freeze-thaw effects creating ground swell. A bit of poetry for a change... Ah, Robert Frost. Too good!

Something there is that doesn't love a wall, 

That sends the frozen-ground-swell under it, 

And spills the upper boulders in the sun, 

[Singlin]

In retrospect I should have just dug a deeper hole.

After digging 1 cubic meter through rock I made myself believe that it was enough although in the back of my mind I had a doubt.

We get plenty of small tremors in the Alps, I guess Robert was referring to those.