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  #21  
Old 23-05-2012, 12:17 PM
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Thats great Peter.
I am glad you are solving your problems.
I hope it is smooth sailing from here.

Cheers
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  #22  
Old 23-05-2012, 03:06 PM
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From the photo you provided I think the focusor is raked out a little too far and that might be causing the DAF adjustment in the model. I would also consider the connection with the camera itself.

The rest of the model is looking pretty good. I would lower the PA by the required amount. try doing 21 points at a time on the polar alignment and use a very small area of the sky, preferrably a small constellation out to the east. Do the adjustments each time and do this 3 times or until you are really happy with the polar alignment. Then do your full sky model. You should be able to get down to 15" at least for pointing with a 100-250 point model.
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  #23  
Old 23-05-2012, 06:13 PM
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Paul,

Thanks for your input! The picture of my camera actually doesn't represent focus. Focus is actually further out....around 95. The camera seems firm and I have no idea short of an entirely different mounting solution how I can improve this. Greg mentioned turning the focuser upside down so I might try that, and I have not tried locking the focuser with the screw. (I'm worried about doing that and trying to electronically focus, but maybe I'd better do that anyway!). Would it be better to have the focuser tube racked in further with a longer extension tube? I really like the Baader Click Lock, but the extension is quite short. How can I get the best of both worlds?

Re T-Point run of 21 points....I cannot image to the east except above 70-80 degrees. To the west is ok. How low to the west should I go? due west. NW or SW?

It also seems clear that I'm going to need to add a field flattener to the equation. The TEC140 flattener is rather expensive and it doesn't reduce. A flattener/reducer I'm told works on the TEC140 is the Borg 7887 (from Cloudy Nights). I'm wondering if I could use a Borg 2" nose piece from the Focuser to the 7887, then use a Borg Cannon EOS adapter and finally a Moravian EOS adapter which bolts to the camera. Is there any chance this would be firm enough? I suppose the EOS adapter is made to support a lens with the camera supported on a bar; this would be reversed with the adapter supporting the camera...

Thanks again,
Peter
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  #24  
Old 23-05-2012, 06:52 PM
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My Tpoint runs have a lowest elevation of 45 degrees. Going lower can give inconsistent results. So I think 45 degrees is the lowest you should go. Others may disagree.

With the camera, am I to understand that this camera has a SLR lens adapter permanently on it? If so this is going to be the source of the flexure. Screw mounting is the only way to go, SLR mounts always have some movement and it does not need to be much. Can the camera be used without this mount?

The usual way to go about things with reducers and flatteners is to have the field corrector after the focusor and then have a custom made adaptor between the field corrector and the camera / filter wheel. Precision parts makes these adapters.

Would you consider another camera? That might help your situation.
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  #25  
Old 24-05-2012, 07:55 AM
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Hi Paul,

Thanks for your comments.

Currently my camera has a 2" standard nosepiece which is bolted onto the camera body with 4 screws. That goes directly into the Baader Click Lock extension tube, which goes directly into the 2" FT Focuser (which has a twist locking compression ring. I was just asking about the possibility of using a Cannon EOS adapter on the camera as a way of nailing the distance to the potential field flattener (also using an EOS adapter). Seems from what you are saying that this would not be firm enough, so I will forget that future solution.

Last night proved frustrating to say the least. I not sure if I've made much progress but did 8 T-Point runs of 21 points, then after the 6th run I accidentally crashed pretty hard right into the counter weight and gave it a huge knock. Yikes. That was around 1 am. I ran T-point 2 more times and got the results in # 8.

The first time I tried to follow your advice exactly. I went due West (cannot go due east very much) to around 50-60 degrees elevation and collected 21 points in a small area. This proved useless as the PA dialog info said not enough points to refine model, collect more points.....so I collected another 15 or so in a pie shaped wedge towards directly overhead, keeping the scope on the same side of the mount. To make a long story shorter on subsequent runs I slightly enlarged the pie shaped wedge of stars to 21 and used this over and again. I got the following super model results, (minus run 4 because I forgot to write the results down):

1. MA = 56.7 Tighten E 1.3 tics
ME = 0.0 Raise 1.3 tics

2. MA = 43.3 Tighten E .9 tics
Raise 1.3 tics

3. MA = 25.7 Tighten E .5 tics
ME = 0 Raise 1.3 tics

4. no data

5. MA = 26.5 Tighten E .5 tics
ME = 0 Raise 1.3 tics

6. MA = 0.0 no adj indicated
ME = 0 Raise 1.3 tics

Walked into mount counter weight!!

7. MA = ??? Tighten E 2.3 tics
ME = ??? Lower 1.3 tics

8. MA = 0.0 no adj
ME = 0.0 Raise 1.3 tics

I'm a bit onfused about these numbers. It sems as if MA was improving a little with each of the first 6 runs, but every time I raised the mount ME wasn't changing. Until I walked into the mount I raised it 1.3 at least 5 times. Could that be correct? Also, I tend not to believe the final result of MA=0.0 even though confidence was listec as "high."

I've attached pictures of the area of the sky I collected the points in, and also photos of the terms and #8 PA recommendations.

Sorry this is so long, but appreciate further help!!

Peter
Attached Thumbnails
Click for full-size image (23rd 8th run t-point pointing samples.jpg)
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Click for full-size image (23rd 8th run Super Model Terms.jpg)
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Click for full-size image (23rd 8th run t-point post super model.jpg)
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  #26  
Old 24-05-2012, 09:55 AM
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That last run looks pretty good. The terms look normal and the alignment looks pretty good, some minor refining later might help, but for now try imaging and see what the results are like.

Using Tpoint can often make you oscillate over the pole if something has just a fraction of flexure. Your numbers overall look good now so doing some imaging will give you a better idea of what is going on. My suggestion is to do some images at 1 minutes, then some images at 5 minutes and some images at 10 minutes (all guided). Doing this will narrow down whether there is flexure in your system and will test your success on polar alignment.
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  #27  
Old 24-05-2012, 09:55 AM
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Quote:
Originally Posted by Paul Haese View Post
My Tpoint runs have a lowest elevation of 45 degrees. Going lower can give inconsistent results. So I think 45 degrees is the lowest you should go. Others may disagree.
I agree with you except that I'm able to get down to 30 degrees okay. But I mentioned this to Patrick Wallace and he disagreed! He thinks one should go as low as one's horizon permits. I hate to disagree with Patrick, but I'm not on a high mountain with perfect atmosphere, so...
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  #28  
Old 24-05-2012, 10:12 AM
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Quote:
Originally Posted by frolinmod View Post
I agree with you except that I'm able to get down to 30 degrees okay. But I mentioned this to Patrick Wallace and he disagreed! He thinks one should go as low as one's horizon permits. I hate to disagree with Patrick, but I'm not on a high mountain with perfect atmosphere, so...

Yeah, that could well be right. I have a site with great seeing but consider that even down low the seeing can give inconsistent results when fine tuning.
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  #29  
Old 24-05-2012, 10:23 AM
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Thanks Paul!

I'm relieved to know I might finally be on the right track after too many false starts.

I've yet to try guiding so that will be the next obstacle. I have an Orion Star Shoot camera/phd kit so will try that out soon on my AT66EDQ. Any tips about setting up the PMX for that would be welcome.

Peter
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  #30  
Old 24-05-2012, 12:56 PM
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That should connect easily. I have been using the SSAG for autoguiding with the PME and it works a treat. Standard settings in PHD worked for me before I switched to Maxim. 2-3 seconds is about what you want with this mount.
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  #31  
Old 25-05-2012, 05:35 AM
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Quote:
Originally Posted by Paul Haese View Post
Ah I see, but that would seem odd for such a scope??? Surely that scope would not have flexure?

Not sure about upgrade, if it ain't broke... well you know. Besides I have to pay for another Tpoint then too. If TPoint was included in the upgrade package I would consider it.
I am not so sure about the Sky X. Yes it had a few more bells and whistles but it also seems less stable at least with a PMX. It will drop out on you if there is any problem. The Sky 6 never did that. Sky X does it regularly.

PEC software in the Sky X also seems bugged and not working reliably.

I agree with if you got your system working well don't change anything. Its hard to get it to that point.

Greg.
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  #32  
Old 25-05-2012, 05:37 AM
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Quote:
Originally Posted by frolinmod View Post
I agree with you except that I'm able to get down to 30 degrees okay. But I mentioned this to Patrick Wallace and he disagreed! He thinks one should go as low as one's horizon permits. I hate to disagree with Patrick, but I'm not on a high mountain with perfect atmosphere, so...
I am not sure who Patrick Wallace is but with amateur gear and amateur locations anything below about 45 degrees gets poor. You can see it in the subs if you image over several hours. The stars just get fatter and fatter in luminance as the scope goes lower. That's at long focal length. With short focal lengths you tend to get away with lots of things!

Greg.
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  #33  
Old 26-05-2012, 04:27 PM
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Patrick Wallace is the author of Tpoint. We were discussing images taken for automated calibration rather than production images. He indicated that images taken at low elevations were important to include for best modeling.
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