Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.

Hitesh

Phd2 doesn't agree with polemaster

Recommended Posts

Im completely rubbish at polar alignment so I got myself a polemaster to aid and speed up the process. I know the manual is pants but I have seen loads of videos on the tube, and I have been able to follow what's going on, and managed to align the scope. When I tried to verify the alignment with Phd2, a huge alignment error is shown (-104). I've also found other problems like non orthogonal axes when calibrating PhD. Has anyone any ideas on solving these issues? God I wish this hobby was less frustrating

Share this post


Link to post
Share on other sites

Hi

Can you post a screen dump of your phd2 drift alignment? It's hard to see how you could have an error of 104 mins!! Make sure you're trying to align in the right direction - it asks for azimuth first (south) then altitude (east or west). Don't rely on the guide assistant PA numbers - they seem to be instantaneous values so you have to be wary especially if seeing isn't so good.

Louise

Share this post


Link to post
Share on other sites

Or better still, post the PHD2 guide log from the session in question. It is usually located in your documents folder in subfolder PHD2. If you don't have a clean calibration then PHD2 doesn't work as it should

Share this post


Link to post
Share on other sites

You've got a bunch of problems there. First up your calibration in PHD2 is off with the two axes nowhere near orthogonal. In this log you used the calibration that was done in an earlier session (at 10:34 PM). Post that log file as well so we can see what happened during the calibration sequence. Without a good calibration PHD2 cannot work out your polar alignment

Another thing I see is that you have a very high signal to noise ratio so I strongly suspect that your guide star is saturated. Next time switch on the star profile display: Menu View > Display Star Profile. Check that the star profile has a pointy top and not a flat top.

 

  • Like 1

Share this post


Link to post
Share on other sites

Thanks for that, I will definitely look into that, and I will try and post up the earlier calibration. How do I sort out the orthogonal axes issue? 

Share this post


Link to post
Share on other sites
8 minutes ago, Hitesh said:

Thanks for that, I will definitely look into that, and I will try and post up the earlier calibration. How do I sort out the orthogonal axes issue? 

Check your balance, my mount gives orthogonal warnings in PHD if the balance is off.

Dave

Share this post


Link to post
Share on other sites

here are the other logs from the night. My balance is off, i think i need a longer dovetail and offset the scope to bring it into balance but that makes me think is there enough clearance for the focuser if i push the scope forwards towards the objective lens to bring scope into balance.

PHD2_GuideLog_2016-05-07_220034.txt

PHD2_GuideLog_2016-05-07_222222.txt

Share this post


Link to post
Share on other sites

That's a pretty bad calibration.

You need to adjust the calibration step size. Go t o the guiding tab on the brain and click Calculate. Then enter the appropriate values.

If you are using ST4 guiding then make sure you enter the declination where you are doing the calibration.

Also make sure the guide rate is the same as you have in your hand controller or EQMOD. And ideally at 0.5 or 1.0x sidereal. It looks like you are guiding at 0.3.

Why did you do the calibration with ST4 guiding then switch to EQMOD pulse guiding? If you are happy with EQMOD then I'd suggest calibrating with that setup also.

You should calibrate either close to where you are imaging or, if you plan to reuse the calibration, close to dec 0. From the data in your calibration either you were calibrating with a different guide rate on RA from Dec or you were calibrating at around Dec 75 degrees

Make sure you have a good calibration before doing anything else with PHD2. Otherwise it simply wont work.

 

  • Like 1

Share this post


Link to post
Share on other sites

Thanks for that, I think I will stick with EQMOD, one less cable hanging around that way. So do the RA and DEC guide rates have to be the same? 

Share this post


Link to post
Share on other sites
2 minutes ago, Hitesh said:

Thanks for that, I think I will stick with EQMOD, one less cable hanging around that way. So do the RA and DEC guide rates have to be the same? 

You need the RA guide rate set to keep up with sidearal rotation, in a perfect world dec wouldn't need to guide .

Dave

Share this post


Link to post
Share on other sites

Don't mix up guiding with tracking. The guide rate for RA should be 1 or less so that eastwards corrections work by turning off the tracking temporarily. Guide rates more than 1 cause eastward corrections to reverse the motor direction which leads to backlash.

The guide rates for RA and Dec do not need to be the same but there's also no reason for them to be different. So you may as well keep things simple.

Share this post


Link to post
Share on other sites

Thought I read somewhere that PHD doesn't reverse the RA motor just stops until it catches up, can't believe everything you read though, unless it's in the Daily Mail :grin:

Dave

Share this post


Link to post
Share on other sites

Its not controlled by PHD. Its the motor controller that determines it. All PHD does is to tell the motor controller to guide East for xxx milliseconds based on the guiding rate and the amount of correction needed. If the guiding rate is less than 1x sidereal the motor controller should just stop for the appropriate time. e.g. If it is 0.5x sidereal it will stop the motor for xxx/2 milliseconds or alternatively it could send out only half the tracking pulses for xxx milliseconds

Share this post


Link to post
Share on other sites

Finally a clear night to test everything again. I've managed to put the scope on a longer dovetail ( thanks for that FLO great service as usual) and shifted the tube up towards the objective lens, this has massively improved my scopes balance and PhD now sees the axes as othogonal with a smallish error, this is can live with for now ( thanks Davey-T for the suggestion) . And having calibrated properly today I even got a very low error on my polar alignment so looks like my original problems are felt with. Now to learn how to guide properly!!!! ??? God I love this hobby when things work

  • Like 2

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Recently Browsing   0 members

    No registered users viewing this page.

  • Similar Content

    • By cesco
      After two deluding years using SkyWatcher AZ EQ6 to handle a Meade 7” ED refractor, I got back to my previous mount, the manual Losmandy G11. I had to have maintenance performed by a specialized firm, and also to inspect the RA and Dec worms bearing screws and Oldham joints most accurately by myself. At last, after a good tweak and regreasing  I reliably got round star images in my frames, without guiding, up to 60 s exposure. I don’t care with longer exposures since I was forced to choose capture of many short shots, useful to increase the combined image S/N ratio, after my once dark sky site was ruined by light pollution.
      Still, a tiny RA drift still remains, as visible after capturing a handful of frames. I use the QHYCCD Polemaster for polar alignment, and I move the mount manually when accomplishing rotations of the RA axis forward and backward. The instruction manual strongly recommends not to do this by hand as it requires clutches release, possibly generating axis unset. Since Losmandy clutches do not need to be released for manual axis motion, I disregarded this advice. As expected, the reference star of Polemaster neatly follows the green circle when I put back the scope to home position. When I align by Polemaster the mount already aligned by the drift method I find exact coincidence of the two methods, not as time consumption, of course! PHD2 evaluation of alignement precision rates 3 arcsec distance of the true NCP.
      My former expectance with Polemaster was  better precision than with drift align in much less time … well, I get similar precision in much less time. Did I attain the best? Is this residual imprecision I get with Polemaster to be attributed to inherent matters of the mount? Is there any optimization for increasing the precision with Polemaster? Can poor mount leveling affect Polemaster  performance? What about imperfect RA and Dec balance?
      Thank you for advice and suggestions.
      Clear skies,
      Cesco
    • By BUDA
      Hi All!

      I have guiding problem with the following guider setup: 9x50 finder + ZWO ASI 120mm mini + PHD2.
      The imaging scope is a 6' newtonian + canon dslr on a HEQ5, driven by a laptop via diy EQDIR cable.
      When the mount is set up and running correctly, polar aligned and all... I connect the guider camera
      and mount with phd2. All nice and easy, I run a calibration, then it starts to guide. All seems ok.

      Then I am starting to take pictures. The first seems OK, then the second have the star trails...
      I check phd2 and there is a message: the camera (ASI) did not take a picture for "xy" seconds so it is disconnected.
      Grrr.... I reconnect try to set up a longer period for "xy" in the settings as mentioned in the message.
      And all the same again and again. Whatever I add for connection timeout for the camera, it just reaches that
      and disconnect the camera.
      PHD + philips toucam has worked for me flowlessly. I changed to PHD2 because I gave myself a birthday present,
      the little ZWO camera. (and PHD did not recognize it)
      Do you have any idea what can be the problem? I will contact PHD2 help also, but maybe somebody had already
      the same problem and figured out how to overcome. I am almost sure I make some dumb mistake in the PHD2
      software settings, however I tried to change only what was needed.
    • By Coastliner
      Hi All,
      I'm trying to balance my AZ-EQ5 as perfectly as I can, all was going well (all 3 axes) until I added the Polemaster. As this is off-axis it applies torque to the RA causing the axis to rotate until the Polemaster is hanging at the lowest point.
      I need to couterbalance this, any ideas how?
      or,
      Do I need to counterbalance this? Am I being too picky?
      I have considered taking the arm off and gluing the Polemaster onto the on-axis point of the top cover, but again, is this overkill?
      Thanks,
      Neil.
    • By Tom Shinal
      Can Nebulosity and Ph.D operate simultaneously and share a single camera. Running Win 10.
       
    • By Forunke
      Ok, so this is a really annoying bug / problem that I have with my setup:
      From time to time, in non regular intervals the image my guiding cam (ZWO ASI120) send seems to get flipped / mirrored or looks like it's from a completely different patch of sky.
      When I'm paying attention to the guide images I can clearly see that the image seems to be flipped in some way.
      It only happens for 1 frame PHD send a warning ( No star found / Star lost Mass changed) and after that everything is fine again. My gear is all connected to a single USB3 Hub which then runs via powered USB3 cable to my Pc.
      I'm not binning and have the noise reduction off (though PHD might got hickups while processing) but it still happens. Sometimes there are minutes between two events sometimes it happens 5 times in a row.
      It also seems like it's only happening during guiding, I haven't seen it happen during calibration yet...
       
      I'm completely clueless what's happening or how to get rid of it, any help / idea is greatly appreciated.
×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.