Optimal settings for PHD for autoguiding?

[Prickly]

Hi,

Michael and I have been trying to get PHD working for autoguiding. I can see some guide stars focussed through my C90 but they appear quite faint and maybe only one or two per chip.

I was wondering whether this was normal or whether I should be seeing a greater number of stars using the QHY5. Also appreciate feedback on the optimal settings under the brain icon for advanced settings or a typical range people might use. Which ones do I need to adjust gain? Not sure about most of the others. Do you use the 3x3 median for noise reduction?

Should I use the darkframe? Seemed a good idea but when I did the image got worse! (Very dark with bright white pixcels) Maybe doing something wrong here.

Finally what time do you set 1sec?

Appreciate any help you could give. We are looking forward to trying some longer exposures. Those round stars are hopefully not too far away!

Cheers
David

[gbeal]

David,
I too struggle with the "optimum" setting, and flounder on hoping.
The "Brain" settings will have a Gain section, and I use 10%. Take a dark for sure, as it will help. Depending on the amount of stars in the section you are imaging, I use from 1 second through to about 5 seconds.
As for the rest (aggressiveness etc) you can at least try the default settings and work from there.
It is a great program, and more so due to its cost.
Gary

[JohnG (John)]

Hi David

I am going to make some asumptions here, there is no mention of the type of mount, whether it is polar aligned or whether it is capable of being autoguided.

I have never used a C90 but it has a Flip Mirror type back, does it not.....

Not having a go at you as a lot of us have done this, have you flipped the mirror so light is getting to the QHY5........

A 90mm scope should show plenty of stars with the 1 second default setting, when you say you are only getting 1 or 2 per exposure and get worse when you do a Dark Frame are sysptoms of light not getting to the camera.

When I use a DSLR camera, I use an 80mm f/7 scope and have no problems getting plenty of stars with a Q-Guider, almost identical to your QHY5.

Have you tried to Calibrate, what happens, do you get Calibration Failed.
Couple of setting I use in 'The Brain' Aggressiveness - 80%, Calibration - 800ms, remainder, Default, my exposure is anything between 1.5 and 3 seconds, depending on conditions.

Try also aiming the scope at a fairly bright star, the 3 belt stars in Orion are a good choice, take a 1 second shot and focus in on that, see what it records, should be nice and bright, take a Dark and a lot more stars should appear.

Cheers

[pjphilli (Peter)]

Hi David
I too have a QHY5 and was pretty disappointed with it at the start until I received the following advice from the good people of IceInSpace.
These were:
1. Focus carefully
2. Use a moderate focal length to give good field of view - I am now using a 100mm Mak focal reduced to 600mm
3. Use a dark frame. This appears to improve the contrast of the stars.
Following this advice I can now usually see several guide stars on the screen when I have the guiding scope collimated with my imaging scope.
If not I move the guide scope slightly until I can see a guide star. Even when the guide stars seem rather dim, PHD seems to guide on them OK all night.
Last night I was imaging when a wind was still gusting up until about
midnight. This occasionally threw the RA guiding off to + or - 2 pixels but it
soon regained its normal sub pixel guiding. The parameters may vary a lot depending on what gear you are using. I find just using near the default figures ok but improvements can be made by adjusting the aggressiveness.
I usually try to use 1 second imaging but will go to 2 or 3 seconds if the guiding appears a bit unstable.
Cheers Peter

[Prickly]

Hi,

Thanks for all the feedback.

The C90 I use is pretty ancient and I need a diagonal in place to reach focus, although I have been able to focus the C90 with sirius.

Must admit I had the gain at 9% for planets from memory but I bumped it up to 60%. Maybe thats too high. I had 750ms set for the calibration step, 120 RA agressiveness, 10 RA hysteresis.

At the bottom force calibration and use subframes is selected. How do you do the calibration?

I really dont know whats happening with the dark frame. It should really improve things and I think has done in the past imaging planets. The image is essentially black with lots of white spots as opposed to the usual uniform background with the odd white star.

Cheers
David

[spearo (Frank)]

hi
i use the QHY5 on a WO80mm for guiding
i tend to use the dark frames as it usually improves contrast, you need to redo it everytime you fiddle with exposute time.
I think that in the "brain" settings i push gain to 100% not the sliding bar at the bottom of the main screen
As was mentionned earlier, focus is critical, if its out of focus a bit its ok but past a poit you really wont see the stars.

unlike others i use 0.2 sec exposures and i always manage to find a guide star, sometimes requiring me to re-aim the guide star.
I'd start off by lining it up on a real big bright star you just cant miss and using a Bahtinov or Hartmann mask ensure the focus is spot on.

cheers
frank

[pjphilli (Peter)]

Hi David
Just on a couple of points that you have raised:
Ra Agressiveness: Going to the max of 120 would appear to be a bit high as this may give too much correction overshoot. I usually find 70% is about right.
Dark Frames: I do find that when a dark frame is employed that the screen has a dim white "wavy" wash against the black background, however the
stars seem better defined. You can fiddle around with the Screen Gamma
slider to improve the visual look of the display but I have found that this does not affect tracking so I just leave it on default.
Calibration: this depends on your scope focal length but I just set it so that it gives noticeable steps across the screen (eg about 1mm) for each
calibration step. I don't know whether and/or how the calibration setting affects guiding but someone may like to comment on this.
Cheers Peter

[seeker372011 (Narayan)]

Originally Posted by pjphilli

Hi David
Just on a couple of points that you have raised:

Calibration: this depends on your scope focal length but I just set it so that it gives noticeable steps across the screen (eg about 1mm) for each
calibration step. I don't know whether and/or how the calibration setting affects guiding but someone may like to comment on this.
Cheers Peter

Ideally you want PHD to calibrate in about 20 to 30 steps in each direction

too few and the guiding doesnt seem to hold as well; too many-well more than 60 PHD gives up; between 30 and 60-its a long time for you to be sitting there waiting for it to do its thing

you control the number of steps by setting the duration of the calibration steps.
very much depends on the scope and also on where you are pointed. Closer to the pole, longer calibration steps-1000ms or more

far from the pole 500 ms may be enough

you dont want it to finish calibration in say 4 or 5 steps which can happen if you have too large a calibration step

[seeker372011 (Narayan)]

Originally Posted by Prickly

Hi,

Thanks for all the feedback.

Must admit I had the gain at 9% for planets from memory but I bumped it up to 60%. Maybe thats too high.

At the bottom force calibration and use subframes is selected. How do you do the calibration?

For my guide camear I have gain set at maximum..doesnt seem to matter.

You calibrate, after selecting a guide star -and after the box around the selected star turns green- by hitting stop and then pressing the "guide" button

if you have "force calibration ticked"-or if you are firing PHD for the first time-it will then go through its calibration routine