High RMS and low guiding results with EQ6-R

[Benjamin Schlicht]

Hi everyone. I wanted to make a sanity check post trying to diagnose what could be my guiding issue. I am getting a bit frustrated and need some advice.

 

Equipment: EQR-6 Pro with USB port. Supposedly it was hypertuned.

ED102MM Explorer Scientific Triplet

Sbvony 50mm guide scope and rings (190mm focal point)

ZWO ASI Mini guide camera

Running off AC power from the house and a converter.

Using PHD2 to guide and sharpcap to PA.

Ascom driver for mount with EQ MOD

 

 

PHD2 Settings

I have Focal point set to 190mm on the scope and default settings on the camera (3.75) gain at 48.

I have a dark library that I took twice.

I have PEC ran last night for 9 cycles. I am now training PPEC.

I Calibrated several times to celestial equator intersecting with meridian. I bumped north until I saw movement on PPHD2.

I cannot feel any backlash in dec, and RA it is so little I can barely see it move. I am to nervous to adjust because I think I will Make it worse.

I ran guiding assistant for 10 minutes after the last calibration and applied the recommended settings.

I have ran at 2-3 seconds with no change in results. All above 1.5 arc seconds or more.

 

 

Possible issues observed.

-My guide scope uses the stock scope rings which do have plastic tips. Could cause flexure.

-My mount is on bricks, possibly need rubber bumpers under tripod legs.

-I did have a slight breeze of 3-5 mph last night, but this problem as persisted since I setup guiding. I haven't got better than 1.5 ever.

-When I run guiding assistant the south backlash never shows up. It always fails. I do not understand why since I can manually move it south with manual guide in PHD2.

-There is a weird noise when I park the mount. It is very very quite though. I just noticed it two nights ago.

-I have the guide scope fixed to the main telescope (ED102mm Explorer scientific) I used to have it attached to the hand on top of it which had similar results.

-I do get round stars sometimes up to 5 minute exposures. Problem being dithering I lose almost half of the shots because it doesnt setting or itll jump causing them not to be round. Also even using a dslr (t4i) like I am when I get to longer exposure times it seems like the stars HFD is higher. IDK, I could be imagining it.

-My cords are currently wrapped together and velcro'd onto one side. Sometimes the mount is a hair unbalanced to the east in RA. The dec is tight as well, but doesn't make grinding noises.

 

I am quickly running out of ideas that do not cost a fortune or involve me diving into the internals of a mount I am nervous about opening. Any suggestions would be welcome.

Logs from last night: https://openphdguiding.org/logs/dl/PHD2_logs_pHsP.zip

[bw_msgboard]

Hi Benjamin.  Unfortunately, I think you have a number of mechanical problems with this setup and it will take some time and effort to sort them out.  To start, I think your guide scope assembly (guide cam and finder-scope) is a real weak point.  Look at the large, abrupt excursions that happen in RA (red):

 

 

Most of these represent excursions of over 5 arc-sec within periods of 8-10 seconds.  This is pretty much hopeless, you can't guide these out.  The guide scope mounting is a likely source of problems - the combination of nylon-tipped thumb-screws and mounting rings is a recipe for poor results.  Because you're using a guide camera with such tiny pixels (3.8 microns), these big guide star excursions can be caused by unwanted movement of as little as 5-6 microns - 10% of the thickness of a human hair.  It's very unlikely that this fairly flimsy guide scope arrangement can prevent movements that small.  The most straightforward way to test this hypothesis is to create a new test configuration that guides through the main scope - no imaging, just guiding in order to see if the guide scope assembly is contributing to your problems.  In my opinion, trying to use a separate guide scope with these tiny camera pixels requires a real guide scope, not a repurposed finder-scope - something with a significantly longer focal length, threaded adapters, and a rigid, clam-shell style of mounting. 

 

It's also likely that there are significant tracking errors in the mount's RA system but these probably shouldn't be pursued until you can temporarily exclude the use of the suspect guiding assembly. 

 

Next, it's clear that your mount produces large delays when the guiding needs to reverse the direction of movement.  Look at how many guide pulses are needed to get the Dec axis turned around and moving:

 

 

Trying to "feel" backlash is a hopeless exercise because the rotational distances are so small.  The backlash test in the Guiding Assistant is trying to tell you there's a significant problem.  You didn't provide a debug log file that had a backlash test so I can't be specific.  But even if the test "fails" you can look at the graph and see for youself what happened.  This is a purely mechanical problem on the Dec axis - you will either need to improve the gear mesh or learn to guide in only one direction.  If you still want to ignore the Guiding Assistant results, you can use the star-cross test to paint a simple picture of what's going on.  All of this is compounded by your use of huge dither amounts in Dec -are 16 arc-sec dithers really necessary?  If you feel this is necessary, you should start using the spiral dither option in order to minimize the number of direction reversals that will occur.  Given all these problems, you won't be able to enjoy the luxury of 2-3 second exposures - you should probably drop down to 1 second exposures and let the multi-star guiding mitigate the seeing effects.

 

Good luck,

Bruce

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From: open-phd...@googlegroups.com [mailto:open-phd...@googlegroups.com] On Behalf Of Benjamin Schlicht
Sent: Wednesday, September 29, 2021 2:43 PM
To: Open PHD Guiding
Subject: [open-phd-guiding] High RMS and low guiding results with EQ6-R

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[Benjamin Schlicht]

Thanks for taking a look Bruce. I will see what I can do to eliminate the guide scope as the issue. The backlash graph from the guide assist just showed a flat line for south. I assume that means it didnt work at all. So I must have a huge RA backlash issue. If that is the case, will the external adjustments help that I see on youtube where I loosen the four screws and adjust the two small ones? If not I guess I will have to pay someone which is a bummer. Thanks again for the help.

[bw_msgboard]

Backlash in RA is irrelevant to guiding, you need to stay focused on declination - that's what the Guiding Assistant is measuring.  I can't give you any advice on how to adjust the mount, but you can ask for that on Cloudy Nights or some other forum with expertise in that area.

 

Again, I think the first thing to do is run tests while guiding through the main scope.  Just be sure you use the new-profile-wizard to create a new PHD2 profile for the test setup.  The focal length, for example, will be the value for the main scope for the test configuration.  You can follow this procedure to get a good baseline measurement of things with the test configuration:

 

https://www.dropbox.com/s/os1thorvswmzaul/How%20to%20create%20a%20baseline%20for%20guiding%20results%20using%20OpenPHD2.pdf?dl=0  

 

Good luck,

Bruce

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From: open-phd...@googlegroups.com [mailto:open-phd...@googlegroups.com] On Behalf Of Benjamin Schlicht

Sent: Thursday, September 30, 2021 2:06 AM
To: Open PHD Guiding
Subject: Re: [open-phd-guiding] High RMS and low guiding results with EQ6-R

To view this discussion on the web visit https://groups.google.com/d/msgid/open-phd-guiding/727554a1-7769-412f-a3b8-001bfdd61f56n%40googlegroups.com.

[Benjamin Schlicht]

ok, i need to figure out adapters and whatnot to get that setup. I was also informed theres a debug i can upload for you to look at. I will try and figure out how to do that when i get home.

[bw_msgboard]

There's no need for the debug log file for this particular problem.  For future reference, this is how you upload log files to us:

 

https://openphdguiding.org/getting-help/

 

Bruce

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From: open-phd...@googlegroups.com [mailto:open-phd...@googlegroups.com] On Behalf Of Benjamin Schlicht

Sent: Thursday, September 30, 2021 2:05 PM
To: Open PHD Guiding

To view this discussion on the web visit https://groups.google.com/d/msgid/open-phd-guiding/8dc35a13-8ad6-48ee-83e8-7c0f0499de43n%40googlegroups.com.

[mj.w...@gmail.com]

On another forum I asked the OP to send the DebugLog because Bruce said: 

"You didn't provide a debug log file that had a backlash test so I can't be specific."

Michael

Wiltshire UK