First T-Point with MEII

[PRejto]

Finally a clear night and finally working equipment.

Some of you are curious about my MEII especially compared to my poor old MX (which was plagued by a crook polar axis bearing that took me 2+ years to sort out).

All I can say is OMG, wow, and to give thanks that I seem to have received a "keeper!"

Using my TEC180 and Moravian G2-8300 camera my T-point runs (just 60 points initially) have given me pointing of 4.3 arc-sec. (after a recalibration into the model not shown in the attached photos. The photos show the results of the first run after an initial drift align of the mount)

After two additional recalibrations ME =10.5 arc-sec and MA = 46.1. I may or may not raise the mount .5 tics.

Next up I will be looking at PE. A preliminary run last week showed uncorrected of ca 1 arcsec peak to peak. If that is true it's almost not worth bothering with. (but I will!)

Peter

[pvelez]

About time you had some luck Peter!

Looking forward to some images now

Pete

[Paul Haese]

That looks like a great pointing model. I have the Rc12 and MX pointing at 6.2" myself and cannot imagine 4.2" pointing.

With the PE just make sure your camera is close to 0 or north. And using a nice brightish star too if you are using the skyX PE system. I found it does not work well with stars over mag 8.

[kimrichards]

Paul,
Can you expand on the point about the brightness of the star used for PEC with SkyX? I still have been unable to get this to work. Everything appears to work correctly but the residual PE is not repeatable nor better than the original. Camera angle is almost perfect and "pointing west" correctly set, if it is not correct the PE is definitely worse.

Thanks
Kim

[frolinmod]

For us Northern hemisphere users checking that checkbox actually means PE data collected with PA=180, not checking it means PE data collected with PA=0 and it doesn't matter which side of the meridian the OTA was pointed. The checkbox is poorly worded. I'm in the Northern hemisphere, always do PE data collection with the OTA on the East side of the mount, pointed to the West side of the meridian with the camera rotated to PA=0. Hence I do not check that checkbox. Confusing, eh? Not to worry, if the PE doubles, just check the checkbox and reprogram it. The whole procedure is supposed to get automated soon anyway.

[Paul Haese]

Hi Kim, through trial and error I have found that the camera add on in the SkyX does not autoguide well or should I say watch a star well if the star is not bright enough. This results in flat zig zag supposed PE readings. The beighter the star the better the response. One sure way to tell if the star is bright enough is that the guide box will be centred on the star. If it is offset in any way, then the star is not being watched by the software.

Just for information, i am using an STXL with 11002 sensor with a guide box of 200x200.

[Paul Haese]

This is quite interst Ernie, because what I have found is that the curve when checked for pointing in the west and the PE is taken in the southern hemisphere; the curve actually gets more out of phase. Once I worked out that the phase seems to get better by applying the reverse of what seems to be required then the PEC correction is very good. Guide graphs in the last week have been very good despite very average seeing in Clayton Bay.

I am not sure if this is an actual problem that others have found too or whether I have some setting balls up.

[frolinmod]

Paul, that's exactly what used to happen to me before I learned (or rather Daniel admitted) what that darn checkbox really means. Here's (http://www.bisque.com/sc/forums/t/16290.aspx) where I reported it back in 2012. Unfortunately my thread got hijacked.

[Joshua Bunn]

Fantastic Peter. You would be so glad you went with the PME ll now hey. The pointing and PE are exceptionally low, that is awesome :)

[frolinmod]

Peter, good pointing is cool, but more importantly I hope your tracking is now a dream (and not a nightmare). :thumbsup:

[PRejto]

I'm stoked. Tracking is amazing. Guiding is so much better. Night to night start up accuracy is so far flawless!!! What a beast.

My uncorrected PE is 1.5 peak to peak measured both in PEMpro and TSX, but so far I have been unable to make an improvement. PEMpro doesn't yet work for the MEII. It will measure but can't make a corection curve due to the different number of cells in the MEII vs the ME. And TSX, well same old same old. Checking E or W makes no difference. I think there may still be a phase error for the SH users. But, I will try some more!

Peter

[frolinmod]

What software are you using for guiding?

1.5 arc seconds p-p. Drool. By comparison my 2010 vintage ME's raw PE is twice that, but does go subarcsecond with PEC, which is where I hope you'll be soon.

That should be fairly easy to demonstrate and package up as a problem report to SB with description, autoguider data files and screen snapshots included. Someone has to test SH operation for them because it's clear they aren't able to do it on their end.

[Joshua Bunn]

Using TSX Pro and a PME, the camera addon by SB works for me to get my Periodic error to 0.7 arc sec Peak to Peak. I dont know if this would be different with the MKS 5000 mounts.

Josh

[PRejto]

I've had such good results with PEMpro that I'm reluctant to invest a bunch of time when there is so much else to do (like actually image!). Ray has indicated that he might write a modification of PEMpro this weekend so that the MEII will work.

In any case, if PEMpro gets a result it will be easier for me to demonstrate whether TSX is working or not. My reasoning is that working curves from either program have got to be basically similar in the overall shape of the curve and the phase (in what is uploaded to the mount).

Stay tuned,

Peter

[PRejto]

PEMpro now supports the MEII (Thanks Ray!). And yesterday proved to be a night of very steady seeing. The results are pretty amazing! As I was collecting data I was convinced that somehow I hadn't turned PEC off.

Uncorrected PE = .8 arc-sec measuring 5 cycles of the worm
Corrected PE = .4 arc-sec

All my previous measurements with both TSX and PEMpro showed 1.5 arc-sec peak to peak so this must be a lesson that poor seeing will not allow the algorithm to work entirely correctly in determining PEC. Following this line of reasoning perhaps TSX simply doesn't do as good a job knocking out bad data as does PEMpro. On nights of poorer seeing PEMpro was able to produce a PEC that worked (1.5 PTP to .7 PTP) whereas TSX measured PTP as 1.5 but would not generate a curve that gave any correction, but put in "upside down" would double error (1.5 to 3). It's either that or some sort of phase error. If I'm bored I may experiment with this further but clearly it will take an exceptional night.

Yesterday I also received an OPtec "Libra" alt-az mount that I have installed in the saddle holding the TEC140. I now have perfectly aligned pointing of both scopes. It appears to be an exceptionally well made product! Now, I still only am waiting on the focusing solution from Starizona. They say soon but I've heard that toooooo many times!

http://www.pbase.com/prejto/image/155505015

Peter

[Joshua Bunn]

Exceptional results Peter.

[frolinmod]

I dunno, my experience with measuring PE on Paramount ME (mind you not an ME II) is that whenever I measured raw peak to peak PE as sub-arcsecond, I was doing it wrong and just measuring noise instead of signal, so to speak. So I'm a bit suspicious of your measuring your raw peak to peak PE as sub-arcsecond. Corrected by PEC peak to peak PE should always be sub-arcsecond, of course.

[Paul Haese]

I agree with Ernie. Something not right there. I recently discovered that you need a bright star to get accurate readings. I had plenty of runs like that which said .8 arc seconds peak to peak. It turned out I was not using a sufficiently bright enough star.

Which programme are you using to connect the camera? Are you using the SkyX camera Add-on. If so you need a bright star of around mag7 or less to get correct autoguiding data.

I would expect that 3.5" peak to peak would be about right or even 2" peak to peak but sub" on the east coast is not likely. I am happy to be wrong and would like to look at your log just to confirm.

[PRejto]

Hi Ernie and Paul,

Well, you guys could be right of course. But, it was a really good night. I was using PEMpro, not TSX, and imaging at .96 arc-sec, .5 sec exposures with the SX Trius camera. During capture of the 5 cycles I could tell it was a good run because as the exposures are plotted on the graph in PEMpro it's quite easy to see how much the atmosphere is affecting things. In poor seeing the points jump all over the place and then on the next cycle they are jumping too but not in the same direction necessarily. Last night there was very little jumping around and the trends over the 5 cycles were quite consistant. And then after applying the correction the result was even flatter. It's kind of hard for me to figure out how that is noise. I'm not saying you guys are wrong but just trying to understand. If the first run was wrong and it was noise how could that then result in an improvement? Or, another question? How can "noise" make it appear that there is no PE? Wouldn't noise make stars jump all over the place?

Anyway, here is a look at the PE capture in PEMpro with PEC off that resulted in the correction curve posted earlier. I've also attached the PEMpro txt file.

Please tell me if you see something wrong! Each cycle of the worm is a different colour. The variations within each cycle can be read in pixels on the left. The reason the cycles don't exactly line up is due to drift in RA due to polar alignment. So over 5 cycles (12.5 min) I've drifted 4-5 arc-sec.

Paul, with PEMpro you cannot select the star as it is done automatically and the exposure adjusted accordingly. Also, I'm not sure I understand what you mean exactly by "East Coast." Sure, the seeing might be poor and normally exceed 2 arc-sec, but that would be the noise. The measured PE would be hidden in the noise, but it would (or should) be the same no matter where the mount was located.

Peter

[PRejto]

I decided to post my results over at the PEMpro forum and Ray responded. I'll sum up since I believe that quoting someone might be against the rules here. He thinks the results are real...

http://ccdware.infopop.cc/eve/forums/a/tpc/f/401101098/m/5647067136/p/2

Peter