PHD2 - 'Star lost - low SNR - Question ?

[Skipper Billy]

I keep getting the message 'Star lost - low SNR' and the flashing screen and dreaded beeping - but there are dozens of stars to choose from and blindingly obvious on the screen !!

Even with the screen gain slider over to the far right (darkest) there are still stars visible - and they aren't hot/cold pixels.

Any ideas ??  The seeing is pretty poor and the moon is awful bright - could that be it ??

 

 

[Tinker1947]

It asked me to increase the DEC/RA aggression i have it at 3500 atm, poor seeing will depend on your guide CCD, i use a Lodestar and it doesn't have a problem with even the faintest, clouds seem to stop it working though....

[Thalestris24]

11 minutes ago, Skipper Billy said:

I keep getting the message 'Star lost - low SNR' and the flashing screen and dreaded beeping - but there are dozens of stars to choose from and blindingly obvious on the screen !!

Even with the screen gain slider over to the far right (darkest) there are still stars visible - and they aren't hot/cold pixels.

Any ideas ??  The seeing is pretty poor and the moon is awful bright - could that be it ??

 

 

Hi

The message refers to the star you had selected. Maybe some cloud came over and you lost it? Maybe it's just a case of selecting a high snr star else could be that your drifting off faster than PHD2 can correct. The guide log should have useful info...

Louise

[Davey-T]

Have you tried letting it select the star itself, I get the same message if the star is too bright but it will auto select stars that I can hardly see.

Dave

[Starlight 1]

1 hour ago, Skipper Billy said:

Even with the screen gain slider over to the far right (darkest) there are still stars visible

This is only for your seeing and do not have any thing to do with Stars or how phd works.

[Freddie]

1 hour ago, Tinker1947 said:

It asked me to increase the DEC/RA aggression i have it at 3500 atm, poor seeing will depend on your guide CCD, i use a Lodestar and it doesn't have a problem with even the faintest, clouds seem to stop it working though....

Aggression is a percentage so 3500 doesn't sound right. Are you sure you adjusted the correct setting? 3500 sounds more like a max duration setting.

[Davey-T]

Yes usually have mine at 90 percent, max duration doesn't seem to matter as it should never reach 3500 hopefully

If something is really out of kilter it will gradually ramp up to the maximum trying to fix it.

Dave

[Tinker1947]

28 minutes ago, Freddie said:

Aggression is a percentage so 3500 doesn't sound right. Are you sure you adjusted the correct setting? 3500 sounds more like a max duration setting.

Could have been i only done it the once........will check next time its clear....

[Skipper Billy]

OK - it seems to work better if I let it 'auto select' a star. It seems the stars I was choosing were too bright even though it said low SNR - maybe it meant SNR too high !!

Either way its behaving itself again now !!

Thanks for the suggestions.

 

[Thalestris24]

1 hour ago, Skipper Billy said:

OK - it seems to work better if I let it 'auto select' a star. It seems the stars I was choosing were too bright even though it said low SNR - maybe it meant SNR too high !!

Either way its behaving itself again now !!

Thanks for the suggestions.

 

Hi

It's a good idea to display the star profile (from the view menu). PHD2 will flash up 'Sat' for saturated if the selected star is too bright/exposure too long. Auto select works quite well for a given exposure time - around 2-3 secs works well for me

Louise

[Ken82]

As Louise explains you want to see the star profile and you need a star that has a nice peak on the top and not flat . This indicates the star isn't over saturated 

[HHank1953]

Here is my problem: My camera is very noisy and no matter how much I try to adjust the focusing, the noise isn't clear enough to even pick a star for tracking. What am I doing wrong. I use default settings, I adjust the brightness/darkness and I still can't get  a clear enough picture. I use the auto star select still nothing. need some help or advice.

[wornish]

On 28/05/2019 at 00:59, HHank1953 said:

Here is my problem: My camera is very noisy and no matter how much I try to adjust the focusing, the noise isn't clear enough to even pick a star for tracking. What am I doing wrong. I use default settings, I adjust the brightness/darkness and I still can't get  a clear enough picture. I use the auto star select still nothing. need some help or advice.

This thread is over two years old.  You might get more replies to your question if you start a new one.

That said, your problem sounds like your focus is way out.  The moon is a great target to check your focussing on  point your guide cam at the moon and see what it shows.  If the picture is very blurred then adjust the focus until it comes clear.  Lock that position on your guide cam and then try again with PHD on stars.

[Thalestris24]

15 hours ago, HHank1953 said:

Here is my problem: My camera is very noisy and no matter how much I try to adjust the focusing, the noise isn't clear enough to even pick a star for tracking. What am I doing wrong. I use default settings, I adjust the brightness/darkness and I still can't get  a clear enough picture. I use the auto star select still nothing. need some help or advice.

What guide camera are you using? What mount and guide scope? What settings, specifically exposure? Is that with PHD2, latest version? Have you made a dark library/bad pixel map? Can you not select a star manually? What is your sky and light pollution like? Generally speaking, you want around 2s exposures and fairly good focus. The range of focus using a typical guide scope e.g. a 50mm one, and guide camera e.g. a qhy5l-ii mono or similar, is quite small so you have to adjust focus carefully. It can be useful to adjust focus during the day using a distant object but you need to block off a lot of light because of the high sensitivity of a typical guide cam. Using a far infra red filter and very short exposure (< a ms.) is one way of doing it, though PHD2 itself doesn't support very short exposures. If you have a qhy guide cam, their ezplanetary software lets you set very short exposures.

Louise