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Guiding doing funny things

Andrew*

By Andrew*
in Imaging - Discussion

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Andrew*

Andrew*

Posted
Posted

This seems to happen every time I try and do some imaging :(

I tried GuideDog. When set to guiding it promptly set the mount going. I could hear the mount doing some hard work - it put the guide graph off the scales and the guide star moved steadily out of the FOV.

Switched to PHD, got it callibrated (woohoo - that's a first!) and set it guiding. It didn't seem to make any corrections, neither audibly nor on the EQASCOM graph like I'd seen with GuideDog. The guidestar moves further and further from the crosshair and the mount seemingly does nothing to get it back. Tried fiddling with the RA agressiveness (tried 90-120) and DEC minimum (150-200ms) and also some settings in EQASCOM. Nothing improved the situation.

Where am I going wrong here?

Andrew

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adamsp123

adamsp123

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Andrew, if PHD calibrates OK ie you see the star move around during this procedure then it is moving the mount about, TBH I don't think you will easily hear the tracking motions as they are so small, well not on my mount.

How many steps did it take to calibrate in PHD?

You could have an inbalance - check balance with scope in different positions especially DEC balance with tube horizontal and Vertical.

Cable drag and flexture need to be eradicated.

I increased the calibration step length so it takes about 10 steps to calibrate, what time have you set in the dropdown box the one next to the stop button? 3 to 5 secs is good.

However I wonder if you have a mount problem, a faulty conection or something as you say you can hear it doing hard work - don't think that should be the case.

otherwise :(

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Andrew*

Andrew*

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Pizza - thanks for your help.

Andrew, if PHD calibrates OK ie you see the star move around during this procedure then it is moving the mount about,

Well, I don't think during callibrating it was even moving the mount. The star drifted in one direction only - up-left. I suspect this was due to regular PE or somesuch, and not controlled movements.

How many steps did it take to calibrate in PHD?

44 in RA and around 30 in DEC.

You could have an inbalance - check balance with scope in different positions especially DEC balance with tube horizontal and Vertical.

Cable drag and flexture need to be eradicated.

I think it was well balanced, and I doubt there was significant cable drag. Just a feeling, but I don't think it's a mechanical issue...

I increased the calibration step length so it takes about 10 steps to calibrate, what time have you set in the dropdown box the one next to the stop button? 3 to 5 secs is good.

You mean the exposure length? I tried one to two seconds. I thought the shorter the better??

However I wonder if you have a mount problem, a faulty conection or something as you say you can hear it doing hard work - don't think that should be the case.

This was only seen in GuideDog. Every exposure it would audibly move the mount, and with increasingly long correction times. In PHD there was no evidence that the mount was responding to the program.

I suspect that somewhere there's some setting I've got wrong. Might it be in EQASCOM? I have guiding enabled, but maybe one of the speed or minimum correction settings? I haven't changed many settings in PHD though.

Any more suggestions very much appreciated :(

Cheers

Andrew

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adamsp123

adamsp123

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Andrew,

to quote you "You mean the exposure length? I tried one to two seconds. I thought the shorter the better??"

In PHD the step length for both RA and DEC are in the Brain settings

so in "calibration step (ms)" increase this as this affects the number of steps for calibration, not the time drop down box in the main window.

For example on my 50mm finderguider I set it between 2000 ms and 2500 ms when I calibrate, I also increase the DEC step as well, I have the time set in main window to 3 secs and increase this once the guiding has settled down to typically 5 secs, not too short otherwise you can chase the seeing.

Make sure you don't have any backlash compensation switched on.

Pete

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Andrew*

Andrew*

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You mean there's a bit where you can reverse RA/DEC and I need to fiddle with that? I thought PHD'd callibration did away with that? But it might have been the issue with Guide Dog...

Andrew

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ollypenrice

ollypenrice

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I only know AtroArt but, yes, in that software you do need to check your orientation after calibration. You can swap x axis for y (if your camera is in at 90 degrees) and reverse directions on both axes if it is upside down relative to what the software is assuming. You have to change one axis after a meridian flip, for instance.

Olly

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dark knight

dark knight

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There was another thread somewhere about this, check to see how many Ascom Driver processes are running, someone found they had 2 instances running, one for PHD and another for Eqmod and their planetarium software, If memory serves me correctly this caused the same problems you are experiencing. The solution was to start PHD first, carry out calibration and then start their other Ascom related software environments. If I get a chance I'll find the thread and post the link here Andrew.

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Andrew*

Andrew*

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Thank you all so much for the support. There's lots here to check, try and tweak, and given a couple more frustrating hours at it I'm sure I will get it going!

I'll start by trying without EQASCOM running, then cycle through the various settings - bound to hit the right spot eventually.

One last thought - just hwo important is the guide star? Imaging Leo, guide stars weren't plentiful, and I picked one up whose SNR averaged 6.0 in PHD, at 1 sec exposure. Is this good enough??

Cheers

Andrew

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Whippy

Whippy

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One last thought - just hwo important is the guide star? Imaging Leo, guide stars weren't plentiful, and I picked one up whose SNR averaged 6.0 in PHD, at 1 sec exposure. Is this good enough??

I've found that if you can't see a star on the screen then neither can PHD Andrew. On the M106 image I did recently I had to use 4 second exposures to get a star!

Tony..

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Andrew*

Andrew*

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Tony, there was an obvious star on the screen. I was just wondering how much it matters to PHD if it's bright or dim.

The stars from the guider were quite elongated. I'm using an OAG, so I assumed that so far off axis, the stars become distorted. I didn't think anything of it, but maybe PHD requires a good quality star of the round variety otherwise it gets confused...

Andrew

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