PHD Guiding Help

[decoyp]

Please can anyone help here. I've just started trying to get going with autoguiding. I took the time over the summer/autumn to build a permanent pier and drift align the mount (HEQ5) as well as I could.

I've just tried setting up the autoguider for the first time (QHY5 camera) using PHD. After getting a guide star on the screen, PHD went through all the callibration stuff and started guiding OK but then after about a minute it started flashing up a warning about "guide star saturated" or something and then lost the guide star.

Having taken a couple of hours just to get to that point I'm cold and a bit fed up. Can anyone point me in the right direction as to what the problem might be. I'm using an old 400mm telephoto lense as a guide scope.

[martin_h]

Dont pick a big bright star - a dimmer/smaller one is better

[Beyond_Vision]

What time have you set the exposure to?

[decoyp]

Sorry I,ve been away since posting this question. Thanks for thereplies.

My exposure time was set to 2 secs. I found I had to do this because with shorter exposures PHD kept telling me "star has not moved enough" after the first callibration routine. It counted 61 exposures then gave me this message. I didn't quite know what it was trying to ask me so I increased the exposure time and then it seemed to be happier with the movement.

Perhaps I've got the gain set too high ? How do you adjust this. This is completely new to me, hence all the questions.

Thanks for your help

Richard.

[mark7331]

Hi Richard.

In PHD try using a 1 sec exposure and in the "brain" advanced settings lower the "Calibration step (ms)" setting. You have a short focal length guider so take the step value down. I have a 1000mm focal length guider and the setting I use is 750. When I used 600ms PHD reported the same error that you had. So change it down to something like 550? and experiment.

Also don't pick a really bright star and get the focus so that you can see some background stars.

I think it's worth giving up a night to "how to guide" where you pick different stars and give it a try. That what I did and I does work because I had 6 hours worth of 10 and 20 minute exposures last night and that was the first night I used it in anger.

All the best

Mark

[decoyp]

Thanks Mark. I'll give your suggestions a try. As you say I will have to spend a few nights getting PHD to work for me and geting the settings right for my particular arrangement. I don't mind doing that although its a bit frusrtating. Anyway we have a full moon at the moment - not optimum imaging conditions so I guess I can use this time to experiment. Will let you know how things progress.

thanks

[mark7331]

My pleasure Richard.

You have the right approach and when you do get it guiding open up the "graph" (tools->enable graph) but don't be alarmed if the RA and DEC lines are bouncing around a bit. Take exposures of different lengths (60s, 120, 180....600) to see if you're getting round stars. If you're not then re-adjust either the guide star or the calibration again. My graph appears to bounce madly within the first divisions but I'm getting 20 minute perfectly round stars.

As you say if you give up a few nights just to guiding you can learn an awful lot.

I look forward to your progress reports