Please Post your PHD Graph and Settings

[ejcruz]

I'm trying to understanding how to further fine tune my guiding with PHD and to get a better understanding what the PHD graph should look like, would much appreciate if you can post:
1. Model of your guide scope
2. Model of your mount
3. Your PHD graph set to 100 iteration
4. Your PHD settings

My current settings are:
1. Guide Scope: SW 80mmx400mm
2. Mount: HEQ5 Pro
3. PHD Graph
http://ejcruz.smugmug.com/photos/734971429_t8Cxp-S.jpg
4. PHD Settings
http://ejcruz.smugmug.com/photos/734971461_xZHRo-S.jpg

Thank you for your help.

Cheers
Eddie

[AlexN]

Eddie - can you post your graph and settings images a little bigger so we can see whats what?

From what I could see in your graph it all looks fairly controlled. an oscillation index of 0.26 is quite acceptable indeed...

[multiweb]

Looking at your specs assuming you guide with a Q-guider (QHY5) your image scale is approx. 2.7arcsec / pixel so your guiding is in the vicinity of +/- 2.6 arcsec. Not bad at all on an HEQ5. Your RMS is very good, your OSC a bit low though. 0.3-0.4 is more the norm?

[ejcruz]

Here is a larger version:
http://ejcruz.smugmug.com/photos/734971461_xZHRo-O.jpg
http://ejcruz.smugmug.com/photos/734971429_t8Cxp-O.jpg

Yes it's a QHY5 guide camera, thank you for the advise however, how do I improve my OSC.

Cheers
Eddie

[g__day]

I'd try up the Hysteresis from 10 to 20 and see if that improves things.

Secondly once you've optimised Hysteresis try varying the minimum move before guide command issued between 0.1 - 0.8 in say 0.05 increments to see what works best for you. You could be chasing the seeing!

[multiweb]

Everytime I got a low (<0.2) or high (>0.5) OSC I was guiding close to the celestial equator. 90% of the time it was a balance issue (west too heavy or too well balanced with high backlash in RA) or poor polar alignment. The rest 10% was the agressiveness in PHD. Lowering it to 60% smoothed things up. Seeing can make your guiding turn to .... real quick too, so something to consider. Bad seeing, longer guider exp. (2-3s). Normally 1s works nicely for me in good seeing. Your RMS is very good though. I typically get 0.3-0.4. May be because I dither and bump the mount all the time though.

To improve your OSC. Be east heavy all the time, get your polar alignment spot-on so you hardly correct in DEC, guide every 1-2s minimum. Pick a bright enough guide star. I found picking the right star makes a hell of a difference. Not too bright but not to dim either. Problem is that PHD will guide on really faint stars too, but the guiding IMO is not as good?

[ejcruz]

Thank you, I'll give Hysteresis a shot

Good points, thank you, will give balancing more to the east and Hysteresis a shot.

I take it the whole idea of the graph is to flat line it as much as possible.

Cheers
Eddie

[multiweb]

If you flat line at your image scale you will be well under +/1 arcsec/pixel :thumbsup:

[AlexN]

Yes, a flat line is the target, however this would essentially mean 0 guide corrections/tracking errors... With a HEQ5, a flat line is unlikely... Providing your tracking errors and guide corrections are lower than your imaging resolution you can be assured that your images will come out just fine...

I don't have screenshots of my Maxim guide graph, however I run 20 ~ 30 min subs day in day out with my HEQ5 and my guide graph looks much the same as yours, oscillations are perhaps a little smoother, but I think Matt's suggestion about increasing the hysteresis should sort that out for you.

[ejcruz]

Ok I get the idea now with the graph, from all the playing around I've done so far it looks like I need to zero in on the Hysteresis, Min motion (pixels), and balance more to the east (as my current setup is perfect balance all round).

Cheers
Eddie

[AlexN]

Yep, Perfect balance is not perfect for imaging! :)

[g__day]

I'd never expect a flat line - for one seeing and scintillation would always produce errors - you just have to try and adjust PHD not to respond to these errors where possible.

Craig is considering multi-star guiding - I've dropped him a few articles, notes and excel files comparing guide performane from 1 -> 20 stars (averaging each star's local gude error can significant improve guiding out drift - not seeing). Hope will get it before Feb 2010 - as even a 5 star guide should halve guide errors based on the MaximDL Multi-star guide add on results.

Matt

[pjphilli]

Hi Marc
I am still a bit confused about "east heavy" when referring to DEC movement since this is in the north south direction. How is "east heavy" achieved to assist DEC guiding. Cheers Peter

[multiweb]

East heavy is for RA. In DEC a slight imbalance is also recommended so you push the load, unless you have zero backlash and no drift. DEC drift will affect your RA guiding regardless.

[pjphilli]

Thanks Marc - got it now! Yes I normally have my balancing east heavy so that RA has a load to work against but have usually had my DEC balance about neutral, so I will change this to hopefully fix the mysterious jumps I have been seeing in my PHD DEC guiding (as mentioned in another thread). Cheers Peter

[OzRob]

I did a Google search to find out the meaning of osc and rms in PHD and ended back here. Some good information.

Scope: WO M72
Mount: EQ6 Pro

I have also used PEC which probably helps with the guiding. I tried to increase the osc but anything I did decreased the value. I think the guiding is pretty good.

[ejcruz]

Rob that's excellent guiding, thank you for posting, can you advise how you did and updated your PEC recording to the handset.

Cheers
Eddie

[OzRob]

Hi Eddie,
I used Pempro to measure the PE and create the PEC. You can then send it to EQMOD or to the mount. The program works very well with the Orion Starshoot so should work with the QHY5 as I believe they are the same camera. A very useful function in Pempro is the polar alignment tool. You can try it for 60 days for free.

[danielsun]

Rob, that is an award winning graph!:thumbsup:

Cheers Daniel.

[pvelez]

So if my Dec keeps dropping off the chart, despite playing with the settings, I have lousy polar alignment - yes?

Pete

[pvelez]

Actually, if my Dec drops off the chart at the same time as I have a spike in RA, I have lousy polar alignment and need to do some serious PEC work - yes?

Pete

[pvelez]

Here is the graph - in all its gory detail

Pete

[multiweb]

Pete, looking at your graph seems that it's a combination of both misalignment and balance. The sudden shift in RA is balance and will effect DEC as well. The progressive drop in DEC can be balance in DEC but most likely poor polar alignment. Disable the guide output in PHD and graph the tracking so you can drift align then start guiding again and it'll be spot on.

[pvelez]

Thanks Marc - I had a suspicion it was poor alignment. I didn't think it was balance. I'll have another go tomorrow night (weather permitting).

I only discovered the graph function last week - it sure is helpful to show how off my alignment can be. I guess EQMOD masks all this as the pointing accuracy isn't too bad when its synced on a few close stars.

Pete

[suma126]

its a silly question but how do you get the graph to work Ive try ed last night but nothing happened

[Octane]

Shane,

Assuming all your gear is hooked up.

Connect to mount
Connect to camera
Choose a reasonable frame interval (to start off with I have 2 seconds)
Start capturing (blue arrow button)
Stop capturing (once stars appear on screen)
Select a star
Press PHD Guide
Click Tools > Enable Graph
Click the button with the number on it to change the scale. I have mine set to 50; when set to 50, each dotted line on the graph represents 1 pixel, so it's easy for me to see how my mount's performing.

H

[suma126]

so Ive got to be connected to the mount to use the graph. cant i just use the camera with the graph.

[Octane]

Good question. I've never tried. If you disable the guide output in the advanced settings (brain button), I don't see why not!

Marc might know.

H

[mill]

Guide scope: modded finder scope
Mount : EQ6
PHD settings first pic.
Graph second pic.

[Astrobserver99]

Here is my graph as an example. The osc index can range between 0.2 and 0.55 depending on the conditions and part of sky being guided.

C8SCT
HEQ5Pro
QHY5
GSO 8x50 guidescope
PHD of course

Polar aligned with alignmaster

[White Rabbit]

I'll post my graph and setting tonight but just wanted to say that PEC training helps, a lot. I use to think my mount was a dud until I pec trained it.
If the light poloution wasnt as bad as it is where I am I'd could do a hour sub no problem.

PEC PEC PEC. if you having issues train it.

[telemarker]

Hi Eddy, :hi:
Thought I'd show you how your old mount is going. This is guiding with a modified finderscope. Still finding my way around Eqmod but getting some reasonable images.

[White Rabbit]

Here's my graph as promised, a little late but...

I recommend pec training if you are having problems, worked for me.

[pvelez]

Any tips on a program to PEC training an EQ6? I use EQMOD

Pete

[White Rabbit]

You'll need two programs Pe Recorder and Pec prep. You will also need a
web cam.
Here is a link to pec prep
http://eq-mod.sourceforge.net/ppindex.html
Here is a link to PE recorder.
http://perecorder.wikidot.com/

Pe recorder will take about an hour to gather enought PE data then you import the file into pec prep for editing.
Pec prep will take a good portion of the rest of you life to figure out what the hell you have to do. I just moved stuff around until my curve looked like a sine wave and it seemed to work.

Have fun.

[wasyoungonce]

Damned if I can get PHD to open a graph it has logged (from the previous night). I opened them OK with PecPrep.

Maybe This is writing something to the log file & upsetting PHD graph function.

[pvelez]

Thanks for that.

One issue for the gurus - as I have to lug my scope outside each time I use it, do I need to rerecord PE each night?

I see from the EQMOD site that if parked at the end of a session, the mount recalls the worm gear position next time its powered up. Is this still the case if I then disconnect and power down my laptop? And will the fact that I need to re-align each night mean I also need to rerecord PE?

Its all new to me - when I master one aspect of this game, something new appears to throw up more confusion

Pete

[bartman]

I actually asked myself this question when I read this post!

So dito to Pete's question....

Bartman

[White Rabbit]

I use the same pec file everytime. I think the only time you have to rerecord your pec is if you change the weight on the mount ie bigger or smaller scope.

[pvelez]

OK - so if I set up afresh the night after recording the PE, I will need to rerecord if I have not positioned the OTA on the mount in precisely the same way or if the counterweights are not in precisely the same spot as when the PE was recorded.

Oh for a permanent set up

Pete

[White Rabbit]

No you wont have to rerecord your pe every night only if you change you set up from a larger or smaller scope. If you scope is balance properly it wont matter where the weights are at any given moment so you pec rec will still be ok.
I pack mine down all the time and have only ever recorded one pec file.

[peter_4059]

Here's mine from last weekend.

[swannies1983]

I've attemptig to guide using PhD and i was wondering if I could get some feedback.

This is my setup
Mount: EQ6
Scope: 8" Newt (f/6)
Guide scope: 60mm refractor (f/11.7)
Guide camera: unmodded toucam
Imaging camera: unmodded Canon 400D
Guiding method: Shoestring. ST4 input is on handcontroller, not on mount.
Guide camera image scale: 1.65 arcsec/pixel
Imaging camera scale: 0.98 arcsec/pixel

I don't have that much DEC backlash but I tend to either guide NORTH or SOUTH in dec. I do run into some issues when in DEC AUTO mode.

My problem is that I'm starting to get drift in RA. This generally only happens when I have DEC guiding off. Take the two shots for example. The first shows guiding with DEC guiding in AUTO mode. I still have to sort out the brain settings to try and reduce the oscillations. I also sometimes experience large jumps in DEC, which also impacts RA. I assume this is a backlash issue?

In the second example, DEC guiding is switched off. There is some drift in DEC (bad ploar alignment), but you can also see drift in RA. I'm not sure why this is the case. PhD does send pulses but it's just not moving the graph back to the central line. I assume this is what PhD is supposed to do? Any ideas?

Also, I'm not up-to-scratch in knowing how much I need to try and reduce the oscillations based on imaging scales. Would my guiding (based on the first picture), be ok with those oscillations? I guess I should just try some pictures and see how they turn out.

[g__day]

Its a good idea if folk always post image scale - arc seconds per pixel. I might guide at +/- 2 pixels, but if each pixel is natively 0.44 arc seconds (then I bin 2*2) - and seeing is really below 3 arc seconds a pixel - I won't see any discernible drift or badness in a 30 minute sub typically as I am oscillating back and forth maybe an arc second - which can just be variances in the seeing for my night skies.

[swannies1983]

I think that's a good idea Matthew. If it wasn't for a thread over on cloudynights (sorry, the link isn't working at the moment), I would still be pulling my hair out trying to get graphs similar to what has been posted in here. I am never going to achieve the "flatness" as shown in here because I'm using a guide scope with a focal length of 700mm.

[swannies1983]

Has anyone had problems with overcorrections in DEC? I mean when guiding in either NORTH or SOUTH, not AUTO mode. I know you can change the aggressiveness in RA but not DEC. I have been informed that you can change the "aggressiveness" by first calibrating and then reducing the DEC guiding rate prior to guiding. Anyone tried this? I will try once I get a clear night.

[pjphilli]

Hi Dan

I also had problems with over correction in DEC about a year ago. A thread on Stark's forum covered this. It appears that some set ups have this problem when the DEC Algorithm is set for Low Pass Filter. I changed this
to Resisting Switching and the problem went. I usually set my DEC for a slight unguided drift in N direction and set the DEC guiding to Auto. For me this provides the best results. Hope this helps.

Cheers Peter

[swannies1983]

I tried doing a search over Stark's but I couldn't find anything. I will try again.

It appears that I am already using "resist switching." Guiding in auto mode tended to produce worse results. I thought stiction might be a problem but I have recently regreased and set the worm gear so there's no binding. It's much smoother compared to what it was prior to the tune up as I did find the dreaded black "glue."

I will try a few different things tonight if the clouds clear.

Cheers

[swannies1983]

I am outside trying a few different things but nothing appears to work. I have calibrated at a high guide rate (1x) and then dropped the guide rate down (0.2-0.5x) prior to guiding but it didn't solve the issue. I think it might be stiction(?) problem. I see that there are times that PhD tries sending a command but there is little movement and then all of a sudden I can hear the belt/motor "click," followed by a large correction, shooting the DEC line well above the 1 pixel line. There's no binding and I can move the DEC axis by turning the pulley/belt.

[swannies1983]

I think I may have found the issue. Thanks to Chuck over on Stark's, he suggested that I check the belt system, making sure it was tight. There may have been some slippage causing the large jumps in DEC. Sure enough, there was a little slack so I tightened it up. It seems to have helped as movement wasn't as large after a few test runs. The graphs were much more stable and the RMS value was around 0.41 which is fairly good given that I'm guiding with an image scale of 1.44 arcsecs/pixel. I will try again tonight to see if it was just "pot luck." Silly me, as this is probably something I should have looked at earlier.

[swannies1983]

I'm getting totally confused about what I should be looking at when guiding with PhD. Can anyone explain the attached graph? In blue, we have RA and in pink we have dx. I haven't included DEC/dy as I wasn't guiding in DEC for this period.

So the RA line is what we look at when determining our Osc index and RMS values. Going by my image scale, the RMS for the blue line is ~0.4, which is good for me because I'm guiding at 700mm. I have been informed that PhD is doing what it's supposed to be doing based on the RA line. However, my confusion is that if PhD is "guiding" correctly, why is there "drift" in dx (pink line), which I can confirm when looking at the star i.e. it's moving away from the crosshair?

[pjphilli]

Hi Dan

From your first para I assume that you had DEC guiding in the Brain turned OFF but you had trained PHD to guide in RA.

If this is the case then your graph is perfectly normal. It shows RA being guided well but as you are not guiding in DEC the red line is drifting up
in a steady manner. This is because your mount is not exactly polar aligned.
To use PHD effectively you first need to polar align your mount at least
approximately as if the DEC drift say up as in your case is excessive, PHD has a hard time continually bringing the rapid drift back to zero (ie guiding in DEC). This appears to be the symptom of your original problem.

I usually set the DEC drift so that is is slightly biased in one direction (say up as in your case). PHD then has no difficult in correcting this small drift and keeping the DEC guiding near the zero line. To reduce your current large drift you may use PHD to trim up your polar alignment.
Firstly chose a guide star fairly high up on the celestial equator. The move your mount's azimuth knobs say half a turn, noting the direction of movement. This will shift the guide star on your PHD screen out of PHD's guiding range so you will have to stop guiding and reselect the star.
Then resume guiding and note the magnitude of the DEC drift. If it is smaller then you have moved the knobs in the right direction, if not, do this again reversing the movement of the knobs. In this way you could then achieve the condition where the red DEC line is oscillating about the zero line. This would indicate near perfect polar alignment. However, as above, I like to introduce a small drift from the zero line so that when
guiding, PHD DEC guiding does normally not have to cross the backlash zone.
Having done, go into Brain and set the DEC guiding to auto and then retrain PHD for both the RA and DEC directions. I usually set the steps so that there is about 10 or so training steps in each RA direction. After this is done commence guiding and you should now find that you may guide normally in both RA and DEC.

BUT, if you do the above and you still find that the red DEC line is continuously drifting above the zero line this could indicated that your
guiding PC is not communicating with your mount in DEC. How do you check this? You can go into the Shoestring site at the following url
http://www.store.shoestringastronomy.com/downloads.htm
and download the software utility GPINT Check or GPUSB Check whichever suits your PC/mount interface hardware. Run this small utility and it will present you with a screen showing RA and DEC direction buttons. These may be selected with your mouse. Select the appropriate connection protocol from the top left hand list (same as you use for PHD). Set up your mount etc at any time (ie daytime and no need to mount scopes ) and select as normal and go to a guide star and the mount head will move to its position and then hit enter to confirm the completion of guide star position. Then on your Synscan paddle select Utility Function and Show Position. Hit enter in this location to show the actual coordinates of RA and DEC.You should see the DEC steady and the RA moving slowly as the mount tracks the "star". Select the utility RA and DEC movement squares on your PC screen with your mouse. If you hit DEC up and then DOWN you should see the DEC coordinates of your mount move up and down. Similarly RA + will move the RA coordinate change faster and RA minus will show the opposite change in RA direction. If these functions work it shows that your PC is communicating properly with your mount.

Long winded Dan but see how the above goes and let me know.

Cheers Peter

[swannies1983]

Peter,

Thanks for the information. I should have updated my post because I feel like an idiot. When guiding, I have been looking at the dx/dy graph when I should be looking at the RA/DEC graph :ashamed: I can see my RA guiding is quite good for my image scale.

I went through a PhD polar alignment process last night but the wind got the better of me.

So, that issue is out of the way. The next is trying to sort out DEC guiding. As you do, I also try to have a little drift in one direction so that I don't have to deal with backlash. My problem is that despite good calibration, I get large jumps in DEC when guiding in DEC, sometimes moving 1-3 pixels. Again, I'm only guiding in N or S so I could understand the large jumps if guiding was set to AUTO.

From what I have learnt, improper balance, binding, stiction are all factors that can contribute to these wild oscillations. I have recently tuned up DEC and it appears to move freely, no binding, not stiff, very little backlash. It's much better than it was before. I balance eyepiece heavy. I have also tried calibrating at one guide rate and then just before I start guiding, I drop the guide rate to it's minimum (0.2x). Nothing seems to prevent the large oscillations when a pulse is sent to DEC. The only option is to get fairly accurate polar alignment so that very little work needs to be done in the DEC direction.

[pjphilli]

Hi Dan

When you have polar aligned your DEC to give a slight drift you may find that your guiding will be better. Personally, I do not pay much attention to balance in DEC but try to get the RA balance reasonable. A couple of points:

I notice that you have an EQ6 mount which can take a good load but apparently you have an 8 in dob mounted on it plus other accessories?
I have found that the manufacturer's guide to mount loading is always a bit optimistic. I have a EQ5 mount which when fully loaded did not guide so well. When I reduced the loading to about 2/3 of the manufacturer's max loading I found that guiding went much better. So check your loading.
I also find that when guiding even a slight puff of wind will cause my guiding to go off a few pixels but when the wind drops it quickly goes back to normal (using 1 second guiding). In this case a few pixels diversion in RA or DEC is not uncommon. Keeping in mind that if this does not happen very often during say a 4 minute image then the stars are only put off for a very short proportion of this imaging time and I usually cannot detect any problem in the image display. If wind gusts occur too frequently I usually give up guiding for the night.
It is hard to reach perfection in this imaging and guiding business so don't
be too concerned if your guiding is pushed off a few pixels occasionally.
Don't worry - be happy! :)
Cheers Peter

[swannies1983]

Yeah I have an 8" on there. That and an old 60mm refractor as a guidescope and a canon 400D. Total payload weight is around 13-14kg. That should be OK given the MAX rating is 25kg? Guiding in RA appears to be fine. I just have to sort out the large jumps in DEC when a pulse is given.

True about the wind. I went out the other night and the wind started to pick up and was averaging about 15km/hr, gusting up to about 25km/hr. This was a complete waste of time. Of course last night was completely calm but we had some high cloud. It was gone by about 11pm but I couldn't be bothered setting up.

Also recently got myself a light pollution filter (thanks Tandum). I also sorted out how to use the filter with my set up (see http://www.iceinspace.com.au/forum/showpost.php?p=777694&postcount=9). Of course the moon doesn't want to play nice and the weather looks terrible anyway.

[pjphilli]

HI Dan
Yes your mount weight should not cause any problem. You will find that your light pollution filter will require about double the exposure times but I live in a very light polluted area and on balance I find I come out in front with use of a light pollution filter. I use the bright Moon period to do any tests and object scoping to be ready for the dark Moon.
Cheers Peter