Filter Change to SII - sudden loss of PHD2 lock...

[Jbro1985]

Hi all,

Wondering if you can help with an error diagnosis.  Ten minutes after I go to bed (very frustrating!) last night I have an issue I have never had before.  PHD2 lost it's lock, which put SGP into abort.  The frame before hand was a good 10 minute OIII capture and it changed filter to SII, re-focused (I use an OAG and autofocus when the filters change - normally makes the guiding go slightly funny but has never killed it before). The OAG is in front of the filter wheel in the imaging train so I can't see that the act of changing filter would have made a difference to the guiding at all...

Here is my SGP log (https://jbconsult-my.sharepoint.com/:t:/g/personal/jbro1985_jbconsult_onmicrosoft_com/ETlde73yTHRBn0OTeM_BL9sB0CFCaY-P3NzzVmeuDoiKGg?e=aG1Bav).  The issue starts at :  [10/29/18 00:41:17.930][DEBUG] [Sequence Thread] AF is complete, continuing sequence...

Here is my PHD2 log (https://jbconsult-my.sharepoint.com/:t:/g/personal/jbro1985_jbconsult_onmicrosoft_com/ESsgHXBl_K5Brg4kYkDXLiEBeyP6eIBxdBZ0RArsx-PZFw?e=iKXpNW).  It looks to me like it's possible that the focussing may have interfered with the guiding on this occassion, which would be annoying...  Otherwise, the clouds rolled in although the image just before was very clear and the night itself was very clear.  If some one has the time, I'd appreciate it if they could take a quick look and let me know if they reach the same conclusion or if I'm missing something.  I am only just starting to analyse logs and I find them a little confusing.  

All assistance appreciated as always.

Jason 

[Toxophilus]

Hi, 

I've not looked at the logs as I don't have the software to analyse them available to me at the moment. The big problem with OAG's is that as you adjust the focus it changes the focus on the guide scope too. So you could have a couple of problems going on here.

If the filters are not particularly par-focal then the focus may be so far off that PHD2 is not able to select an appropriate guide star or it can but the seeing was pushing the star mass out too much or it was loosing it all together. This would be apparent for just viewing the screen and your stars would be obviously out of focus or really faint. 

What I suspect is more likely is that as the SII filter is so strong it needs longer exposures to get sufficient data to calculate the focus on. If PHD fails to obtain focus on its initial run it pushes the focus even further to try to find focus at a different range of values. This can push the focus out sufficiently for PHD to give up as it has lost the star. With an OAG the best thing to do is (and I can't off the top of my head remember where the settings are) is to increase the exposure time for that filter and disable guiding whilst autofocus is in progress, this will avoid this issue. This does assume that your mount can hold sufficiently tight stars for say 10-15 seconds (or even more) which may be required for SII to get enough data to calculate the focus values.

Hope this helps

Mark

[geoflewis]

29 minutes ago, Toxophilus said:

If the filters are not particularly par-focal then the focus may be so far off that PHD2 is not able to select an appropriate guide star or it can but the seeing was pushing the star mass out too much or it was loosing it all together. This would be apparent for just viewing the screen and your stars would be obviously out of focus or really faint. 

What I suspect is more likely is that as the SII filter is so strong it needs longer exposures to get sufficient data to calculate the focus on. If PHD fails to obtain focus on its initial run it pushes the focus even further to try to find focus at a different range of values. This can push the focus out sufficiently for PHD to give up as it has lost the star.

I agree with Mark. I don't have PHDLogviewer on this laptop, but just opening the log in a text viewer shows that the last dozen or so lines were PHD2 reporting lost star due to change in star mass and low SNR. I also suspect that is due to SGP's autofocus routine taking the guide camera too far out of focus for PHD2 to hang on to the guide star. Mark's suggestion to pause PHD2 during autofocus runs sounds like a good option worth trying.

Good luck, Geof

[steppenwolf]

Something that you could consider is making all your focus adjustments using the Luminance filter (or an IR reject filter) and then apply offsets for each of the narrowband filters that you use. This method works pretty well for me and the method is apparently supported in SGPro although I don't use that software. I would further adjust the OAG camera so that it is in focus for the 'middle focus position filter' in your set so that it is less out of focus for those filters either side of the 'middle focus' one. I always uncouple guiding during a focus routine.

[Jbro1985]

If it sheds any light...

I'm using the baader c7nm set for Ha OIII and SII and have guided through each filter previously without an issue though, including autofocus.  Weird there's an issue this time.  

I didn't realise there was an option to not guide through autofocus - I'll have a look for that in SGP (or do you mean to manually do this?).

I did reduce my PhD exposure setting to 3 seconds from 4 the other day.  Perhaps that is it.

Thanks everyone

[Toxophilus]

19 minutes ago, Jbro1985 said:

If it sheds any light...

I'm using the baader c7nm set for Ha OIII and SII and have guided through each filter previously without an issue though, including autofocus.  Weird there's an issue this time.  

I didn't realise there was an option to not guide through autofocus - I'll have a look for that in SGP (or do you mean to manually do this?).

I did reduce my PhD exposure setting to 3 seconds from 4 the other day.  Perhaps that is it.

Thanks everyone

When I get home I should be able to have a look at where the options are in SGP. But you can set focus duration for individual filters, if you are using on exposure setting for all filters then 3 seconds probably won't be enough for the autofocus mechanism to pick up sufficient star data. Yes there is an option to disable guiding whilst performing an autofocus in SGP, again I'll see if I can find where it is in the configuration. But have a poke around its all in the the equipment profiles somewhere, but a little buried in the dialogs. Let me know if you find them before I get chance. Good luck.

[geoflewis]

20 minutes ago, Jbro1985 said:

I didn't realise there was an option to not guide through autofocus - I'll have a look for that in SGP (or do you mean to manually do this?).

Look at settings in control panel - 2nd item under other options on right side of the panel (screen shot is from autoguide section of SGP manual)...

[Jbro1985]

Cheers guys.  Amazing help as always.

[Toxophilus]

OK as promised this is where everything that I was talking about is set.

First go into your Equipment Profile Manager and select the profile you want to edit.

Select the focus tab and ensure use auto focus is set and then click set to configure it

Setup auto focus on filter change and disable auto focus with filter and then click the 'For Filters' button

Configure the times that you want for the filters 

The select the guiding tab and ensure pause guiding during auto focus is enabled

That should fix your problem for focusing with an OAG using narrowband filters. alternatively you could use the technique that steppenwolf has suggested which is to focus with a clear filter and then use offsets to bring everything into focus for a specific filter. The downside to that is that you need to work out the offsets for each filters (the settings are all in the dialogs that I have added) and any temperature compensation you may need. The upside is that focusing between filters will be faster than using each specific filter for auto focusing. The advantage of using each specific filter is that it will take account of any changes in your kit as temperatures or conditions change with less 'up font' work, but it will take more time out of your active capturing time. 

Hope this helps and Good luck, let us know you get on.

Mark

[Jbro1985]

Thanks Mark.  That's a massive help!

[Black Apron]

On 29/10/2018 at 03:41, Jbro1985 said:

Hi all,

Wondering if you can help with an error diagnosis.  Ten minutes after I go to bed (very frustrating!) last night I have an issue I have never had before.  PHD2 lost it's lock, which put SGP into abort.  The frame before hand was a good 10 minute OIII capture and it changed filter to SII, re-focused (I use an OAG and autofocus when the filters change - normally makes the guiding go slightly funny but has never killed it before). The OAG is in front of the filter wheel in the imaging train so I can't see that the act of changing filter would have made a difference to the guiding at all...

Here is my SGP log (https://jbconsult-my.sharepoint.com/:t:/g/personal/jbro1985_jbconsult_onmicrosoft_com/ETlde73yTHRBn0OTeM_BL9sB0CFCaY-P3NzzVmeuDoiKGg?e=aG1Bav).  The issue starts at :  [10/29/18 00:41:17.930][DEBUG] [Sequence Thread] AF is complete, continuing sequence...

Here is my PHD2 log (https://jbconsult-my.sharepoint.com/:t:/g/personal/jbro1985_jbconsult_onmicrosoft_com/ESsgHXBl_K5Brg4kYkDXLiEBeyP6eIBxdBZ0RArsx-PZFw?e=iKXpNW).  It looks to me like it's possible that the focussing may have interfered with the guiding on this occassion, which would be annoying...  Otherwise, the clouds rolled in although the image just before was very clear and the night itself was very clear.  If some one has the time, I'd appreciate it if they could take a quick look and let me know if they reach the same conclusion or if I'm missing something.  I am only just starting to analyse logs and I find them a little confusing.  

All assistance appreciated as always.

Jason 

I think your problem might not have to do with PHD itself directly... it happens to me from time to time that vibrations from the filter wheel turning (especially if the destination filter is several slots away), is strong enough to make PHD loose its lock. If you have a long FL scope, any small vibration will impact the star and if on top of that the focus changes, then you might end up having this kind of problem.... I've been looking for a way to have SGP automatically stop guiding for a couple of seconds before moving the filter wheel and resume after a few seconds to allow for settling (or after autofocus), but I haven't found a way...