Strange tracking in RA on PMX

[Somnium]

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.

[Somnium]

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?

[gregbradley]

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.

Greg.

[Somnium]

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.

[Somnium]

actually, my guiding is better without PEC, Protrack or guiding corrections ... i think i need to spend some more time in this, something is not right

[rustigsmed]

hi aidan,

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.

Rusty

[gregbradley]

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.

[Somnium]

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

[PRejto]

Hi Aidan,

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

[Somnium]

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

[Somnium]

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:confused2:

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.

[PRejto]

Aidan,

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

[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.

[Somnium]

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



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

[PRejto]

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

[Somnium]

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.

[gregbradley]

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.

Greg.

[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

[gregbradley]

I noticed in Pempro the other night there is a feature to shift the curve.
I wonder if that may be of use.

Greg.

[Somnium]

interesting ... i will have a look into that but not sure if that will solve the issue



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

[PRejto]

I'm not sure at all that you can make the assumption that the worm periods are the same for the MX and MX+. The motors and basic design are totally different. Just ask the question on the PEMpro forum to be absolutely sure. The fact that you have trouble doing PEC with TSX in the Southern Hemisphere is not an isolated event. I know there are a few who have done it successfully, but those of us that couldn't do it, as far as I know, have always had good success with PEMpro. This makes me suspect that possibly PEMpro is using the incorrect worm period.

Maybe you can check this yourself by looking at the worm period time in the Bisque TCS. Then compare the time to the plot in PEMPro. Are they exactly the same? Another comparison you could do is to compare the correction curve generated by TSX and PEMpro. They really should look about the same! Do they? If they look the "same" but one is shifted it would mean one (or both!) have the wrong phase.

Peter

[Somnium]

i just trawled through the SB user manual and it appears that the MX and MX+ have identical worm periods. i also came across this piece which was reassuring

When the counterweight shaft is oriented “non-vertically” and one or more counterweights are on the
counterweight shaft, and the right ascension axis is in the Track position, the extreme lateral force placed
on the worm and gear forces them to separate. At this point, the right ascension axis rotates to a
“balanced” position, and you will hear a chattering noise caused by the teeth of the precision gear
bouncing past the teeth of the precision worm gear. Despite the gut wrenching feeling this sound brings on, damage to the worm and gear is usually minimal.

[gregbradley]

I also had that happen a few times (it took me a while to get used to the 3 way switch thingy) and it didn't affect the mount at all. It will slip mainly if your cam pin is not fully in. Cam pin not tight though I don't think affects the PE though.

Greg.

[Somnium]

yeah i have been super careful with the pins, seems like something that is really easy to mess up. i have nightmares about leaving it in the lock position when i leave. but that makes me a lot more comfortable and eliminates 1 possible cause.

the issue appears to be mechanical. i am going to grab some logs tonight and post them to SB.

[Somnium]

i have decided that the only way i can get any decent images is to take 15 second subs and choose which ones are okay. i am currently keeping about 50% of the subs i take which is a time consuming task. even the images i am keeping are not great. i am using it with PEC turned off, with it on it is even worse. i am really hoping i can figure this out because this is not a workable solution, and can only really be done on bright objects.

[gregbradley]

+1

I think its mechanical also. Sounds like other PMX's - it needs a new worm.

Greg.

[PRejto]

Yes, that is totally unreasonable! Something about tracking is completely messed up.

It seems that SB isn't paying enough attention to your posts. Perhaps if you start a new thread, re-post the tracking data, and possibly ask that only SB respond that might help. When the threads get a bit long, or just end up further and further down the list of new posts they can get totally lost.

Peter

[Somnium]

i will give them another day or so. Steve did respond and since then it has been the weekend. if i dont get a response tomorrow night then i will do that.

the strangest part of this is that i cant train the PE out at all. anyway it is becoming stupid. the subs i am taking are unusable, it is frustrating. the moon is good, the weather forecast is great but i cant get any good data

[Somnium]

looking at this plot, taken while guiding, it looks like the main error in tracking is not perfectly aligned with the X axis. is this consistent with PE issues? or is there something else amiss?

[PRejto]

Aidan,

What you see on the guiding graph is totally depends on the guide camera PA. If the guide camera is PA=0, or PA=180 then RA=X and DEC=Y. If PA=90 (or 270) then of course RA =Y.

So, if your camera is PA=0 then your guiding graph is showing drift in both axis.

If this were my mount I would start by eliminating T-point from the polar axis alignment equation. Since you want to collect PE data at DEC=0 why not use PEMpro to drift align the mount? This would establish excellent PA and essentially very little drift right at DEC=0. This will facilitate your PE collection and you can then try guiding knowing that your PA is pretty accurate for that region of the sky. It just eliminates one of many variables. Personally I have had trouble with T-Point and PA because I cannot see eqidistant E and W from the meridian when collecting data. Because of that I actually refer to use PEMpro to set my polar alignment. Then I build a very large model and ignore T-Points PA recommendations. This has worked quite well for me!

Here are other important easy mechanical tests for hysteresis and for backlash. Find a bright star and put the camera in focus mode. Bring up the cross hair. Now use the jog control and slew the scope 1 or 2 arc-sec? Does the star move in short slews in both RA and DEC? More importantly does the star re-center when you reverse the jog? If not, this is backlash. The next test involves putting the star in the center of the FOV/crosshairs and gently pushing on the mount in RA, and then DEC. Of course the star will move away from being centered but the essential part is when you remove pressure the star must exactly re-center. If it doesn't this is hysteresis. Dan Bisque told me my MX should not fail these tests. Do these tests because they could be very important!

EDIT: One more test while you are at it!!! Use PEMPro for this test as if you are collecting PE data. You have probably noticed that when the plots are completely horizontal that means the star is not drifting in RA. If the plots move at an angle (to horizontal) then that is drift in RA. Slew the mount West about a degree or two and immediately start collecting data. You should get a pretty straight line. Now, slew the mount East and immediately collect data. Is the line still straight (better hope so!) or not? If not, how long until it becomes level? (By the way, to do this test turn off Protrack and be sure to have drift aligned first so you know it's not polar alignment causing the drift!) Hopefully your mount passes this test. Some don't and it's a major problem as slewing East can cause bad drift for up to one worm cycle...meaning you essentially cannot guide for 3-4 minutes after an eastern slew.

Good luck!

Peter

[gregbradley]

Very good advice. Eliminate TPoint recommendations with drift alignment as drift alignment at the end of the day is what you are trying to do -eliminate drift.

I have had Tpoint tell me my PA was spot on only to see significant drift using PHD2 drift (very similar to Pempro drift). Once adjusted I got rounder stars so TPoint was off. I had used accurate polar alignment which seemed to give an odd result as TPoint said I was very close yet the accurate polar alignment had me doing some fairly large adjustments.

Greg.

[PRejto]

I do want to clarify something that might be taken from a casual read of my post. I am not at all saying that drift alignment is somehow superior to T-Point alignment. The reality is that there is no such thing as perfect PA. It really depends on where one is imaging, whether field rotation is a factor, etc, etc. The atmosphere through refraction will modify alignment and will be different depending on the altitude, etc, etc. So at best PA is a big compromise. The only reason I drift align is because of my limited visibility to the East. The only reason I've recommended that Aidan drift align is that at Dec=0 he will not have much drift, if any. That will certainly not be true at different sky locations! If I can digress, PA reminds me quite a lot of the musical term "equal temperament"....a basic compromise in pitch where every interval save an octave is "equally" out of tune..... a system where there is no difference, for example, between d# and e flat. It's a wonderful compromise that allows keyboard instruments to play completely out of tune all the time but "equally." Fortunately our ears adapt and put it right. I think PA is sort of like that; we try to put the PA where things are kind of equally good (or bad, you choose) over most of the sky we might care to image in. T-Point can do this job brilliantly as long as the data points are carefully selected. My experience says this means collect points equally on both sides of the meridian. I'm not sure Patrick Wallace agrees with me on this last point but it is my experience for what that is worth!

Peter

[Somnium]

Hi Peter,

i ran an autoguider calibration, the results of which are on the left of the image i posted. my understanding, and correct me if i am wrong, is that there are 2 axis, the camera axis and the RA/Dec axis. the RA axis with respect to the camera is outlined on the left, the movement of the star in relation to the camera is outlined on the right. have i missed something? judging by that, it looks like there is movement in both axis but primarily in the RA.

i did run a polar alignment with PemPro a few days ago and it was bang on, within an arc minute. the strange thing about that test is that it started to drift, telling me i was quite a bit off the alignment and then it eventually came back to give me a good polar alignment score ... i guess that is consistent with my graphs but makes no sense as there should be periodic error in the dec axis :shrug:

i will give those 2 tests a go and see how they fair. thanks for the trouble shooting tips, i have exhausted my knowledge a long time ago.

[Somnium]

i will have a look at the polar alignment again tomorrow because it seems the closer i image to the pole the worse the issue gets ...

[Atmos]

That sounds a bit like a PA issue.

[Somnium]

that is what i thought too. the close i image to 0 degrees dec the better. i got some decent images last night right on 0 dec. however, i wanted to test the out so last night i imaged NGC 6872 Iwhich is what these tracking logs are from, but i let it go from midnight to 5 am. i was watching the angle that the stars egged, if it was PA then you would expect that the angle would change over the course of the night but it didnt, it stayed exactly the same, not sure if i can explain that one

[PRejto]

Hi Aidan,

I'm in China as of today for the next 10 days so sorry for the delay in answering. Firstly, make your life easy and change your guide camera PA so that X=PA. That will make things so much easier to ID.

If you drift aligned near DEC=0 I wouldn't expect to have great tracking getting closer to the pole. In fact guiding near the pole can be very difficult!

But, something might be learned from your statement. After drift aligning you say "it started drifting, then was good" can you explain further? I take it that you drift aligned one night, started up later (or slewed?) and then you saw drift for a while which then got much better. If so this is exactly what I was proposing you test for where I said "edit" in a previous post. My MX did this and it was an unfixable mechanical error! It's quite rare for sure but when it's there it is a pretty serious. Were you testing in the same area of the sky you drift aligned in? If not then you would expect to see some drift.

As for an interpretation of your guiding graph I think this pretty tricky given your guide camera PA. Both axis contribution will blend together. The length of the angled drift shows that guiding just isn't happening over time. The back and forth excursions seem to show either horrid seeing, PE, or over correction, or all. It might be interesting to just look at a guide graph with corrections turned off. If the camera is a PA=0 the y axis excursions will represent "seeing" jumps given that Y isn't moving (no dec corrections). X will show seeing + any errors in RA (such as PE or crud on the worm/gear combination). This assumes that you drift aligned and testing in the same sky region.

Why guiding isn't fixing these issues (even a lot of PE) is a mystery. If you have backlash or hysteresis guiding is very difficult and you shouldn't see anything significant in a mount like the MX+. Do the tests to rule these issues in or out. Do all 3 tests at DEC=0 where you have drift aligned.

Anyway, this is all I can think of at the moment.

Peter

[RobF]

Great post Peter. Belongs as a sticky somewhere in a thread where people are learning about PA. Love the equal temperament analogy - very apt actually for explaining that perfect PA is a myth.

Aidan, hope you get to the bottom of your woes soon. Can only imagine how frustrating this is currently for a top of the line mount. This hobby really can be a torture chamber at times.....

[Somnium]

Thanks Peter, i really appreciate you spending the time to help me work through these issues. have a lot of things to try to troubleshoot the issue now and i will give them a go, i have found that tracking is the best on Dec = 0 so i am going to spend the amazing weather i am getting to image a target on that line then work through my issues during the next full moon.

in response to your questions, i would have to physically change the guide camera to align with the X axis as it is an OAG. i have a rotator and have got it set up so that the main imaging camera is aligned with the RA axis. that has enabled me to diagnose the issue a little better. when i mentioned the drift alignment, what happened was that the plots PemPro was taking started to wonder off, telling me i had a huge polar alignment issue, but it slowly wondered back to the correct line, telling me that i didnt have a polar alignment issue. this was done in the same PA routine, i am not sure if i slew just prior to capturing that data.

i will run through all the tests at Dec = 0 and see what is what.

thanks again for your input, it has been valuable.

[PRejto]

I understand your desire to image during a new moon and good weather. I don't blame you! And, I know your mount is remote. Next time you go out though I'd certainly rotate the guide camera so it is the same as the imaging camera. It will help you diagnose guiding issues. And to "push" on the mount obviously you need to be there. I can't think of how this test could be done remotely. It really seems as if something mechancally is wrong. When I'm back from China if you think I can help somehow don't hestitate to ask given we are both in Sydney.

Peter

[Somnium]

arrrrgggg

nothing i try has worked and nothing is narrowing it down. i think a large part of the problem i have is just horrible seeing and that is messing up things. i mentioned before that i tried to do some planetary imaging and it was just not worth it, jupiter was a blob, i could see europa dancing around like crazy on the screen when i was shooting at high frame rate, an issue i am pretty sure was due to just atrocious seeing. i have tried rebalancing, i have tried testign on a still night and no matter what i do i cant train the PE out of the mount. i consistently record a PE of around 5-6 arc seconds, the chart looks really consistent and like it should correct out, i save the curve to my mount and apply PE and it makes things worse. i have tried inverting the curve too just in case but no luck... i am thinking that i just shouldn't do a PEC, though i would like to get the best possible tracking out of the mount.

[PRejto]

Hi Aidan,

I can feel your frustration!! Been there big time when I first got my MX (original model). I could NEVER get TSX to work. Period. There was a bug that SB wouldn't admit to. Finally they "fixed" it but it still never worked for me though others in the Southern Hemisphere claim it works. It always worked with PEMpro and I continue to use PEMpro to this day with my MEII.

So, were your most recent tests with PEMPro or TSX or both? If you tried with both have you tried comparing the two correction curves. They ought to look very similar (I'm talking about the actual curve you paste into the Bisque TCS. If they look really different that might provide some sort of clue.

I think you wrote in a previous thread that you did try the slew tests....moving a few arc-sec back and forth and you saw zero backlash. Is that correct? I'm not sure if BL in RA would prevent PEC from working. I think it wouldn't since the motion is always in the same direction....just faster or slower (no reversal as in DEC corrections).

You have now clearly run many PEC measurements over many different nights, some in better or worse seeing. Do the curves look similar? They should if they are valid curves. On your latest results what is your peak to peak uncorrected value?

Peter

EDIT: Can you post a picture of your correction curves? One made by TSX and saved to the mount and another of the curve generated by PEMpro and saved to the mount?

[Paul Haese]

Hi Aidan, if you are not using it, I think you need to use Pempro. I had the same results using the SkyX PEC and it never worked. I used Pempro and it was sorted in an hour or so.

[Somnium]

Hi Paul, i have tried TSX and PEMpro v3 beta. i ran pempro for over an hour and each time it laid down a really consistent PE curve. you would think that it should correct out really well. when i compute the curve and save it to the mount, it definitely makes a change to the tracking so it is doing something, but just makes it worse. i think i will either create a video or do some screen shots of the process to see if someone can point out if i am doing something really stupid (the most likely cause)



Hi Peter

i haven't done a direct comparison from TSX or pempro curves, i will load them individually tonight and have a look. from memory they are pretty similar but it looks like the TSX one is more complicated.

i haven't done the BL test, i will do that tonight as well. I made the adjustments to my guide camera so that it is aligned to the RA axis.

i just wonder whether the horrible seeing is causing the issue. perhaps there is a boundary layer on the mirror causing issues with that, i have tended to run the fans permanently to try and keep the mirror close to ambient ...

[Somnium]

I just went back and looked at some of the old curves i created, and i thought i would share it here to see if it sheds any light on the issue.

pic 1. is an image of the PE curve created by running TSX
pic 2 (red line) is the PE curve run by pempro
pic 3 (red line) is the PemPro PE curve just inverted, it seems to fit better to the TSX one
pic 4 (red line) is a PE curve i collected through PemPro on an earlier night.

Pic 3 and Pic 4 look very similar just phase shifted, i wonder if the cycles are not synced properly

[Shiraz]

hope you don't mind a nonPMXer butting in, but I guess I can't do any damage..

FWIW, looks to me like the two softwares show the same pattern, but PEMPRO is using a different (wrong) timebase (it is only showing 1/2 the cycle) and TSX is possibly using an optimistic conversion of pixel error to arc sec (results in it displaying roughly half the actual error?). That might suggest a very thorough going over the setting for the two programs to get the same timebases, focal lengths, pixel sizes etc. and ensure that dec correction is on in TSX (actually, come to think of it, that could be one place where they might have issue getting the correction right for the southern hemisphere). Again FWIW, maybe put aside TSX and try getting PEMPRO to generate full length PE cycles (that is if it isn't doing so now).

[Somnium]

you might be onto something there Ray ... let me look into it a bit more, i am not sure why it would be doing that

[Somnium]

during my lunch break i reloaded the PEC data into PemPro and took a screen shot. so it looks like the data is appropriately collected with the right worm cycle, but something has happened when that data was transposed into TSX, it only took half the cycle and assumed it was the full cycle i cant immediately see a reason why this would be the case.

[Somnium]

i just wanted to see how this would affect things, i took the data and just removed every second point through excel and then pasted it into the PEC module in TSX and this is what i got. the curve aligned with the TSX one, but it is the wrong scale. in PemPro, it says the error is +3.4 / -2.8 but when it comes in to TSX it is -6.7 / + 5.4
the image scale does say the correct figure in PemPro 0.465 arc seconds per pixel ...

[gregbradley]

Have you done an image link in Sky X to confirm that image scale?
What camera and scope is that (focal length)?

Greg.

[Somnium]

Yeah I have, I am using a ml8300 with a fl of 2,467 mm

[PRejto]

Aidan,

Your results are rather unusual to say the least.

When you used PEMpro, after you collected data on the analysis page what does the graph there say about your peak to peak error? Is this error the same value that you see when pasted into the Bisque TCS? Similar to running PEC in TSX? (Sorry! I missed your post above). It's really curious how you got the curves to align by removing 50% of the points. I'm not sure at all what that means.

I take it that before using PEMpro you went through the mount wizard where you measure the star trail lengths, etc? Then on the first page of the mount/camera settings page you synched the worm period before collecting the data?

I wanted to check on your assertion that the worm periods are the same for the MX and MX+. I found this so that is not the issue (I had a bit of a doubt remaining):



ME and ME II: 576 cycles in 24h → 2m30s of sidereal time
MX and MX+: 375 → 3m50.4s
MYT: 320 → 4m30s

I'm not remembering if this was previously suggested (and I know your scope is remote!) but perhaps you could eliminate some of your concerns re seeing/large aperture by mounting a smaller scope (a refractor?) and guide camera perhaps on top of the RC and measuring PEC. In any case you would have a point of comparison. Either way the results should be very similar.

Another random thought, perhaps for your seeing .45 arc-sec is asking too much. You might try binning 2x2 which still puts you below 1 arc-sec. I also notice that your exposures were around 3 sec. I think you can do better if binned. Try 1 sec.

Finally, if you can't figure out why only 50% of the curve from PEMpro ends up pasted into the Bisque TCS (and why the Peak to Peak vale changes so much) by all means post the question at Ray's forum at CCDWare. He always has answered me quite quickly!


Peter

[Somnium]

yeah i ran the wizard, synced the worm cycle. the issue happens when it is copied to TSX. PEMPro comes up with a curve that looks right but it gets screwed up when i copy and paste it into TSX. Maybe we could meet up given that we are both in Sydney and i can step you through what i am doing. there might be something really obvious.

[Shiraz]

I don't know either Pempro or SkyX, so please forgive this question if it is a silly one. Are you using the 8300 to gather the PE data? In the EQMOD world, PE data comes from the guide camera and the guide image scale is the one that is used - although I suppose there is no reason why the main camera could not be used.

[Somnium]

the suggestion from TSX is to use the main imaging camera, i have used that for both PemPro and TSX capturing

[Shiraz]

thanks - told you it could be a silly question :thumbsup:

[Somnium]

not a silly question Ray

[PRejto]

Aidan,

The other day, at lunch you said, you pasted the PEMpro data into the Bisque TCS. Simple question, were you at that time connected to the mount? Did you save to the mount and then retrieve the data?

If not, I believe TSX will possibly default to the ME where the worm period is about half that of the MX+. Maybe that is why you see only half the curve?

Peter

PS Maybe next clear night I could remote into your imaging computer via Team viewer and watch you run through things. Just an idea. Late is better than early. Feel free to contact me by email and we can exchange tel #s. (prejto at oberlin.edu)

[Somnium]

so it looks like there is an error in PemPro v3, Ray is fixing this up and should have a new version soon. i am looking forward to seeing whether this resolves my issue completely

[Somnium]

GGGRRRRR AARRRRRRGGGG

just another cry by me, the seeing looks good but i am still getting major errors in RA. this was taken while imaging M16 so not near the pole. i am trying to get the PEC working, the new version of PemPro keeps crashing on me. might give it another go tomorrow.

[PRejto]

Hi Aidan,

You are getting pretty large errors in DEC as well, though not as bad as RA. Remind me of your guide settings. For sure you need to bin the guide camera at your focal length. Regardless of your PEC status you ought to be able to guide better than this. What ADU is your guide star? How long are your exposures? min/max settings?

To me it looks like corrections are not being applied soon enough or aggressively enough to prevent the "clumping" on either side of X and Y. It doesn't look like seeing. If seeing, I would expect to see jumping in random direction on both sides of X/Y, not clumping on one side or the other. Perhaps what you are seeing is PE; the question is why can't you guide this out?

Peter

[Somnium]

Hi Peter, i am seeing a lot better tracking now that i have been able to run a PEC training run through the new version of PemPro and i have been able to get tracking like this tonight.

Maybe this is about as god as it gets for me. i think i just have horrible seeing conditions ...

FYI, guide set up is a MMOAG with a lodestar X2 at ~98" FL , binned 2x2

[Atmos]

What do you get if you run it through PHD and just track (no corrections)? That'll give you an idea on what the pure tracking is like without having to take guiding corrections into consideration. At least it'll rule something out, if it looks bad without any guiding corrections then you know where the problem is.

[Somnium]

it is pretty bad without corrections, enabling corrections definitely doesnt make it worse in dec

[Somnium]

i took the light shroud off with the assumption that it was getting caught in the breeze and messing up the tracking. that seems to have helped enormously

[gregbradley]

Some scopes are very susceptible to wind. I take the shroud off my CDK17 if there is any breeze.

I used to have an RCOS12.5 inch with a closed tube. It sat in the back of my car at my dark site on way too many occasions when it was windy as my mount could not handle the wind induced errors.

FSQs are good that way or a dome.


Greg.

[Somnium]

After talking about this issue for months, I am being shipped a new RA worm block, hopefully that will solve the issue

[strongmanmike]

BTW (sorry to digress slightly Aidan) Greg, was this the scope I saw in the classifieds recently...?

Good luck with the new worm/block Aidan

Mike

[Atmos]

Hopefully this will fix your issues!

[Somnium]

fingers crossed.

[gregbradley]

I am not sure. I sold it about 6 years ago to a chap in the Bathurst area.

Greg.

[gregbradley]

Ahh, how annoying. I thought that was only the initial offerings that had that problem. Gee they have had several years now to get their quality control sorted. Naughty and slack. So does that make everyone who owns one of these mounts on this site have had to have a new worm block or has there been one or two lucky ones that somehow managed to escape?

Well you have the patience of a saint and I am pretty certain you will indeed find it was the worm. Good that they send a new one, bad they didn't get it right in the first place despite this being an old problem with production. SB after sales service is quite good. But I think we all would like to be assured we will get a working mount for that sort of money in the first place and not a work in progress you are the quality control person type mount.

While you are at it I would check that the belts are the correct ones as that was the other problem. They should be a grey colour not black. The black ones shed material and cause bumps in your PE.

Greg.

[PRejto]

Well, I too hope Aidan's issues are solved with a new worm. But, to be fair to Software Bisque I think any judgement ought to be reserved to see if indeed that is the outcome. Personally I'm a bit sceptical given that errors in declination are ca of the same magnitude as errors in RA. Given that declination is not moving much compared to RA that would point to some sort of error in guiding. Another possibility might be that the worm is contaminated and requires regreassing. It is in spec as far as PE is concerned though it remains a mystery as to why PEC enabled doesn't seem to improve PE with either TSX or PEMPro. Gee, I hope I'm wrong about these things and a new worm does the trick. But, having replaced the worm 3x on my original MX without addressing the underlying issues (which was totally different than this issue!) the jury is out.

By the way, Greg, this one is an MX+ so the belt thing is not in play.

Peter

[Somnium]

to be honest, i think they are chucking me a new block to shut me up for a while and it might actually not solve the issue. i really hope it does, but i am all out of ideas. the RA variability is definitely more than the Dec variability and like you said, enabling PEC doesn't help PE. well if nothing, this will remove one element.

[PRejto]

Hi Aidan,

I agree with you. The worm might be a "hail Mary" pass. Maybe it will help. I'll say this here and not at SB but I think they really don't read the posts through in their entirety each day so, as you might imagine with the large number of issues, it is difficult to remember each thread from day to day. Even when I try to follow certain posts I find it difficult to manage all the facts from day to day and the evidence for that is in my last post over there to you. Yes, I know and you know what you have previously posted but my recommendation to you is that you post complete easily accessible info of exactly what you are trying to show with each post even if you area repeating yourself. And when a thread gets long and you have new info start a new thread and don't assume anything is remembered. This was my experience and it eventually bore fruit.

Peter

[gregbradley]

Time will tell but I am pretty confident the new worm will fix things. Perhaps there is some play in the worm meshing with the gears or the axle of the worm is a bit off etc.

I guess we'll find out soon. PMX+ would still have belts right?

Greg.

[Somnium]

i agree that SB don't have the time to look at every post each time, sometimes i get other people entering the conversation meaning well but it puts the questions i had for SB further up the chain and they don't respond.

SB support has been ok, though i had a faulty MKS 5000, then the issue with tracking and now i am starting to get the tell tail signs of more hardware related issues (mount hit something and port in use errors). all my other gear has worked relatively flawlessly but i have not been overly impressed with the quality of SB.



we will find out soon ... i am also looking to move my telescope in the next few months so hopefully i will get improved seeing as well. i just might be able to produce some half decent images.