Continued PHD Problems !

[Deneb]

Hi

As I thought my PHD problems had gone, they came back last night, it was a decent night & I was faffing about with my DEC problems from the other night, im starting to clutch at straws now.

I've checked the pins of the st4 connections this morning to see if theres nothing out of the ordinary eg. bent or something, but everything seem fine, I even took off the ccd camera off last night just to see if the dec axis was out of balance with it on, while just guiding with the scope. im now thinking could it be the flimsy st4 cable im using. Someone please help mmmmeee!

I've attached the graph from last night also the log & settings window, the dec gradually walks off the graph.

Cheers

Nadeem

PHD_log_10Apr11.txt

[Deneb]

Sorry I've put this in the wrong section, It should be in Imaging Discussion.

Nadeem.

[Deneb]

Just found this:

Yahoo! Groups

Nadeem

[Glider]

Is the mounting hitting a programmed limit and stopping moving in dec?

[Deneb]

Is the mounting hitting a programmed limit and stopping moving in dec?

not far as I know it's not, I have set no limit on it... nor programmed the mount to stop moving the dec axis at a certain point. I had this guiding for about 5mins the other night without an issue.

Nadeem

[jnp]

Bad luck mate. I've still get the odd DEC issues on EQ5/EQ3 with backlash suddenly catching up and it suddenly flying off the scale . but I haven't seen your problem before though.

The deviation can be caused by several issues including:

1. the DEC motor is getting the wrong signal (i.e. errors in calibration) leading to a feedback effect. Did you recalibrate in the same part of the sky etc?

2. the DEC motor has stopped getting any signal (in which case the drift is significant polar misalignment). The cause could be physical connection or software issue.

It's important to know if the mount is responing correctly when guided from PHD. Try using the "Tools\Manual Guide" buttons in PHD to see if the mount responds as expected.

You mentioned 480mm focal length in the other post, is that a newer guidescope, the older 60mm one was approx 220mm?

John

[Deneb]

Noted John, sorry my mistake your correct it is 220mm, i think i was thinking about an st80 or something...

I Did recalibrate the same part of the sky, thinking I had to after mucking around with the phd config.

Nadeem.

[Glider]

It could be worth checking the default limits. What were you imaging?

How many steps did PHD take to train in RA and DEC? Did it have to clear a lot of backlash during the process?

What versions of HC and MC software is your mount using?

[Merlin66]

I agree with the manual checking of the PHD movements - this will quickly show if the commands are getting to the correct motor.

[Deneb]

hopefully it will clear tonight, Manual/Guide seems logical, i'll try that tonight..

Nadeem.

[martin_h]

I had exactly the same problem and found it was Dec backlash. Now before I calibrate in PHD I center up the image then move it south, then bring it back north-taking out the Dec backlash, then calibrate in PHD it now takes 2-3 secs to remove backlash.

[dc509]

Have you tried increasing the max dec duration? I had a similar problem and upped it to 500 - sorted it straight away

d

[James]

Have you tried increasing the max dec duration? I had a similar problem and upped it to 500 - sorted it straight away

d

Seconded - 100ms is a bit short - guiding through a Megrez 72 I needed to bump the Max Dec duration way up (750 ish I think). Also taking up the slack in dec can help as mentioned above.

Polar alignment using the mounts inbuilt routine is worth trying. With the EQ6 it's easy to roughly polar align using the polar scope and actually get quite close, certainly close enough for autoguiding whereas on my CG5 for example if you just got Polaris visible in the polar bore hole the polar alignment could still be 1-2 degrees off.

James

[RobH]

It's not somethging as simple as a cable getting caught is it?

Guide camera not rock solid?......I've seen graphs like that caused by these issues.

[Deneb]

checked all that Rob..

Nadeem..

[RobH]

Thought you would have Nadeem, but it's always worth asking

I had awful issues caused by a slightly loose prism in an OAG once that took a good while to pin down.

Cheers

Rob

[Uranium235]

Have you tried changing the guiding direction to north or south only?

Ive found that if the max dec duration needs to be any longer than 350, then somethings seriously not right (PA, balance, cable drag). Because high values will punish you with massive overcorrections when it finally does catch up.

PHD ey? Just when you think its sorted, it comes back and bites you on the nads

[Deneb]

Have you tried changing the guiding direction to north or south only?

Ive found that if the max dec duration needs to be any longer than 350, then somethings seriously not right (PA, balance, cable drag). Because high values will punish you with massive overcorrections when it finally does catch up.

PHD ey? Just when you think its sorted, it comes back and bites you on the nads

Done that as well, Im just waiting on a better night to tryout the max dec duration settings, last night was too murky to do any type of imaging... I think the Polar Alignment is the issue, as I was relying on the mounts software for alignment. On the CGEM the polar scope is not included, now that i've bought one - just have to polar align the mount using the scope then see how much that makes a difference...

Nadeem

[Deneb]

Hi

I have tried what James had suggested increasing the max dec to 750ms it worked for around 8mins then the Dec flew off again, I had to set the Max Dec again upto 900ms, but after 5 mins that started to drift slightly as well, not sure what else to try now.

Checked the usual things again & even replaced the ST4 Cable with one supplied by Astronomiser. Im just wandering could it be the mount playing silly..?

Cheers

Nadeem.

[shaunster]

Is it possible polar allignment is way off? I dont know the allignment technique with the Cgem but maybe it isnt working?

[Deneb]

I have polar aligned with the polar scope & the alignment of the Mount software with the Calibration Stars.

Nadeem.

[kookoo_gr]

last night i had similar problems with you deneb. everything were as they were supposed to be but my phd graph at random intervals drifted like yours and also at random times i had a spike at the opposite direction. after a discussion i had i may have issue with my power supply to the mount since i supply my mount and laptop from the same battery. how do you supply your mount? if you supply your mount from battery just like me try to supply your mount from a different source. i didn't try yet this solution as it got cloudy and after a few hours it started pouring cats and dogs, but it's an alternative.

[Deneb]

last night i had similar problems with you deneb. everything were as they were supposed to be but my phd graph at random intervals drifted like yours and also at random times i had a spike at the opposite direction. after a discussion i had i may have issue with my power supply to the mount since i supply my mount and laptop from the same battery. how do you supply your mount? if you supply your mount from battery just like me try to supply your mount from a different source. i didn't try yet this solution as it got cloudy and after a few hours it started pouring cats and dogs, but it's an alternative.

Hi

The power source is supplied by a 110ah Deep Cycle Leisure Battery, for the mount, camera, Filterwheel & dew heater if needed.

Nadeem.

[kookoo_gr]

try to power the mount from a different power source if you can supply it from your car do it. i will try it tonight for my mount if the weather permits

[Merlin66]

Nadeem,

Looking back over the thread you seem to have done everything right, but I gather you're still having Dec guide problems....

Exactly which guide camera, which mounting arrangement, are you using? Is there any chance the guide mount is moving/ slipping/ sagging?

It seems very strange that you get 8 mins of OK guiding and loose it.

That sounds like the period of the worm wheel??? Is there any binding obvious????

I use PHD all the time with the HEQ5 and NEQ6 for spectroscopy and any problems I find, are usually related to cables/ connections or balance (too much-too little) So whatever is actually happening it must be resolvable......