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Drift Alignment with PHD2 - The Bookmark Technique

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#26 Jeff2011

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Posted 21 August 2014 - 09:11 AM

I was going nuts looking for this thread until I realized it was pinned.  I am glad, however, that it is pinned.

 

I tried this last night with my AVX.  One thing I discovered was that my ASPA put me close requiring only a small adjustment rather than the adjustment that PHD2 suggested with the magenta circle. 

 

Jon was right about very small adjustments making a big difference.  Fortunately I did not run into any issues adjusting the Alt/Az and elevation knobs.  I guess the AVX is light weight enough to where these could be easily adjusted.  I am sure the big knobs also helped. I think this was one of the redesigns when they came out with the AVX.   My horizons are obstructed by my house and garage, but I was able to drift on a star in my eastern horizon that was at an elevation of 12 degrees.

 

I messed with this for over an hour.  I imagine I will get better with practice.   After doing the drift align, I took a 10 minute test sub with dec guiding turned off and got reasonably round stars.  This will help me do narrow band if my dec guiding starts acting up.

 

Oh, and I did guide through Ascom instead of ST-4.

 

Thanks again Jon for taking the time to put this tutorial together.

 

 

 

 

 



#27 NicholasP

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Posted 21 August 2014 - 09:21 AM

This is my favorite topic at this time...because i am a beginner and just getting involved with learning the drift alignment......My question is:

 

''Prior to drift alignment you must calibrate PHD2 , does that mean that you must find the correct settings for your mount as if perfect guiding, or, it doesn't mind for drift alignment ???''

 

Thanks.

Nikolas



#28 Jeff2011

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Posted 21 August 2014 - 09:32 AM

I don't know if there is such a thing as "perfect guiding".   There is good guiding and poor guiding.    For my setup,  good guiding is anything less than 1 arc second RMS.  I recommend getting your guiding working  first before attempting a drift alignment.  On the graph,  PHD2 will show numbers in arc seconds if you enter the focal length of your guide scope and pixel size of your guide camera in the 'brain' settings. 



#29 NicholasP

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Posted 21 August 2014 - 09:35 AM

So, i can not do it, if for example, i have the default guiding settings in PHD...????

 

Nikolas.


Edited by NicholasP, 21 August 2014 - 09:35 AM.


#30 Alex McConahay

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Posted 21 August 2014 - 09:54 AM

>>>>>'Prior to drift alignment you must calibrate PHD2 , does that mean that you must find the correct settings for your mount as if perfect guiding, or, it doesn't mind for drift alignment ???''


Nikolas,

To calibrate, you do not need to know the "perfect" settings. Just set it up with the defaults, grab a shot with the capture loop ikon, pick a star by clicking on it, and Press Here Dummy on the Phd ikon. The software will guide the mount through the calibration routine, and you should be calibrated enough to do the drift alignment.

After that, you can go off looking for the "perfect" settings for your rig. As has been pointed out, there are no perfect settings, but they can be optimized if you fiddle and experiment.

Alex

#31 NicholasP

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Posted 21 August 2014 - 10:40 AM

Vanguard, thanks for your answer.....its clear !!

 

Nikolas  :waytogo:



#32 Jon Rista

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Posted 21 August 2014 - 11:09 AM

Yup, Alex nailed it. Calibration is an actual PHD2 thing...it will move the guide star by a little bit in RA up to a specified step count, then move it back in RA, then move it a little bit in DEC up to the same specified count, then move it back in DEC. That lets PHD2 know the orientation of the guide camera sensor to the orientation of the mount. That way, it knows when the star is moving in RA vs. moving in DEC, so it can send the right kind of guide pulse to the mount. You have to have calibration done first, before you will be able to do drift align, as PHD will still guide in RA while drifting in DEC. 


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#33 Jon Rista

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Posted 21 August 2014 - 07:14 PM

I have pinned this topic as a sticky.  I think the topic will be of use to many new to autoguiding so this will be easily available toward the top of the list.  At some point if this is not used regularly, it will be unpinned and back to a normal topic.


Thanks! I'm glad people found this so useful. I hope it helps alleviate polar alignment problems for a lot of beginners...it's been a huge bonus for me, and having better PA has definitely helped improve the precision of my guiding. I can usually sleep through the night and just let the system image on it's own now, too, which is the best thing ever! :D

Jon, at the bottom of your first post, there is a comment of (Image here).  If you have it and can add it in, that would be great.  If is has been too long and you can't edit that post, if you will post it with instructions, I would be glad to add it in.

 
Sorry, I did not see these until now. It does appear as though the post is not editable...however, I don't remember what image I had planned to put there before. I'll see of I can remember what it was...but for now, you can just remove that (Image here) thing.

#34 17.5Dob

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Posted 21 August 2014 - 08:26 PM

I was going nuts looking for this thread until I realized it was pinned

 

 

+1

 

Thanks for putting this together, Jon !

I am about to step out of the stone age (or is the dob age) and get my auto guider set up. My very first laptop arrived yesterday, my USB to serial cable with the EQ mod is on the way, and thanks to Puck Ja for buying my TOAG, I have a mini 50 on the way as well. The QHY5L II shipped today (it's only $299 at Astrofactors right now) so I'm sure it will be cloudy again for the next month.



#35 torsinadoc

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Posted 24 August 2014 - 11:44 AM

awesome.  I tried PA with PHD last night and was just lost.  I can't wait to retry it. Much appreciated!



#36 torsinadoc

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Posted 24 August 2014 - 05:52 PM

PART 2: Getting started

 

First things first, you need to get PHD2 ready to use for drift alignment. You will need to start it up, point at a star near the

meridian and celestial equator (for azimuth alignment, which the drift align wizard defaults to on startup), and calibrate PHD.

Calibration must be performed before doing drift alignment. If you forget to calibrate, the drift align wizard will only

momentarily display a message in the status bar indicating that calibration is required for the wizard to work.

 

After calibrating, choose a high SNR star (over 10) within the middle quarter of the frame. It is important to choose a star

here, as when you start adjusting, the star can move in any direction in the frame, by as much as a quarter of a frame initially.

Picking a star near the edge could result in adjustments moving the star right out of the frame.

 

fGW0Wvb.jpg

 

Before starting the drift alignment wizard, you should make sure that bookmarks are enabled (shown), and that you delete any

existing bookmarks. This will assure that you don't end up confused abot which bookmarks mean what (especially if you had tried

to drift align earlier, and ended up needing to repoint the mount.) It probably goes without saying, but saying it anyway for

good measure: Make sure you are pointed a bit ahead of the meridian, and any of your mount's stop limits, so you have time to

perform drift alignment without running into a meridian or horizon limit during the process. It also helps to make sure that

there are no trees or other obstructions that might find their way into the frame while your aligning.

 

Finally, set your exposure time to 1 second, so you can see an immediate response to any adjustments you make. It also helps to

set the history period to 200 ticks, and the y axis to 8. I've found that these settings are best for early drift checks...later

on, when you require longer drift checks, you might want to up the period to 400 ticks.

 

k60dsrT.jpg

 

Once all the above things are done, your ready to start the drift alignment wizard. You can find it in the Tools menu, Drift

Align. You should see a window like this appear when clicking on that menu option:

 

rTsojEr.jpg

 

The Scope Pointing feature will only be accurate if you are using ASCOM Pulse Guiding. If you are using an ST-4 cable to connect

your guide camera to the ST-4 guide port on your mount, the information here will not be accurate. If you are using ASCOM Pulse

Guiding, you can even control your mount from within the PHD2 drift align window, and it will show you how close you are to the

meridian and celestial equator, making it very easy to get right on top of it for really good drift check.

 

 

How do we change the workflow if we are using ST-4 cable to connect to the mount? I guess a better question is how do I  know if I am using ASCOM pulse guiding or  set up the Orion SSAG for ASCOM pulse guiding ?


Edited by torsinadoc, 24 August 2014 - 06:10 PM.


#37 telfish

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Posted 24 August 2014 - 10:40 PM

Jon. 

 

I managed to get my Az down to fine limits then started on Altitude. Can you confirm that I need to still get the Dec line flat while adjusting altitude and not the RA Line.

 

Thanks Terry



#38 nitegeezer

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Posted 25 August 2014 - 12:18 AM

 

How do we change the workflow if we are using ST-4 cable to connect to the mount? I guess a better question is how do I  know if I am using ASCOM pulse guiding or  set up the Orion SSAG for ASCOM pulse guiding ?

 

 

I am new at this also, but I believe this is correct:

 

When you click on the camera in the lower left portion of PHD, it will open a configuration window.

 

When you select the mount, if you select "On Camera" then you are using the ST-4, otherwise you are using ASCOM.

 

The Orion SSAG does not generate the ASCOM commands, that would be coming from the computer and going directly to the mount.



#39 Jon Rista

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Posted 25 August 2014 - 02:20 AM

Hi guys. To switch from using ST-4 to ASCOM for guiding, in PHD, you need to stop guiding, then click the Camera icon in the bottom toolbar to the lower left. That brings up the dialog you use to pick the things to connect to. If you were using ST-4, then the mount will be "On Camera". To switch to ASCOM Pulse Guiding, change the mount from "On Camera" to whatever your mount is, or, if your mount is not listed, pick the ASCOM Chooser, which will then open up the standard ASCOM Mount chooser window where you can pick it. Once you have picked your mount, click connect all, and PHD should directly connect to both the guide cam and the mount, ignoring any ST-4 cable if one is still attached.

 

@Terry: Yes, all drift is done in declination. The full and proper name for drift alignment is actually "Declination Drift Alignment", since it is drift in declination that your watching for. Drift may occur in RA, but you should generally ignore that when doing drift alignment, since the mount will normally be tracking in RA anyway, counteracting any "RA Drift". You should only be concerned with movement in declination. PHD should be guiding RA while you are doing drift alignment, so your adjustments should not really be affecting the RA tracking. Even if PHD stops guiding RA, the key is to get the graph flat in declination. 



#40 telfish

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Posted 25 August 2014 - 07:21 AM

Thanks Jon.

 

Appreciate the confirmation.



#41 NicholasP

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Posted 26 August 2014 - 06:21 AM

Guys, one stupid question :)

 

when the drift align shows me -25 degrees or +25 degrees.....it means North South East West ??????

 

Nikolas.  :flowerred:



#42 Jon Rista

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Posted 26 August 2014 - 12:07 PM

I think it depends on which side of the mount your on, and how you calibrated. You have to experiment to figure out which direction the knobs move the star. You can easily do that by setting a bookmark, making a largish move, and seeing what happens to your drift.

#43 torsinadoc

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Posted 26 August 2014 - 12:28 PM

Followed the tutorial.  I had PA prior of 0.1 so I had to mess it up a little to retry with PHD2.  I was able to get it back with drift. Book marks and making notes (how many turns in which direction) helped. 



#44 Jon Rista

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Posted 28 August 2014 - 11:15 PM

I don't even bother taking notes these days. Tonight, I managed to dial in 0.2' in one bookmark and two moves. Bookmarked after the first drift, made a move...drift was worse. Made a move about twice as big the opposite direction, and that was it. I had a PA that I was happy with...mostly because the dec plot in PHD2 stayed pretty much flat after letting it drift for nearly five minutes. Total amount of time spent actually drift aligning was about 2 minutes today. :D (I spent the rest of the time, while I let it drift, looking up my other crescent images to figure out what my centering needed to be.) More luck than anything, but I thought I'd mention it...as once you get this technique down, you really don't have to spend a lot of time on it to get a really good PA, one that minimizes your DEC guide RMS to the point where it pretty much doesn't matter much.

#45 egratudo

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Posted 03 September 2014 - 02:37 PM

I hope this isnt a silly question. I am fairly new to this hobby. How important is it to perfectly align my guide scope to the main scope? Would i get a better drift alignment if i hook my SSAG directly to my C9.25? Or is it neccessary to have the SSAG on my guidescope?



#46 Jon Rista

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Posted 03 September 2014 - 02:40 PM

Good PA reduces one more thing you have to hassle with. You'll never get it perfect, but you can get it very good, and not with a lot of effort.

 

Regarding where to put your SSAG, if your using and external guide scope, put it on that. If you are using OAG, then put it on the OAG. You should not remove your regular imaging camera and put the SSAG directly on the telescope...it's probably best to polar align with whatever guiding setup your actually going to use. 



#47 torsinadoc

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Posted 23 September 2014 - 03:21 PM

I have been getting quicker with this technique.  I have a stupid question. When do I adjust the altitude knobs?  I assume it is during the altitude adjustment after completing the first part of the drift. 



#48 Jon Rista

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Posted 23 September 2014 - 05:45 PM

Yeah, there are two phases to full drift alignment. By default, the PHD drift align wizard starts out in Azimuth mode. Once you get that dialed in, you switch to Altitude. There is a button in the dialog that pops up for the drift wizard that says "Altitide >", just click that to get to the second phase. 



#49 greathouse670

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Posted 15 November 2014 - 12:50 PM

This is awesome.  You know, I struggled with manual drift alignment for some time until I figured it out. I spent over an hour at times and then even wasn't quite there (I have a blocked horizon in both the east and the west).  This is sooooo much easier for me.  There is a bit of a learning curve at first but once you get it, it's not bad at all.  The first time I had good alignment I was looking at the screen in disbelief thinking, "is that it?"  It was.  



#50 daw316

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Posted 16 November 2014 - 07:37 PM

Thanks for the tutorial!  Just started using PHD2 for polar alignment a couple days ago.  Now I have quite a few great new tricks and tips.

 

It seems too good to be true.  I have a limited view, so use the southern most and eastern most stars I can see, but it seems to be working great.




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