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Your guiding graph - please share it here

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#201 gotak

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Posted 13 March 2018 - 08:40 PM

Hello!

 

I have SW EQ5 with astrodevices Goto kit with belt drive. Here is the result before hypertune:

 

And after:

 

I have replaced the grease (with superlube) and polished the interfaces. And the load is with SW 80/600ED. With canon camera.

Looks impressive until I notice the pre tune pic you have 4 arc/sec per pixel scale. Then in your after tune you have unspecified. Now I don't know about you but that tells me your two graph is meaningless. All you have shown is two graphs. Maybe if you can retake your after tune with actual image scale set then people can see if the hyper tune actually did anything.


Edited by gotak, 13 March 2018 - 08:41 PM.


#202 dciobota

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Posted 14 March 2018 - 12:28 PM

Fwiw, here is my guide graph I posted some time ago (RA only guiding):

 

skyuiderpro-phd2.jpg

 

This was guided via the st4 port with an asi120mm clone (RisingTech), 3.75micron pixels and an Orion 30mm mini guidescope (130mm fl).  This makes for 5.95 arsec/pixel. 

 

I have since switched to an asi290mm mini, which has 2.9 micron pixels and a pixel scale of about 4.6 arcsec/pixel.  Hopefully that will give me even better guiding results (haven't tested yet).  This was also guiding an unbalanced load of around 4.5lb (EOS M5 with 70-200 f2.8 lens on a ball head).  Not too shabby imo for a "barndoor tracker" mount.

 

I've actually managed (slightly) better numbers in subsequent guiding sessions.  They key is sensor orthogonality and good polar alignment (I was off in both in the above example).  Oh and also, in the case of this mount, not overtightening the RA clutch.

 

One other thing to note about this mount is that it is belt driven,


Edited by dciobota, 14 March 2018 - 12:29 PM.


#203 555aaa

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Posted 23 March 2018 - 02:00 AM

Here's a better one for me - homemade mount (Byers 440 tooth worm & wheel), Meade 16" f/10 ACF, 3900mm focal length. This is RA guiding only. 1.65" guide star FWHM and nice profile. 0.27" per pixel guide cam scale. I upgraded to a larger servomotor with an improved control scheme over the winter - seems to be working better.

Attached Thumbnails

  • gggraff.png

Edited by 555aaa, 23 March 2018 - 02:02 AM.


#204 Tonk

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Posted 17 September 2018 - 05:04 AM

Can someone tell me why the target graph shows the pointing cluster offset to the NE (in this case) from the target center. I've only tested auto guiding on 3 nights so far so I'm very new to it  and I get the same offset pointing cluster every time. The cluster is tight so I guess its not really important that its offset. I'm just wondering why this is so and if this is because I've set PHD2 up incorrectly in some way.

(Lodestar2 on a QSI 386 OAG on a TOA130 working at 720mm FL if this has any importance). The guide camera exposures are 15s - the graph shows pixel y axis. Clouds stopped play on this occasion.


PjvX3vnKAcKC_1824x0_wmhqkGbg.jpg


Edited by Tonk, 17 September 2018 - 05:10 AM.


#205 spokeshave

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Posted 17 September 2018 - 07:59 AM

Your Aggression on both axes is set very low at 20. That means that of the calculated move PHD2 has determined is necessary to move the star back to center, you have instructed it to only move it 20% of that value. You also have MnMo set at 0.2 pixels for each axis. That means that if the star is within 0.2px of center PHD2 is satisfied and does nothing. So, your low aggression only moves the mount a tiny amount and once the star gets within 0.2 of center, PHD2 stops correcting.

The good news is that your mount is doing exactly what PHD2 is telling it to do and your guiding is excellent, even if about 0.1px off-center in each direction. If you want the graph to be more on the centerline, you can gradually increase aggression and decrease MnMo. I generally recommend that MnMo be set just a bit above your RMS error when guiding is good - in your case, I would try around 0.13 on both axes. Then bring aggression up incrementally until corrections bring the trace back to center but do not overshoot.

Tim

Edited by spokeshave, 17 September 2018 - 09:05 AM.

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#206 Tonk

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Posted 17 September 2018 - 09:07 AM

Brilliant - thank you :).

How do I ask PHD2 to make corrections every minute and not faster?



#207 spokeshave

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Posted 17 September 2018 - 09:35 AM

Brilliant - thank you smile.gif.

How do I ask PHD2 to make corrections every minute and not faster?


I don't think that's an option (but maybe worth mentioning on the PHD2 forum as a feature request). PHD2 does have the "Time Lapse" property on the Camera tab in the brain. This specifies how long PHD2 should wait between guide frames. But the maximum allowed is 10 seconds. Still, if you're doing 15 second exposures and tell PHD2 to wait 10 seconds between exposures, that's 25 seconds between corrections.

Tim

#208 Tonk

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Posted 18 September 2018 - 08:02 AM

There you go Tim. I followed your advice and adjusted minimum motion (MnMo) to match prior total RMS, then systematically upped RA and DEC Aggression to shift the pointing closer to the target graph center. The target graph has all the sampled guide star points before during and after this tuning. What do you think?

 

 

7xxmL0lA4iKT_1824x0_wmhqkGbg.jpg


Edited by Tonk, 18 September 2018 - 08:03 AM.


#209 spokeshave

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Posted 18 September 2018 - 10:32 AM

Well, Tonk, your guiding was excellent before and it is still excellent - just closer to the centerline. It is rare indeed to see total RMS error of less than 0.3" and total peak errors less than 0.6". I don't think there is much room for improvement. The only other observation I have is that you are reaching the limit of PHD2's accuracy. The developers claim to reliably be able to calculate a centroid to within about 1/10 of a pixel. You're right there, and in fact are below 1/10 of a pixel (0.07) in Dec. So it is possible that your guiding could be even better if you used a guide camera with smaller pixels. Having said that, if I was getting the results you are getting, I would not change a thing.

 

Tim



#210 Alex McConahay

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Posted 18 September 2018 - 11:34 AM

You know, looking at everybody's graphs.....I am surprised at the number of people who use +/- 8 or something as the scale. I use +/- 2 generally. I only go to 8 when my guiding looks depressing. 

Alex


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#211 Tonk

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Posted 18 September 2018 - 11:40 AM

It is rare indeed to see total RMS error of less than 0.3" and total peak errors less than 0.6". I don't think there is much room for improvement. The only other observation I have is that you are reaching the limit of PHD2's accuracy.


Indeed - 10Micron recommend that you don't guide on a GM2000 mount if your exposures are under 15 minutes as unguided tracking is accurate to 1" in 15 minutes assuming very good PA and the pointing model is large and you have live pressure data for refraction compensation. They say that guiding can worsen the tracking if you are not careful. I was guiding because I was running 20 min Ha exposures as a learning exercise.

As a note about the DEC tracking. I had the "dual tracking" feature enabled which allows the mount controller to compensate in DEC for PA error and atmospheric refraction. 10Micron advise you to turn dual tracking off if you are guiding as the two systems might start a fight but I found that PHD2 was not bothering sending many DEC corrections - just a hand full in 20 minutes with Dual Tracking on as the mount controller was doing a better job. Turning it fully over to PHD2 gave slightly wider excursions in DEC which I might have been able to tune down but I didn't try this.

Thanks for your input Tim, its confirmed that my investment in the GM2000 was worth it. Its being moved to the new ICAstronomy facility in Spain next spring were it will hopefully run for at least 10 years -  until it or myself wear out


Edited by Tonk, 18 September 2018 - 12:18 PM.


#212 spokeshave

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Posted 18 September 2018 - 11:51 AM

You know, looking at everybody's graphs.....I am surprised at the number of people who use +/- 8 or something as the scale. I use +/- 2 generally. I only go to 8 when my guiding looks depressing. 

Alex

I agree that graphs can be made to look great or terrible depending on scale. I rarely pay much attention to graphs when assessing overall performance and instead and typically concentrate on RMS and peak error in arcseconds. Graphs (with corrections displayed) can be very useful in determining what the mount and PHD2 are both doing though.

 

Tim


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#213 555aaa

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Posted 18 September 2018 - 12:00 PM

Tonk, what does the 10micron mount do with the guide inputs when it is using encoder feedback? Does it restart the control loop based on the guide input? What does it believe?

#214 Tonk

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Posted 18 September 2018 - 03:38 PM

Tonk, what does the 10micron mount do with the guide inputs when it is using encoder feedback? Does it restart the control loop based on the guide input? What does it believe?


Encoder feedback is just telling the mount controller the absolute position of the RA and DEC shafts - the guide inputs are layered on top as move commands. Actually the way I'm using it, it doesn't know its a guide input as I'm not using the guider port. I'm using an ASCOM driver (Per Frajvall's) so it just looks like the user nudging the NSEW controls - that is if you are adept at millisecond nudges (that s what PHD2 is reporting - very low ms duration NSEW pulses). Being a newbie at guiding - is this "pulse guiding" ? - sort of sounds right.

#215 freestar8n

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Posted 18 September 2018 - 04:10 PM

Guiding used to be done with the guide software itself turning on motion in some direction and then turning it off - all timed by the computer clock and driving the st4 inputs.  Later more mounts provided direct pulseguide inputs that allow the timing to happen in the mount itself - so the mount receives a command to move E for 30ms and it does it.

 

ASCOM just provides a PulseGuide command in the form of a direction and a duration - but it's up to the driver and the mount to implement either with timing by the computer or the mount.  For a high end mount the firmware should be doing the right thing with that command so it all happens internal to the mount.

 

In practice it's not clear how much this matters - but I prefer to have all the timing done in the mount.

 

Frank



#216 freestar8n

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Posted 18 September 2018 - 04:16 PM

Well it's been over a year since my posts around #156 and I don't think anyone has shown star profiles in their actual images - to go along with the guide plots.  It's nice to see all these plots - and that is the topic of the thread - but also being able to see the resulting star images and fwhm's would help show just how much the guide plot means - in terms of actual results.

 

This is a lot like threads that compared periodic error curves - without showing how good the guided images are with a given amount of periodic error.

 

If there isn't a strong correlation of guide error plots with actual results - that would be good info.  And I expect only weak correlation at best.  But for a given system/setup I expect that improving the guide plot will result in improved images.  But there may be people with 1" rmsd who are getting 2" fwhm, and others with 0.1" who are getting 4" fwhm.

 

Frank


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#217 karambit27

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Posted 18 September 2018 - 10:39 PM

Here's a recent session with my Mesu 200 carrying to 102mm WO refractor at 795mm and a guiding scale of 0.98"/px. The mount has been rock solid since I got it. It just works night after night and it smooth and quiet with zero backlash. My settings stay fairly similar across sessions. The only thing I really adjust is the MinMo depending on the seeing that night. It is quite incredible how much seeing effects guiding. My RMS is typically <0.30" on a night of good seeing and 0.60" on a night of bad seeing. I am typically between 0.40-0.50". I keep my Y axis scale at +/-8" simply out of personal preference.

 

mesu.JPG



#218 Tonk

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Posted 19 September 2018 - 09:26 AM

OK - this is the image that goes with the last guide graph I posted a few slots back (show again here for ease). Results images (below) are crops shown at 200%, 600%, 1400% in SGPro - you need to discount the single pixel hot pixels - its the raw FITS file shown in the viewer (which appears to have applied a mild Gaussian blur to the display!). There are a few non overexposed stars to look at to assess the guiding results. This is a 20 minute Ha exposure.

7xxmL0lA4iKT_1824x0_wmhqkGbg.jpg

aTS-kBsNSh3s_1824x0_wmhqkGbg.jpg3VEaG73AxVkT_1824x0_wmhqkGbg.jpgGf1SZ-7iR5VE_1824x0_wmhqkGbg.jpg


Edited by Tonk, 19 September 2018 - 01:34 PM.


#219 Tonk

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Posted 19 September 2018 - 09:50 AM

For a high end mount the firmware should be doing the right thing with that command so it all happens internal to the mount.


Yes the ASCOM driver for the 10Micron sends a command to move the scope with direction and duration as parameters. This means that the mount controller is doing the timing

#220 freestar8n

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Posted 19 September 2018 - 03:22 PM

OK - this is the image that goes with the last guide graph I posted a few slots back (show again here for ease). Results images (below) are crops shown at 200%, 600%, 1400% in SGPro - you need to discount the single pixel hot pixels - its the raw FITS file shown in the viewer (which appears to have applied a mild Gaussian blur to the display!). There are a few non overexposed stars to look at to assess the guiding results. This is a 20 minute Ha exposure.


 

Thanks for posting.  Yes, SGP applies smoothing to images when you zoom in and I don't think you can turn it off.  There was a request a long time ago to be able to see the individual pixels but I don't think they did it.  The stars certainly look round and that's a 20 minute exposure - so that's good.  Can you say what the fwhm is in arc-seconds?

 

You have a very high end mount and oag so the results should be about as good as possible with the given OTA and conditions.

 

I would be surprised if you were hurt by making corrections faster than once per minute.  The error in every correction should follow the same distribution - so there shouldn't be any harm in correcting more often than "needed."  If it is indeed tracking perfectly between corrections then the error during that whole time will be whatever the original correction error was.  Somehow people think that each correction adds error and doing more corrections will add more error - but that makes no sense if each correction is independent and the mount has fully stabilized after the last correction.

 

Frank



#221 Tonk

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Posted 19 September 2018 - 04:41 PM

Frank my corrections in this case were every 5 seconds. 10Microns concern is having both guiding and dual tracking on at the same time as they can compete and work against each other.



#222 555aaa

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Posted 21 September 2018 - 01:21 AM

OK Frank I'll bite. For the guiding graph I showed in post #203, I think this is a representative star profile:

 

bin2x_example_3_19_180sec_exp.png

 

That is 180 seconds guided, 3890mm focal length, 9 micron pixels binned 2x (0.95" per pixel scale). FWHM is 3.0 arc seconds; guiding RMS was as shown above (0.5" total?) but the peak is worse and the peak is what I think really counts. It has a nice, smooth profile and is therefore pretty round (the little dots would spread out across the red line if it was an oval. Not the best I have done, but typical at my site and with my level of patience for focusing. Under good conditions, I can get to 2".

 

This summer I switched to 3x binning (1.43"/pixel) in order to get the deepest images in the shortest time, based on my seeing and guiding capability:

 

bin3x_example_9_16_180sec_guided.png

That was guided 180 seconds, 1.43" per pixel.

 

For a comparison with no guiding for 30 seconds, good  example:

bin3x_example_9_16_30sec_unguide_good.png

Bad unguided, but still usable:

bin3x_example_9_16_30sec_unguide_bad.png

 

Finally, this shows that the system can get below 20th magnitude in a single 3 minute exposure.

 

bin3x_example_9_16_180sec_faint_star.png

 

 

and here is the associated image showing some pesky nebula (it's somewhere in Cygnus I think) - appx 30 arc min on the long axis (which is N to the left).

test_full_3x_bin.jpg

-Bruce


Edited by 555aaa, 21 September 2018 - 01:29 AM.

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#223 freestar8n

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Posted 21 September 2018 - 02:57 AM

Thanks very much, Bruce - that's a nice presentation - where you can see the stars on the scale of the pixels, along with the profiles.

 

I think that if we can collect data on 1)  guide error rmsd  2)  fwhm in arc-seconds  3)  pixel size in arc-seconds - a trend may appear.  There are always issues of seeing and focus - but seeing should show at least partly in the guide rmsd.

 

I include pixel size in arc-seconds because smaller pixels, in arc-seconds, tend to lead to smaller fwhm's - especially in stacked images.  And that's a separate factor from the guide error rmsd.

 

Thanks again,

Frank


Edited by freestar8n, 21 September 2018 - 03:00 AM.


#224 pyrasanth

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Posted 21 September 2018 - 08:48 AM

You need later version of TSX. I'm using 9334. Also you must enter the guide scope parameters in the guide camera settings. It already knows the pixel size based on the camera, it just needs the focal length. If the information is entered, TSX automatically shows the pixel scale in the graph.

Secret of guiding with a paramount is basically not to guide it. If you get your polar alignment really good, set your minimum move high and make guide exposures long, get a good PEC, the mount works like a glider.

I use the SkyX & T-point with my MX+

 

I'm about to redo my polar alignment as it is out as shown by T-point. I hope to get a good alignment before I retest guiding. With my C14 I have an RMS & PSD currently of about 15 with a small model of 105 samples- only because the weather finished my last calibration early, I normally have around 250 samples in my model. However the 100 point model seems to work okay albeit with the polar error to be sorted.

 

Can you let me know what settings you use in your auto-guider settings on the SkyX tab- minimum & maximum move & aggression? I seem to struggle with getting these right as my image scale for the C14 is quite small on a 1x1 bin of 0.34 arc secs per pixel on the Atik 460 and I know from my seeing conditions this is vastly over sampled.

 

I'm going to experiment with a far larger minimum move and maximum move (if ever needed) I was thinking of setting 0.5 & 2.00 arc secs (min max) with an aggression of 5 using direct guide with the Starlight Instruments Ultrastar guider at full focal length through the ONAG- your thoughts on this possible setting would be welcomed. I see the point of not chasing the seeing and my logic was not to over guide if the model and pro-track is working as it should.



#225 tolgagumus

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Posted 21 September 2018 - 11:02 AM

I use the SkyX & T-point with my MX+

 

I'm about to redo my polar alignment as it is out as shown by T-point. I hope to get a good alignment before I retest guiding. With my C14 I have an RMS & PSD currently of about 15 with a small model of 105 samples- only because the weather finished my last calibration early, I normally have around 250 samples in my model. However the 100 point model seems to work okay albeit with the polar error to be sorted.

 

Can you let me know what settings you use in your auto-guider settings on the SkyX tab- minimum & maximum move & aggression? I seem to struggle with getting these right as my image scale for the C14 is quite small on a 1x1 bin of 0.34 arc secs per pixel on the Atik 460 and I know from my seeing conditions this is vastly over sampled.

 

I'm going to experiment with a far larger minimum move and maximum move (if ever needed) I was thinking of setting 0.5 & 2.00 arc secs (min max) with an aggression of 5 using direct guide with the Starlight Instruments Ultrastar guider at full focal length through the ONAG- your thoughts on this possible setting would be welcomed. I see the point of not chasing the seeing and my logic was not to over guide if the model and pro-track is working as it should.

Here are the settings I would recommend for MX C14 ONAG Ultrastar at 2-3" seeing

 

Bin the guide camera 4x4

exposure time 8" minimum

Min move 0.7

Max move 2

Aggressiveness 2-5




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