Mark's Acquisition Program

[MarkS]

I've finally written the acquisition program I've promised myself for so long!

It is as minimalist as possible to perform long exposures and to perform the all important dithering.  
It fires the Canon via the serial lead and it interfaces to PHD Guiding to perform the dithering.

To preview images, I'll use Canon Utilities to read them to the laptop where they can be opened in IRIS (or similar).

Here's a screenshot of it in action:



Tonight it will get its first proper live test.

Mark

[Carole]

Clever you, fingers crossed it works well.

Carole

[Fay]

Not only a trouper, but so clever as well.....................

[RobertM]

Looking good.  The only thing i would say is that settle accuracy might need to be tweaked down a bit.

[The Thing]

HI Mark,

Looks really useful and to the point.

One thing APT adds to the PHD integration is an 'Auto cancel exposure' function which has a distance parameter. I believe it is to cope with the PHD allowing drift (cloud? star lost? cable caught? hit leg?) during the exposure, too far and it cancels the exposure and starts dithering for the next one. If there is cloud then presumably dithering will time out and exposures will stop, What I would want in either scenario is an alarm to rouse one from the pastis-ification so you can check what's going on.

Another nifty feature would be it to tell you the time it will finish the sequence with all the dithering and and interframe waits added in so you can set an alarm...

BTW Try Deep Sky Stacker Live for showing the subs as they arrive, it works really well for monitoring a folder. It will also give you running graphs of FWHM, skay background, number of stars detected and a few others. And you can always get it to do a quick live stack!

[MarkS]

One thing APT adds to the PHD integration is an 'Auto cancel exposure' function which has a distance parameter. I believe it is to cope with the PHD allowing drift (cloud? star lost? cable caught? hit leg?) during the exposure, too far and it cancels the exposure and starts dithering for the next one. If there is cloud then presumably dithering will time out and exposures will stop, What I would want in either scenario is an alarm to rouse one from the pastis-ification so you can check what's going on.

That's fairly simple to implement.  The PHD sever can be interrogated at any time for the distance of the guide star from where it should be.  So in principle the user could define another threshold which, if exceeded, would allow the exposure to be terminated mid-exposure.

BTW,  I've written this so all the user inputs (except COM port number!) can be altered at any time, including during mid-exposure.

Mark

[Mike]

Nice one Mark. Good to see you've been putting your unemployment to good use instead of standing around on street corners drinking cider.

[JohnP]

Mike - RU trying to say Tony is unemployed.....?

[Tony G]

 

Don't tempt fate.

Tony G

[Fay]

Mike, never thought of the world as sucking!

[Mike]

Oh I can think of quite a few things that suck, but the world isn't one of them.

[MarkS]

After a couple of midnight code fixes, it seems to be working 

The biggest problem I had when using it live was that the program sent the dither command to PHD Guiding and then immediately read the star distance and assumed PHD had settled whereas PHD had not even had time to react to the dither command.  So I've added a delay of a couple of seconds after sending the dither command before then interrogating the guide star distance.  This didn't show up in earlier testing when I was using PHD in simulator mode.

Mark

[The Thing]

Would you not need the delay to be the same as the length of guiding exposure (plus a little reaction time) as won't that be the delay in PHD knowing the guide star has moved the dither distance? I don't know if you can get this via the server.

[MarkS]

Would you not need the delay to be the same as the length of guiding exposure (plus a little reaction time) as won't that be the delay in PHD knowing the guide star has moved the dither distance? I don't know if you can get this via the server.

I think you're right but it's impossible to get from the server.  The user will need to make the interframe delay large enough.
I wonder how Nebulosity gets around this potential problem?

Mark

[The Thing]

You could ask Ivo at APT how he does it...