View Full Version here: : PHD2 Errors

14-10-2017, 11:18 PM
First time user of PHD2.

Had a few hours tonight outside just practising and learning to use the software with my QHY. Polar alignment wasn’t that great but I was having some errors with the program.

- Low SNR error
- Lost star error

Not sure how to resolve these.

Can anyone help?


14-10-2017, 11:24 PM
Increase your exposure time ( try 2 -3 seconds to start), this can typically improve SNR and thus prevent lost star. Of course a cloud moving over your guide star can cause star lost due to poor SNR. Aim to keep the SNR letters green at the bottom of the frame. Of course guide camera sensitivity plays a role as well.

15-10-2017, 01:00 AM
You could also try increasing the gain on your guide camera. Did you get PHD2 to autoselect the guide star?

15-10-2017, 08:02 AM
I probably should have mentioned some numbers from my guiding!

- SNR was around the 30 mark. I tried another section of the sky with another star and at one point it was 8
- Exposure I think was 1 second
- I did both a manual and automatic star

15-10-2017, 08:13 AM
I had similar problems to start of with. I found that better focusing helped a lot and enabling noise reduction in PHD2 also improved things with my zwo120mc camera. Advanced settings (the brain icon), camera, noise reduction.

15-10-2017, 08:26 AM
Yeah focusing was the hardest bit as you have to move the entire camera back and forward and the refresh rate isn't quick enough.

15-10-2017, 08:32 AM
Some advice suggests that slightly defocused stars are better for guiding.

15-10-2017, 09:31 AM
Thanks for the advice all.

I will give it another crack tonight if the weather permits!

15-10-2017, 10:14 AM
I was at the point you are a month ago..things starting to work and sorting out the problems ...then the weather went sour and I missed the only good nights available to run the gear since then (nights where there was little cloud)...and now because I replaced the tripod with a pier cant now get back polar... and the dec is still sloppy... but I will give PHD a go ..I hope it is the answer to the tree cover here... same problem as you here... Michael from Bintel up here said the best bit of astro gear he could recomend was a chain saw...

Good luck


15-10-2017, 10:33 AM
I think this is true for brighter stars, but a dim star is brighter when well focused.

15-10-2017, 10:37 AM

Would be a good investment!

15-10-2017, 10:37 AM
Focus on a bright star with a quick refresh rate. Have the Star Profile enabled so you can see the HFD/FWHM and have a zoomed in view of the star.
Then move to your target.

15-10-2017, 02:00 PM
I personal found focusing my ASI120MM-S and a guide scope in PHD a pain. I would use another software package to focus (I used MaximDL because I've got it but SharpCap would be good and free).

Following the SNR and FWHM numbers in PHD I'd think that I'm close to focus and then I'd check in MaximDL and it would be way off. PHD does an excellent job at dealing with out of focus stars and centroid calculations. It is because it does what it is supposed to do well that makes focusing a bit difficult.

15-10-2017, 09:12 PM
This seems to be happening with my PHD2 tonight.

Does anyone know what would be wrong?

15-10-2017, 09:28 PM
Oh my god!

I would give someone a gold star if they guess why my image is like that.

I feel so dumb right now...

15-10-2017, 09:35 PM
Lens cap on the auto guider?

15-10-2017, 09:44 PM
Yep! :lol:

15-10-2017, 09:45 PM
I do keep getting a "Your max dec duration setting is preventing PHD from making adequate adjustments corrections to keep the guide star locked."

15-10-2017, 09:56 PM
That is most likely a polar alignment issue or bad dec backlash in the mount. Have you increased the max dec setting?

15-10-2017, 09:57 PM
Let Guide Assistant make the corrections. Try running it and accept the recommendations.

15-10-2017, 10:00 PM
I left it as default.

15-10-2017, 10:00 PM
Will give that a try now!