while guiding for my latest images i noticed a clear issue which resulted in egg shaped stars. i have attached an image of the tracking plot and you can see the issue. the line that is being traced is in line with the RA axis. i have run PEC and re run it (i will do it again with PEMPRO3 tonight) and it still has the issue. everything is solidly connected, no matter what part of the sky and what guiding settings i have, the issue is consistently in the RA axis. The 2 possibilities i have come to are
1) the use of a CW extension bar might be introducing flex and causing a pendulum effect. but would it be this severe? (the error is around 7 arc seconds)
2) does the gear need to be greased. i assume that if the gears are not running smoothly it could cause an issue like this but that is an assumption.
i am open to any other suggestions or trouble shooting recommendations. i am keen to solve this issue because if i can, it looks like i can get some really good images, if the tracking in Dec is anything to go by.
I am going to add another possible solution to the mix which i will test tonight. During the computing and applying of the PEC curve, TSX asked me if i took the data while the telescope was pointing west, meaning the OTA was on the east side but pointing west. However, when i hovered over the text it says to tick it for northern hemisphere users if you are pointing to the west. being in the southern hemisphere should this remain un-ticked when computing the PEC curve if the data was collected from a star on the West? because i had this ticked. could this cause the issue, making the guiding having to fight the PEC?
Did you run Pempro with the new PEC uploaded to the PMX? You should see a reduction in PE when you do this and its part of Pempro procedure.
If you setup your mount in Pempro using the mount wizard your curve should be correct. But it may need to be inverted if its making things worse ie its pushing when it should not be etc.
Try inverting the curve or better do the mount calibration wizard and then do a fresh PEC.
Also there is no need to go near that whole page for uploading the pec curve from Pempro to PMX. You setup the mount in Pempro and select PMX and when you create the PEC curve it should come up with an option to create Paramount PEC curve. When you click on that it copies to clipboard and its ready to go into Sky X.
You open TCS, open PEC, clear existing curve then paste which pastes the new curve that was copied to the Clipboard then save to mount once you see it.
My PME curve is somewhat like a bumpy sine wave with the peak of the sine wave on the left side of the TCS PEC display of the curve.
I just did a fresh one last night so this is all fresh in my mind.
Thanks Greg, i have been on this all night. i got PEMPRO to work nicely, however, no matter what i do it doesnt seem to help my tracking much at all. i start with 6.7 seconds of error, after applying the PEC it comes down to about 4 ... not really good. i am really struggling wit this one.
i'm not familiar with the software, i setup from scratch everynight. could you have a tiny bit of cone error with the scope/mount? you have a decent FL and i know the multi point star mapping is meant to help but that is about all i can bring to the party i'm afraid.
Check the usual. 6.7 arc secs to start is within SB specs but rather poor in my experience.
1. How good is your Polar alignment?
2. Double check your balance in both axes.
3. Are there any cables that are dragging?.
4. What build version are you using for Sky X? (there were polar alignment instructions about 5 months ago that were reversed in error for RA when you used accurate polar alignment).
High guide errors are usually PA above.
Also with Pempro did you run the mount wizard first? It says it syncs with the worm automatically but it can't hurt to hit that sync button. The curve has to be synced to the worm otherwise I would not match. That is a long shot though.
Can you take a screen shot of your PE Curve and post it here.
Check the usual. 6.7 arc secs to start is within SB specs but rather poor in my experience.
1. How good is your Polar alignment?
2. Double check your balance in both axes.
3. Are there any cables that are dragging?.
4. What build version are you using for Sky X? (there were polar alignment instructions about 5 months ago that were reversed in error for RA when you used accurate polar alignment).
High guide errors are usually PA above.
Also with Pempro did you run the mount wizard first? It says it syncs with the worm automatically but it can't hurt to hit that sync button. The curve has to be synced to the worm otherwise I would not match. That is a long shot though.
Can you take a screen shot of your PE Curve and post it here.
Greg.
so the upshot of last nights efforts are that it appears that the PEC process, rather than helping is hindering tracking. the results in terms of FWHM are similar but the starts are not elongated when i have PEC turned off.
looks like another trip is on the cards for me, in terms of Polar alignment, i have just used TSX to run a Tpoint model and adjust my PA, it says that i am around 1 arc min out on both axis which should be fine enough but tonight i will test it out with different methods but i would expect the axis of the error would change while pointing at different parts of the sky if this were the case.
I am on TSX version 10.3.0 (build 8461) if i can avoid upgrading the software that would be good, i have it working well and i really don't want anything to screw up.
as far as cables go, i dont have any that drag on the ground but i have combined a few at the back of the OTA and it does hang a bit. i could fix this up a bit and reduce the weight.
i will have to wait till i can get down there to check if the balance is good. perhaps there are some refinements i can make, we will have to see.
the thing with PEM pro, it lookked like i was getting fairly consistent PE and i would have expected it to be effectively corrected. i will have a go again tonight (if it is cloud free) and see if i can't get it working, perhaps the worm gear is not syncing, which would cause the issue i am seeing
I would strongly recommend that you upgrade to the latest daily build. This buld has greatly improved guiding and I can see from your guide graph that you are using an old version.
I went back and read your previous post about the out-of-balance near disaster. You said it was mostly a slip in the dec axis so that doesn't entirely rule out a slip also in RA. Did you have a look at the ring gear and any associated damage in RA? Hopefully none, but if there is it might explain your inability to train PEC.
Your .45 resolution is quite good but you would need really good and steady seeing to take advantage. I take it that you are looking at PE again after applying the correction and that you are seeing PE go from ca 6 to ca 4. If you compare the original curve to the corrected curve do they look similar in terms of phase or is the corrected curve different? If different I might guess that the phase of the initial curve is possibly incorrect. But, if similar in phase it might just mean that not enough correction is beng applied.
As far as your polar alignment, it certainly could be better. Also, if your T-Point model isn't large enough Protrack probably won't work very well. A cursory look at your guiding graph has me head scratching. Even with high aggression and a small min move your tracking seems to oscillate above for a while, then below for a while. At those settings I would expect the mount to bounce back and forth from one side to the other. It's almost as if the errors in RA are so large that guiding cannot keep up! But, now I'm seeing something else; your star strength signal is below 80%. That would indicate passing clouds and that will positively mess up guiding especially if your guide star is weak? What ADU are you looking for with a guide star? I usually get excellent guiding around 10K adu. In any case the new DB for TSX greatly improves centroid calculation on weaker guide stars. Oh, you might also find it really useful to rotate your guide camewra such that RA=X. That way you can tell what is going on in both axis. Unlike most other guide programs TSX does not plot RA to X and dec to Y! You probably know that but it has tripped up many! Wish I could help more. Good luck,
I would strongly recommend that you upgrade to the latest daily build. This buld has greatly improved guiding and I can see from your guide graph that you are using an old version.
I went back and read your previous post about the out-of-balance near disaster. You said it was mostly a slip in the dec axis so that doesn't entirely rule out a slip also in RA. Did you have a look at the ring gear and any associated damage in RA? Hopefully none, but if there is it might explain your inability to train PEC.
Your .45 resolution is quite good but you would need really good and steady seeing to take advantage. I take it that you are looking at PE again after applying the correction and that you are seeing PE go from ca 6 to ca 4. If you compare the original curve to the corrected curve do they look similar in terms of phase or is the corrected curve different? If different I might guess that the phase of the initial curve is possibly incorrect. But, if similar in phase it might just mean that not enough correction is beng applied.
As far as your polar alignment, it certainly could be better. Also, if your T-Point model isn't large enough Protrack probably won't work very well. A cursory look at your guiding graph has me head scratching. Even with high aggression and a small min move your tracking seems to oscillate above for a while, then below for a while. At those settings I would expect the mount to bounce back and forth from one side to the other. It's almost as if the errors in RA are so large that guiding cannot keep up! But, now I'm seeing something else; your star strength signal is below 80%. That would indicate passing clouds and that will positively mess up guiding especially if your guide star is weak? What ADU are you looking for with a guide star? I usually get excellent guiding around 10K adu. In any case the new DB for TSX greatly improves centroid calculation on weaker guide stars. Oh, you might also find it really useful to rotate your guide camewra such that RA=X. That way you can tell what is going on in both axis. Unlike most other guide programs TSX does not plot RA to X and dec to Y! You probably know that but it has tripped up many! Wish I could help more. Good luck,
Peter
Thanks for taking the time to respond Peter. i will go through point by point
i am downloading the new version as i type, i will see how that goes
i didnt check the ring gear, i will add it to my to do list when i get down there
yeah i did check it pre and post PEC and that was the figures i was quoting. i cant remember if it was the same curve but i will run it again tonight and see how it goes
my T point model is around 200 images, is this enough? i would have thought so.
i am running another PEC now, i will let you know if the pattern persists, i will also post pictures of pempro to show you what i am getting
i checked my polar alignment using PemPro and it was bang on, so no issues there, the guiding was a little cloude interrupted but i get teh same issues on clear nights.
i agree that the graph is weird that it spends time on one side of the graph then switches over ... i think the posting of my PE curve will help to shed some light on that. anyway i will post again shortly when i have all the details
the first screen capture is the output from PemPro when the mount was not trained. the second one is the curve produced after training. what is clear is that the training has reduced a lot of the higher frequency fluctuations and put in one big frequency fluctuation, with the overall product being no reduction in PE.
i am going to try to run another uncorrected PE to see if the graph stays the same
arrggggg
i guess this explains why i am correcting one side for a while then the other ... massive movement in the corrected curve. once i have finished the next run i will test how tracking goes with the software version uplift with PEC on and off.
Can you post a shot of the fitted curve after applying PEC? You might want to post these results on the PEMpro forum. Ray usually responds quickly and may have some insight!
I doubt this is your problem but I thought I'd mention it anyway. I have had it happen with the PMX when it was exactly balanced I would get an oscillation in the guiding. Like constant correct one way then the next then the original way.
Shifting the balance a tad stopped that.
Some suggest its better to have the balance slightly shifted so the mount has to pull the scope up when pointing east so the gears are fully engaged and no backlash causes things like I just mentioned.
My best guess is your worm is not up to spec. That would show up as high PE without PEC.
Can you post a shot of the fitted curve after applying PEC? You might want to post these results on the PEMpro forum. Ray usually responds quickly and may have some insight!
Peter
I will have to do that tonight, unfortunately pempro 3 beta is a little crash happy and I never actually got to run the curve on this one. Last night I was actually able to get some decent images when I turned pec off, it would be good to see what I can do with a sub arc second pe
Quote:
Originally Posted by gregbradley
I doubt this is your problem but I thought I'd mention it anyway. I have had it happen with the PMX when it was exactly balanced I would get an oscillation in the guiding. Like constant correct one way then the next then the original way.
Shifting the balance a tad stopped that.
Some suggest its better to have the balance slightly shifted so the mount has to pull the scope up when pointing east so the gears are fully engaged and no backlash causes things like I just mentioned.
My best guess is your worm is not up to spec. That would show up as high PE without PEC.
Greg.
I have heard a few people say that it should be slightly out of balance, I will give that a go. I will also post my pec curve to the SB forum and see what the SB guys think about the worm gear spec
I'm not doubting Greg's advice but it is contrary to SB recommended practice with their mounts. Personally I've never needed to do this with either my MX or MEII.
Aidan, which MX is yours? The original or new MX+? Is it in warranty or did you buy it used? I'm not remembering your history with the mount. Did you previously use it successfully? Have a PEC curve? (Did previous owner, if used?)
Not to be an alarmist, but to fully consider all possibilities (!) when you suffered that out-of-balance accident the dec gear let go and clearly the scope exterted considerable force when coming to a stop. Whilst the RA gear may not have slipped is it unreasonable to think that it probably also received quite a shock? Perhaps that shock has damaged the worm. I think you might want to post that scenario at SB and ask what their opinion would be about this.
I'm not doubting Greg's advice but it is contrary to SB recommended practice with their mounts. Personally I've never needed to do this with either my MX or MEII.
Aidan, which MX is yours? The original or new MX+? Is it in warranty or did you buy it used? I'm not remembering your history with the mount. Did you previously use it successfully? Have a PEC curve? (Did previous owner, if used?)
Not to be an alarmist, but to fully consider all possibilities (!) when you suffered that out-of-balance accident the dec gear let go and clearly the scope exterted considerable force when coming to a stop. Whilst the RA gear may not have slipped is it unreasonable to think that it probably also received quite a shock? Perhaps that shock has damaged the worm. I think you might want to post that scenario at SB and ask what their opinion would be about this.
Peter
Hi Peter
it is a new PMX+, i am the first owner. to give you some history of the tracking. i was using a 10" F4 newt previously with a orion guide scope. i was getting similar issues well before any balance issues. my assumption at the time was that i was trying to PEC with too short a focal length and as such it wasnt accurately registering the PE. i decided to wait until i got the new scope, using a MMOAG to try to retrain the mount and resolve the issue. even at the 40" fl i was surprised that the mount was not tracking as well as i was expecting, it is just now that i have the data to back it up.
I don't know for sure but if there were a shock to the worm and it got damaged wouldn't cause a sudden spike in the PE when the worm turned to the damaged area rather than overall poor performance?
SB definitely had quality control issues with their worms (sounds funny) early on. So its quite possible you have a dud worm.
As to the balance thing yes it should not really be required and I think in my case it was symptomatic that the cam pin had slipped and needed readjustment. The off balance thing was more of a quick fix until I reset the famous cam pin (what a design??!!).
Perhaps see the you tube videos about the cam pin because it can come loose at least on the original PMX. I can't say if they changed the design of that in later models. I hope so as it was a weak point of the original design.
it is a new PMX+, i am the first owner. to give you some history of the tracking. i was using a 10" F4 newt previously with a orion guide scope. i was getting similar issues well before any balance issues. my assumption at the time was that i was trying to PEC with too short a focal length and as such it wasnt accurately registering the PE. i decided to wait until i got the new scope, using a MMOAG to try to retrain the mount and resolve the issue. even at the 40" fl i was surprised that the mount was not tracking as well as i was expecting, it is just now that i have the data to back it up.
OK, that is valuable information. It seems likely that the RA worm was not damaged. I woudn't post your scenario.....
You probably know this but both worms are identical. You could try swapping the worms to see if the basic PE of the dec worm is inherently better. My MX (and MEII) both had just over 3 arc-sec to start with. I'm sure that makes it easier to correct.
Does PEMpro distinguish between the original MX and the MX+? I'm not sure they share the same worm period. That would for sure mess up the correction!
I noticed in Pempro the other night there is a feature to shift the curve.
I wonder if that may be of use.
Greg.
interesting ... i will have a look into that but not sure if that will solve the issue
Quote:
Originally Posted by PRejto
OK, that is valuable information. It seems likely that the RA worm was not damaged. I woudn't post your scenario.....
You probably know this but both worms are identical. You could try swapping the worms to see if the basic PE of the dec worm is inherently better. My MX (and MEII) both had just over 3 arc-sec to start with. I'm sure that makes it easier to correct.
Does PEMpro distinguish between the original MX and the MX+? I'm not sure they share the same worm period. That would for sure mess up the correction!
Peter
i can give it a go to swap out the worms and see if that fixes the issue, but the Dec worm might have its own issues from the balance problems. PEMpro only has a PMX option, not a PMX+ but i am sure that wouldn't be the issue, i am not the only one to run pempro with a PMX, besides, this started before i used pempro. i started using pempro to investigate the issue. prior PEC training was done in TSX
