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Glatter Tublug Question

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#1 cliff mygatt

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Posted 20 January 2013 - 12:09 PM

I have the glatter collimation system for my XT12i and have used the Blug for some time. Last year I purchased the TuBlug (which I should have done to begin with) and really like the ease of collimation. With all the clouds and cold, I decided to clean my Primary and secondary to get ready for the the observing season. Once cleaned and back together, I collimated to make sure all was in line and it was! However, I notice the barlowed laser light hitting the TuBlug white face is not concentric with the reflection of the primary mirror donut. I noticed this last season but did not worry about it as the collimation was great but it got me to thinking maybe the secondary was not quite centered correctly under the focuser. So, I fiddled with it moving it sligthly while the center screw was loosened and I was able to get the reflected light around the hole but when repeating the collimation the refelected donut and light are not together. I have not star tested yet as the clouds and fog have taken over here in the Pacific Northwest. Is this normal with the TuBlug? PS I tried to get to Howie Glatter's website but there is an error so could not ask him or look up the information.

#2 Vic Menard

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Posted 20 January 2013 - 12:20 PM

I assume that, after cleaning your secondary and primary mirrors, you used the unBarlowed laser to assess/correct the focuser axial alignment (laser beam is aligned to the primary mirror center spot) and then followed with the TuBlug to align the primary/optical axis.

If so, then your axial alignment should be fine and any subsequent star alignment should also be fine (as the star alignment/assessment only verifies the primary/optical axis alignment).

...I fiddled with it moving it sligthly while the center screw was loosened and I was able to get the reflected light around the hole but when repeating the collimation the refelected donut and light are not together.

If you loosened the center mounting screw of the secondary holder, it's possible you've changed the rotational alignment of the secondary mirror. Have you tried looking into the empty focuser drawtube to assess the concentricity and roundness of the secondary mirror relative to the bottom edge of the drawtube and the reflected edge of the primary mirror?

FWIW, it takes a pretty severe rotational error to impact the axial image performance.

#3 cliff mygatt

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Posted 20 January 2013 - 12:28 PM

Vic, I did as you stated test the secondary alignment unbarlowed to assure alignment and then barlowed. So, I should have nothing to worry about as I tought but was curios. Thanks for your response and clear skies.

#4 cliff mygatt

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Posted 20 January 2013 - 12:30 PM

My first step was to use a sight tube to assure mirror general alignments first and then laser to primar and then Barlowed alignment. I have completed all the other axial alignment steps as well.

#5 Howie Glatter

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Posted 20 January 2013 - 01:06 PM

Hi Cliff,

From my tuBlug instructions, which should have come with the tuBlug : "The diverged beam impact on the primary may be irregular and not centered, but this does not matter. ."

This is true as well of the reflected laser light on the tuBlug screen. The diverged beam is an enlarged version of the somewhat irregular cross-section of the original laser beam. The irregularity of the beam perimeter does not matter for the collimation; all the rays in the primary-reflected beam are still parallel.

#6 cliff mygatt

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Posted 20 January 2013 - 04:43 PM

Thanks, Howie and I should have looked at the instructions again! Great product by the way and I heartily recommend your system to ALL my astronomy friends. I have become the Club Collimator.

#7 GeneT

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Posted 20 January 2013 - 04:47 PM

PS I tried to get to Howie Glatter's website but there is an error so could not ask him or look up the information.



Howie makes the best stuff, and has the worst web site in the business. :grin: (I do love you and your stuff, Howie.)

When his site comes back up, note his e-mail address and phone number. He will answer e-mails quickly and is helpful and fun to talk to on the phone.

#8 howard929

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Posted 20 January 2013 - 10:34 PM

I think he's transitioning to a new web site but just in case, here's his phone number,(718) 796-3203

#9 starman345

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Posted 21 January 2013 - 05:56 AM

New site is up

#10 Cotts

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Posted 21 January 2013 - 07:34 AM

Cliff, are you removing the aperture stop on the laser when you move to the barlowed step? This widens the beam and it won't appear to be off center....

Dave

#11 psandelle

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Posted 21 January 2013 - 01:42 PM

OMG! It's a new website!

Yup, Howie makes the best stuff. I had the same off-center for the line-y stuff, but my center spot was dead-on, and what-do-you-know...so was the collimation later that night. Amazing!

Paul

#12 cliff mygatt

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Posted 21 January 2013 - 04:13 PM

Thanks for all the input, it was an acedemic question as my collimation is spot on!






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