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Losmandy Gemini guiding question - Another

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#1 Freddy WILLEMS

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Posted 29 April 2009 - 09:53 PM

I have the Losmandy TITAN 50, and it is well polar aligned.
So when I take images in the SE - S - SW, I really have good guiding and well aligned. Can take images for 5 min and more before the Light Polution kicks in.
But a few weeks ago I started imaging some objects in the N - NE, like M 51 and I had star trailing after 90 sec.
How or what are the steps to make to get it also well aligned in the N - NE to minimize the trailing.
I'm still working on the auto guider setup to help this guiding issue out of the way, but I just want to know why I have star trailing in the N faster then in the S.
I used the link:

http://www.petesastrophotography.com/

which help me really well for good alignment. But North seems to be a mistery.
Freddy

#2 EricJD

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Posted 30 April 2009 - 06:05 AM

Don't have the answer to your question but wanted to state that I have the same problem, in the opposite direction, as you with my LXD75. Very strange.

#3 David Pavlich

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Posted 30 April 2009 - 08:45 AM

I have an MI250 with Gemini. The only thing I do is change the balance slightly when going from one side of the meridian to the other. It guides well anywhere I put it. I'm not quite sure why it would guide in one area and not another. Balance is the only thing that comes up.

David

#4 Cotts

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Posted 30 April 2009 - 09:08 AM

Freddy, have you used the Polar Align routine in your Gemini? It works great! I fail to understand how a properly polar aligned mount will trail images in one part of the sky but not in another. I do know that a slightly non-polar-aligned scope (off by about a degree or a bit less) will trail images more and more as you image nearer to either celestial pole. If your 'SE-S-SW' imaging is quite a bit closer to the celestial equator than M51 then you may not be really accurately polar aligned.
The Gemini polar alignment routine can get you inside one arc-minute from the pole which might solve your problem.

#5 Freddy WILLEMS

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Posted 30 April 2009 - 09:20 PM

I'm using my Meade 10" so that is really sencitive for trailing. Thanks for the Gemini Polar Align routine tip, will try that out !!
In an other forum, somebody explained to use more alignment stars in the N, I mean the area to be images, that might be better too, but indeed a better polar aligment is the solution.
Thanks.

#6 Freddy WILLEMS

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Posted 30 April 2009 - 09:43 PM

Wow, by reading that menu in the manuel:
3.4.2.3 Gemini Polar Alignment Tools / Polar Align Assist,
Looks great !!! Never did that, that will solve some of the problems I hope !
Thanks again.

#7 Freddy WILLEMS

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Posted 01 May 2009 - 04:58 AM

I did the routine !
Aligned around 5 stars and then did the Polar axis correction, Works great, but you have to do this a few times ! The first time I screwed up my good aligned mount, but after a few try's it got better and better.
Took a few 4 minute exposures north and south and they look really acceptable for the Meade 10", the refractor will get better results.
I will do this one more time tomorrow, because the clouds started to roll in :jump: but anyway I saw s nice fireball tonight ! Must be a blessing.
I did not use the Polar align assist, will try that option tomorrow to and see how that line up with the Polar axis correction.
Fredddy

#8 Cotts

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Posted 01 May 2009 - 05:50 AM

This is really good news, Freddy. Well done!!! :bow:

#9 David Pavlich

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Posted 01 May 2009 - 09:40 AM

Skip the PA assist. The correction routine is more accurate.

David

#10 blueman

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Posted 01 May 2009 - 03:57 PM

Be sure to polar align first with the polar scope, aligning all three stars not just Polaris.

Polar Align Correction works great, just remember to do it twice.

Run a normal 3 star alignment on one side of the Meridian, then have it Go-To a star ( I use the SAO Star Catalog and Go-To to get this done) very close to the Meridian & Equator intersection, closer the better. Then do the Correction. Now go back to the 3 stars ( using Align, Go to Bright Star funtion) and just do a sync with each of them after you center them in the crosshair.
Then do the same Correction routine (same SAO Star) again and repeat the sync on the 3 stars as before. This will take about 5-6 minutes and you will have a very close Polar Alignment with little or no drift over many hours.
You can then do more Star Alignments on the other side of the Meridian if you wish, this will give you great Go-To for all the sky.
Blueman

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#11 Freddy WILLEMS

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Posted 01 May 2009 - 10:54 PM

Thanks again guys for the help here.
Amazing image Floyd !
Freddy

#12 blueman

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Posted 01 May 2009 - 11:53 PM

The Freddy, hope the information is helpful.
Blueman

#13 Freddy WILLEMS

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Posted 02 May 2009 - 04:06 AM

All the information was really helpfull.
I'm maging righ now and it looks great with the almost perfec polar alignment.
Thanks Floyd
Freddy

#14 Freddy WILLEMS

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Posted 03 May 2009 - 04:28 AM

I think I have a perfect alignment now !
Stars do not even move in the field anymore, no trailing for at least 10 minutes !
Images taken with the Meade 10" do not show an star trailing !
I did the Polar Align axix correction two night in a row and aligned on 5 stars, over and over again, and after a few slews I finaly did the last Axis correction and bam righ on the money ! Just a little bitsy adjustment.
I'm really happy that this is solved.
CN is a great forum.
Freddy






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