Strange problem with guiding

[angryowl]

Hi all, first time poster here on SGL and I’ve run into some issues with PHD guiding, maybe someone can point out what I’m doing wrong

Equipment:

HEQ5 pro

30mm test guider with webcam

Synscan hand controller version 3.36

EQASCOM v1.28k

PHD 2.5.0

Setup:

Synscan hand controller in PC Direct Mode connected to laptop via a RJ-11 to DB9 female cable which goes into a DB9 male to USB adaptor cable.

Problem:

Whatever I’ve tried I cannot get PHD to move the mount in the RA axis when it’s doing its calibration or by the use of the manual controls.

I can however issue manual North and South declination pulses to the mount from PHD just fine and the mount moves no problem but manual East or West buttons don’t do anything.

When issuing manual DEC pulses from PHD, in EQMOD I can clearly see the mount position clock changing correctly for DEC but not for RA. I also only see DEC pulses being received in the EQMOD Message center when trying the manual controls.

Here’s the funny part – with no tracking on obviously PHD calibration will not complete as it tries to move the RA axis first to the West and then East and once it sees the star not moving at all it simply fails with error ‘the star did not move enough’. However if I turn on sidereal tracking from within EQMOD and start the calibration procedure in PHD then the calibration will complete as it can actually see the star move on the RA axis. But as you can imagine you wouldn’t be able to guide much with this calibration.

Also after completing the above-mentioned calibration and get PHD to guide I can clearly see Pulse guide messages in the Message Center from both RA and DEC.

I tried increasing the calibration step size and MAX duration for RA and DEC in PHD to no avail. I also tried PHD 1.14.2 and EQMOD 1.27k and still the same result, even tried MetaGuide still no luck.

I know I can manually issue RA pulses from EQMOD during PHD calibration just to get a good enough calibration to get my guiding going but I question the accuracy of guiding this method could provide.

I have not looked at upgrading the SynScan to latest version 3.37 and if all else fails that might be my next step towards fixing this strange issue. From Skywatcher’s site:

SYNSCAN V3 HAND CONTROLLER FIRMWARE V3.37
Supports more PC commands with increased compatibility with ASCOM software.

If any of you fine people care to shed some light on this one would be very thankful

Thanks all

[Tinker1947]

I use a EQDIr adapter not sure if one would make any difference, hope fully somebody can say yes or no.....Welcome to SGL....

http://www.firstlightoptics.com/astronomy-cables-leads-accessories/hitecastro-eqdir-adapter.html

[kens]

I don't understand your problem. Once you turn on Sidereal tracking your calibration completes and you should be able to guide. I also found I need to turn on Sidereal before being able to guide in RA.

Are you confusing Tracking (following the stars as they traverse the sky) with Guiding (incremental changes to keep the star centred due to imperfections in tracking) 

Having said that, like the previous poster I quickly changed to the EQDIR cable which is much more reliable

[jsmoraes]

If you can move RA and DEC by EQMOD manually, the connection is OK.

You must set sideral speed in EQMOD if you are trying stars and DSOs.

Did you set correctly your mount in EQMOD?

Wich is the parameters for calibration: milliseconds for calibration steps ? If they are small, RA will not work well.

Did you set the parameters for your guiding equipments in PHD: camera pixel, etc.?

The Calculate button will set parameters to you. You can modify for better performance after.

Do the calibration with Dec guide mode in Auto. You can change it after the calibration

Take a read at:

http://openphdguiding.org/man/Advanced_settings.htm#Guiding_Tab

http://openphdguiding.org/man/Advanced_settings.htm#Camera_Tab

http://openphdguiding.org/man/Advanced_settings.htm#Mount_Tab

http://openphdguiding.org/man/Basic_use.htm#Automatic_Calibration

[angryowl]

Thanks for all the responses guys

One thing I stupidly forgot to mention was that I only ever attempted calibration with an artificial star as I wanted to get familiar with the process and I just assumed that PHD would let you send manual and calibration pulses to

the mount when sidereal tracking was off. It seems as though it doesn't and the only way to get it done is with tracking on.

Does this mean that on an artificial star when tracking is on PHD can still get a good calibration as even though the star is moving across the image (tracking is on and star is still) the RA pulses sent to the mount still slow down or speed up the RA movement?

If not is there no way for someone to practice guiding or calibration on an artificial star? It would be a nice feature to be able to trick PHD or any other guiding software into thinking tracking is on so it can send RA pulses to the mount. That way one could play around with the star by moving it slightly to see how well the guiding software stays on it. 

Is this default behaviour with all guiding software out there?

[Dr_Ju_ju]

Yes, you need to have tracking in EQMOD on. PHD then 'nudges' the mount to keep it pointing in the right direction. 

[kens]

I can't imagine how you could learn anything by calibrating and guiding on an artificial star,

There's no need to test how well it guides - it does it better than you can imagine.

Most of the things to learn on PHD are to do with how it interacts with real stars.

Just go outside, make sure you have your guide scope focal length and pixel size correct, pick a star then start guiding. PHD will automatically start its calibration run.

Once you've done that do a PHD drift alignment to get reasonably close to the pole and you are ready to start autoguiding.

Then just sit back and watch the pretty red and blue graphs

[ollypenrice]

Surely what you're trying to do with an artificial star is impossible. If the tracking is on then the mount will drive away from the star . If it is isn't on then there will be no response, I don't suppose, from the guide inputs. (Just thinking playfully, you could always set up a second mount parallel with the one you're testing and fix an artificial star on the end of a long pole for the other one to track... I've had better ideas!  )

Olly

[jsmoraes]

What is guiding ? And why use it ?

1) All mounting has a Periodic Error due to imperfection of the gears. Therefore you will have errors of speed of movement. Sometimes the star will be left to East (fast speed) and others times the star will be left to go toward West (slow speed). The guiding will correct this error, sending pulses to speed or slow down the mouting. The star guiding will be the target, and will tell to PHD if the speed is faster or slower.

2) If you have some error with Polar Alignment the star will scape to up or down in the scope field. Despite the RA speed is absolutely correct. The guiding will correct this error - if the error is small.

So, you only can use PHD in real scene ! With true stars and with sideral speed of movement of your mouting.

[ollypenrice]

Guiding also corrects for the shift in apparent stellar position due to the changing refractive index of the atmosphere with altitude.

Olly

[angryowl]

Surely what you're trying to do with an artificial star is impossible. If the tracking is on then the mount will drive away from the star . If it is isn't on then there will be no response, I don't suppose, from the guide inputs. (Just thinking playfully, you could always set up a second mount parallel with the one you're testing and fix an artificial star on the end of a long pole for the other one to track... I've had better ideas!  )

Olly

Correct if tracking is off there is no response in PHD. I was under the impression there would still be and PHD could still move the mount on the RA axis by sending manual guide pulses

What is guiding ? And why use it ?

1) All mounting has a Periodic Error due to imperfection of the gears. Therefore you will have errors of speed of movement. Sometimes the star will be left to East (fast speed) and others times the star will be left to go toward West (slow speed). The guiding will correct this error, sending pulses to speed or slow down the mouting. The star guiding will be the target, and will tell to PHD if the speed is faster or slower.

2) If you have some error with Polar Alignment the star will scape to up or down in the scope field. Despite the RA speed is absolutely correct. The guiding will correct this error - if the error is small.

So, you only can use PHD in real scene ! With true stars and with sideral speed of movement of your mouting.

I fully understand what guiding is/does. My idea was to move the artificial star by millimetres or so in random directions just to test if PHD would actually work with my setup and follow the star. Now I understand what I was trying to achieve is not possible and can only really be done in an imaging session.

I was not sure if this was normal PHD behaviour, not being able to send manual West and East pulses to the mount whilst tracking was off, and thought my guiding setup went wrong somewhere. 

Funny thing is all guiding tutorials and articles I found never mentioned that the RA West and East manual buttons on the guiding software in question don't actually work unless you have tracking on so I think that threw me off even more.

Anyway, thanks to all for helping out a newbie   and I guess I'll just have to wait for the weather to clear up, whenever that'll happen   , to test guiding out

[jsmoraes]

Maybe a small contribution to your thinking. The following words is how I understand the guiding action from PHD. 

However if I turn on sidereal tracking from within EQMOD and start the calibration procedure in PHD then the calibration will complete as it can actually see the star move on the RA axis. But as you can imagine you wouldn’t be able to guide much with this calibration.

Also after completing the above-mentioned calibration and get PHD to guide I can clearly see Pulse guide messages in the Message Center from both RA and DEC.

It is not the pulse from PHD that will go to the mounting as motor pulse. The RA motor is always receiving pulse from its control with frequence selected (sideral, Moon, Sun, etc.). PHD will transmit time pulse with request to change for plus or minus that frequence.

pulses to the motor from internal control of mouting:

sideral speed -  |...|...|...|...|

faster speed  -  |...|.|.|.|.|...| - PHD cause change for a while in the factor of division of main clock that generates pulses to motor to less value

lower speed   -  |...|......|.......|...| - idem above with factor of division greater.

The lower and greater factor value is determined by control of the mounting, not by PHD.

PHD only change the time of pulse that does this changing of frequence. In other words: the time that the frequence of internal generated pulses will be maintained changed.

PHD use a time pulse for correction.

It is different from ST4 interface that changes the actual value of frequence by its analogic level signal for correction.

note 1: my understanding can be wrong although.

note 2: the Dec motor is usually stopped. PHD send request to start the motor to one or to other direction. Time pulse, also. I understand that with the frequence determined by the factor value you set in EQMOD to DEC movement. The same used for manual DEC movement. I can be wrong, also.

You can play with artificial star if you turn on the sideral tracking.

Guiding also corrects for the shift in apparent stellar position due to the changing refractive index of the atmosphere with altitude.

Thank you Olly for completing my description. I forgot it !

[jsmoraes]

A little correction.

The DEC and RA frequence can be a percentual of sideral frequence adjusted  in EQMOD: ASCOM pulse guide settings Tab. With these adjustment you can do a faster or slower movement of mounting during the time of pulse generated by PHD.

ST4 PORT  method issues pulse commands directly to the stepper motors to reposition the guide star (From EQMOD manual). Sorry, I never used ST4 port. Actually I don't know well this interface.

[angryowl]

jsmoraes - thanks, I must admit I have not read the complete PHD manual (still in the process as we speak)   but thanks to your explanation it makes perfect sense now

[Merlin66]

Guys,

There actually IS a guiding software which does allow you to set up an "artificial star" on the PC monitor which moves across the screen to replicate the sidereal motion.

It can be fun (!!) to set this up to trial/ verify settings on a cold wet Sunday avo.

http://sweiller.free.fr/SGE/SGE-star-guiding-emulator.htm

I do disagree with the issue raised that the pulse guide through the EQ handcontroller is somehow suspect and unreliable. I know the EQMod (which I also use) guys may warn against it - but in over four years of use I've NEVER experienced any problem/ difficulty.

[chrisshillito]

I do disagree with the issue raised that the pulse guide through the EQ handcontroller is somehow suspect and unreliable. I know the EQMod (which I also use) guys may warn against it - but in over four years of use I've NEVER experienced any problem/ difficulty.

....but on the other hand in 9 years of providing EQMOD support I have come across folks who HAVE experienced problems/difficulty.  That's not to say that PC Direct won't work for you, just that some folks have experienced issues.  Please consider that Skywatcher make no promises that PC Direct mode is designed to work with EQMOD and EQMOD itself is not designed or tested  to to work with PC-Direct. That it works is a happy coincidence that could break with any new release of EQMOD or synscan firmware (and it has broke in the past).  Anyone seeking the most robust EQMOD setup is advised to use a direct connection to the mount.

Chris.

[angryowl]

Guys,

There actually IS a guiding software which does allow you to set up an "artificial star" on the PC monitor which moves across the screen to replicate the sidereal motion.

It can be fun (!!) to set this up to trial/ verify settings on a cold wet Sunday avo.

http://sweiller.free.fr/SGE/SGE-star-guiding-emulator.htm

I do disagree with the issue raised that the pulse guide through the EQ handcontroller is somehow suspect and unreliable. I know the EQMod (which I also use) guys may warn against it - but in over four years of use I've NEVER experienced any problem/ difficulty.

That's precisely what i was looking for. Now I can have a play with guiding indoors and know what to expect from it when I get out.