Star trails while phd guiding

[Craig123]

Hi all

I was already last night to nail my focus with a bhatinov for the first time and then try imaging the Veil again or Elephants trunk but as has happened before i seemed to take a couple of steps backwards.

First i was getting trails on shortish subs where i had been fine on 20 minutes last week.Phd was following a guide star and that seemed ok although i'm not good at understanding the graph yet and what each movement means.I polar aligned with sharpcap and settled for good instead of excellent...could this be the reason.Other possible thoughts were cable drag or even putting the scope on the other way round and messing up the balance.Has anyone ideas on this? It seems to happen every so often.

Second,when i did slew to the veil i couldn't spot it with an Ha filter on my atik 314 mono this time.Last attempt it was pretty clear to see on my Artemis capture screen so i centred it and got some images.The moon was brighter last night and also closer to the target and even though i had a look around i did not see the familiar shape in the fov.Does a brighter  moon make spotting narrowband targets nearby harder or has something else gone amiss in the process since last weeks more successful sessions .Many thanks

Craig

[carastro]

Take a look in the brain on PHD.  Sometimes PHD switches off one of the axes if it is unhappy with the calibration, and you could have been guiding on Dec only (or is it RA only, can't quite remember which it switches off).  I have a feeling it will stay like that until you switch them both back on.

Now if it did that it could be because you did not PA very well.  

It definitely sounds like you missed your target.  

I believe you use Artemis, when I am "looking for my target" I bin x 3 and put the view into negative as the nebulosity shows up better and then move the leg slider to the left (opposite to viewing it in the positive).  Think I might have mentioned this to you before.   This method works really well and I almost always use it for framing a target.

Carole 

[Craig123]

14 minutes ago, carastro said:

Take a look in the brain on PHD.  Sometimes PHD switches off one of the axes if it is unhappy with the calibration, and you could have been guiding on Dec only (or is it RA only, can't quite remember which it switches off).  I have a feeling it will stay like that until you switch them both back on.

Now if it did that it could be because you did not PA very well.  

It definitely sounds like you missed your target.  

I believe you use Artemis, when I am "looking for my target" I bin x 3 and put the view into negative as the nebulosity shows up better and then move the leg slider to the left (opposite to viewing it in the positive).  Think I might have mentioned this to you before.   This method works really well and I almost always use it for framing a target.

Carole 

Hi Carole.

That's a good tip using the negative with the slider  that  i didnt know thanks.I usually make the effort to get alignment excellent  but settled for good with clouds coming in.I did bin x3 and eventually got some nebulae around the Veil but it wasn't the area I was looking for and was all abit haphazard considering I had geared myself up for perfection last night !

I did get to use the Bhatinov and felt I moved focus forward abit  ?

[kens]

If you post your guide log it will tell us pretty much everything there is to know.

[Craig123]

1 hour ago, kens said:

If you post your guide log it will tell us pretty much everything there is to know.

Unfortunately I didn't save this..not that I am aware of anyway.Had a look on PhD just now and couldn't find it.

[Davey-T]

1 hour ago, Craig123 said:

Unfortunately I didn't save this..not that I am aware of anyway.Had a look on PhD just now and couldn't find it.

I think PHD stores log files in your documents folder by default.

Dave

[Craig123]

8 minutes ago, Davey-T said:

I think PHD stores log files in your documents folder by default.

Dave

cheers Dave..i will just have a look

[Craig123]

2 hours ago, kens said:

If you post your guide log it will tell us pretty much everything there is to know.

Does this info shed any light?...i should have taken a screen shot of phd guiding/not guiding aswell. I can see it clouded over at the end and i fell asleep for abit.?

PHD2_GuideLog_2018-07-31_232726.txt

[Davey-T]

At a quick glance it seems to be doing a lot of switching between east and west this can be sometimes avoided by having the balance east heavy so it is always pushing west.

Also worth checking your Polar alignment.

Dave

[Craig123]

Thanks.It wasn't a great night all round Dave.The focusing tube kept slipping and wouldn't move in again with the weight of the camera and reducer pointing straight up.I fixed that now. I didn't get PA bang on but figured PhD would 'fix it'.Still learning..a lot to go.

[kens]

That log does not look pretty. The calibration looks ok but there is visible drift on both axes. Whats is particularly odd is that the RA rate is higher than the Dec rate.

The guide graph is very spikey. Also unusual is that the RA and Dec graphs look like they are transposed. That is, the Dec graphs shows a clear periodic curve whilst RA shows a linear drift. I'm wondering if you've got some wires reversed somewhere - possibly a crossover cable instead of the ST4 cable.

[Craig123]

I think the st4 cable was ok. Very strange.Could it be a fault with the mount or even cables dragging?

I will post a log from the last two sessions just in case anyone can help. I'm concerned something is up with the mount as the hand controller  wouldn't centre the target on the previous session.I started again and eveything seemed to work ok.The session before seemed fine.

 

[Craig123]

PHD2_GuideLog_2018-07-23_010326.txt

PHD2_GuideLog_2018-07-24_235530.txt

[kens]

Theres a lot of confounding issues going on. On the 24th your guide exposures were taking 14s even though the setting was for 2s. On the 23rd they were about 2.5s each which is closer to expectation.  Your main problem is due to a large number of dropped stars. Some of that could be due to the long exposures where the star drifts out of the search region. But you also had a lot on the 23rd where you spent about half the session without a guide star.

I would look first at your camera and what is going on there. There is an option in PHD2 to log lost star events with the image captured from the guide camera. I suggest you enable that so we can see what is happening. Also check you camera settings. Do you have another application using the guide camera at the same time?

 

[Davey-T]

You can watch the green cross and see if it drifts away from the star until you get the star lost message which means the mount is ignoring the guide commands.

If you set the pulse length to something high and the mount doesn't respond the pulse lengths should gradually lengthen to your max' setting.

Which mount have you got ? can't see it mentioned anywhere.

Dave

[Craig123]

14 minutes ago, Davey-T said:

You can watch the green cross and see if it drifts away from the star until you get the star lost message which means the mount is ignoring the guide commands.

If you set the pulse length to something high and the mount doesn't respond the pulse lengths should gradually lengthen to your max' setting.

Which mount have you got ? can't see it mentioned anywhere.

Dave

It's the Heq5 pro.Where do I change the pulse  rate..on PHD ?

[Craig123]

9 hours ago, kens said:

Theres a lot of confounding issues going on. On the 24th your guide exposures were taking 14s even though the setting was for 2s. On the 23rd they were about 2.5s each which is closer to expectation.  Your main problem is due to a large number of dropped stars. Some of that could be due to the long exposures where the star drifts out of the search region. But you also had a lot on the 23rd where you spent about half the session without a guide star.

I would look first at your camera and what is going on there. There is an option in PHD2 to log lost star events with the image captured from the guide camera. I suggest you enable that so we can see what is happening. Also check you camera settings. Do you have another application using the guide camera at the same time?

 

Yep..i don't ever remember changing the guide exposures on PhD.Hopefully it's nothing drastic.I polar align with sharp cap with the guide camera first and I think.ive left that running while i fire up PhD...i wonder if that's the problem.. there was also a lot of cloud around.

[cjdawson]

First think I'd suggest is, if you can drop the ST-4 cable and use pulse guiding instead of ST-4 guiding.   PHD2 was designed with pulse guiding directly in mind, the ST-4 stuff is added to increase compatibility.

I do this using the POTH Hub in ascom.  This lets multiple pieces of software control the mount at the same time, without clashing.

[Craig123]

Hiya.

Thanks for this, makes sense.My plan for the last month has been to get Ascon up and running but i realised my focus was not dead accurate and I got sidetracked with Bhatinov and focusing ha fliters having got eveything in place( Eqmod ,cables etc ).Do you think it's possible to set up Ascom in the day and input info.The last session at night ended in a right muddle  and i feel like ive gone a mile or so backwards just as I had inched forwards !

[david_taurus83]

It is BEST to set up Ascom in the day and not waste clear nights! You can set it up and connect all your gear to make sure it's all working.

[Craig123]

Ah..thanks David.Just what I needed to know.

 

[spillage]

1 hour ago, cjdawson said:

use pulse guiding instead of ST-4 guiding

+1 for this and also setting up ascom in the daytime. As long as phd2 connects to the camera then thats good enough. I would not worry too much about focus for now and put more time into sorting out your guiding. Are you using the stable version or the development version or phd.

[Craig123]

7 minutes ago, spillage said:

+1 for this and also setting up ascom in the daytime. As long as phd2 connects to the camera then thats good enough. I would not worry too much about focus for now and put more time into sorting out your guiding. Are you using the stable version or the development version or phd.

Thanks.It says phd2 guiding 2.6.2.