Who, what, when, how star calibration!

[Rustang]

Ditched tonights session of imaging, too many issues right from the start! Part of the issue tonight was star calibration in PHD2. I was going to image the Soul nebula tonight even with the bright moon as it is a clear night so why not! . When I pressed calibrate, it came up with something to do with possible errors due to calibrating near the equator!? So whats this all about? Also when pressing shift click on the green target it always says do you won't to 'force' calibration which led me to think am I do it all wrong? Why 'force' calibration!? Its been working how I've been doing it but it's made me think. My process each session is to chose a star, shift click to force calibration when at target then it does what it needs to. Do you always re calibrate every single session and if so where, at the target? Because if tonight has thrown up that warning in regards to the equator, what am I supposed to do!? I ended up giving up because the guiding was crap so need to understand what the correct process is or why I'm going wrong/miss understanding. 

Edited November 3, 2020 by Rustang

[alacant]

23 minutes ago, Rustang said:

errors due to calibrating near the equator

Hi

I think that the error may have been not calibrating near the equator. Please tell us what mount you are using and how it is connected to phd2. If you want to know exactly what went wrong, then post -a link to- the phd2 log files.

How to post log files.

Cheers

Edited November 3, 2020 by alacant

[michael8554]

If you don't have a connection to the mount that gives PHD2 the Dec position of the mount, typically a basic ST-4 connection, then you have to carry out a Cal "On Target," every night, every new target.

If you do have that connection, you carry out a Cal at Dec 0, the Celestial Equator, and near south, and then PHD2 will compensate for whatever Dec you subsequently go to.

The Soul Neb is at about Dec 60, so if you Calibrated there, I'm not sure what that message was about.

I do see a reminder that if you WANT to ReCal, you press Shift as you press Guide.

Michael

Edited November 3, 2020 by michael8554

[Rustang]

5 minutes ago, alacant said:

Hi

I think that the error may have been not calibrating near the equator. Please tell us what mount you are using and how it is connected to phd2. If you want to know exactly what went wrong, then post -a link to- the phd2 log files.

Cheers

My mount is the HEQ5 Pro which is connected to the laptop via a EQ DIR cable. Your probably right, I forgot to right down what exactly the error message said. So I was pointing fairly high up around North East at the Soul nebula, the message came up when I tried forcing the calibration at target. I would say my guide issue was due to ignoring that message and calibrating in that area. If it's best not to calibrate if that message is given, where do I calibrat then!? 

Edited November 3, 2020 by Rustang

[Rustang]

7 minutes ago, michael8554 said:

If you don't have a connection to the mount that gives PHD2 the Dec position of the mount, typically a basic ST-4 connection, then you have to carry out a Cal "On Target," every night, every new target.

If you do have that connection, you carry out a Cal at Dec 0, the Celestial Equator, and near south, and then PHD2 will compensate for whatever Dec you subsequently go to.

The Soul Neb is at about Dec 60, so if you Calibrated there, I'm not sure what that message was about.

I do see a reminder that if you WANT to ReCal, you press Shift as you press Guide.

Michael

So every session, every new target I press Shift as I press guide and it asks if I would like to force calibration to which I press yes, I've never had any issues with this, but I'm guessing this is wrong though!? I'm connected to the laptop via a direct cable. 

Edited November 3, 2020 by Rustang

[michael8554]

2 minutes ago, Rustang said:

If it's best not to calibrate if that message is given, where do I calibrat then!? 

Like I said, at Dec 0 and near south.

But you can Cal at Dec 60 if you really want too, but at Dec 0 PHD2 can work out your RA and Dec guide rates more easily.

Michael

[Rustang]

4 minutes ago, michael8554 said:

Like I said, at Dec 0 and near south.

But you can Cal at Dec 60 if you really want too, but at Dec 0 PHD2 can work out your RA and Dec guide rates more easily.

Michael

So do this just the once then each new session just press guide, or calibrate at that position still, every night? Also, once it's calibrated it starts guiding so how does it work when you calibrate in a different area then slew to target!? 

Edited November 3, 2020 by Rustang

[Rustang]

Also to confirm that when you say DEC 0, from this screen grab, do you mean the area in the Sky where it says +0? Just below where Mars is? 

 

Aplogies, I'm still very much learning at an embarrassing level! 

Edited November 3, 2020 by Rustang

[michael8554]

37 minutes ago, Rustang said:

so how does it work when you calibrate in a different area then slew to target!? 

Like I said, PHD2 compensates for whatever Dec you then actually image at.

30 minutes ago, Rustang said:

do you mean the area in the Sky where it says +0?

Yes, the vertical scale is Declination, and the horizontal scale is RA.

Dec 0 is where the stars appear to move the fastest across the sky, so is the best place to Calibrate.

Near Dec 90, the stars hardly move, in fact Polaris at Dec 89 is all but stationary - Calibration on Polaris comes out very strange !

PHD2 is very like assembling an Ikea Flat Pack, best results come from following the instructions in the Help File in the PHD2 Help tab.

Michael

[Rustang]

Cheers guys 👍

[Rustang]

Thanks again guys, took on board your advice and things are going well so far for tonights session. Another thing learnt and understood! 👍

Edited November 4, 2020 by Rustang

[rickwayne]

According to the PHD troubleshooting doc, the best practice is to calibrate on a star near the equator/meridian, as has been noted. If your setup tells PHD the mount position -- as yours does -- it can work out the correction factors for other parts of the sky from there. In fact if you don't change anything (e.g. orientation of guide scope or camera), you should be able to reuse the same calibration for quite some time, no need to shift-click every night.

It is a good idea, however, to run the Guiding Assistant pointed at the target. This will read the actual behavior of the mount while it's tracking (but not issuing guide commands) so that it can fine-tune the parameters. I've had it tell me some surprising things. One night the seeing was particularly good and it advised that I could use a 1-second exposure for the guide camera; I had always gone with the conventional "don't chase the seeing" wisdom and selected something in the three-second range. Bang, the performance went from 2-3" RMS to under 1. At my image scale, that's plenty good enough.

[Rustang]

Cheers, I definitely need to start running the guiding assistant, I keep forgetting! 

[Rustang]

29 minutes ago, rickwayne said:

According to the PHD troubleshooting doc, the best practice is to calibrate on a star near the equator/meridian, as has been noted. If your setup tells PHD the mount position -- as yours does -- it can work out the correction factors for other parts of the sky from there. In fact if you don't change anything (e.g. orientation of guide scope or camera), you should be able to reuse the same calibration for quite some time, no need to shift-click every night.

It is a good idea, however, to run the Guiding Assistant pointed at the target. This will read the actual behavior of the mount while it's tracking (but not issuing guide commands) so that it can fine-tune the parameters. I've had it tell me some surprising things. One night the seeing was particularly good and it advised that I could use a 1-second exposure for the guide camera; I had always gone with the conventional "don't chase the seeing" wisdom and selected something in the three-second range. Bang, the performance went from 2-3" RMS to under 1. At my image scale, that's plenty good enough.

Does the orientation of the imaging camera make a difference then? Why is this? I calibrated with the imaging camera vertical yesterday for the Soul Nebula, so I'm guessing I will have to re do it next session if the camera is horizontal. 

Edited November 5, 2020 by Rustang

[alacant]

30 minutes ago, Rustang said:

Does the orientation of the imaging camera make a difference

No.

[Rustang]

1 hour ago, alacant said:

No.

My bad, miss read it! 

[michael8554]

4 hours ago, Rustang said:

Does the orientation of the imaging camera make a difference then?

No, but if you change the orientation you will need a new Calibration, so that PHD2 knows where north and west are 😆

Michael

[Budgie1]

16 minutes ago, michael8554 said:

No, but if you change the orientation you will need a new Calibration, so that PHD2 knows where north and west are 😆

Michael

Surly that would be true for the guide camera, not the imaging camera?

[michael8554]

Correct, I misread the question, my bad.

Michael

[Rustang]

5 hours ago, michael8554 said:

Correct, I misread the question, my bad.

Michael

We both got confused !! 😊