Lot of lost stars

[Julien T]

Hi,

I encounter difficulties to find the correct parameter for my setup.

The mount is a Pegasus Astro NYX-101
The scope is a Takahashi FSQ-85
The main camera is a Player One Zeus 455M Pro (IMX455)
The guide camera is a Player One XENA-M (IMX249) mounted on an OAG


My problem I that I get a lot of stars lost error. But I can't figure out why, when I look at the saved image by diagnostic image logging I can clearly see stars.


For the initial configuration I followed the profile creation wizard and the Pegasus Astro recommendations ( https://pegasusastro.com/nyx-101-guiding-recommendations/ ).
And I used the calibration wizard to do the calibration.

Attached files contains configuration screenshots and an example of a star lost image log.

Regards,

Julien

[Brian Valente]

Hi Julien

Please upload your relevant logs as per these instructions

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

Brian

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[Julien T]

Hi Brian

Here are the logs : https://openphdguiding.org/logs/dl/PHD2_logs_TfmR.zip

Regards,

Julien

[Bruce Waddington]

When you used the new-profile-wizard, you evidently decided to shine on the option to build a dark library. :-)    So you're running with neither a dark library nor a bad-pix map, and the diagnostic image you posted shows a nice view of hot pixels and sensor noise - but no real stars.  You need to fix that.  The sensor noise occasionally shows bright clumps that are larger than 1.5 px in size, which is the value you're using for Min-HFD.  With your camera and setup, that's almost certainly too small.  This combination of mistakes means that PHD2 may select one of these transient noise areas on the sensor, start trying to guide, but then find that the transient noise area falls below the 1.5 px threshold - hence, a "lost star" event. Behind all of this, I suspect your guide camera isn't really focused properly and you aren't seeing any real stars at all.  If you're using an OAG, you need to spend the time to reach critical focus using the Star Profile tool or some other app that gives you quantitative feedback.  You should be using longer guide cam exposures to do this, probably 2 sec or more to be sure you can see real stars. You also need to be sure the OAG is fully illuminating the guide camera sensor.  Once you get that sorted and can run for extended periods with no lost-star events, you should use the Star Profile tool to measure the HFD values of faint but usable guide stars in your guide camera images - then set the Min-HFD value just below that.  While you're in the area, you can also disable the star-mass detection in PHD2, that's no longer needed.

Regards,

Bruce

[Julien T]

Hi,

> When you used the new-profile-wizard, you evidently decided to shine on the option to build a dark library. :-)

I built the dark library after having done the configuration. And I did some test with and without dark library. But as using dark library or not didn't change anything I have done the subsequent attempts without dark, especially when trying to adapt the camera gain.

> So you're running with neither a dark library nor a bad-pix map, and the diagnostic image you posted shows a nice view of hot pixels and sensor noise - but no real stars

Noise, I agree. But no real stars ???

> 1.5 px in size, which is the value you're using for Min-HFD.  With your camera and setup, that's almost certainly too small.

Ok, I will try to increase the this value

> Behind all of this, I suspect your guide camera isn't really focused properly and you aren't seeing any real stars at all.  If you're using an OAG, you need to spend the time to reach critical focus using the Star Profile tool or some other app that gives you quantitative feedback.

I have used the NINA focus routine to focus the main camera. Then I used SharpCap focus tool to focus the guide camera. Not sure it will be possible to improve a lot.

> You should be using longer guide cam exposures to do this, probably 2 sec or more to be sure you can see real stars.

Ok, I will have to find a compromise with the recommended settings for the mount. 

> While you're in the area, you can also disable the star-mass detection in PHD2, that's no longer needed.

OK. Maybe this parameter should be disabled by default ?

Regards,

Julien

[bw_m...@earthlink.net]

IMO, the .fit image you sent had no real stars in it.  So that’s the problem you will need to figure out, whatever the source.  It had significant sensor noise so you should always be using a dark library – doing so is not going to reduce your ability to find real stars assuming it’s been built correctly (meaning there were no light leaks while collecting dark frames). In the current dev releases, the new-profile-wizard does disable star-mass detection but that was a comment unrelated to your problem.   I suggest you slew the scope to a star-rich field, one with a range of star brightness values, and re-examine the focus.  Use whatever exposure times you need to find stars.  Once you can confirm focus and collect guide cam frames that have usable stars – based on how auto-find behaves - you can move ahead knowing that the guide camera and focus are right.  Then is the time to consider whether the necessary exposure times are too long for your mount. You can capture a guide cam image with the File/Save menu option at any time to record what’s happening.   If you become convinced that the frames do have usable stars despite what I’m telling you, you can reduce the Min-HFD value to 1.0 and start guiding.  If you’re guiding on sensor noise, you will know it very quickly based on the guiding results.

 

Good luck,

Bruce

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