Are there any PMX PE measurements yet?

gregbradley · #1 12-10-2011, 02:56 PM

Has anyone taken their PMX for a test run yet and measured the PE?

Is it smooth? Any spikes? I got an email from someone complaining their PMX worm was no good and it gave a couple of nasty spikes and it took a while to get SB to agree to replace it. It would bump the autoguider off.

Hopefully its just teething problems with their production line. I hope they are not in such a mad rush to fill orders a few quality issues are overlooked.

A bit worrying.

Greg.

nickbtx (Nick) · #2 13-10-2011, 12:39 AM

Hi Greg,
I've measured the PE on mine at 5.6 arc seconds, uncorrected. I've tried it a couple of times and have gotten different results (5.6 being the lowest). I suspect the seeing may have had something to do with that.
Nick

gregbradley · #3 13-10-2011, 08:19 AM

Yes the seeing would definitely affect the measurement. That sounds pretty good.

Greg.

Ross G · #4 13-10-2011, 08:59 AM

Hi Nick,

Is that measurement peak to peak or +-.

Thanks.

Ross.

Paul Haese · #5 13-10-2011, 09:22 AM

Just one thing for those unfamiliar. Make your exposures around 0.11 and get it to watch the star for 25 minutes as a minimum. You will get a good reading then.

cventer · #6 13-10-2011, 10:08 AM

Have not done pe yet, but was polar aligning last night. Afterwards did a 2 min test exposure at 1400mm fl. I watched the guide relays in tcs and they lit up twice for a few ms in the whole exposure. Had lovely round stars afterwards. No PEC . Me happy so far.

frolinmod · #7 13-10-2011, 10:21 AM

Quote:

Originally Posted by Paul Haese

Just one thing for those unfamiliar. Make your exposures around 0.11 and get it to watch the star for 25 minutes as a minimum. You will get a good reading then.

25 minutes is a long time to go with no guiding and ProTrack disabled unless your polar alignment is very good indeed. A great big R Lee Ermey "Hoorah!" to you if your polar alignment is that good. In my case, in order to go that long in CCDsoft I had to increase the tracking box size or whatever it's called so that the star didn't slowly drift all the way outside the box.

gregbradley · #8 13-10-2011, 01:01 PM

Quote:

Originally Posted by frolinmod

25 minutes is a long time to go with no guiding and ProTrack disabled unless your polar alignment is very good indeed. A great big R Lee Ermey "Hoorah!" to you if your polar alignment is that good. In my case, in order to go that long in CCDsoft I had to increase the tracking box size or whatever it's called so that the star didn't slowly drift all the way outside the box.

I was able to get 20 minutes and could've gone 25 minutes but as you say that was only after several iterations of improving my polar alignment and making sure balance was spot on.

By the way how do you increase the size of the tracking box in CCDsoft?
That could be handy at times.

Greg.

Paul Haese · #9 13-10-2011, 02:08 PM

If you get you PA right Ernie you will find you can go that long. Tom from SB said this is what you should do to get PE sorted. I use Precision PEC and CCDsoft for that job. I want to do another run soon, when I have time. Will need to do it for the 12" refinement. Only done PEC for the TSA so far. The parameters are a lot wider given the focal length.

cventer · #10 13-10-2011, 02:17 PM

Quote:

Originally Posted by gregbradley

I was able to get 20 minutes and could've gone 25 minutes but as you say that was only after several iterations of improving my polar alignment and making sure balance was spot on.

By the way how do you increase the size of the tracking box in CCDsoft?
That could be handy at times.

Greg.

Greg and others, with regard to balance what are you doing to weight east side once you have balanced ? Do you use a movable weight or do you adjust the counterweight on the shaft.

Paul Haese · #11 13-10-2011, 02:22 PM

If the MX is anything like the PME. Then you will find that balance must be perfect as written in the manual. Balance cannot be biased.

gregbradley · #12 13-10-2011, 04:05 PM

I balance the mount with the scope horizontal in both axes.
I check it isn't wildly different at the usual imaging angle. With a scope mounted on top that will be different to horizontal so I check at the usual imaging angle and adjust to that rather than to horizontal.

As far sensitivity to balance I find my PME very tolerant. It has been at times somewhat out of balance but I still got round stars. The beauty of a heavy duty mount.

But for PEC etc you don't want any other factor in the way. I don't have a shifting weight balance. I know a lot of mounts say to weight the west side slightly so the gears are always meshed. I am not sure if that is true with the PME as it is belt driven but perhaps it is.

PMX - it may be different, its not as beefy as a PME so weight balance may be more important but I suspect its not as critical as with other mounts.

Greg.

frolinmod · #13 13-10-2011, 04:41 PM

With the ME, imbalance definitely causes increased power usage and drains your batteries faster in the field. I have measured this using the device linked to below.

I'll lay odds that the MX is similar in this regard.

Put one of these on your battery (or power supply) and you can measure and graph the power usage with excel:

http://www.powerwerx.com/digital-met...tware-usb.html

rat156 · #14 13-10-2011, 06:56 PM

You need clear skies to do this don't you

Cheers
Stuart

nickbtx (Nick) · #15 13-10-2011, 11:07 PM

Quote:

Originally Posted by Ross G

Hi Nick,

Is that measurement peak to peak or +-.

Thanks.

Ross.

Ross,
That was peak to peak.

frolinmod · #16 17-10-2011, 01:19 PM

Oh, I increased the tracking box by following this article:

http://www.bisque.com/sc/forums/p/442/426.aspx

Don't forget to substitute the name of your camera for the one in the article.

gregbradley · #17 17-10-2011, 03:00 PM

Thanks for that.

In CCDsoft under the camera menu box and under colour.

I wonder if there is anything you can download to increase the number of columns in the colour tab in cameras. LRGB is all you can do when its often HaLRGB. It would be nice if it could be increased to 5 columns not 4.

Greg.

frolinmod · #18 17-10-2011, 04:36 PM

Greg, you're not the only one. I've seen that request before. Perhaps it'll get into the Camera Add On once it achieves parity with CCDsoft, assuming that is the goal.

cventer · #19 27-10-2011, 07:44 PM

For those we MX or ME when you are training PEC

Where are you pointing your OTA ? From the instructions it looks like we shoudl have dec close to zero and a star within 5 or 10 degrees from Meridean ?

Is this what you do ? I assume you dont want star to cross the merdean while logging data ?

Also the instructions say to orient camera so X = RA

Question i have is what is X relative to ? My CCD is rectangular. So shoudl X axis be across the long side ? Or do they mean x axis relative to the imaging software ie X axis is horizontal when looking at screen ?

In CCD soft my rectangular camera image is allways shown in Portrait mode. Ie longer side vertical in Y axis.

So do I irent camera to move star up and down the long axis when I move RA or sideways left to right on short side of rectangle when I move RA ?

Seems to be important to ensure DEC drift is not captured and only RA PE is captured.

frolinmod · #20 28-10-2011, 02:16 AM

Quote:

Originally Posted by cventer

Where are you pointing your OTA? From the instructions it looks like we shoudl have dec close to zero and a star within 5 or 10 degrees from Meridean?

Yes, that's where I do it, just to the West with the scope on the East side so that I don't have to worry about the post meridian stop. Of course with an MX you have much longer leeway (2 hours) there than I do with the ME (20 minutes), so you really don't have to worry about which side of the Meridian you're on.

Quote:

Also the instructions say to orient camera so X = RA.

You want RA to be X to be left right movement across your screen. You want DEC to be Y to be up down movement on your screen. Use image link to determine your position angle. Get it as close to zero degrees as possible. You really don't have to be all that close, the software doesn't really care that much, but it's helpful to be perpendicular so that you can see how things are going along while you're tracking and see how much drift is occurring either from polar misalignment or flexure. It doesn't matter that you have drift. That won't affect the measurement so long as the star doesn't drift entirely out of the track box while you're collecting data. I purposely use a large track box in CCDsoft so that I don't have to worry about drift at all, no matter how bad my polar alignment might be at the time.

Quote:

Seems to be important to ensure DEC drift is not captured and only RA PE is captured.

Not really. I saw your graphs. They look good. That little amount of DEC drift is of no consequence to PE measurement. However, you really should improve your polar alignment (if that's what's causing the DEC drift) for obvious other reasons.