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My PHD2 graph[Problem]

Blackrose

By Blackrose
in Getting Started With Imaging

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Blackrose

Blackrose

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Hey Stargazers,

I've recently started guiding, and my graphs don't look good at all (who would have guessed :D). I wanted to ask you guys for advice. I have an iOptron ZEQ 25GT mount, I use Explore Scientific ED80 as main scope and I'm guiding with a 50mm, FL163mm guidescope. The guide camera is monochrome 3.5um pixel size.

Here are some observations that I made during my session with the guider.

 

1) It seems my mount does a lot of random movements, which is the reason in the first place that I've got guiding going on. Without guiding I had 50-60% success rate on 1 minute exposures with 480 FL. I don't know how to fix it. I try as best as I can with PA and balancing( Also tried east and camera heavy to no avail).

2) There are some spots in graph that it seems autoguider has picked up the drift and tries to get back on track, so it sends the signal out, but the mount does not go towards the signal. It somehow is stuck sometimes, even on RA, which is not on resist switch algorithm.

3) I also tried to record PEC and use it, but it got even worse.

4) there is also another problem that, manufacturer says my guidecamera is 3.5um, but PHD2 through ASCOM has it at 7.5um. I really don't understand what the problem is.

 

Thanks in advance,

Kamyar

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mikeyj1

mikeyj1

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Hi you need to read the setup guide of PHD 2...  exposure should be 2.5-4 secs, you need to run the calibration procedure so that the programme knows about the backlash and movement direction (CAL is yellow), and you need to change the FL and pixel size to the correct settings from the brain menu..

once you have done this, run the guiding assistant also, this will help determine the best settings.

you'll get there ?

Mike

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wimvb

wimvb

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It seems to me (with limited guiding experience), that the main cause is the pixel scale, ie using 7.5 um vs 3.5 um pixel size. The rms error in pixels is quite small, but due to the large pixel scale, it seems huge in the graphs. Check camera configuration in PHD.

2nd, the exposure time is quite short, and part of the problem is that you may be chasing the seeing. Try an exposure time of more than 1 second.

3rd, the corrections in dec are all onesided, which indicates an imbalance or polar misalignment. That's not necessarily bad. You can activate onesided dec corrections in PHD.

4th, forget about pec for the time being.

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Blackrose

Blackrose

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1 minute ago, wimvb said:

It seems to me (with limited guiding experience), that the main cause is the pixel scale, ie using 7.5 um vs 3.5 um pixel size. The rms error in pixels is quite small, but due to the large pixel scale, it seems huge in the graphs. Check camera configuration in PHD.

2nd, the exposure time is quite short, and part of the problem is that you may be chasing the seeing. Try an exposure time of more than 1 second.

3rd, the corrections in dec are all onesided, which indicates an imbalance or polar misalignment. That's not necessarily bad. You can activate onesided dec corrections in PHD.

4th, forget about pec for the time being.

1st, the problem is in the camera configuration I can change that, but as soon as I connect to my camera via ASCOM to PHD, it changes to 7.5um and it is grayed out and I cannot change it.

2nd, When I go 1 sec exposure or over that, graph gets out of hand, since it goes out of sync very fast.

 

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Blackrose

Blackrose

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11 minutes ago, Thalestris24 said:

Hi

It looks like you're maybe not selecting the guide camera correctly (Ascom Starguider??). Can you clarify which guide camera you have and if you've installed the Ascom driver for it. What is your imaging camera?

Louise

This is what I have:

https://www.teleskop-express.de/shop/product_info.php/info/p8963

It has a software with starguider name and also camera is installed perfectly and I can see the stars. 

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Thalestris24

Thalestris24

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26 minutes ago, Blackrose said:

This is what I have:

https://www.teleskop-express.de/shop/product_info.php/info/p8963

It has a software with starguider name and also camera is installed perfectly and I can see the stars. 

But there appears to be a problem with phd2 recognising it correctly. Are you pulse guiding or using st4?

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Blackrose

Blackrose

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15 minutes ago, Thalestris24 said:

But there appears to be a problem with phd2 recognising it correctly. Are you pulse guiding or using st4?

ST4 I guess. I connect camera to laptop via USB and then Camera to guideport via telephone thingy. I chose on-camera in mount selection part.

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Thalestris24

Thalestris24

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4 minutes ago, Blackrose said:

ST4 I guess. I connect camera to laptop via USB and then Camera to guideport via telephone thingy. I chose on-camera in mount selection part.

In that case you have to select 'on camera' for the mount in phd2. What options does PHD2 give you for the guide camera selection? What camera are you using for imaging?

Louise

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Blackrose

Blackrose

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1 minute ago, Thalestris24 said:

In that case you have to select 'on camera' for the mount in phd2. What options does PHD2 give you for the guide camera selection? What camera are you using for imaging?

Louise

Name is ASCOM Starguider driver. Starguider is the name of my camera and also it has been shipped with an application with the same name, which works perfectly.

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Blackrose

Blackrose

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1 minute ago, Anthonyexmouth said:

not sure about your mount but with ascom/eqmod the st4 port is unused as guiding is sent via ascom and not through the camera

Then I need a cable directly going to my laptop from Mount? Since my laptop only has USB as I/O, what cable should I buy to connect computer to the mount? I dont have anything  other than cables, which are shipped with Camera.

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Davey-T

Davey-T

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1 minute ago, Blackrose said:

Then I need a cable directly going to my laptop from Mount? Since my laptop only has USB as I/O, what cable should I buy to connect computer to the mount? I dont have anything  other than cables, which are shipped with Camera.

Did it come with 2 cables ?

Dave

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Blackrose

Blackrose

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2 minutes ago, Davey-T said:

That's all you need then, what connections are on the mount ?

Dave

Two free ones. iOptron port and guiding port. Right now my setup is like this. Camera goes into Laptop via that USB cable. And Camera connects to Guidingport via telephone cable.

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wimvb

wimvb

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48 minutes ago, Davey-T said:

You should be able to use ST4 guiding with the supplied cables.

Dave

Yes, my idea also. At the moment there's no need to add pulse guiding, since st4 works. The screen grabs show rms errors below 0.5 pixels. But since the pixel scale is so large (7.5 x 206 / 163 = 9+ "/pixel), the guide error seems huge, 4 ". In reality it's half of what the screen grabs indicate. The wild swings are imo caused by seeing, and maybe a bit too aggressive settings.

@Blackrose: can you change the camera settings in ascom? Can you also adjust the gain of the camera? It's a cmos camera, and these usually have adjustable gain.  (I believe you can even set this in PHD.) If you use a lower gain, you can increase the exposure time. This will calm down the swings a bit.

Btw, the pixel size of your camera is 3.75 um. The 7.5 um (= 2 x 3.75) in ascom suggests that you have a binning option. Make sure you bin 1x1, and not 2x2.

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