#601  
Old 13-06-2014, 09:46 AM
AstroShomy
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Quote:
Originally Posted by orion69 View Post
Has that spike problem when guiding with Lodestar using PHD2 been resolved using latest firmware?

Can't find confirmation for this...
My EQ8 arrives in 2-3 weeks.
I am also interested in this...
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  #602  
Old 30-07-2014, 04:40 PM
Ajemsa (Andrew)
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I have read a few of the previous posts about the declination issue (whether it be binding or too much backlash) and would like to get some opinions on what is acceptable for what I am trying to achieve.
My Eq8 has a drive gear that is slightly non-concentric giving me a tight spot and not-so-tight spot as I rotate the declination 360deg. I would like to image at 1500mm focal length using PHD and would like to know what level of backlash is acceptable or can be handled by the software. I am only starting to understand the Eq8 and PHD and so I don’t have much experience to know what is achievable. If the mount isn’t going to achieve the result I want I will obviously have to contact the supplier for a replacement.
Thanks,
Andrew
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  #603  
Old 24-08-2014, 01:10 AM
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orion69 (Knez)
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Quote:
Originally Posted by orion69 View Post
Has that spike problem when guiding with Lodestar using PHD2 been resolved using latest firmware?

Can't find confirmation for this...
To answer my own question, my EQ8 came with latest motor firmware and PHD2 with Lodestar seams to be working fine.
This is 7x30 min:

http://www.astrobin.com/full/114292/0/?real=&mod=

(Best viewed in full resolution)
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  #604  
Old 24-08-2014, 01:13 AM
AstroShomy
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Quote:
Originally Posted by orion69 View Post
To answer my own question, my EQ8 came with latest motor firmware and PHD2 with Lodestar seams to be working fine.
This is 7x30 min:

http://www.astrobin.com/full/114292/0/?real=&mod=

(Best viewed in full resolution)
Could you please copy the link to the high resolution image?
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  #605  
Old 24-08-2014, 01:14 AM
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orion69 (Knez)
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It should be OK now, sorry...
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  #606  
Old 24-08-2014, 01:15 AM
AstroShomy
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Perfect result
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  #607  
Old 03-11-2014, 04:30 PM
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Shiraz (Ray)
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another EQ8 result FWIW.

Has been a bit too windy to get a stable PE curve, but the RA was keeping quite tidily within a +- 2 arc sec band between gusts. The curve (such as it was) showed one region/cycle with relatively high rate of change, but it guided out effectively at 1sec update rates. Lots of backlash in both axes, but there are workarounds for that (and I don't feel happy trying to adjust it when Skywatcher provides no advice on how to do it - in fact the SW attitude seems to be "we sold it, you bought it - and that's that"). However, the thing feels unbreakable - hardly notices a 22kg load.

Overall, it has exceptional PE and guiding performance, excellent load capability but much more backlash than my EQ6. Worth the money? - no doubt. Could it be better? - with a bit of work it could be up there with the best, but it isn't there yet. Even so, it can be made to work very well as is.

attached a single sub (stretched a bit) showing typical guiding in average/good seeing with 0.91 arcsec sampling.
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Last edited by Shiraz; 03-11-2014 at 04:51 PM.
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  #608  
Old 03-11-2014, 07:58 PM
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Stars look pretty round to me Ray. Maybe you need to get into the mount and adjust the backlash out. Have you taken a look at all to see if that is adjustable?
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  #609  
Old 03-11-2014, 08:04 PM
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mill (Martin)
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Just sign up here https://groups.yahoo.com/neo/groups/SkywatcherEQ8/info and there is plenty of info in the files section on backlash adjustment.
I adjusted mine and it has zero backlash in both axes.
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  #610  
Old 03-11-2014, 08:31 PM
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Shiraz (Ray)
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Quote:
Originally Posted by Paul Haese View Post
Stars look pretty round to me Ray. Maybe you need to get into the mount and adjust the backlash out. Have you taken a look at all to see if that is adjustable?
It is adjustable Paul, but SW is silent on how to do it - so there is an implication that fiddling around with it might invalidate warranty. Some of the mounts have backlash that varies with wheel position (I haven't checked this one and really don't want to know just yet) - these cannot be adjusted up fully without having the drive seize, and the motors have enough torque to damage things. I am wary of adjusting mine, but will probably have a look at it at some stage. In the meantime, there is stuff all PE and it guides very well if the backlash is managed. SW really needed to put spring loaded worms on them, but I guess that has its own set of problems and would probably have taken the cost well above current levels. As it stands though, it is a bit like a Russian military truck - big, tough and very capable, but with no frills or finesse (no tinsel ).

Last edited by Shiraz; 03-11-2014 at 10:26 PM.
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  #611  
Old 03-11-2014, 08:35 PM
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Shiraz (Ray)
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Quote:
Originally Posted by mill View Post
Just sign up here https://groups.yahoo.com/neo/groups/SkywatcherEQ8/info and there is plenty of info in the files section on backlash adjustment.
I adjusted mine and it has zero backlash in both axes.
thanks Martin - will do. The first one that I had was one of the horrid "variable backlash" versions - this replacement one is better, but haven't properly checked yet.

Last edited by Shiraz; 06-11-2014 at 09:04 AM.
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  #612  
Old 05-03-2015, 03:22 PM
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h0ughy (David)
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just a quick note I think there is a new version of the hand controller software - I think it is 3.37?
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  #613  
Old 06-03-2015, 08:48 AM
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rustigsmed (Russell)
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Quote:
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just a quick note I think there is a new version of the hand controller software - I think it is 3.37?
from the SW website: seems minor I haven't had the parking issue and don't use ascom software so will wait for the next one.

SYNSCAN V3 HAND CONTROLLER FIRMWARE V3.37


  • 1. Fix the bug which causes failure on resuming from Parking.
    2. Supports more PC commands with increased compatibility with ASCOM software
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  #614  
Old 29-03-2015, 08:42 AM
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Is anyone using PEC on the EQ8? If so, what was your peak to peak error before and after?

Measured mine recently using PEMPro and my before was 5.4" peak to peak. Haven't applied the PEC yet so I don't know what the after will be.

Given the same data, PECPrep gave me roughly 7" peak to peak. In the scheme of things both are good, but that's a relatively large difference.

My PA was out a fair bit on DEC, so I wonder if that's got anything to do with differences. Maybe the former deals better with that.

I tried to use Astrotortilla to improve my PA earlier that night. According to Astrotortilla I went from 14' low in DEC to 8" low, which is obviously a massive improvement, but resulting alignment was actually significantly worse. I won't be using that again. I probably could have left it how it was originally, but how it is now definitely needs improvement.

Anyway, just curious to see who's using PEC on the EQ8 and what I can expect to get after applying PEC.
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  #615  
Old 29-03-2015, 09:53 PM
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Ryderscope (Rodney)
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EQ Periodic Error

Quote:
Originally Posted by codemonkey View Post
Is anyone using PEC on the EQ8? If so, what was your peak to peak error before and after?

Measured mine recently using PEMPro and my before was 5.4" peak to peak. Haven't applied the PEC yet so I don't know what the after will be.

Given the same data, PECPrep gave me roughly 7" peak to peak. In the scheme of things both are good, but that's a relatively large difference.

My PA was out a fair bit on DEC, so I wonder if that's got anything to do with differences. Maybe the former deals better with that.

I tried to use Astrotortilla to improve my PA earlier that night. According to Astrotortilla I went from 14' low in DEC to 8" low, which is obviously a massive improvement, but resulting alignment was actually significantly worse. I won't be using that again. I probably could have left it how it was originally, but how it is now definitely needs improvement.

Anyway, just curious to see who's using PEC on the EQ8 and what I can expect to get after applying PEC.
Lee, there is a discussion (link here) on the EQ8 Yahoo users group on Periodic Error. The post shows that they were seeing about 8" periodic error as measured using PECPrep which is consistent with your results. I haven't read further yet to see what improvements might be gained by implementing PEC.

I am interested in following this discussion as I am about to start tweaking the polar alignment of my EQ8 and have been contemplating the implementation of PEC as well. I have just moved from a 900mm refractor to an RC10 with a 2 metre focal length and I can see now that the tracking is not quite as good as I would like it to be.
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Old 30-03-2015, 12:47 PM
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Shiraz (Ray)
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mine measured at 7 arcsec p-p in PECprep as well, with two regions of fairly rapid change. These guide out OK at my typical seeing and at 0.91 arc sec sampling.

attempted PEC as follows:
1. autoPEC - why not give it a go I thought... It generated a reasonable curve, but assumed an EQ6 worm period. I redefined for an EQ8, but the new auto curve had a phase error????.
2. then tried using PECprep with data out of phd (not phd2) - it has to be done exactly by the book. I got a good curve that was very consistent across 5 worm periods and almost removed PE entirely in the simulator, but it had a phase shift as well and I could not get it synchronised, even though I had done time stamping and parking. The phase shift slider did not allow shifting across the whole of the worm cycle, so something? was clearly not quite right.
3. Then both phd and phd2 stopped guiding properly - presumably because EQMOD was applying crap PEC as a carryover from an earlier attempt. disabling PEC did not help and I could only get it all back working by reloading everything.

when I get another marginal night and bit more courage, will try again with PECprep, but not with autoPEC. I don't think it is actually too difficult, but everything has to be done exactly by the book. Rate based PEC is in principle a great idea and should clean up the PE very effectively. In the meantime, I get about 0.6 arcsec RMS guide error at 1 sec update on a good night, which is fairly good anyway.

Last edited by Shiraz; 30-03-2015 at 02:17 PM.
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  #617  
Old 30-03-2015, 05:17 PM
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codemonkey (Lee)
Lee "Wormsy" Borsboom

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Quote:
Originally Posted by Ryderscope View Post
Lee, there is a discussion (link here) on the EQ8 Yahoo users group on Periodic Error. The post shows that they were seeing about 8" periodic error as measured using PECPrep which is consistent with your results. I haven't read further yet to see what improvements might be gained by implementing PEC.

I am interested in following this discussion as I am about to start tweaking the polar alignment of my EQ8 and have been contemplating the implementation of PEC as well. I have just moved from a 900mm refractor to an RC10 with a 2 metre focal length and I can see now that the tracking is not quite as good as I would like it to be.
Thanks Rodney :-) Having acquired an old RC8 with a 1.8m focal length somewhat recently myself I know the feeling. It's not an easy task, but I think with the EQ8 we'll get there :-)

Quote:
Originally Posted by Shiraz View Post
mine measured at 7 arcsec p-p in PECprep as well, with two regions of fairly rapid change. These guide out OK at my typical seeing and at 0.91 arc sec sampling.

attempted PEC as follows:
1. autoPEC - why not give it a go I thought... It generated a reasonable curve, but assumed an EQ6 worm period. I redefined for an EQ8, but the new auto curve had a phase error????.
2. then tried using PECprep with data out of phd (not phd2) - it has to be done exactly by the book. I got a good curve that was very consistent across 5 worm periods and almost removed PE entirely in the simulator, but it had a phase shift as well and I could not get it synchronised, even though I had done time stamping and parking. The phase shift slider did not allow shifting across the whole of the worm cycle, so something? was clearly not quite right.
3. Then both phd and phd2 stopped guiding properly - presumably because EQMOD was applying crap PEC as a carryover from an earlier attempt. disabling PEC did not help and I could only get it all back working by reloading everything.

when I get another marginal night and bit more courage, will try again with PECprep, but not with autoPEC. I don't think it is actually too difficult, but everything has to be done exactly by the book. Rate based PEC is in principle a great idea and should clean up the PE very effectively. In the meantime, I get about 0.6 arcsec RMS guide error at 1 sec update on a good night, which is fairly good anyway.
Thanks Ray! Sounds like a pain in the nether region, really, but maybe worth it in the end.

I read on another forum of a woman who was using her EQ8 to get very long unguided subs (30mins before trailing started to show if I recall correctly, and I think at a long FL as well). I made the (fairly reasonable, I think) assumption that she was achieving this by applying PEC, thus my sudden interest.

Given that, I thought I'd try PEC myself, as if I can get away without guiding, I'd rather do that. For broadband imaging I think I can get away with 220 second subs, which I'm hoping might be achievable at 1.8m FL with PEC. I guess we'll see!
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  #618  
Old 04-04-2015, 05:56 PM
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codemonkey (Lee)
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After some tweaking in PECPrep, this is looking very promising. Can't wait to get out and load this up into EQMOD. I wonder how EQMOD knows the worm cycle so that the corrections are in sync though... guess I'll find out soon enough.

I culled out the first and last cycles because they were clearly not aligned with the rest; not sure what happened there. If I keep them in, the residual RMS is still only 0.34". Note that the recorded peaks seem to be unchanged regardless of which cycles I include.

Anyway, if I can keep it at that (<0.34"), and get my alignment nailed then I should be able to do unguided even at 1.8m. Broadband with my skies and equipment only needs 220s exposures, so this may well be doable.
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Old 04-04-2015, 06:14 PM
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Shiraz (Ray)
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Quote:
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I wonder how EQMOD knows the worm cycle so that the corrections are in sync though... guess I'll find out soon enough.
it uses a timecode, which as far as I could tell is stored by EQMOD when you push the timestamp button, so that it can determine which PE file to use. I think that it looks for a file with a "last modified" time that matches the timestamp and then assumes that the worm is still synchronised to the worm positions in that file through the park/unpark process. At least that is what I think happens..

If correct, I think that means that you cannot edit the PE log file to remove false starts - it has to be perfect to start with.

Anyone please correct if this is wrong.

Last edited by Shiraz; 07-04-2015 at 08:26 PM.
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  #620  
Old 31-05-2015, 10:16 PM
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EQ8 PE Capture with PHD2

After many interruptions from work and weather I've finally gotten around to getting a clean capture for the PE for my EQ8. This is captured with PHD 2.0 using a 900mm F9 refractor as a guide scope. Guide camera is the Orion SSAG. Capture period was approximately 30 minutes at a DEC angle of -10 deg. Guiding was off during this capture.

In DEC I see a gradual drift showing a movement of a little under 15" during the capture period. Whilst the PA is clearly not spot on, my thinking is that a 15" movement after 30 minutes at DEC -10 is possibly ok to the extent that I can rely on guiding to remove this. Am interested in the view of others on this.

In RA I see a fairly consistent PE in a sinusoidal waveform shape but I also see a gradual RA drift of about 12" during the capture period. The peak to peak PE measure is about 7" which is consistent with what other EQ8 owners are reporting.

On the calibration graph I note that the RA calibration is not showing at 90 deg to the DEC calibration. I am wondering if this is telling me something I should know?

Observations and Questions:
1. Is the DEC drift acceptable to the extent that guiding will get rid of it or should we try tweaking the PA again?
2. What would be causing the drift in RA? Is this simply to do with the DEC drift? I note that it does seem to follow the DEC drift.
3. Should I be concerned that the RA and DEC axis are not at 90deg on the calibration graph? I raise this as the PHD documentation indicates that they should be at 90deg.

Thanks in advance.
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