I am reposting this image of my best PHD graph - because I have been unable to replicate it since.
My guiding setup details:
QHY5 (5.2 micron pixels, 1280x1024)
Skywatcher 70mm f7.1 achro (f=500)
Guiding image-scale: 2.14 arcsecs/pixel
Guided 'on-camera' via PHD
Mount: Orion EQ5 fitted with synscan goto, driven by EQMOD via USB-Serial/PC Direct mode on handset.
I don't have any screen shots of my more recent guiding attempts - I was too busy trying to figure out what was going on, but it would proceed through the calibration, but as soon as it started guiding, the guide star would wander off. The mount sounds like it is trying to keep up - the DEC motor is pretty distinctive, not sure about RA though.
Sometimes the RA and DEC graphs would head off in different directions and just keep going until the star was lost, other times one trace or the other would head off the chart...
At the moment my prime suspect is my guiding cable from the camera to the motor controller, as I can slew via EQMOD etc. I have tried guiding with EQMOD, but I am not sure of the settings, so although I couldn't get that to work either, I am less sure of where the problem lies with that approach - but I suspect it is more with my lack of knowledge.
My next step - after reading some helpful advice given to another guiding newbie by Marc (multiweb) is to graph just the tracking of the mount by turning off the guide output in PHD, and see what I get.
What else can I do to track down the problem?
Where do I get another guiding cable - is there anything I can substitute - phone cable?
Am I right in thinking that the graph below at a scale of 2.14asp is pretty good for an EQ5?
Hello. I have found that PHD sometimes is put off by seeing, not saying that is your problem but maby. if the star wobbles because of seeing the mount will try to keep up and loose its place. you could try raising the minimum pixel movement value. on bad nights i sometimes have to go as high as 2.5. this number relates to your guide cam image scale of course and will be different for your setup. I also found as leon has said, a good drift alignment helps a lot. and lowering the frame rate of the cam to 1 or 2 sec helps the system keep up, especially if you are using long USB cables.. usb is not very good over about 5m, however i am managing to guide from 15m away so it is definitely possible.
Hello. I have found that PHD sometimes is put off by seeing, not saying that is your problem but maby. if the star wobbles because of seeing the mount will try to keep up and loose its place. you could try raising the minimum pixel movement value. on bad nights i sometimes have to go as high as 2.5. this number relates to your guide cam image scale of course and will be different for your setup. I also found as leon has said, a good drift alignment helps a lot. and lowering the frame rate of the cam to 1 or 2 sec helps the system keep up, especially if you are using long USB cables.. usb is not very good over about 5m, however i am managing to guide from 15m away so it is definitely possible.
Best of luck
J.Green
It could be polar alignment....I have marks where I plonk down the tripod, but I suppose the mount itself could have moved - I have kids who like to fiddle with stuff!
I am going to try tonight if there is a small hole in the clouds to just get a graph of the mount tracking, not guiding, and see whether it looks mechanical..
ok i see the problem, you can't just plonk it down where you had it last night. I do a drift alignment every night. you should consider learning how to do it, It's a bit hard at first but after a few goes it becomes second nature. and if you can show the guide cam image on screen with a target overlay on the screen it becomes very easy.
Hey mate, with your guiding it doesn't matter about which program you use if your polar alignment is off from what you say your RA is out by a country mile DEC is quite easy to sort out to make sure your close but RA.. that is the hard one.
You can use the old plonk trick, but you have to have something that accurately gets you where you where last night. i have 3 bricks set into the lawn with 3 holes i have drilled that makes the legs sit perfectly. as for the head mount, i have lines where it was perfectly drift aligned at. This generally gave me repeatable results.
As for maxim it is very easy to guide with and far superior to PHD, in speed of calibration, accuracy of calibration and it also will give you how many arc seconds your guiding is moving relative to your imaging scope. I look at it this way, if your arc sec to pixel ratio on the imaging scope (i will use my set up) is 0.98 Arc sec per pixel and your average guiding adjustments are 1.2 arc per pixel you will loose clarity/ resolution.
To give you an idea, i got caught out on the weekend i have backlash in the DEC which meant that the guiding was bouncing, the average corrections where 1.7 arc sec per pixel. in the images you could see the stars all smeared in the same direction by about half a star either side of where the main star was.. something like this
( ( ) )
so with close to double the resolution in adjustments everything was bung. That is just one reason why maxim is a lot better. If you would like me to help you with it, let me know and i can always do a remote desktop session with you that way i can show you a heap of great little tricks to make your session a lot more productive and easier.
I am really interested in what version of PHD you are using, my graph output screen looks nothing like yours.
Ver 11 has numbers in the left hand of screen for Osc and RMS and is also a black screen, not grey.
Also an OSC of 0.06 is in my expectations, way beyond the capability of an EQ5. On a good night with a G11, my OSC-Index is around 0.2-0.25 with an RMS of about 0.15. (Guiding @ 450mm FL with SSAG/QHY5 on ST80)
I am really interested in what version of PHD you are using, my graph output screen looks nothing like yours.
Ver 11 has numbers in the left hand of screen for Osc and RMS and is also a black screen, not grey.
Also an OSC of 0.06 is in my expectations, way beyond the capability of an EQ5. On a good night with a G11, my OSC-Index is around 0.2-0.25 with an RMS of about 0.15. (Guiding @ 450mm FL with SSAG/QHY5 on ST80)
my version of PHD says 1.8.2 - where do you get Ver 11?
I don't know how PHD comes up with that number for OSC, but there it is on the screen. Maybe it hadn't been going long enough to generate a meaningful average?? But if you have a look at this image, you will see that I got some nice round stars that night....!
I've just updated to 1.12...
looks like some decent extra features - being able to change some settings while guiding probably the most helpful, and some better logging options.
Adam, I've been using PHD 1.12.1 for a week or so now, 1.11.3 before that. Still trying to get up the enthusiasm to try the Maxim learning curve.
I've also been having some erratic problems, although not your sort. (Had those about two months ago, went away by themselves!). Two nights ago I was getting "Changed star mass" alarms from PHD, that would come and go, even on reasonably decent stars. Never did find the reason, but I've noticed that the high altitude cloud that's been cursing Brisbane the last few nights may be screwing the seeing a lot.
I'm just about to take the plunge on an EQ6 Hypertune, so hopefully that will get one more unknown out of the way.
In my view that means only one thing - you were trying to guide off a hot pixel, not a star. It would explain your symptons as well.
James
This is what PHD help file has to say about OSC...
Quote:
In the lower-left of the graph, an "oscilliation index" is shown. This is the result of calculating (in the current window's worth of data), the odds that the current RA move is in the opposite direction as the last RA move. If you are too aggressive in your guiding and over-shooting the mark each time, this number will head towards 1.0. If you were perfect and not over- or under-shooting and your mount had no periodic error, the score would be 0.5. Perfect with periodic error and the score may be closer to 0.3. If this score gets very low (e.g., 0.1), you may want to increase the RA aggressiveness (and/or decrease the hysteresis). If it gets quite high (e.g., 0.8), you may want to decrease the RA aggressiveness (and/or increase the hysteresis).
so I am not sure that 0.06 is such a good thing after all....
Guiding off a hot pixel has happened to me before and you just get a flat line graph in DEC and RA - which makes sense. THe hot pixel doesn't move at all, so no corrections are required to keep it in the same spot.
Adam, what are your Pulseguide settings in EQMOD control panel? Just interested, as there are no specific numbers given in the EQMOD docs. BTW, EQAscom is up to V122b, I just downloaded it.
I had tried a lot of different settings in EQMOD trying to get it to work - so I don't really know. What settings do you use?
I think I have worked out what my problem was - simple polar alignment. Last night I spent 3 hours going back to basics, making sure that I had everything level, doing a good long drift alignment etc, and I got some good guiding going....finally.
My EQMOD settings are:v1.22b, RA & Dec rate .5, min pulse width 40, Dec backlash 10, RA & Dec pulse width override 2500 but boxes not ticked.
PHD is 1.12.1, RA agg 50, RA Hyst 30, Max RA dur 1000, Search region 10, min motion .1, cal step 2500, time lapse 10, LE port 378, Dec guide mode Auto, Dec alg res switching, Dec slope 5, Max Dec dur 100, star mass tol 1 (Disabled?, Noise red 3x3 median. I normally use 2.5 seconds exposure time to give a slower guide update. I'm still using the finderguider with the DSI II mono, seems OK for me even with guiding the 2000mm C8.
I would imagine with a 200mm newt on an EQ5, you would need pretty good balance and alignment to guide, it's probably pretty much on the EQ5 limit. I had my SW200 f6 (1200mm long) dob scope mounted on my EQ5, and it seemed right at the limit of what the EQ5 go to was happy with. If you have the shorter f5, probably a lot better though.
You are right the 200mm is probably a little too heavy for the EQ5, but I have had it guiding ok a couple of times. Lately I have been using the ED80 as my imaging scope, and the mount likes that much better - not so touchy...
Now that I have the drift alignment sussed out properly, I can concentrate more on settings and may even try out MaximDL for guiding
Yep, I'd like to use Maxim, but after a few locked up computer problems back when, I decided to dedicate a little surplus eeePC to just looking after my mount. It does it very reliably, just handles EQMOD and PHD. Solid as a rock.
I can then play around with imaging on my Dell laptop, which is far less reliable, without worrying about upsetting the mount at all. Never had a problem since I went this route. Of course, having things in an obs helps
