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Glatter Circular Projection vs Rect. Projection

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#1 saadabbasi

saadabbasi

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Posted 11 September 2013 - 08:38 PM

Hi all,

I have been following instructions from this link to collimate my ATRC8. My main source of confusion is that the author uses holographic rings attachment to perform the collimation of the secondary. See video here: http://www.youtube.c...h?v=RUOza5EHRNg

I don't have a rings attachment but I do have an attachment that produces a square pattern. How do I use this to collimate my secondary?

#2 Howie Glatter

Howie Glatter

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Posted 12 September 2013 - 12:40 PM

"I don't have a rings attachment but I do have an attachment that produces a square pattern. How do I use this to collimate my secondary?"

Both patterns are symmetrical around the central beam, and can therefore be used for collimation, but the concentric circle attachment is better for Cassegrain scopes slower than approximately f/5.6 because it is brighter than the square grid and it is also easier to precisely align using the circles. The square grid pattern is wider in order to cover scopes as fast as f/2.7, but dimmer because it is more extensive.
You could align the secondary with the square grid, provided the secondary is not entirely within the “hole” in the central square, but it would be more difficult to see, and precisely align.

#3 saadabbasi

saadabbasi

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Posted 12 September 2013 - 02:19 PM

Howie - thank you VERY much for responding. This is the projection on my wall:

Posted Image

I have already ensured that the focuser is square by tilting it such that the laser beam strikes the center spot and then adjusting the secondary such that the beam folds on itself. This is now OK. However, the pattern is still not symmetrical. Notice the arrows in the image. Should I now adjust the primary?






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