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Old 04-06-2015, 08:24 AM
Garbz (Chris)
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Exclamation Confirmed: Windows RDP causing guiding problems

I want to share with you some guiding problems I’ve found which I have determined to be the result of Window’s Remote Desktop Protocol. I have been battling with this problem over the past year and managed to resolve it by switching to TeamViewer or VNC for remote control of the guide computer.

Problem description

From the screenshots below you can see quite a clear difference in guide performance. The good shots were done with TeamViewer and the bad shots were done with Remote Desktop Protocol. Basically it looks like the guide commands to the scope are hanging and causing the scope to start taking off massively in one direction or another. In many cases this introduced an error in excess of 6 arcsec naturally ruining the photo. From the zoomed in example below you can see a small guide in the direction of the massive overshoot.

Also if you look at the calibration chart, the last east step appears to have massively overshoot compared to all the other steps. This shouldn’t be as the step spacing should be consistent between all commands in a specific direction. Even if the mount is massively misaligned it should only result in the steps not returning to the centre at the end, or the east/west and north/south combination not tracing over itself. There’s nothing that can explain a step suddenly overshooting, except for the first step where backlash is involved.

Also I don’t believe this to be a problem associated with PHD2 as I have experienced similar behaviour when slewing using my game controller. I originally thought that was Bluetooth acting up but it did it via USB too, every so often a button seemed to be “sticking” and the scope would dramatically overshoot where I was aiming.

History

The history of when and how this happened has been the source of my grief. Early last year I changed everything. Switched from laptop guiding to using a Fit-PC, switched from VNC to Remote Desktop Protocol, switched Windows XP to Windows 7 and updated all the software. So basically nothing was the same. Over the past year I’ve tried various combinations of drivers, and rolling back to earlier versions of software and even using the laptop again thinking the FitPC itself was the source of the issue, but none of that resolved it. At one point I blamed the mount itself but the problem persisted even after mount modification (belt drive) and hypertuning.

Recently I found a random post in Stargazers Lounge about someone asking about remote desktop programs and one person mentioned he had issues with RDP affecting performance of his mount, so I decided to try and see if this was the issue and switched to TeamViewer. It seemed to work and last night I decided to give it a decent controlled before and after test.

Testing methodology

I should start by saying there was zero wind yesterday, guiding SNR was good, stars were visible, no clouds, and no there was no possum playing with my telescope for the first half of the night.

I started the night by logging into the fit-pc with remote desktop and pointed the telescope at a-crux. This was at about the 11’ on the RA axis. I then proceeded to calibrate and guide on a star near a-crux (overly bright stars can’t be guided on). I left this running unattended for about 40min monitoring it from remote desktop and noted several spikes in the guiding. I also disconnected the remote desktop session and when I logged in again I noted that the spikes continued (this is what led me to discount remote desktop being a problem some 6 months ago).

When I hit the meridian I stopped guiding and closed PHD. I slewed the mount back to 11’ on the RA and parked it in place. I then sent a shutdown command to the PC, walked out to the scope and power-cycled the entire setup. I then logged in again using Teamviewer, opened up all the same software and started another calibration and guide on a star with a decent SNR.

The final results speak for themselves.

So my recommendation: Don’t use RDP if you have a problem. Maybe this is fixed in Windows 8, but I can understand the technical reasons for the differences. Teamviewer and VNC do screen grab and transfers. RDP has deep hooks into not only the window manager in the operating system but also into the hardware allowing things like remote USB passthrough. It’s a shame really since RDP is far more efficient over the network and provides a far better picture than Teamviewer or VNC.
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  #2  
Old 04-06-2015, 08:35 AM
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Shiraz (Ray)
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excellent bit of detective work Chris. glad you got it sorted and thanks for posting your results. Your explanation of what goes wrong makes sense. I use RD on win8.1pro and haven't noticed any issues, but will keep a closer watch from now on.
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Old 04-06-2015, 10:00 AM
Garbz (Chris)
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Quote:
Originally Posted by Shiraz View Post
I use RD on win8.1pro and haven't noticed any issues
Good to know. I can't even confirm if the problem is universal across windows 7. It may still be a specific combination of hardware software and drivers.

But I do know a few people talking about fit-pcs so I thought I'd share what I found.
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Old 04-06-2015, 12:29 PM
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Octane (Humayun)
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I had other issues with RDP as well. It would interfere with MaxIm DL when plate solving (PinPoint) had been enabled in an image sequence.

Once I switched to TeamViewer, the problems disappeared.

I also use CCDCommander nowadays, so, RDP would probably work again as there's no PinPoint popup during plate solves.

Either way, good detective work!

H
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Old 04-06-2015, 01:47 PM
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multiweb (Marc)
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Very interesting thread. The fact that even with RDP connection severed the guiding was still affected baffles me. Made it real hard to figure out. Probably some service still running in the background. Windows integration at its best. Good on you for sticking with it, figuring it out and especially sharing that info. Won't need a toupe for a little while longer then.
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Old 04-06-2015, 04:53 PM
Garbz (Chris)
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Quote:
Originally Posted by multiweb View Post
Probably some service still running in the background.
Yes RDP does some very different things compared to logging directly into a computer. For instance on my home computer when I log in via RDP and then log in locally again my display calibration software says DDC is unavailable and I can't load a colour profile without rebooting or unplugging and plugging in the display again. There's a lot of foolery that goes on in the low levels of the system so I can imagine that the system is never quite left in the same state.
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Old 04-06-2015, 07:33 PM
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Interesting. Can you use Team Viewer over a LAN (ie without internet) with the free/home version? I'm thinking Astrofest.
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Old 04-06-2015, 08:54 PM
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Interesting report, I wonder if this has to do with excessive and conflict in threads with cpu cycles.

Autoguiding is deemed to use alot of cpu cycles as its constantly polling the cpu for img download, calc and correction.

I did briefly google some posts on windows and RDP; and some mentioned cpu cycles were excessive with the way RDP renders the screen and I/O.
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Old 04-06-2015, 09:12 PM
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Quote:
Originally Posted by troypiggo View Post
Interesting. Can you use Team Viewer over a LAN (ie without internet) with the free/home version? I'm thinking Astrofest.
This is the reason I've been using RDP. While it says Teamviewer can be used over LAN only, I've always had issues connecting - RDP worked, so I've just been using it for stuff on my local network. I use Teamviewer to remotely administer some computers at my folks house - works very well over the interwebulator.

I don't seem to be having similar troubles guiding with Maxim when using RDP - Windows 7 on the PC at the scope, Mac inside running RDP. Thanks for the heads up though - I'll try alternatives if any troubles arise.

I've always thought PHD was very intensive on the CPU. Other programs always seemed to "stutter" if PHD is running. Comments??

DT

Edit - here's a screenshot of my guiding graph from tonight. Using multistar guiding in Maxim, so lots of USB traffic to download the whole field from the Lodestar. The screenshot was captured from my Mac while accessing the PC via RDP.
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Old 04-06-2015, 09:35 PM
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Hi Chris,

Just wondering and data logging !

Was this done over ethernet or Wifi ?
What screen resolution were you using ?

Thanks

Rally
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Old 04-06-2015, 11:40 PM
Garbz (Chris)
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Quote:
Originally Posted by troypiggo View Post
Interesting. Can you use Team Viewer over a LAN (ie without internet) with the free/home version? I'm thinking Astrofest.
Yes. Just type in the IP address of the target PC instead of the Partner ID. That said if you're worried about the server / client relationship that Teamviewer has with 3rd parties another solution would be any VNC client like TightVNC which is also free, and open source.

Quote:
Originally Posted by leinad View Post
Interesting report, I wonder if this has to do with excessive and conflict in threads with cpu cycles.

Autoguiding is deemed to use alot of cpu cycles as its constantly polling the cpu for img download, calc and correction.

I did briefly google some posts on windows and RDP; and some mentioned cpu cycles were excessive with the way RDP renders the screen and I/O.
RDP is more CPU intensive on the client as the client renders the final graphic, not the server. In many regards the actual Fit-PC on the telescope should have a lower CPU load using RDP than Teamviewer / VNC as there's no local rendering going on, compared to the Teamviewer process of rendering the screen locally, screen grabbing it, compressing it and then transporting it over the network.

Quote:
Originally Posted by rally View Post
Hi Chris,

Just wondering and data logging !

Was this done over ethernet or Wifi ?
What screen resolution were you using ?
A mix between WiFi -> WiFi (802.11n on both sides) and WiFi -> Ethernet. I initially set everything up using a tablet via WiFi, but I typically monitor via the desktop. In both cases the wifi setup / desktop monitoring was the same.

RDP was 1920x1080, Teamviewer was 1600x1200 because ... well Teamviewer was written by people who clearly don't own decent screens. If you're thinking about the load placed on the Fit-PC to process this remember that Teamviewer will render the image on the server (fit-PC) and then screen grab and transmit over the network, whereas RDP will send the window draw commands directly over the network and render on the client. I.e. It doesn't matter how big the resolution is on the client as long as the PHD window is still the same size.
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Old 05-06-2015, 12:04 AM
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Hi Chris,

I also have a fitpc. This past weekend running windows7, maximdl, I had numerous issues, even 3 bsod shutdowns which drove me mad. I've now reloaded my old XP image to the fitpc and will test this out next time I get a chance.

In the past I also had issues on a laptop, running windows 7.

Although I didn't see any guiding issues, I did have some crashes which I can only think might maybe be hardware drivers, USB, OS related. I'll report back when I can.

I was running over Ethernet to the fitpc using realvnc
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Old 05-06-2015, 08:30 AM
Garbz (Chris)
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I've never had a BSOD on mine (Fit-PC3), as a side note the Fit-PC3 had new drivers issued 6 months ago (after nearly a year of no updates).

One thing I have noticed is the Fit-PC3 is very sensitive to power issues. Before I put some filtering in my the 12V section of my power hub, when the fit-PC shared the powersupply with my camera it would lock-up when I powered on the TEC cooler.
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Old 05-06-2015, 10:39 AM
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Camelopardalis (Dunk)
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Not sure why you guys would want a high resolution display of essentially a headless, hands-off system you'd be better off using a file share and downloading the images to your PC with a nice screen on it in the nice and warm

I've not found PHD2 to be particularly CPU thirsty...I use a 5 year old AMD powered netbook which is far from a powerhouse and it seems to work OK...
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Old 05-06-2015, 12:31 PM
Garbz (Chris)
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High resolution comes down to monitoring. Being able to see on the screen at the same time: PHD guiding graph, guide star profile, EQMod, the most recent image downloaded, and the progress through the capture is invaluable. It may be headless, but it's not hands off

Unfortunately at present this is all actions from different overlapping apps for me. I'm aware that programs like Sequence Generator or Maxim will distill this down to a far more compact form with the most recent image in the centre, and then guide statistics and graphs telescope orientation etc in a decent format on the side bar.

Ultimately though I don't appear to be limited by CPU or Network bandwidth so why wouldn't you want use the highest resolution you can afford?
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Old 05-06-2015, 05:33 PM
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Ive operated my remote rig "manually" via Radmin (teamview would be much the same) for years on a FitsPC without trouble with a hi res display (thats essential, as Chris details). The bandwidth cant be that high, as I have often operated via 3 or 4G at starparties etc, albiet slower and clunky, but useable. Via satellite internet was not good at all though, the lag was troublesome. Along with an IP power switch board, I can pretty much operate my scope as if I was in front of it with Radmin on any form of internet service (even satellite, painfully).
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Old 05-06-2015, 06:01 PM
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What about over a LAN when no internet?
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Old 05-06-2015, 06:04 PM
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Quote:
Originally Posted by troypiggo View Post
What about over a LAN when no internet?
I would think that would be perfect, no speed restriction at all, exactly the same as having the scope PC screen and keyboard in front of you.
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Old 05-06-2015, 06:21 PM
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Cheers.
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Old 07-06-2015, 12:24 PM
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I'm now using Splashtop. It's cross platform - Mac and Win. It allows me to remote in from any device - Ipad, Android, Windows etc. It's very stable. Just another option out there
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