Dithering question

[Starwiz]

Just trying to get my head around how dithering works.

Guide camera is connected to mount (1 lead) & laptop (2nd lead).

Canon camera is connected to laptop (3rd lead).

APT is used to control the camera.

PHD2 is used to control guiding.

So, let's say with a 5 min x 20 exposures controlled by APT, how does PHD2 know when it has to dither between each exposure?

John

[Ouroboros]

If APT works like BackYardEOS it tells PHD to dither between exposures. It was just a matter of clicking the right settings in BYEOS and PHD2. I imagined it would be more difficult, but actually it just works seamlessly. 

[StuartJPP]

Within PHD(2) you need to "Enable Server" this allows APT to tell PHD that exposure has ended and a dither is about to take place. Additionally since you are not using ASCOM to control the mount it has to be driven direct by the camera (via the ST4 cable).

I find it better to connect the camera to the PC as well as the mount to the PC (ditching the ST4 cable from the camera to the mount), that way the PC knows where the mount is pointing, though it isn't strictly necessary. You will need ASCOM drivers for your mount and the right cable to do this depending on your mount.

[Ouroboros]

Yes. However, I've stayed with using an ST4 cable between the guide camera and mount (exactly as you have it Starwiz) and can confirm it works absolutely fine with dithering as Stuart says. 

I've  been looking back at the PHD2 manual, which you can download from Here.  The information you need to set up dithering is on page 27.  It's not written very clearly, but how to do it is there if you read it carefully.  Essentially you need to set parameters in PHD2 so it enables a server, how much to dither by and how long to allow the mount to settle  down after dithering and before taking the next exposure. It sounds complicated, but I just followed my nose and got it to work. 

The difficulty I had was how to determine how much to dither by. In the end I had to play with a scaling factor in one of PHD2's parameter settings until I saw a definite shift in star positions between exposures. There's probably an optimum shift value but I don't know how to determine what that might be. What I do seems to work anyway.  

 

[Starwiz]

Thanks for your help everyone.

I've tried connecting my guidescope and DSLR to my laptop, then ran PHD2, and then APT.

When APT starts up, I could see it flash on the screen 'Connecting to PHD'.

However, it shows the PHD status as 'NC' and when I try to connect using the 'Guide [D]' button, I get a message saying it can't connect.

I have 'Enable Server' ticked in PHD2.

Does it actually have to be guiding before it will connect?

Any thoughts?

Thanks

John

[Starwiz]

I've just found the PHD server isn't running even though the box is ticked.  Now trying to find out why.

[Starwiz]

Firewall is stopping the server from running.

[Starwiz]

It seems no matter what I do in the firewall settings, I can only get the PHD2 server to run if I turn off the firewall.

I've tried....

Installing latest version of PHD2.

Enabling PHD2 and APT in the firewall settings.

Deleting PHD2 from the firewall settings and re-assigning a rule for it to be enabled.

Running PHD2 as administrator.

Rebooting my laptop.

Now I can't think what to do next other than isolate from the internet and turn off the firewall when I want to guide.

John

 

[Ouroboros]

 A problem very similar to yours is discussed on this forum.   It might help. Good luck. 

[Starwiz]

Thanks Ouroboros,

I've tried what it said in the forum, but no luck.

[spillage]

Have you made sure that phd2 and apt have full access through the firewall? Which version on windows are you running?

[Starwiz]

Yes, I think so.  I'm running Windows 10.

Thanks

John

 

[spillage]

You also need to check outbound setting and it may be worth opening up port 4400.

[Starwiz]

I also have the outbound setting enabled.  How do I open up port 4400?

Thanks

[alacant]

Hi. APT has moved on quite a way since then. Try v3.4. HTH

http://www.ideiki.com/astro/APT_UnReg3_40.zip

[Starwiz]

Thanks, I've installed APT v3.4 but have the same problem. 

The PHD2 server isn't running so I don't think APT will connect without this.

[Starwiz]

So I managed to give dithering a try on a very windy night on Monday.  Disconnected the WiFi and switched off the firewall so PHD2 server would run.  Had to throw away several frames due to the wind moving the telescope and cloud being blown across, but ended up with nine usable 5 minute frames at ISO 800.  I could see that dithering was actually working and was pleased with the half-decent result given the conditions (M33).

 

[Ouroboros]

@StarwizGood! How did you solve the problem? 

[Starwiz]

Thanks.  I didn't get to the root-cause of the problem, but at least have a work-around.  i.e. Switch off the WiFi, so it's safely isolated from the internet, then switch off the firewall.

John

[Ouroboros]

42 minutes ago, Starwiz said:

Thanks.  I didn't get to the root-cause of the problem, but at least have a work-around.  i.e. Switch off the WiFi, so it's safely isolated from the internet, then switch off the firewall.

John

OK liveable with then. I disconnect my laptop from the Internet anyway when I'm imaging to stop it getting distracted by emails or checking on updates and downloading them.