Quick question on Guiding set up / PHD2

[scotty38]

15 minutes ago, kens said:

Also, try to stick with 2 second exposures. 1 second guiding exposures wont really help you.

I'm a bit suspicious of the normalised guide rates: Ra 17.2 and Dec 15.6 when 13.5 is expected.

Make sure you are tracking at sidereal rate and that the controller knows you have a EQ6R

I did read somewhere, maybe it was on my "guiding" thread recently, that shorter exposures of say 1sec are preferable (acceptable?) when using multi star in PHD. I must admit I didn't see a difference in 1sec and 3 secs when i tested though but who knows....

[michael8554]

From your GuideLog:

The 5.8 degree orthogonality error in the Cal  with the new Profile was tolerable and due to the poor PAE of 21arcmins.

Get that PAE down to no worse than 5arcmins.

As others have said, it's worth spending a few minutes Calibrating each night, as your setup isn't permanent.

Immediately followed by a Guide Assistant run, which would have alerted you to the poor PA, you ran for about 30 minutes before doing the GA run.

The Seeing during the only significant run after that was poor, causing low camera signal, Star Lost messages, and large RA spikes.

In the short periods when the Seeing was good your guiding looked okay, but should be better with good PA.

Michael

 

 

[Priesters]

12 minutes ago, wimvb said:

SharpCap gives you an accurate PA allright, but where do you set up?

It’s on a flagged patio with no wobbly flags.  That said I appreciate there is still potential for small movements that will affect PA.  I’ll give it some thought whether I can PA with the tripod on the patio but me off it. 

[Priesters]

ok, so this didn't turn out to be a 'quick question' after all. 🙄

Nearly full moon last night but clear so ideal guiding practice.  Set up using Altair GPCam as guider this time, polar aligned etc then fired up PHD and immediately calibration failed.  So much for my theory that the problem was caused by having two nearly identical cameras as imager and guider! To my horror the previous 'fix' of deleting the profile and re-running the new profile wizard didn't work either.   Checked all cables etc and re-did the new profile 'fix' and still no joy.  In a slightly deranged way I just kept trying and randomly it calibrated, I ran GA, applied changes and some pleasing guiding followed - around the 0.5" RMS mark. 

I think I must then have shut PHD down because when I moved target I had to re-calibrate and it failed again.  So after a little cry I tried shutting down all applications and then only opening PHD.  It worked, calibration was successful and guiding was back on - between 0.4" RMS and 1" RMS depending on which part of the sky I was in and how long I left it running.  My theory is now that its down to the fact everything runs through a USB 2 hub as opposed to USB 3.  For the record its a Startech USB extender over ethernet so not a cheap Amazon job.  I've posted this story of woe for two reasons:

• any thoughts / experiences with the USB 2 theory?
• is the very noticeable kink in the attached backlash graph anything to worry about?

Thanks for reading.

 

PHD2_GuideLog_2022-01-16_190144.txt

[wimvb]

You aren’t the first to experience problems with usb hubs, and for testing purposes you should try taking it out of the equation.

The kink in the backlash graph is probably due to mild ”stiction”. You can probably ignore it, since your backlash is do small.

Edited January 18, 2022 by wimvb

[ollypenrice]

On 08/01/2022 at 12:54, kens said:

Also, try to stick with 2 second exposures. 1 second guiding exposures wont really help you.

 

I don't find this with EQ6 or Avalons running EQ6 electronics. However, I guide in ST4 and sometimes use much shorter exposures, down to 0.5 seconds. I do use longer guide subs (4 secs) with the accurate Mesu mounts. It's odd that our findings differ.

Olly

[michael8554]

12 hours ago, Priesters said:

So much for my theory that the problem was caused by having two nearly identical cameras as imager and guider!

GPCAM has 2.9um pixels, ASI294 has 4.63um pixels - nearly identical cameras ??? 

It is not good practice to delete Equipment Profiles.

Better to create a new-name  Profile using the Wizard, then you have a choice of Profiles at all times.

Your connections allow PHD2 to know the RA and Dec of the mount.

So you only need to Calibrate once each night, close to Dec=0, and use that for all targets.

When you close PHD2 it remembers the Cal, so you don't need to ReCal after opening PHD2 again.

Only ReCal the next time you set up.

Your first seven Cals were truly awful, not getting past the RA phase, but the eighth Cal was good, no error messages, you could have used that all night.

Later you made two more awful Cals at Dec = 29, but the third was fine ?

If you know what you were doing wrong on the awful Cals you could save a lot of time.

Re the guiding:

You ran GA and applied the settings, exposure was 2 seconds, PA was around 2 arcmins.

And guiding was sub-1arcsec throughout.

So all good but guidecam focus was poor for most of the night, HFD = 6, but was an acceptable HFD = 3.85 on the final run of the night.

And since these are colour cams, every little helps, so you should make Dark Libraries for them.

Why do you think you had USB problems ?

If you believe it caused the poor Cals, then you should upload the PHD2 DebugLog to the PHD2 Help Forum.

Using the instructions in the Help menu, choosing files with relevant dates in the filename.

https://groups.google.com/g/open-phd-guiding

Michael

 

[Priesters]

Thanks for looking through the logs and points noted.  

42 minutes ago, michael8554 said:

Your first seven Cals were truly awful, not getting past the RA phase,

Yes, this is my point.  When I first set up it won’t calibrate at all which I think is caused by USB problems because when I shut down other apps it worked.  I’ll retest my theory next clear night.  

43 minutes ago, michael8554 said:

GPCAM has 2.9um pixels, ASI294 has 4.63um pixels - nearly identical cameras ???

See earlier in thread - initially I was guiding with a 294MC and imaging with a 294MC Pro, both 4.63 um

50 minutes ago, michael8554 said:

If you believe it caused the poor Cals, then you should upload the PHD2 DebugLog to the PHD2 Help Forum

Will do 👍

Thanks again.

[iantaylor2uk]

When you calibrate use 1 sec exposures but once guiding I find it is better to up this to 2 or 3 seconds, so you are not chasing the seeing. For my set up I also tend to have the RA and DEC aggressiveness set to around 50%, but you'll have to play with these to find what's best for your mount. I tend to use the ASI Air Pro for polar alignment and even though that may report it as 3', the PHD2 logs usually report it as higher (6' or so). I find anything less than 10' works OK.

[newbie alert]

8 hours ago, michael8554 said:

 

So you only need to Calibrate once each night, close to Dec=0, and use that for all targets.

When you close PHD2 it remembers the Cal, so you don't need to ReCal after opening PHD2 again.

Only ReCal the next time you set up.

 

 

 

Michael

 

Only if you tick the box🤔

 

[newbie alert]

How good is your balance?  Stiction has been suggested, how well does your axis move, any tight spots? 

[Priesters]

Reckon it is stiction as when there’s no weight on it it’s pretty stiff.  That makes balancing tricky but I do my best to balance in three axis.  I haven’t really properly checked for tight spots but I will do next time I’m setting up.  

Edited January 18, 2022 by Priesters

[newbie alert]

8 hours ago, Priesters said:

Reckon it is stiction as when there’s no weight on it it’s pretty stiff.  That makes balancing tricky but I do my best to balance in three axis.  I haven’t really properly checked for tight spots but I will do next time I’m setting up.  

The tightening collar is worth a check as from the factory they sometomes tighten them too much , locking things up, try this

 

[Priesters]

17 minutes ago, newbie alert said:

The tightening collar is worth a check as from the factory they sometomes tighten them too much , locking things up, try this

Great, I’ll give that a go.  Looks like that adjustment is even within my technical capabilities.  Thank you 👍