PHD or My Mount: Who's Fault Is It?

[Mav359]

Hi guys

I was auto guiding using PHD the other night, i was tracking M42, the scope was on the East side of the mount and M42 in the west. My PHD graph was good and i could image for 8mins with no star trailing. Great

Then i turned my attention to the Eskimo nebula, the scope slewed across to the west side of the mount, NGC 2392 was still east of the meridian but close to crossing it.

PHD at this point had a complete fit, looking at the graph the RA would fly of in one direction then come back and shoot off in the other direction.

I slewed back to M42 and there was no issue

I don't know if the problem is the mount or PHD, i checked to make sure there were no cables snagging but i don't know where to start troubleshooting this

Can anyone help?

[martin_h]

Did you re-calibrate PHD after the move?

[Bizibilder]

Did you have limits enabled? ie the mount set to "stop" when it reached the meridian or other preset limit. Alternativly was the scope touching the mount somewhere causing a physical "stop"?

[Mav359]

Did you re-calibrate PHD after the move?

No, i didn't know i had to do that!

[Mav359]

Did you have limits enabled? ie the mount set to "stop" when it reached the meridian or other preset limit. Alternativly was the scope touching the mount somewhere causing a physical "stop"?

I'm sure there are no limits set, at least i didn't set any up, (i'll double check this) as for the scope and mount there was deffo nothing impeding the movement.

[martin_h]

Yes you have to re-calibrate after a big move like that, if you are only moving a few degrees (or at least in the same part of the sky) then there is no need. but after a flip or a move from east to west, then you will need to re-calibrate. Click on the Brain Icon and tick Force Calibration.

[Mav359]

Yes you have to re-calibrate after a big move like that, if you are only moving a few degrees (or at least in the same part of the sky) then there is no need. but after a flip or a move from east to west, then you will need to re-calibrate. Click on the Brain Icon and tick Force Calibration.

Ooops, easy when you know how. something new i've learned.

Cheers Martin i'll give that a go

[martin_h]

Ooops, easy when you know how. something new i've learned.

Cheers Martin i'll give that a go

Everything is easy.....when you know how

[Interested]

I always go completely out of PHD when going for a new target, then start from scratch once the new target is framed. I have never had a problem with PHD by doing so .

[Mav359]

So i think we established the answer to the original question is...

Neither, Its My Fault

[themos]

Hold on, the whole point of an equatorial platform is that the north direction does not change as you swing around in RA or DEC. It's only when you do a meridian flip that you need to re-calibrate PHD. Problems that only occur at certain mount positions could be due to balancing issues and backlash.

[Mav359]

I don't have an issue on targets west of the meridian its when i slew back past the meridian and i didn't recalibrate PHD that i saw the issue. I'm sure my setup is balanced correctly.

I think in hindsight what i was seeing as an problem is just PHD having and issue because i didn't re-calibrate as i should have.

Its supposed to be clear tomorrow so i'll have a go then and report back

[themos]

I think there is a "flip calibration data" menu item that should just invert PHD's idea of what is where and you can use that when running on the opposite side of the meridian (to the one you calibrated on).

[Mav359]

Cheers Themos i'll check that out

[dmahon]

I always go completely out of PHD when going for a new target, then start from scratch once the new target is framed. I have never had a problem with PHD by doing so .

Only problem with that is you have to redo any dark frames - which means physically going to the scope and placing the cap on the scope. Instead, you can just tell PHD to "force recalibration", then you can stay in your nice warm office and continue with remote control.

[Interested]

Only problem with that is you have to redo any dark frames - which means physically going to the scope and placing the cap on the scope. Instead, you can just tell PHD to "force recalibration", then you can stay in your nice warm office and continue with remote control.

I have a library of darks as my camera has set-point cooling - always worked for me.

[dmahon]

A library of darks and set-point cooling for your guide camera?

I'm not even sure how to apply a library dark in PHD.

You must have some setup.

[Interested]

A library of darks and set-point cooling for your guide camera?

I'm not even sure how to apply a library dark in PHD.

You must have some setup.

Sorry....I didn't read properly. I've never used that utility in PHD - never had to as yet!

If I move targets I stop PHD. Once the new target is framed I restart PHD and re-calibrate. That's my way of doing, it works for me as I haven't had any guiding issues (so far).