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nyway Ill have another update tonight...its going to be a perfect night with above average seeing.

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Based off Meade's specifications its 1 arc second RMS. Still this is around +/- 1.4 arc seconds on average.

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Either way ill be very happy if they can achieve +/- 2 arc-seconds (my typical seeing anyway), and achieve this CONSTANTLY.

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I think this is one point were all forgetting. Its one thing to be able to guide nicely on a specific object with a nice guidstar, and completely different to be able to do so constantly and at every place you point it at and every time.

Anyway Ill have another update tonight...its going to be a perfect night with above average seeing. I finally got the mount communicating with Pempro correctly so Ill be able to do a very good polar alignment, and will get some concrete PE data.

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Jared:

Your statement: I wouldn't worry too much about the total amount of PE. As long as the tracking is smooth, it is quite possible for the autoguider to keep things down at 1" RMS.

You must be kidding. $7,500 mount, 20 PE Native. That is funny.

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Well Jared,
Personally, I do worry about PE, it is a sign of what is going on with the mount. It tell the tale of how precise the machining and tolerances are in the build. Plus, when you get to over $7,000, well you kind of expect a bit better everything really.
Blueman

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Jared:

Your statement: I wouldn't worry too much about the total amount of PE. As long as the tracking is smooth, it is quite possible for the autoguider to keep things down at 1" RMS.

You must be kidding. $7,500 mount, 20 PE Native. That is funny.

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Nope, not kidding. I don't honestly care what my mount's native PE is. I only care about whether I can get my mount guiding or tracking at or near the seeing limit.

The GM8 I referenced above had really bad periodic error--in excess of 20"--and also had relatively rough tracking. I had to get the balance perfect on that mount to get well guided images. The problem, though, wasn't the total PE--it was the roughness. I also, for a short while, owned a Vixen Sirius mount that had even more PE than the GM8. However, it was quite smooth and predictable. Getting well guided images with it was a breeze. I think PE is used to measure a mount's quality because it's a single number that is easy to understand and because small PE values virtually guarantee smooth tracking.

I'll admit I would much rather have a mount with low PE--but it's only because I know with low PE that the tracking won't be rough. If you could guarantee smooth tracking, I wouldn't really care what the PE number was. Even if I paid a lot of money for a mount.

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anyone believing that an LX800 will ever produce 1 arc second PE. Given it's LX200 guts

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Not sure there yet are we
We know the boards and software appear to be LX200 variants, but raw PE is a function of the worm and wormwheel construction/tolerances.
We need to see what is in the LX800 before saying its the same. The earlier PEC plot posted showed a large high freq ripple superimposed on the main PE, so it looks more like the problem is in the external gears.
The PEMPro FFT plot will allow that to be seen/analysed.
The PEC granularity in the LX200 appears to be more than double that of the LX200s, so it wont help with rapid changes. The guider is going to be the crucial bit here.


Andrew

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Well Jared,
Personally, I do worry about PE, it is a sign of what is going on with the mount. It tell the tale of how precise the machining and tolerances are in the build. Plus, when you get to over $7,000, well you kind of expect a bit better everything really.
Blueman

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Well Jared,
Personally, I do worry about PE, it is a sign of what is going on with the mount. It tell the tale of how precise the machining and tolerances are in the build. Plus, when you get to over $7,000, well you kind of expect a bit better everything really.
Blueman

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Jared:

Your statement: I wouldn't worry too much about the total amount of PE. As long as the tracking is smooth, it is quite possible for the autoguider to keep things down at 1" RMS.

You must be kidding. $7,500 mount, 20 PE Native. That is funny.

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Nope, not kidding. I don't honestly care what my mount's native PE is. I only care about whether I can get my mount guiding or tracking at or near the seeing limit.

The GM8 I referenced above had really bad periodic error--in excess of 20"--and also had relatively rough tracking. I had to get the balance perfect on that mount to get well guided images. The problem, though, wasn't the total PE--it was the roughness. I also, for a short while, owned a Vixen Sirius mount that had even more PE than the GM8. However, it was quite smooth and predictable. Getting well guided images with it was a breeze. I think PE is used to measure a mount's quality because it's a single number that is easy to understand and because small PE values virtually guarantee smooth tracking.

I'll admit I would much rather have a mount with low PE--but it's only because I know with low PE that the tracking won't be rough. If you could guarantee smooth tracking, I wouldn't really care what the PE number was. Even if I paid a lot of money for a mount.

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Edited by Whichwayisnorth (05/17/12 08:35 PM)

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You use Starlock to do a drift alignment and this disable it since you can't use both at the same time. Now you are left with a mount that is 15-20+"a/s of PE.

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Andrew did you and John get the ASCOM driver worked out?

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We know what the problem is, but i dont work with/on ASCOM drivers, as they require viruses to compile them.
John tried the Maxmount driver, and that works for most functions he needs, but i dont know how compatible it is for all functions. There are some big changes in the LX800 code re PEC and Guiding, and i am working on that so my Editor can at least read out the data correctly before i move on.
Till then, maybe try the MaxMount driver and see what breaks

Andrew

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I didn't see any indication in the literature that PPEC has been eliminated.

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Manual, Pg36 last para
Based on the code to date, it also appears there is no PPEC.
There are no PEC sensors fitted to the unit
and the home sensor plate moves with the RA head, hence moves relative to the wormwheel, hence cant be used as a datum.
Also, not tested yet, but it looks like every time you turn PEC to ON, it does a factory reset. ( Thats not 100% confirmed yet, but i reckon its right. )
Also, there are only 60 PEC bins per worm rev, vs 200 in the LX200s.
For LX200s PECbins are approx equivalent to 36arcsec at the OTA.
This beastie gets 96arcsec/bin so that will be the smallest granularity it can work to.

Andrew

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I think his point was smooth PE out ranks total PE. Jared wasn't attempting to quantify total PE.

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Here's what is funny however, anyone believing that an LX800 will ever produce 1 arc second PE. Given it's LX200 guts and poor QC start, I'm sorry to say - it will never happen. I feel bad because I really wanted this to be a great product.

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I found the you tube video very upsetting as I watched someone who spent hard earned cash become defeated with frustration. Always maintaining his composure however. A class act I must say.

Joe

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I made that same point to Meade. They are leaning HEAVILY on Starlock. The concern I mentioned is for people with longer focal length telescopes that want to use those longer focal lengths. I would say the focal length of Starlocks narrow band OTA is too fast to accurately guide a long F/10 or F/11 main scope. Also if you have an older OTA you are putting on it like a 12" ACF 3048mm F/10. I would predict that if you want to image at 3048mm that you are going to opt for a Off axis guider. Now you plug that into the control box where it is labeled "autoguider". You use Starlock to do a drift alignment and then disable it since you can't use both at the same time. Now you are left with a mount that is 15-20+"a/s of PE. It has been pointed out that if the PE is a nice smooth predictable curve then that is easy to guide out. However if it is not... Myself? I probably will not be interested in imaging at anything slower than F/8. Once the F/5 reducer ships I will spend most of my time at F/5.

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Well Jared,
Personally, I do worry about PE, it is a sign of what is going on with the mount. It tell the tale of how precise the machining and tolerances are in the build.

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Gday John

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I didn't see any indication in the literature that PPEC has been eliminated.

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Manual, Pg36 last para

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I didn't dig out a manual, but I looked at the ad copy again. It appears that the Starlock trains PEC each time it is enabled. That's not PPEC (and thus requires no index switch), but would be nearly as convenient. Just have to wait a worm cycle for it to get engaged. I don't have an immediate opinion about it but it's an interesting approach.

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it's an interesting approach.

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Well Jared,
Personally, I do worry about PE, it is a sign of what is going on with the mount. It tell the tale of how precise the machining and tolerances are in the build.

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No, it doesn't. You can have perfect machining tolerances in the making of the gears and still have a lot of PE. In the gear world, what we call PE, is called transmission error. There are a number of design trades when you design a gear mesh, but one of them is transmission error versus other parameters such as root bending strength, tooth sliding, and gear efficiency. The point is, if the mesh isn't inherently designed for low transmission error (which somewhat compromises the performance of other features), even perfect fabrication of that mesh will yield large PE.

Now, here's the catch. A lot of worm drive applications are virtually completely immune to transmission error, and thus the gear mesh isn't designed to minimize it, but rather to maximize the performance in the other parameters. I don't know what Meade does, but they might be using stock gears originally designed for a different purpose, or even if they are special for them they might have been designed in a standard way without the objective to minimize transmission error.

My point is, PE isn't necessarily a manufacturing problem, and in fact it usually isn't. If it were, it would vary greatly from cycle to cycle. Usually it doesn't, even if the magnitude is quite large.

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