Please help me before i go mental .... guiding problems
ok, so i have a setup for imaging, an Orion ED80, with an ST80 ontop, an Orion Sureshot Autoguider, a Canon 1000D, all lumped onto an EQ6 mount. I am fairly tech savvy, and am sure i have this all setup right, but my results are utter rubbish, and i dont understand why.
To me, in short, it looks like the mount is not guiding, although PHD looks fine, i select a star thats not too dim or too bright, it does the N.S.E.W calibrating thing, the crosshairs turn green, and off i go... and the results i get back are awful. i can see pulse guide instructions being sent to the mount (the flashing red LED on the autoguider?) I mean, i dont expect to be an expert overnight, but the fundementals of it all are quite simple, yes?
here are some examples.
The Triffid Nebula, this is a guided (yes, guided) 5 min exposure.
Eta Carina, a guided 5 min exposure
Eta Carina, a guided 3 min exposure
and a close up of the star trails, incase they give any clues.
Incidentally, all these shots where taken with the Astronoik EOS CLS slip in camera filter for light pollution, so at least you can see it does quite a good job of getting rid of sky glow!!
but anyway, what could be causeing this? could it just be as simple as bad polar alignment? or does it look like something is knackered? This is a pain in the tonsils for me, as i have no permanent setup, and have to set this up, everytime i wanna try.
at this stage, before i go mental, and end up selling the lot, any suggestions are welcome.
Your second photo practically says it all. You are nowhere near polar aligned. You must be well polar aligned before you attempt any sort of guiding. Your guider will struggle hugely to try and compensate. Have a look for thread talking of polar alignment routines, Alignmaster, WCS or eqalign.
Hi Duncan,
whats your pulse guide rate on EQMOD interface?
The pulseguide speed rate can be set between x0.1 to x0.9 of the sidereal rate at increments of 0.1 independently on each motor (RA or Dec).
At times i get into similar problem even when my alignment is quite spot on.
There are few posts which suggest you to set them to .9x rather than default .1x. I am new to guiding as well so cant say for sure but from my personal experience .1x takes very long to calibrate and sometime gives me trail. I usually set my rate to .7x - .9x region.
How do your 30sec or 1min exposures look? If it is polar misalignment then lower exposure times should be slightly better. If the error is the same then maybe its something else (like periodic error in the drive or something like that?)
How do your 30sec or 1min exposures look? If it is polar misalignment then lower exposure times should be slightly better. If the error is the same then maybe its something else (like periodic error in the drive or something like that?)
yeah, i am starting to think its the polar alignment
To get that much movement in your pics you should be able to see the stars drifting in Phd. Find a bright star, stick your mouse pointer on top of it, have monitoring turned on but don't click on the PHD tracking button. If its moved more than a few mm on the screen within a few minutes you're going to be pushing it to get good pics.
From some of those I think you'd find the drift was >1 cm every few mins.
I still find my polar alignment can be bollocks when I set up in an unfamiliar remote site, even doing tricky webcam routines. Probably 'cause I get lazy at home having marked the pavers for the mount
I'm pretty new at this too Duncan. But here's the things I found with my set up.
By the looks of the trails, not guiding in DEC.
Polar alignment not close enough. If you can get reasonably round stars on a 2 min or better unguided exposure, its ok.
Your guiding on a hot pixel (done that myself, as have experienced others who shall remain nameless )
Too much backlash in the drive train, probably the DEC.
Step settings in PHD too big, inclined to make it "hunt" a bit.
From your description probably not this, but do the calibration after slewing to the object and re-do it (force calibration in the "brain" menu ) when you change to a new target.
Bill
Last edited by Glenhuon; 20-06-2009 at 07:32 PM.
Reason: More info
I dont think these are your problem but, just a few quick tips with your setup, as mine is almost the same;
Let the autoguider settle for a minute before shooting subs.
Turn off live view on the 1000d bofore starting an light, dark or flat to prevent hot spots.
Take the screws off the control panel of your eq6 and pull the motors out and check how hard it is to turn the gears (worm) in the mount. You can autoguide all you want with these mounts and if thats not right, you are chasing your tail. My mount was so tight I couldn't turn the gears by hand.
These are just a few tips that could have saved me a lot of time if I had known them sooner.
Here is a little check list, when you have all of these confirmed then we can start looking elsewhere.
Polar both axis to at least 4 minutes with a 12mm reticle. That is do the meridian and then eastern star and back to meridian and each should be polar aligned to 4 minutes. Meaning no movement whatsoever until 4 minutes has passed.
Next check all you cables, are they plugged in properly.
Check the mount fixings, like how the scope is fixed onto the mount, the mount head itself and the guide scope and cameras. Any thing that is not really tight will need tightening.
When PHD is calibrating is the star moving very far? Watch it to see that it is. If no movement at all then once again check your cables.
Check the aggression in PHD. For your mount it should be on the default of 100%
Check to ensure that the mount is tracking in sidereal. Sounds silly but it might well be in lunar or solar. Also check what speed the guide corrections are too. Not sure if the software will tell you that, but you could check. Is the mount set for the southern hemisphere?
From what I can see in those images it can only really one of two things. Either the mount is not polar aligned (most likely cause) or there is a setting that is not correct in the mount control. PHD will usually not give you guiding if it cannot calibrate. So it is likely that Polar alignment is the real culprit. You have to be very accurate with polar alignment. Have you done, much polar aligning?
Let me know when you have answered all these questions. I will then come up with more questions.
You wouldn't believe the frustration though trying to work out why things wouldnt work for me before
