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ZEQ25 PE Curve

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#1 Astronewb

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Posted 24 October 2013 - 12:18 AM

Just for info, I guess some ZEQ owners and shoppers want to know how the Z Balanced mount stacks up? For $800 bucks you could do a lot worse....

This is from PecPrep V1.84 and a PHD log file from Sept 24th, corrected for DEC. I was imaging M33, guiding with a Lodestar/Borg 50mm/250mm combo. Main scope was a Borg 125SD.

This PecPrep isn't cherry-picked, I have tons of them like this, some better, some a little worse.

Hope someone on the fence for a splendid little 10 pound mount finds this interesting, and helpful.

Clear skies,

Paul

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#2 orlyandico

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Posted 24 October 2013 - 02:58 AM

but that is the error while it is being actively guided - hence that's not the true PE of the mount (see the EQ8 PE thread) but rather the measure of how tight it guides.

The PE would be measured by disabling guide outputs in PHD..

#3 Astronewb

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Posted 24 October 2013 - 10:02 AM

but rather the measure of how tight it guides.


Very true Orly. If iOptron ever puts their excellent Two Star align routine back into the HC firmware, I could post a raw PE curve.

That routine reports Polar Offset, and allows you to dial out the offset to '00-00' by using the az and lat adjusters.

iOptron replaced that routine with a 'Bright Star' type routine for users that don't have a view of the pole stars (or couldn't figure out how to use the polar offset?) at the expense of users that can see the pole stars. The new routine is not even close to being accurate enough to dial out polar offset.

I have no easy way to drift align to get to that reference point, since I have no views to the West, and my view to the East has 5 streetlamps between me and the horizon, which makes selecting a suitable star frustrating, if not hopeless..:(

If I had to estimate, with my tightened mount, the resident PE is probably under 5 arc-seconds peak to peak.

But, this result is off a tripod, with just a basic polar align and a One Star go-to, and guided, which is how most of the users of this mount will be using it, so it's still relevant?

And it certainly does show how well it tracks when guided.

Clear skies,

Paul

#4 PGW Steve

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Posted 24 October 2013 - 11:25 AM

It is deceiving to see "ZEQ25 PE Curve" and then come into the thread thinking that an $800 mount makes my Astro-Physics Mach1/1200/1600 look like junk. :-P


Take the mount somewhere you can drift align it properly and repeat the test, and not make any assumptions that is 5 seconds peak to peak.

#5 tjugo

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Posted 24 October 2013 - 11:34 AM

Hi Paul,

You don't need perfect polar alignment to measure PE... PECprep will remove the drift caused by polar misalignment.

Residual Error after guiding is not very meaningful cause it is tie to seeing, guiding equipment, mount operator etc.

Just be careful to compensate for DEC when reporting tracking error.

Cheers,

Jose

#6 core

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Posted 24 October 2013 - 11:36 AM

I'm looking forward to see the raw PE curve of the ZEQ!

#7 Astronewb

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Posted 24 October 2013 - 12:57 PM

Hi Paul,

You don't need perfect polar alignment to measure PE... PECprep will remove the drift caused by polar misalignment.

Residual Error after guiding is not very meaningful cause it is tie to seeing, guiding equipment, mount operator etc.

Just be careful to compensate for DEC when reporting tracking error.

Cheers,

Jose


Thanks for that useful info Jose, I will give it a shot the next time I have a break in the weather.

Best...Paul

#8 andysea

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Posted 24 October 2013 - 02:06 PM

0.33" RMS seems to be an excellent value. That's what I get with my Mach1 and NJP, unless the seeing is exceptional.

#9 ramasule

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Posted 25 October 2013 - 11:04 PM

http://www.cloudynig...Board=lxd55&...,,All_Forums,,&Words=&Searchpage=1&Limit=25&Main=6081789&Search=true&where=&Name=208311&daterange=&newerval=&newertype=&olderval=&oldertype=&bodyprev=#Post6082579

Mind you I haven't had a good night to get better data since.

#10 anat

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Posted 26 October 2013 - 03:45 AM

Could you tell me the PE in arcsec?

#11 ramasule

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Posted 26 October 2013 - 11:51 AM

8 peak to peak about. Next time im out I will try for a better graph.

#12 Tony Finnerty

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Posted 28 October 2013 - 12:19 PM

No PE curve, but two nights ago I got PHD Guiding graphs for my tuned ZEQ25 (thanks for the videos, Paul!) that looked like this consistently:

Posted Image

This is crazy-good for the crazy system I'm developing for winter AP from my balcony with its flexible floor boards. The tripod is set on a plywood triangle and I step on separate plywood sheets to distribute weight to minimize tilting the mount when I move. The tripod is set on three 8x8x16 inch concrete blocks standing on end for 16 inches of lift, to raise the polar scope high enough to see Polaris over my roof. I stay off the balcony during exposures.

#13 nomosnow

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Posted 28 October 2013 - 06:21 PM

Very nice graph indeed , Tony what declination was the object that you were imaging ?
John

#14 orion69

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Posted 28 October 2013 - 06:30 PM

This is crazy-good ...


This was probably guided with finder scope, if so it doesn't say much.

#15 Astronewb

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Posted 28 October 2013 - 08:32 PM

This is crazy-good ...


This was probably guided with finder scope, if so it doesn't say much.


On the contrary, I think it says it all. That's how most imagers will use the mount?

A mount that won't guide smoothly just adds to the frustration of imaging, taking up more time with PHD than with actually taking some images.

If you don't want to use a guide scope, there are plenty of mounts in the $7~10K price range that will deliver 5 minute unguided images. But I guarantee you're not going to be carrying them out every time it's clear enough to image.

This mount takes all of ten minutes to set up, polar align and star align, and then start imaging. Tear down at the end of the night is the same.

Just my humble opinion... Paul

#16 Mkofski

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Posted 28 October 2013 - 08:45 PM

Completely agree with you Paul. My take on Orion69's comment was that using a finder size guide scope wasn't very meaningful and that a longer fl guide scope is in order.

#17 orion69

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Posted 28 October 2013 - 08:58 PM

On the contrary, I think it says it all.


Most mounts will have PHD graph that smooth if guiding with finder. So, no, it does not say all at all. ;)

Of course, that does not mean that resulting image can't be good.

#18 Falcon-

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Posted 28 October 2013 - 11:33 PM


On the contrary, I think it says it all.


Most mounts will have PHD graph that smooth if guiding with finder. So, no, it does not say all at all. ;)

Of course, that does not mean that resulting image can't be good.


Actually I would say that most mounts in this price range do NOT necessarily give such good results, even with 50mm finder-guiders.

There is a reason I got my ZEQ25 to replace a CG5....

#19 Tony Finnerty

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Posted 29 October 2013 - 10:56 AM

Hey nomosnow, I imagine you get tired of the white stuff up there in Saskatchewan, but we're looking forward to the small amount we get in winter in Nevada City, in the Sierra Nevada foothills! I was shooting M31 at the time, which was located at DEC +41 deg 20'. I'm chasing down a flexure issue, so no image to post. An early version shot with a different lens can be seen here .

Knez, I was guiding with a Lodestar on a Stellarvue 60mm finderscope. My post is a bit off topic in the sense that it doesn't measure periodic error, only what is possible when guiding the ZEQ25. I'm very pleased with what I got for $950 (mount + polar scope + 2" tripod). Until my 4" refractor arrives the mount is carrying only telephoto lenses like a 50-200mm zoom lens + mirrorless camera. Paul has shown us the ZEQ25 can perform with a ridiculous payload compared to its own weight. I bought this mount based on his early results - thank you, Paul!

Paul, you are very correct that this quality of guiding can be achieved with 10 minutes to setup, polar align and one-star align, even in the hands of a total newb in the midst of acquiring his first telescope and mount. The ZEQ25 combined with a 4" refractor will be an awesome mobile AP system.

Mike, Knez and Falcon - the bottom line is the quality of guiding. A very expensive mount can track accurately for long exposures without guiding. A less expensive mount compensates for less expensive mechanicals by way of software (guiding). The key is smooth performance so guiding can be precise. The ZEQ25 mechanicals are smooth enough so guiding is very effective. I never expected to afford performance this good.

#20 rmollise

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Posted 29 October 2013 - 12:16 PM

Actually I would say that most mounts in this price range do NOT necessarily give such good results, even with 50mm finder-guiders.


Which mounts are you speaking of specifically? I've found the VX and the Sirius give results pretty much identical to these. ;)

#21 tjugo

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Posted 29 October 2013 - 03:48 PM

This is crazy-good ...


This was probably guided with finder scope, if so it doesn't say much.


On the contrary, I think it says it all. That's how most imagers will use the mount?

A mount that won't guide smoothly just adds to the frustration of imaging, taking up more time with PHD than with actually taking some images.

If you don't want to use a guide scope, there are plenty of mounts in the $7~10K price range that will deliver 5 minute unguided images. But I guarantee you're not going to be carrying them out every time it's clear enough to image.

This mount takes all of ten minutes to set up, polar align and star align, and then start imaging. Tear down at the end of the night is the same.

Just my humble opinion... Paul


C'mon, don't let your love for the mount cloud your judgement. A pretty flat PHD graph not even with pixel resolution is useless.

PE profile is important because you can infer how hard/easy would be to autoguide the mount.

If you like nice flat graphs just bin the guide camera, buy a guider camera with bigger pixels or get a shorter FL guide scope.

This is a surprisnsitly good mount for the price, I had one of these mounts and it was very easy to guide, no tweaks or tuning requiere. I returned the mount because the ASCOM driver was (is?) a joke

Cheers,

Jose

#22 orlyandico

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Posted 29 October 2013 - 07:22 PM

The new PHD2 can take your guider focal length and camera pixel size in microns as inputs, and graph the guiding profile directly in arc-seconds (and you can adjust the scale - just like in MaximDL).

Just when I had gotten used to super-flat guiding graphs (e.g. 0.01 rms) in PHD1..

Ah.. and PHD2 can store your calibration data so no need for that tortuous calibration exercise every time you start it up. It can also save the darks from your guide camera. And, the interface no longer locks up during long exposures with my Meade DSI. Some very nice and worthy improvements.

#23 John Miele

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Posted 29 October 2013 - 08:07 PM

I'm surprised no one is posting any raw plots here...here is my unguided Zeq25 PE curve. Guide star was at 30 deg. Dec. Scope was AT72. Total payload on the mount was maybe 10 lbs. plus 1 CW. Used PHD and a 50mm guider with Orion SSAG for a pixel scale of about 6 arc-sec/pixel. Have done no tuning of the mount. This is what I got out of the box. Is this good or is this poor...I don't really know :shrug:. It does guide pretty well up to 5 minute subs so far. I have a LOT more testing planned. I want to try Paul's tuneup and repeat this test. Hope the graph here is a useful data point for someone...
John

EDIT: My first plot had the wrong gear period so I deleted it. The other following plots are corrected...John

#24 orlyandico

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Posted 29 October 2013 - 08:25 PM

I am surprised as well, people are throwing around 8" peak-to-peak. Maybe they are looking at "Av. PE+" and "Av. PE-" which IMHO is incorrect?

The above graph shows +14 / - 12 or about 26" peak-to-peak, which, if representative of ZEQ25's means it is not the wonder-worker that many think (or want) it to be, but a thoroughly middle-of-the-road Chinese offering, with the value proposition of being light.

Can you re-post the plot but with only the first two harmonics checked? (the magnitude 100 and magnitude 80 ones) - but also change the mount type to "Vixen GP" (since the ZEQ25 has the same number of worm gear teeth as the GP, which is 144 teeth).

From your graph looks like there is a fast component with a 160-second period that's even bigger than the worm fundamental. Shades of the CGEM 8/3? the 80 magnitude component is most likely the worm fundamental, since a 144-tooth worm has a 598-second period.

To measure only the worm fundamental, only check the 80 magnitude component.

However, since the 100 magnitude component is even bigger than the fundamental, it must be accounted for when measuring PE. So the best measure of PE would be the 100 and 80 magnitude components.

All of the other components are tiny and can be ignored.

#25 Astronewb

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Posted 29 October 2013 - 08:51 PM

Hope the graph here is a useful data point for someone...
John


A couple of minor points John. The worm period for the ZEQ is 600 seconds, so you need to set that in PecPrep. You have it set to 479.

After you load your PHD log, check 'Mag Period' and uncheck all the other boxes to see the raw PE in the mount.

Oh, once you tighten up the mount a bit, it will improve.

Good luck and thanks for the data.

Paul






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