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.

sgl_imaging_challenge_banner_30_second_exp_2_winners.thumb.jpg.b5430b40547c40d344fd4493776ab99f.jpg

Recommended Posts

Thank you Ian for such a comprehensive post about PHD :-)

This post will be stickied for immortality!

  • Like 2

Share this post


Link to post
Share on other sites

An excellent guide, should be made a sticky!

I have a little extra for the pot in regard to PHD and finderguiders, the following link contains posts from Craig Stark (the author of PHD) as to the settings that should be used for 50mm finderguiders:

http://www.cloudynig...psed/sb/5/o/all

Also, how to work out whether you're getting backlash. It manifests itself in the form of an slow drift in dec, followed by an overcorrection. If left for long enough you will notice a sawtooth pattern forming in the graph history.

Whoops! Tim beat me to it in the sticky request! :)

Edited by Uranium235
  • Like 2

Share this post


Link to post
Share on other sites

Great write up Ian, many thanks for that!

Unhelpfully in my example, the OSC index is greater than 0.5, which suggests the mount is correcting more in RA in one direction than the other over time. I'm man enough to admit I don’t know what that means!

Could that not be simply refraction towards the lower east or west?

/Jesper

Share this post


Link to post
Share on other sites

Superb guide Ian thanks. Answered a few querys for me :grin:

Steve

Share this post


Link to post
Share on other sites

Fantastic, I'm just about to start with PHD.

thanks

Share this post


Link to post
Share on other sites

Thanks for a great tutorial. I read through it yesterday and although I have been guiding for over a year I but picked up some great tips from this.Last night I got by far the best guiding I have ever achieved,so thanks a lot Ian for taking the time to post this

  • Like 1

Share this post


Link to post
Share on other sites

Hi! I calculated my pixel scale for my guiding rig and I get 4.28" ( Starlight Xpress Lodestar with ST-80). How big should my Calibration Step Size be? 4000?

Share this post


Link to post
Share on other sites

What is a good SNR in PHD?

Hard to say.  Even Craig Stark doesn't really say.  The bottom line is that bigger SNR numbers are better than smaller numbers. So when you are selecting a guide star, setting exposure/gain and focussing the guide scope just pick the combination that gives you the biggest SNR you can find that night.  If you get 'Star Saturated' errors then your chosen star is too bright, the gain/exposure is too high/long or maybe de-focus a tiny amount.  If you get 'Star Lost' errors a lot, then you need to do the opposite and try to get a brighter star, increase gain/exposure or focus better.  Make sure you don't have dew on the guidescope objective and check for high clouds.

Hi! I calculated my pixel scale for my guiding rig and I get 4.28" ( Starlight Xpress Lodestar with ST-80). How big should my Calibration Step Size be? 4000?

Yes I'd say that somewhere between 3,000 and 4,000 is a good starting point for that pixel scale.  Remember 15-20 steps in each direction should give a good calibration.

Share this post


Link to post
Share on other sites

Ok - my SNR is about 25-30 on 0.5s exposures with a QHY5 on a 9x50 finder scope.

Share this post


Link to post
Share on other sites

Hard to say.  Even Craig Stark doesn't really say.  The bottom line is that bigger SNR numbers are better than smaller numbers. So when you are selecting a guide star, setting exposure/gain and focussing the guide scope just pick the combination that gives you the biggest SNR you can find that night.  If you get 'Star Saturated' errors then your chosen star is too bright, the gain/exposure is too high/long or maybe de-focus a tiny amount.  If you get 'Star Lost' errors a lot, then you need to do the opposite and try to get a brighter star, increase gain/exposure or focus better.  Make sure you don't have dew on the guidescope objective and check for high clouds.

Yes I'd say that somewhere between 3,000 and 4,000 is a good starting point for that pixel scale.  Remember 15-20 steps in each direction should give a good calibration.

I've set the Calib. Rate to 3500, but PHD only takes 3-4 steps in each direction. Nevertheless i managed to image for nearly 10 mins without star trails (Perseus Region). Next I slewed to Cepheus and had small trails. I presume that if i lower the rate more steps will be taken, right?

Share this post


Link to post
Share on other sites

I've set the Calib. Rate to 3500, but PHD only takes 3-4 steps in each direction. Nevertheless i managed to image for nearly 10 mins without star trails (Perseus Region). Next I slewed to Cepheus and had small trails. I presume that if i lower the rate more steps will be taken, right?

Right.  Fewer than 7-8 steps is likely to result in a poor calibration.  As you've found, it might work sometimes.  I'd decrease the step size a bit (maybe try 3,000 and see) before you change anything else.

Share this post


Link to post
Share on other sites

I've been thinking about getting into guiding lately and this guide has been the perfect intro. Thank you Ian.

Share this post


Link to post
Share on other sites

Have played with PHD yesterday night. Finally foxed out some settings. I've successfully used ASCOM pulse guide settings and am now calibrating how ever long I want to. Nice to be in control.

I'm now aiming at 15 to 20 steps. My RMS was between 0.12 to 0.32 - nice and smooth graph.

The ST4 settings though fail on me. I've tried all 0.25 to 1.0 settings but none achieve enough movement, so the calibration fails. Confusing, but doesn't really matter. This actually means that I can get rid of my ST4 cable, isn't it?

Share this post


Link to post
Share on other sites

By the by, I now usually calibrate at 0.5s, which usually gives me nice SNR's around 30 or more. This speeds up the process quite nicely as well.

Share this post


Link to post
Share on other sites

Right.  Fewer than 7-8 steps is likely to result in a poor calibration.  As you've found, it might work sometimes.  I'd decrease the step size a bit (maybe try 3,000 and see) before you change anything else.

I changed the rate to 3000 but the steps didn't go over 5. But I tested on more than 10 different regions of the sky for 10 mins each and the stars were perfectly sharp. I even imaged M52 with the Bubble Nebula. Any suggestions or should I leave at as it is?

Share this post


Link to post
Share on other sites

I changed the rate to 3000 but the steps didn't go over 5. But I tested on more than 10 different regions of the sky for 10 mins each and the stars were perfectly sharp. I even imaged M52 with the Bubble Nebula. Any suggestions or should I leave at as it is?

As I said in the guide "If it ain't broke, don't fix it!"  If you are getting reliable guiding at 5 steps then leave things as they are.  Calibration is a means to an end, not the objective.

If you do run in to trouble later, then try reducing the step size more until you get the recommended 10-15 steps, but don't fiddle with it for no particular reason; plenty of other problems to solve further down the line so get on with imaging.

Share this post


Link to post
Share on other sites

You'll get more steps if you change the EQMOD pulse guide settings from 0.9 to 0.1 and go down from 50ms to 20ms.

Unless you're guiding per ST4, then you'd reduce the rate from 1x to 0.25x

Share this post


Link to post
Share on other sites

Hi Lan,

Thank you very much for this excellent and detailed instruction guidelines.

I plan to implement some (or all) of the above during my next observing session, as my gear for guiding is ready for setup.

The only Q I have is regarding the SW installation procedure, as I got confused by the various components mentioned...

i.e. PHD app., ASCOM app., EQMOD drivers, manufacturer drivers etc.

Can you comment and advice on what is necessary to install (Win 7) and in what order?...

I use NEQ6 and plan to attach the Orion's StarShoot cam connected to a separate small scope fixed to the side of the OTA.

Thanks,

Romi

Share this post


Link to post
Share on other sites

Hi Lan,

Thank you very much for this excellent and detailed instruction guidelines.

I plan to implement some (or all) of the above during my next observing session, as my gear for guiding is ready for setup.

The only Q I have is regarding the SW installation procedure, as I got confused by the various components mentioned...

i.e. PHD app., ASCOM app., EQMOD drivers, manufacturer drivers etc.

Can you comment and advice on what is necessary to install (Win 7) and in what order?...

I use NEQ6 and plan to attach the Orion's StarShoot cam connected to a separate small scope fixed to the side of the OTA.

Thanks,

Romi

I am assuming you are using the standard Orion Starshoot Autoguider (http://www.telescope.com/Orion-StarShoot-AutoGuider/p/52064.uts)?

Are you using the handset to control the mount, or are you using EQMOD?  (EQMOD runs on a laptop and replaces the handset for all mount control operations.  You would typically have an EQMOD adaptor plugged in between the laptop and the mount's handset port if so).

I haven't used a Starshoot, but roughly speaking if you are using the handset you would set things up as follows:

- Install PHD guiding.

- Install the camera drivers from the supplied CD.

- Connect the Starshoot's USB port to the laptop and complete the set-up procedure.

- Connect the camera's ST4 port to the mount's ST4/auotguider port using the supplied ST4 cable (looks a bit like a telephone cable).

- You'd then press the camera button to connect to the camera in PHD and select the Starshoot Autoguider from the camera driver list.

- You would then select 'On Camera' from PHD's 'Mount' menu and then press the mount button to connect.

Guiding commands will be sent from PHD via the camera through the ST4 cable directly to the mount.

On the other hand if you are using EQMOD, then it is a bit more complicated:

- You'd need to download the ASCOM V6 platform (http://ascom-standards.org/) and install it.

- Then you'd need to download EQMOD (http://eq-mod.sourceforge.net/) and install it (specifically the EQASCOM software, everything else is optional).

- Installing and setting up EQMOD is a bit beyond what I can cover in this post - there are manuals on the site and plenty of guidance.

- You would then need an EQDIRECT adaptor to replace the handset (or use the handset in PC Direct Mode, but this is unsupported).  Details here http://eq-mod.sourceforge.net/reqindex.html.

- Most likely you'd also want a planetarium (either Cartes du Ciel http://www.ap-i.net/skychart/start, or Stellarium http://www.stellarium.org/ AND Stellariumscope http://www.welshdragoncomputing.ca/ ), plus you'd probably also need a gamepad to control the mount via EQMOD (this is optional as you can use the buttons on screen, but it does make life a lot easier).

- Once you have set up EQMOD and learned how to use it, which is probably several days of effort in its own right, then you can get on with guiding.

- You'd install the Starshoot drivers, connect the camera USB and connect to the PC as above.

- What is different this time is that you would select 'ASCOM' from PHD's 'Mount' menu, press the mount button and select your NEQ6 as the mount.

In this scenario the guiding commands are sent via software from PHD through ASCOM to EQMOD, which processes them and sends the instructions via the EQDIRECT connection to the mount.

As you can see, the ST4 option is the simplest way to get started, as there is far less software to install, test and learn.  If you already know how to use the mount handset then I would go down the ST4 route to get started since you'd have far less to learn and worry about at this stage.

EQMOD is a really good way of controlling the mount as it opens up lots of other options (such as using a planetarium to find and slew to targets, or using Astrotortilla to do plate solving and find them automatically, etc.).  EQMOD has now got a new AutoPEC feature which makes it simpler to set up PEC without needing to use external software to record and analyse the mount's period error.  In the long run EQMOD is definitely worth the effort to learn, but there are definitely more things to go wrong up front.

Share this post


Link to post
Share on other sites

Great explanations Lan !!

I do use the handset and not the EQMOD at this stage (and bought the standard Orion Starshoot Autoguider as you mentioned above).

So, (only to make sure I understand the whole thing):

1. If I use the handset on the mount (e.g. SynScan), which is the way I currently work, I should connect the ST4 cable from the cam to the mount (should I still connect

   the USB cable?) and set the PHD to "on Camera",

2. If (in the future) I would start controlling the mount with EQMOD (following your instructions in this regard), then I should connect the USB (do not connect the ST4)

    and select 'ASCOM' from PHD's 'Mount' menu etc.

You have truly simplified the technical process for me here.

Thanks a lot.

Romi

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 gustavo_sanchez
      Hello to all,
      It would be great if any of you can give some insight on how to solve my current problem, which is that I cannot achieve round stars in exposures longer than 3 minutes. Less than that, I get round stars. First of all, my setup:
      Imaging scope: Meade SN-6 (762mm FL, f/5)
      Imaging camera: Atik 314L+ CCD
      Guiding scope: Celestron TravelScope 70 (400mm FL, f/5.7)
      Guiding camera: Orion SSAG (with GSO 0.5x Reducer threaded directly to 1.25" nosepiece)
      Mount: Orion Sirius EQ-G
      I am attaching my PHD Guiding Advanced Settings, hoping that anyone can suggest any changes to the existing parameters. I consider my polar alignment good, and use the 3-Star Alignment option. With these parameters, the guiding graph in PHD looks very good, without big spikes or strange jumps. Both RA and DEC lines look fairly flat and smooth.
      Let me add that using these parameters, I can achieve 10 minute exposures (more than enough for me) using my William Optics GT81 (478mm FL) instead of the Meade SN-6, and my 50mm finder guider instead of the TravelScope and GSO Reducer.
      Any help will be very appreciated.

×
×
  • Create New...

Important Information

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