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Can not merge images, Baader Maxbright

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#1 pjensen

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Posted 23 June 2013 - 06:51 AM

Just got Baader Maxbright binoviewer and tested them for the first time. Scope is a HD C8 with a Televue short visual back and Maxbright T2 diagonal. Eyepieces are 2 Tevevue 15mm Plossl (purchased new last week). This gives 156x with 0.31 degree FOV.

When looking at Polaris, I get two bright stars separated by 1/10 of the field of view. Each side is perfectly focused and each side's star test looks perfect.

Tried every interpupil distance - no change in the star separation.

I loosened the collimation screws completely and can spin each eyepiece - no change in the offset image. I can rock the eyepieces in any position - stars appear slightly closer but no merge. I swapped the eyepieces back and forth - no change.

I removed the diagonal and sighted the binoviewer directly in the 2" visual back - same star separation.

I tested the 15mm plossls with my old visual back. Did a star test on each. Both were absolutely perfect - and both were parafocal (no focus re-adjustment was needed after swapping eyepieces).

What next? :(

#2 HTJ

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Posted 23 June 2013 - 07:39 AM

Can you try and move a star to the edge of the field in both sides and up+down in order to see if the two images show the same? You can also do this during the daytime, with pretty much anything that has a sharp defined point/edge. If you can see something at the edge in one eyepiece and not the other, the binoviewer is out of collimation and merging will be very tricky and strenuous.

When my Maxbright arrived it was out of collimation. I send it back to the shop which collimated it and send it back to me. However the binoviewer lost collimation during transit, so I ended up collimating it myself.

You can collimate it by loosening the screws that hold the eyepiece holder to the body itself and moving it around. This requires a fair bit of patience and trial and error. The manual should also cover this if I recall correctly. But check that the fields line up first.

Merging is also easier with eyepieces that have longer focal lengths. Do you have a pair of 25 mm plossls? I am only using 18 and 25 mm eyepieces with mine and have largely given up on my 12 mm pair - I do use them for collimating the binoviewer though.

#3 vahe

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Posted 23 June 2013 - 08:00 AM

Here is what I do whenever there is a problem with image not merging;

Center a bright star in binoviewer eyepieces, slowly start moving your eyes away from the eyepieces while looking at the object, at about 2” away from the eyepieces start turning one or both eyepieces, you will notice that as you turn each eyepiece the image of the star will begin to move closer and or further away from each other, once they get close enough you can now move your eyes right up to the eyepiece and the image will be perfect.

Vahe

#4 mich_al

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Posted 23 June 2013 - 09:17 AM

I'm new to binoviewers and often have trouble merging when I first start a session but laters get good merges. Relax and let it come to you. To adjust interpupil distance I close one eye and center the other, then without moving my head open the other and adjust until the image is centered. Repeat a few times until no adjustment is needed. Make sure the interpupil adjustment tension is snug so it doesn't move unexpectedly after adjustment. An adjustment that causes me even more trouble is up/down (chin to forehead). Loosen the binos in the diag just enough so they can rotate. Do the one eye at a time test like above. Repeat this an the interpupil adjustment till it comes together for you. Also try a different set of eyepieces. For me some are easier to merge than others. Relax, it will come to you.

#5 pjensen

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Posted 23 June 2013 - 09:50 AM

Can you try and move a star to the edge of the field in both sides and up+down in order to see if the two images show the same? You can also do this during the daytime, with pretty much anything that has a sharp defined point/edge. If you can see something at the edge in one eyepiece and not the other, the binoviewer is out of collimation and merging will be very tricky and strenuous.


Yes this is what I am seeing. I am looking at a roof pipe 1/2 mile away. If I move the pipe to the edge of the field, it will disappear on one eyepiece.

You can collimate it by loosening the screws that hold the eyepiece holder to the body itself and moving it around. This requires a fair bit of patience and trial and error. The manual should also cover this if I recall correctly. But check that the fields line up first.


Ah yes - just found this in the manual. Weirdly 5 of the 6 lateral collimation screws (on the two eyepiece holders) were loose. I was able to move the eyepiece holder and get the images a bit closer.

Merging is also easier with eyepieces that have longer focal lengths. Do you have a pair of 25 mm plossls? I am only using 18 and 25 mm eyepieces with mine and have largely given up on my 12 mm pair - I do use them for collimating the binoviewer though.


Right now all I have are the 15mm. Thanks for your help.

#6 johnnyha

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Posted 23 June 2013 - 11:53 AM

I would say you are definitely out of collimation.

The binoviewers are collimated by moving the eyepiece holders up-down and left-right on a flat plane, in your case using collimation screws. As I have learned now with my new collimatible Binotron 27s, the important thing is for the image of each side to line up vertically up-down - so if one image point is, say, at the very edge of the very top center (or bottom center) in one eye, the other eye should be also exactly the same. However horizontally, they images do not need to line up and in fact, at least with my new Binotron 27s, I cannot merge the images unless they are slightly offset left-right. So you do not need to line the images up perfectly left-right on the horizontal axis and in fact I think they should be slightly offset. This is also confirmed in the B27 manual and from my tinkering with the B27s. So you may see an image, say, on the very edge of the right side in one eye, and the image may be slightly offset to the left or right in the other eye.

What I would do is make sure the images are lined up vertically and then experiment with the collimation screws left-right until you get a nice merge. You will know when they merge, the images just pop together into one image.

The collimation is fairly sensitive to very small adjustments so it's not surprising that many people have trouble merging images - I strongly suspect it is not the fault of the person but rather the collimation is indeed slightly off and needs a little proper adjustment. One thing I think everyone should check is to make sure the images are lined up vertically top and bottom, this appears to be critical for a good comfortable merge.

#7 pjensen

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Posted 23 June 2013 - 12:17 PM

What I would do is make sure the images are lined up vertically and then experiment with the collimation screws left-right until you get a nice merge. You will know when they merge, the images just pop together into one image.


Just finished doing this - getting a vertical alignment exact and horizontally the two images as close as possible. Now I can merge the images when looking at a cell tower 5 miles away.

Thanks for all the help. :)






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