Guiding Problems - Poor Polar Alignment?

[michael8554]

From the GuideLog:

Signs of large Dec Backlash in the Cal, which skewed the reported Dec Guide Rate a bit.

The start of the final 25minute run shows that:

 

 

After the Backlash was driven out the  PA drifted on the south side, so backlash didn't come into play.

About halfway through that run you enabled Dec Backlash Comp.

But you hadn't run Guide Assistant at any point in the evening, so PHD2 hadn't established a starting setting for Dec Backlash ?

Or suggested suitable Minimum Move settings, or measured PA Error.

Guide Errors were RA = 1.43arcsecs, Dec = 1.69arcsecs, so round but bloated stars.

Guidecam focus was poor HFD = 7.64

Michael

 

[Ian McCallum]

15 minutes ago, michael8554 said:

From the GuideLog:

Signs of large Dec Backlash in the Cal, which skewed the reported Dec Guide Rate a bit.

The start of the final 25minute run shows that:

 

 

After the Backlash was driven out the  PA drifted on the south side, so backlash didn't come into play.

About halfway through that run you enabled Dec Backlash Comp.

But you hadn't run Guide Assistant at any point in the evening, so PHD2 hadn't established a starting setting for Dec Backlash ?

Or suggested suitable Minimum Move settings, or measured PA Error.

Guide Errors were RA = 1.43arcsecs, Dec = 1.69arcsecs, so round but bloated stars.

Guidecam focus was poor HFD = 7.64

Michael

 

I was trying to image and guide at the same time, probably not a good thing to do for a newbie...🙄  I remember trying to align the object in the laptop screen, whilst pressing the guiding buttons on the controller, perhaps this contributed to some of the spikes?  I completely forgot about Guiding Assistant, I'll look into that when the weather allows.

I've got a Bahtinov mask coming this week, so that should help with focus.  I've got one for the guidescope and one for the main telescope.  The lag is taking an exposure and showing up on the screen is rather frustrating, especially when it comes to focusing.

This is where being part of a club or organisation that met up (lockdown conditions allowing), would be extremely useful.  Hands on experience beats 'distant learning' methods, in my opinion.

[malc-c]

Normal practice is to frame your target in the imaging camera, and once your happy, then let PHD pick a star in the guide camera's  image, let it calibrate, run the guide assistant and apply its recommendations and then either run guide assistant once more or just start guiding.  Once guiding has been running I typically let it run for a few minutes to settle down and then start the imaging run.  Once its all running I walk away and make a cuppa and let it do its thing.

Imaging is something you can't rush... it is a learning curve, sometimes steep and frustrating...  Vlaiv may remember a thread a while back were between us we wrote a very detailed step by step process for a guy who was struggling to grasp the basics - and then he simply stopped posting - so no idea if he gave up or it resolved his issue.  I don't think you are at that level, but people here are here to offer advice and guidance... just be patient and you'll get there.

[vlaiv]

2 hours ago, malc-c said:

If you place an old image on a new PC the only thing that is required is to re-activate windows as the change in hardware gets detected.  I can't recall the last time I built a windows install from scratch and installed all the programs needed.

One of the issues was with drivers - no drivers available for Win7.

I guess support really ended for Win7 and we are forced to move forward (although I was quite happy with that version).

[Ian McCallum]

2 hours ago, malc-c said:

Normal practice is to frame your target in the imaging camera, and once your happy, then let PHD pick a star in the guide camera's  image, let it calibrate, run the guide assistant and apply its recommendations and then either run guide assistant once more or just start guiding.  Once guiding has been running I typically let it run for a few minutes to settle down and then start the imaging run.  Once its all running I walk away and make a cuppa and let it do its thing.

Imaging is something you can't rush... it is a learning curve, sometimes steep and frustrating...  Vlaiv may remember a thread a while back were between us we wrote a very detailed step by step process for a guy who was struggling to grasp the basics - and then he simply stopped posting - so no idea if he gave up or it resolved his issue.  I don't think you are at that level, but people here are here to offer advice and guidance... just be patient and you'll get there.

Two problems that I can see. Firstly, I've been manually aligning the telescope with a eyepiece, as I don't have any Goto facilities. 

I can mitigate that by fitting a Telrad finder on the OTA, the 1, 2 and 4 degree rings should help, if used in conjunction with planetarium software. 

[Ian McCallum]

55 minutes ago, vlaiv said:

One of the issues was with drivers - no drivers available for Win7.

I guess support really ended for Win7 and we are forced to move forward (although I was quite happy with that version).

I'm still using Windows 8.1 on my laptop. 

[malc-c]

25 minutes ago, Ian McCallum said:

Two problems that I can see. Firstly, I've been manually aligning the telescope with a eyepiece, as I don't have any Goto facilities. 

I can mitigate that by fitting a Telrad finder on the OTA, the 1, 2 and 4 degree rings should help, if used in conjunction with planetarium software. 

You don't need goto to polar alight.  Many ways to polar align, some use software such as Sharpcap or NINA which have built in routines (Sharpcap required a subscription  ) or you could use the polar scope built into the EQ5

When selecting a target,  you don't need a planetarium program as you don't have goto.  Release the clutches and swing the scope to the target area, using the finder to help.  Lock the clutches and engage the motors so the scope is been set to track, and then with your eyepiece in place use the direction buttons to centre the target in the eyepiece.  Remove the eyepiece and place the camera in the focuser, then take an exposure to get focus and also a rough framing to see if the target is where you want it.  Use the directional buttons to frame the target how you want the final image to look if required.   Then launch PHD2 and run through the calibration as described.  Once PHD is guiding you can then do your imaging.

[michael8554]

You don't need a Bahtinov Mask for the guidecam.

Just point the guidecam at a bright star, and with a fast refresh, say 0.5 sec exposure, adjust focus for lowest HFD figure in the Star Profile window.

A B Mask for the imaging camera does help.

 

3 hours ago, Ian McCallum said:

I was trying to image and guide at the same time,

What's wrong with that ?  That's how you get good images !

Michael

[Ian McCallum]

35 minutes ago, malc-c said:

You don't need goto to polar alight.  Many ways to polar align, some use software such as Sharpcap or NINA which have built in routines (Sharpcap required a subscription  ) or you could use the polar scope built into the EQ5

When selecting a target,  you don't need a planetarium program as you don't have goto.  Release the clutches and swing the scope to the target area, using the finder to help.  Lock the clutches and engage the motors so the scope is been set to track, and then with your eyepiece in place use the direction buttons to centre the target in the eyepiece.  Remove the eyepiece and place the camera in the focuser, then take an exposure to get focus and also a rough framing to see if the target is where you want it.  Use the directional buttons to frame the target how you want the final image to look if required.   Then launch PHD2 and run through the calibration as described.  Once PHD is guiding you can then do your imaging.

 I never mentioned polar align in my previous reply.  I use the built in polar scope for that. I was referring to the target I was wanting to image.

[Ian McCallum]

11 minutes ago, michael8554 said:

You don't need a Bahtinov Mask for the guidecam.

Just point the guidecam at a bright star, and with a fast refresh, say 0.5 sec exposure, adjust focus for lowest HFD figure in the Star Profile window.

A B Mask for the imaging camera does help.

 

What's wrong with that ?  That's how you get good images !

Michael

I was getting one 3D printed for £5, so not too much to lose.

[malc-c]

4 minutes ago, Ian McCallum said:

 I never mentioned polar align in my previous reply.  I use the built in polar scope for that. I was referring to the target I was wanting to image.

my mistake

[Ian McCallum]

29 minutes ago, malc-c said:

my mistake

No worries. 👍

[Ian McCallum]

Last night, I targeted the Orion Nebula.  I used the laptop, after discovering it had a USB 3 port on it.  I had the ZWO ASI120MM mini in the 9x50 guidescope and the ZWO ASI224MC in the main telescope. I left the 120MM mini guiding under PHD2 on and off, for a while.  There were some small clouds passing by, during the process.  I tried multi star guiding and did use the Guiding Assistant for a little time.  I also had to move the main telescope, as the guidescope wasn't aligned with the main OTA.🙄

I also did some imaging of the moon, but found that the guidescope was able to give me good as focus as it could have. 😡 I'm going to have to investigate that, as I feel that may have caused some star bloat issues during previous guiding sessions.🤔

Here's the guiding log from PHD2, if anyone fancies a wee look.😉

PHD2_GuideLog_2022-02-10_185613.txt

[malc-c]

Sorry to say that there is a lot of "user error" in the logs... It would seem that you continued PHD guiding when you moved the scope seeing the huge peak at the end of one trace.  This skews the data somewhat.  Ideally a guide log of a few hours is better than one lasting 11minutes as it will pick up the harmonics of the drive.   But as my old teachers used to say "good effort ! "👍

Maybe Michael will be able to decipher something from it?

[alacant]

2 hours ago, Ian McCallum said:

log from PHD2

Hi

We can't advise much on it I'm afraid. The guide stars got obscured anyway. Clouds? You really need a steady night to check if everything is working or -even better- someone else guiding alongside you with a setup which is known to be optimum. An astro club would have you up and running in no time at all.

But anyway, before the software can get anywhere near, the mount must be as mechanically perfect as possible. It's always a good idea to dismantle, clean, re-lubricate and adjust (even on a new mount) so as to eliminate any mechanical issues. Then look at balance. Then polar alignment. Then electrical connections. You can then turn your attention to learning the software in the knowledge that any problems lie within. It just has to be methodical, otherwise you'll end up bald!

Cheers and good luck.

 

Edited February 11, 2022 by alacant

[Ian McCallum]

I can only but hope that astro clubs and organisations start meeting again.

[scotty38]

Where are you? You never know you may have a friendly SGLer nearby....

[Ian McCallum]

2 minutes ago, scotty38 said:

Where are you? You never know you may have a friendly SGLer nearby....

North Ayrshire, in SW Scotland.

[scotty38]

Thanks, fingers crossed then. Bit far for me I'm afraid 🙂

[alacant]

57 minutes ago, Ian McCallum said:

clubs and organisations start meeting again.

http://www.ayrastro.com/

Rings a... Something... I think we had a visitor from there not too many new moons ago.

 

Edited February 11, 2022 by alacant

[michael8554]

Hi Ian

From the GuideLog.

PHD2 had to clear 23 steps of Dec Backlash before the North part of Cal could start.

It would really help to improve the Cal if you pulsed north until the guidestar moves, then add a couple more pulses as there's so much backlash, THEN Calibrate.

This is in the PHD2 instructions that I'm sure you've read........ ?

Guidecam focus was good HFD = 3.14 px,  until 19:44 when it became HFD = 5.72 ,  something loose ?

Instead of running the Guide Assistant straight after Cal, you left it until much later.

PA Error =>11.5arcmins, usually needs to be 5arcmins or better,  but with bad Dec Backlash this error can be used to your advantage, see later.

MultiStar Guiding allows fast exposures that would normally be "Chasing the Seeing".

But in those conditions 1 second exposures were too fast, giving very choppy camera output and Star Lost messages.

In the only long session at 19:30, Dec Backlash predominated for the first 3 minutes, as shown in alacant's screen grab,

Once PHD2 had pulled Dec back, Dec drifted south due to PAE, and so backlash didn't come into play.

If you can't improve the Dec performance, this may be how you have to guide.

The calculated Guide Rates were Norm rates RA = 6.3"/s @ dec 0, Dec = 5.9"/s.

Higher Guide Rates may help, say 10arcsec/sec.

Michael

 

[malc-c]

Ok please don't take this as in a condescending way, but here are some suggestions, which I also apologies if any sound patronising - it's not my intention, just ignore any points that seem obvious.

• In the day time, confirm that the mount is operating smoothly with no binding when the clutches are released. 
• Check that the scope is balanced with all the camera gear in operation.  It's critical to get the centre of gravity correct too - have a search on youtube for Astronomy Shed.  Dion's videos are quite old now, but the information on how to balance a scope within the tube rings (more applicable to newts) is still relevant. 
• Place the scope in the default home position facing North, ideally at twilight so that you can still  see to set up the hardware and have everything operational.
• When a bright star is visible in deep twilight, power the mount up, launch whatever software you use to position the scope and unpark it, then select sidereal tracking 
• Release the cutches and point the scope at the star, until its centred in the screen of the imaging software, and lock the clutches.
• launch sharpcap or similar and connect to the guidescope camera.  Adjust the positioning screws on the guidescope until the image has the same star centred in the software screen.  You now have the guidescope and main scope aligned as both applications will have the same star in the centre of the window 
• Release the clutches and set EQMOD or whatever software to the default home park position.
• Position the scope in the default home position and lock the clutches.
• I would suggest paying a years subscription to Sharpcap Pro as it has an excellent polar alignment tool.  Using this you should be able to fine tune your polar alignment better.  If you are relying on the polar scope in the mount, it could be that this is out of alignment and causing you such a large PA error.
• Having polar aligned the mount, check a few settings in EQMOD (and I'm sure NINA or GSServer have similar options) and that is to set the pulse guiding rates to x0.9 for both axis
• Now here comes the bone of contention.  Some will suggest you run the PHD2 calibration at the target, where others suggest selecting a star that is as close to the intersection of the meridian with the celestial equator.  I would suggest the latter as this is where things move fastest.
• With a star selected, launch PHD2, which should still retain the profile containing camera and guidescope details.  Set the exposure to around 1.5 - 3 seconds and run a calibration routine, followed by the guide assistant for a good 2-4 minutes
• Accept the recommendations. - Hopefully it won't find anything too bad, and then once complete stop guiding if PHD2 reverts back to that state.
• Clear the graphs and target screens in PHD2 and then let PHD2 auto select a single guide start and engage guiding.  If it runs another calibration routine so much the better.
• Let the guiding run for a good 20 - 40 minutes or more to gather some  decent data, taking care not to touch the scope or do anything that will upset the guiding.
• Stop guiding and clear the graphs and target track in PHD2
• Slew to the target you want to image.
• Let PHD2 auto select a single star, and begin guiding.  Again, if it does a calibration that's fine.
• Once the guiding graph has settled down after a couple of minutes, then start your imaging run, again, taking care not to move the mount or do anything that will upset the guiding.
• Once the imaging run has started walk away, make a cuppa, and just keep an eye on things as it runs.  A long guide log helps give a true picture on how the mount is performing.
• Once the imaging session is complete stop PHD2 guiding before moving the scope, such as issuing a park instruction.
• Close down the software, power down the mount and retire to bed

Hopefully this workflow will help, and provide a decent set of logs to allow the likes of Michael and Vlaiv to provide feedback on the performance.

[Ian McCallum]

I'm actually thinking of having everything set up, but not to do any active imaging - just concentrate of the guiding aspect for the whole session.

[malc-c]

8 minutes ago, Ian McCallum said:

I'm actually thinking of having everything set up, but not to do any active imaging - just concentrate of the guiding aspect for the whole session.

That's entirely at your discretion, but at least at the end of the session if you imaged you would be able to see what results you are likely to get.  

[Ian McCallum]

1 hour ago, malc-c said:

That's entirely at your discretion, but at least at the end of the session if you imaged you would be able to see what results you are likely to get.  

I don't think there's issues with the clutches, but the usual toffee grease that the manufacturers use. 🙄

I've stripped down an old EQ-1B mount before and degrease/regreased it. I'm not looking forward to doing it on a relatively new mount, that I believe is more complicated than the previous mount I worked on.