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Old 15-08-2009, 08:40 PM
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EQ6 Track Speeds

Hi all

I have got my new EQ6 Pro out for the first time and have a question regarding track speed. After several hours of balancing and aligning and testing and aligning again, I think I finally have it pretty close. But it appears that it is tracking a bit too fast - there is drift in the RA axis.

In the handset setup, there is an option to "Set tracking". By default, this is set to Sidereal Rate which seems to be right.

So how do I slow it down? Or is this not possible and I do it through guiding?

Thanks
Darrell
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Old 16-08-2009, 08:17 AM
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Hi Darrell, I'd check my polar alignment. Have you drift aligned?
Peter
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Old 16-08-2009, 01:43 PM
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Peter

Well, the whole drift alignment / polar alignment question was going to be another thread. I thought I had it pretty well worked out with my trusty EQ5. But now... I am not so sure.

I have been doing the long exposure drift test. Normally, I set the tripod and balance. Then aim at a convenient star, using Fomalhaut at the moment. Then I set the EOS to bulb, drift for 1 minute to the west (RA numbers decreasing), then come back to the east for 50 seconds. I compare the resulting lines and done.

Then what I like to do, once alignment is complete and tracking underway, is centre on a star and take a shot. I then leave everything sit for a period of time (typically 30 minutes or 1 hour depending on what I am going to do) then take another shot. I overlay the two exposures and see how much drift there has been during the period. With my EQ5 I could get pretty close. Well, close enough for me anyway.

Rather than use a lot of words, have a look at the attached. It is three shots combine in RGB. All three shots were taken using Fomalhaut.

The Blue line is my two minute drift exposure. Lines up okay.

The Green star represents the first shot in the series. The Red star is the second shot taken 30minutes later.

There is a bit of Dec drift, but I can fix that. If I am reading all this right, the "bad" drift is in RA. This is what has me perplexed.

The weather looks like it is going to be good here tonight, so I am going to have another play with it and see how I go.

Any comments, suggestions would be appreciated.
Thanks
Darrell
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Old 16-08-2009, 07:40 PM
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Peter

I'm much happier now. Have a look at the attached. Same details as the first pic - Blue is the 2 minute drift test. The Green star is the first shot. The Red star is the second shot 30minutes later.

It looks much better than the combo image from yesterday. I suspect it may have been a weight issue (distribution). Does that sound feasible?????

Anyway, it looks like I now only have a Dec problem. I am still a bit confused by this. I would have thought that since the drift returned a pretty close result, the Dec axis would not have been out at all.

Am I missing something?

Thanks
Darrell
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Old 16-08-2009, 08:02 PM
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I think it's your polar alignment still, not the weight. Are you using one or two stars to check your alignment? Remember you need to check a star low in the east (or west) and another star up near where the meridian and celestial equator meet.


With practice, drift alignment can be surprising fast. If you are taking 30 min images, drift alignment will be much faster for sure. I watch the star and as soon as I see it moving, I move the mount. No need to wait 5 minutes, then come back and check. If I see it move after 1 or 2 minutes, then I move it then.

Last edited by Moon; 17-08-2009 at 06:37 AM.
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Old 17-08-2009, 06:25 AM
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I only use the one star to actually check the alignment. Normally one about 45degrees up in the east. So two would be better!!? I will give it another go tonight.

But just to clarify one point. In the picture I attached, the two minute long exposure drift I did resulted in a very close lineup of the west then east lines. (Not perfect, but pretty damn close.) So I thought my alignment must have been very good. But then I still seemed to get a fair amount of drift on the dec axis, as indicated by the two shots of the same star 30minutes apart. I wouldn't have thought that would happen.

I will see what happens tonight.
Thanks
Darrell
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Old 17-08-2009, 06:53 AM
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Using 2 stars is better. It's helps isolate if you need to adjust Azimuth or Elevation. Therefore you are only adjusting one direction at a time (either the left/right knobs or the altitude bolts)

If you are only using 1 star at 45 degrees, the drift will not be as pronounced and you will need to wait longer to see the drift. Also I think it could get more confusing.



The method I adopted for my setup is really simple.
  • Use the Left / Right arrows on the keypad to determine Left / Right. Rotate the illuminated reticle eyepiece to be in alignment with the way the star moves.
  • Azimuth: Use Star on Meridian. If the star drifts UP adjust Azimuth to move the star LEFT
  • Elevation: Use Star in West. If the star drifts UP, adjust Elevation bolts to move the star UP.

Last edited by Moon; 17-08-2009 at 10:24 AM.
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  #8  
Old 17-08-2009, 08:20 AM
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Quote:
Originally Posted by darrellx View Post
I only use the one star to actually check the alignment. Normally one about 45degrees up in the east. So two would be better!!? I will give it another go tonight.

But just to clarify one point. In the picture I attached, the two minute long exposure drift I did resulted in a very close lineup of the west then east lines. (Not perfect, but pretty damn close.) So I thought my alignment must have been very good. But then I still seemed to get a fair amount of drift on the dec axis, as indicated by the two shots of the same star 30minutes apart. I wouldn't have thought that would happen.

I will see what happens tonight.
Thanks
Darrell
Hi Darrell, before I start this rather largish comment, my apologies in advance if I'm intruding on this thread, but my comments and questions also refer to drift alignment of an EQ6, so rather than start another thread..... Please let me know if I should.

I have also just finished a week of learning to drift align my EQ6 in Brisbane, where the night skies have been clear for some time. Like Darrell, for simplicity I decided to just use one star, basically in Crux, as they're bright and in a convenient direction for the scope.

I use a SP900NC webcam on my ED100 with wxAstrocapture, which has a screen reticule. Each night, I spent about two hours adjusting and checking. I've got alignment down now to minimal drift (zero?) for at least 10 minutes. Attached is a pic of general Milky Way area at/near Zenith last night, 6 min exposure with EOS 1000d just for alignment drift check.

Would you be so kind as to comment on whether you think the stars are adequately rounded for that length of unguided exposure. I'm just a newbie and have no idea if they're acceptable. It's actually my first star photo. Up until now it's been planets and moon.

My post is to comment on the confusion factor as mentioned by James. I had it in large doses, especially when coming back the next night to continue the alignment checks.

James' simplified two-star description seems very easy for me to remember, most other two star descriptions left me a bit confused, so I'd like to thank James and I'll also test it tonight.

BTW, on a slightly seperate subject, it was really nice to finally be able to sit inside the house and control CDC, EQMOD, the mount and camera all with confidence, using Remote Desktop. That also was just a trial
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Last edited by mldee; 17-08-2009 at 08:21 AM. Reason: spelling errors
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  #9  
Old 17-08-2009, 08:34 AM
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For a 6 minute exposure, it looks really good to me.

I think with just a small amount of practice, you will be able to get aligned much faster than 2 hours, no matter which technique you use.

I orginally started off trying to use a web cam to get aligned. Then I bought a illuminated reticle eyepiece. For me it's so much faster, intuitive and easier all round.
Of course your mileage may vary, but my main point is to stick at it. It gets easier and easier each time. Before you know it, it's second nature.
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Old 17-08-2009, 09:22 AM
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For a 6 minute exposure, it looks really good to me.

I think with just a small amount of practice, you will be able to get aligned much faster than 2 hours, no matter which technique you use.

I orginally started off trying to use a web cam to get aligned. Then I bought a illuminated reticle eyepiece. For me it's so much faster, intuitive and easier all round.
Of course your mileage may vary, but my main point is to stick at it. It gets easier and easier each time. Before you know it, it's second nature.
Thanks for the comments, James.

I'll let Darrell get back to his thread now, and I may start another on "Why I like to use webcams for drift alignment"
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Old 17-08-2009, 10:11 AM
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Mike
No problems at all. Please intrude, I am trying to learn as much of this as I can. It actually helps me when I realise I am not the only one going through this. It can be so frustrating.

I hadn't thought of using a web cam. I do have an illumiated reticle, but I have put off using it. I am still not sure how to line up the lines properly and I thought it may confuse me even more. I might have to bite the bullet on that one.


James
Thanks for the simplified steps you have listed. I will try this tonight and see how it all goes. This will be three long nights in a row trying to get this worked out. I hope it happens soon.

Thanks
Darrell
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Old 17-08-2009, 10:35 AM
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I hadn't thought of using a web cam. I do have an illuminated reticule, but I have put off using it. I am still not sure how to line up the lines properly and I thought it may confuse me even more. I might have to bite the bullet on that one.


I edited my post above to make this bit clearer. Use the left / right buttons on the hand controller to move the star left/right. Then rotate the illuminated reticule eyepiece so that the star moves along one of the lines. This line is now your 'left' / 'right' axis. Now it should be obvious which way is UP (12 O'clock or North) and DOWN (6 O'clock or South). I find it easier to position my diagonal / body / eye so that I'm oriented correctly as well.

You may have to reverse the instructions I gave if your setup has a different number of mirrors to mine (odd), but this is a once off adjustment.
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Old 17-08-2009, 12:25 PM
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Mike
No problems at all. Please intrude, I am trying to learn as much of this as I can. It actually helps me when I realise I am not the only one going through this. It can be so frustrating.

I hadn't thought of using a web cam. I do have an illumiated reticle, but I have put off using it. I am still not sure how to line up the lines properly and I thought it may confuse me even more. I might have to bite the bullet on that one.


James
Thanks for the simplified steps you have listed. I will try this tonight and see how it all goes. This will be three long nights in a row trying to get this worked out. I hope it happens soon.

Thanks
Darrell
Thanks Darrell.
Since you mentioned webcams......As James said, YMMV, and I had previously bought a 12mm illuminated reticle EP, but found it way too bright, and very inconvenient to be squinting into, especially while adjusting the mount to bring the target star back on track if the scopes pointing high.

I was also underwhelmed with webcam resolution, but eventually read a thread on how to set that up, and then the webcam gives a nice usable white star dot on the lappie screen. A screen reticule then is far easier to follow than the EP one, for an old creaker like me at least!

The little webcam also doesn't get in your way as much as (say) using liveview from my Canon, so for me, the combination of James' methodology and my webcam setup will be tried again tonight, although as I mentioned I'm pretty happy with my present alignment done on one star, it just takes a lot more time and chance of confusion.

PS, If you use a webcam, make sure your finder scope is well aligned on the target star before you start, so it is easier to slew back into the webcam field of view if you move the mount too far.

Good luck.

Last edited by mldee; 17-08-2009 at 12:31 PM. Reason: replaced guide scope with finder scope. Duh.
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Old 17-08-2009, 01:13 PM
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Thanks for all the pointers. Maybe tonight is the night.

But I have had a thought while pondering all the points you have raised. I have a fairly fundamental question for you.

James, you said earlier, "I watch the star and as soon as I see it moving, I move the mount." This suggests to me that you might just rotate the base of the mount to correct any Dec error in the alignment. Would this be right? Do you leave the scope pointing at the star and make the adjustments?

What I have been doing after the drift alignment is estimate how much adjustment needs to be done, then park the scope. Make any adjustments, normally by rotating the base on the tripod, and finish by making sure the scope and counterweights are sitting square. Then start the process over again.

Darrell
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Old 17-08-2009, 01:38 PM
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I look at how fast the star is drifting and then move the mount (either in Alt or Az) a corresponding amount. Usually I just uses the bolts to move it. If it's drifting really fast, then let's say one turn of the bolt moves the star the width of the FOV, I might do 3 turns, so the star is no longer visible in the FOV. Then I move the star back into the FOV with the hand controller. It's not a problem because I know which direction that star has moved, so it's easy to relocate it again. If it's only drifting slowly and I thing I'm getting close, then maybe only 1 or 1/2 turn. The the star stays in the FOV and it really fast to get it back in the centre and begin the next iteration.

No need to park the scope or physically move the tripod (less you are way way out). I'm never too far out when I set up at home because I have 3 marks on the ground to get the tripod roughly in the same spot each night, also I don't touch the Alt bolts when I pack up for the night. So it's also pretty close for the next time I use the mount.

Quote:
and I had previously bought a 12mm illuminated reticle EP, but found it way too bright, and very inconvenient to be squinting into, especially while adjusting the mount to bring the target star back on track if the scopes pointing high.
I had all sorts of problem with my illuminated reticule EP until I got the PulsGuide Pulsing Eyepiece Illuminator . This thing is one of the best astro investments I ever made. I can't recommend it enough!
The other thing I do is use a 1 1/4 inch diagonal to make the viewing position comfortable.
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Old 17-08-2009, 03:38 PM
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James

I realise that I am moving away from the topic of the thread, but since we have already moved onto this, I figure it is okay. The illuminated reticle.

How do you align the reticle (the lines) to the axis of the scope and mount? Everything I have read so far seems a bit of a nonsense to me. The articles seem to be saying; centre a star; use the hand controller to move the star to the edge of the field; rotate the reticle.

I just can't work it out.

Thanks
Darrell
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Old 17-08-2009, 04:04 PM
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Ok I will try to explain without pictures!
Let's say you look in the eyepiece and you see an X (two diagonal lines)
Then using the hand controller, move the scope so there is a star in the center of the X.
Now press the 'right' arrow on the hand controller.
To keep this example simple, let's say the star moves from the center of the X to the right hand side. (i.e. the 3 O'Clock position)
So this means your eyepiece is not aligned correctly. How to fix it? Just loosen the eyepiece and rotate it 45 degrees so it looks like a +
Now the star is at the tip of the right hand side of the plus symbol. Now you are aligned correctly!

Using the hand controller, press the left arrow and the star will move back to the center of the +. How do I know this for sure? That is you home work .

Summary - (just like you said) put the star at the centre of the cross hairs.
Move the star in one direction using the hand controller until it get near the edge of the field of view.
Now rotate the eyepiece until the star is on any of the lines.
If you have been using the left/right buttons to move the star, then this is the basis for the polar alignment instructions I gave above. Forget about North/South/Dec/RA etc. Just work on UP/DOWN/LEFT/RIGHT.

Do it a few times and it's very easy. First few times, yes it's painful.
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Old 17-08-2009, 05:11 PM
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Ok I will try to explain without pictures!
Let's say you look in the eyepiece and you see an X (two diagonal lines)
Then using the hand controller, move the scope so there is a star in the center of the X.
Now press the 'right' arrow on the hand controller.
To keep this example simple, let's say the star moves from the center of the X to the right hand side. (i.e. the 3 O'Clock position)
So this means your eyepiece is not aligned correctly. How to fix it? Just loosen the eyepiece and rotate it 45 degrees so it looks like a +
Now the star is at the tip of the right hand side of the plus symbol. Now you are aligned correctly!

Using the hand controller, press the left arrow and the star will move back to the center of the +. How do I know this for sure? That is you home work .

Summary - (just like you said) put the star at the centre of the cross hairs.
Move the star in one direction using the hand controller until it get near the edge of the field of view.
Now rotate the eyepiece until the star is on any of the lines.
If you have been using the left/right buttons to move the star, then this is the basis for the polar alignment instructions I gave above. Forget about North/South/Dec/RA etc. Just work on UP/DOWN/LEFT/RIGHT.

Do it a few times and it's very easy. First few times, yes it's painful.
Good words. Basically adjust with the mount bolts then return to centre with the hand controller. And there's always the final check on your progress: Put the star in the centre of the crosshairs, (EP or Lappie), have a cup of coffee and see if it moves.
Oh, BTW, if you use a webcam, obviously you don't rotate the EP to adjust the reticle, you rotate the webcam. My apologies again if I insult your intelligence. "Just trying to help, based on my stupid mistakes"

Last edited by mldee; 17-08-2009 at 05:15 PM. Reason: added rotate webcam
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Old 17-08-2009, 05:13 PM
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James

I have some heavy cloud moving in here at the moment. Can I get an extension on the homework til Wednesday?

Everything you have said makes sense, to a point. And is quite clear. But there is just one point of contention. Regardless of how the scope is aligned in relation to the pole, these steps would work but I don't see how it helps to polar align.

Just say you had the mount perfectly aligned. And lets say that points to 182 degrees (a little bit to the right of magnetic south). The centred star will move to the edge of the FoV and look good.

But lets say you were not perfectly aligned and were pointing at 184 degrees (to far to the right). Or even 183 degrees - 1 degree off. The centred star will still move to the edge of the field of view and look good. The star will still line up in the reticle or rather on the lines in the reticle as I rotate the ep. If I press the opposite arrow to move the star back to the centre it will move there okay.

Ah, hang on; hang on. IF you are not aligned properly the star will drift away from the lines as you try to move back to the centre. Okay, that may be where my confusion is. I thought you used the reticle STARTING from the middle and let the star drift as it moved to the outside of the FoV. But there is no frame of reference for that. Do you check the drift as the star moves from the OUTSIDE back to the middle? Yes, this would work.

I am still going to press the post button here after all this typing. Even though I feel I should cancel; go away and try this then come back.

Sorry to be painful about all this. I just seem to have a mental block.
Darrell
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Old 17-08-2009, 05:32 PM
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James

I have some heavy cloud moving in here at the moment. Can I get an extension on the homework til Wednesday?

Everything you have said makes sense, to a point. And is quite clear. But there is just one point of contention. Regardless of how the scope is aligned in relation to the pole, these steps would work but I don't see how it helps to polar align.

Just say you had the mount perfectly aligned. And lets say that points to 182 degrees (a little bit to the right of magnetic south). The centred star will move to the edge of the FoV and look good.

But lets say you were not perfectly aligned and were pointing at 184 degrees (to far to the right). Or even 183 degrees - 1 degree off. The centred star will still move to the edge of the field of view and look good. The star will still line up in the reticle or rather on the lines in the reticle as I rotate the ep. If I press the opposite arrow to move the star back to the centre it will move there okay.

Ah, hang on; hang on. IF you are not aligned properly the star will drift away from the lines as you try to move back to the centre. Okay, that may be where my confusion is. I thought you used the reticle STARTING from the middle and let the star drift as it moved to the outside of the FoV. But there is no frame of reference for that. Do you check the drift as the star moves from the OUTSIDE back to the middle? Yes, this would work.

I am still going to press the post button here after all this typing. Even though I feel I should cancel; go away and try this then come back.

Sorry to be painful about all this. I just seem to have a mental block.
Darrell
Sorry to butt in again, but what you are saying is exactly how I felt, very confused! And it's wrong. You don't "check" the drift when moving back to the middle, just brute-force bring the star back to the centre with the hand controller and see where it then wants to go.
Only move the mount bolts after you've established the trend of movement from centre of the star.

OMG, Who am I to be giving advice?
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