Guiding doesn't always work properly

[Carole]

After all those horrid problems I had earlier with my SC3 as a guide camera (and having to put it in the airing cupboard), I took notice of various recommendations and bought myself a QHY5 as that SC3 has given me nothing but problems since I bought it.  (Remember it would not work in LX and so I relegated it to a guide cam).

I now have loads more stars to guide on, which is great and used it for the first time last night to do my M45 and Rosette. 

However it was not plain sailing and this was the sighs of frustration that Phil was listening to when he happened to ring me while I was in the POD trying to get it all going.  Was setting up while I was talking to him. 

Guiding with QHY5 & PHD:
This calibrated OK, but examining the first few 5 minute subs the guiding was awful, I was getting double zigzag stars.  Then all of a sudden with no further intervention, it started guiding OK and I got those images last night.

Now tonight I am out there again and got the same thing, first 1/2 doz subs the guiding was awful and then suddenly it started guiding OK. 

Is there any logical explanation?

Could this possibly be associated with my previous problems I wonder and maybe it wasn't the camera after all. 

Carole

[MarkS]

I really don't know what the likely cause is.  Is it possible that some high level cloud passed over the guidestar?  This happens to me quite frequently.

There is also a menu option in PHD to produce a log file i.e. it writes a history of everything it does.  I've never really looked at the logfile but it might well contain enough information to work out what was going on during those "strange" periods.  I would switch this on permanently and then next time the guiding goes weird you'll have a log available which you can send to us.

On the whole though, it does sound like you're getting a fair amount of success now!

Mark

[mickw]

Does the graph in PHD show that the guiding is OK ?

I read that if you move the scope around to compose/centre a target, PHD can take some time to settle down again.

[RobertM]

Hi Carole,

Make sure that both the guide camera and scope are firmly fixed in place and that there is no drag on any cables going to them.  Also make sure that both telescope axes are just a little off balance; the RA should be setup so the motor is driving against the slight off balance.

If the camera were to loose signal because of clouds then the corrections should stop and you'll get a guide star lost message.  I very much doubt that is the problem if the guide star is bright enough.

Hope that helps
Robert

[Carole]

Does the graph in PHD show that the guiding is OK ?

well I did turn it on Mick, but the trouble is I don't know what it is supposed to look like.  I think I did a screen print to save it so will have a look on the laptop later and see whether it is still on the clip board.

There is also a menu option in PHD to produce a log file

I think I've seen that somewhere, will have a look for that too.

On the whole though, it does sound like you're getting a fair amount of success now!

It works when it feels like it, as I tried at the beginning of the evening and also at the end to image M81/M82, but just could not get the guiding to work on this target.  I even did half a drift alignment to see whether the polar alignment might have been out.  
I did south and after 10 minutes the star did not move at all.  But could not see a star in the West and there are houses in the way in the East.  I realise now that there might have been stars available through the telescope Duh!

Also make sure that both telescope axes are just a little off balance; the RA should be setup so the motor is driving against the slight off balance.

I can't quite work out the legistics of that.  I am sure it is simple, maybe you could draw me a sketch next time we meet.

I couldn't see any clouds, and it's strange that it was when guiding first started each time for the first 4 - 5 5min subs.  I would have thought I would get a low SNR signal if it was clouds, and you could still see the guide star on PHD.

no drag on any cables going to them.

I'll watch out for that, thanks.

Thanks every-one

Carole

[Carole]

There is also a menu option in PHD to produce a log file

I think I've seen that somewhere, will have a look for that too.

OK I've found the logs, they are long pages of data.
Do you want that posted on the Forum, or shall I put it in my drop box, or E mail it to some-one.

Carole

[MarkS]

OK I've found the logs, they are long pages of data.
Do you want that posted on the Forum, or shall I put it in my drop box, or E mail it to some-one.

No - don't post it on the forum - email it me and let me know roughly when the guiding went awry i.e. the beginning or the end or the middle of the PHD session?

Mark

[MarkS]

For the benefit of others, the PHD log files that Carole sent me clearly showed that there are long periods when the guide pulses in Dec generated by PHD seem to have no effect at all on the Dec error.   However, guiding is RA always appears to be working fine.

The question is why?

Any ideas?

Mark

[The Thing]

On my Meade that problem was caused by handset software bugs a the serial connection connects to the handset.

My 2p worth...

If Carole is using the eq6 guide port then surely it must be an intermittent connection either in the cable or interally to the dec relay.

[mickw]

Carole has experienced camera fouling the mount on occasion, has this been corrected ?.

[Ian]

Mick, I recommend Mike's new book "How to House Train your Astronomical Equipment"

[MarkS]

the PHD log files that Carole sent me clearly showed that there are long periods when the guide pulses in Dec generated by PHD seem to have no effect at all on the Dec error.

I should also add that there are long periods where the Dec guiding works perfectly i.e. the problem is kind-of intermittent.  The mount is a CG5.

[Carole]

Carole has experienced camera fouling the mount on occasion, has this been corrected ?.

Hi Mick, it was the dec lock lever that fouled the mount and that has been re-adjusted.  

I also have a problem with the top plate of the pier fouling the telescopes (or camera) when slewed to far RA

and nothing I can do about it unless I stop imaging before it gets to this point (or change my mount, or maybe piggy back might help I have yet to try this out).  However I had none of those problems during these sessions.

Carole

[mickw]

I recommend Mike's new book "How to House Train your Astronomical Equipment"

It's OK the Pod is like a telescope kennel  

Carole did you ever try new cables at the time when you were swapping virtually all your equipment trying to sort your guiding issues the first time round ?

[Carole]

Carole did you ever try new cables at the time when you were swapping virtually all your equipment trying to sort your guiding issues the first time round ?

I swapped the handset and 12V cable, but I don't have a second set of guide cables to try. 
I can't remember if I swapped the Dec cable, but am going to swap it now.

I think one of my 12V cables is dodgy but found this out BEFORE this session.

As I now have a QHY5 I don't use the GPUSB any more.  So if any-one has an ST4 cable I could borrow for testing that would be handy. 

Carole