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richyrich_one

Disappointing Collimation with Catseye Infinity XLKP

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On 17/04/2018 at 16:15, 25585 said:

Would the Howie Glatter parallizer,  an exact centering tube, be what you need? FLO sell those & other HG kit. 

Thanks, but that looks like a reducer as well. The catseye products are 2".

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Hello Rich,

When you mentioned the free evaluation stock for those involved in this thread, I assumed you got a free one for evaluation. I misunderstood.

It has always been recommended to position the autocollimator mirror at or very close to the primary mirror focal plane for optimal precision -- it is written in Catseye instructions. Meeting this requirement is highly doable for visual reflectors but can't be done for imaging reflectors without using a 2" extension tube. Stacking a visual XLKP autocollimator on the top of a 2" extension will not have the same mechanical precision as using a single calibrated imaging XLKP autocollimator that comes with a elongated barrel.

Jason

 

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Posted (edited)
42 minutes ago, Jason D said:

Hello Rich,

When you mentioned the free evaluation stock for those involved in this thread, I assumed you got a free one for evaluation. I misunderstood.

It has always been recommended to position the autocollimator mirror at or very close to the primary mirror focal plane for optimal precision -- it is written in Catseye instructions. Meeting this requirement is highly doable for visual reflectors but can't be done for imaging reflectors without using a 2" extension tube. Stacking a visual XLKP autocollimator on the top of a 2" extension will not have the same mechanical precision as using a single calibrated imaging XLKP autocollimator that comes with a elongated barrel.

Jason

 

So we are back to the fact that standard Catseye autocollimators are not suitable for imaging reflectors. My opinion from the start. 

Why haven't the extended versions always been available? Is it coincidence that they have only become so since this thread? 

Edited by richyrich_one

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On 3/28/2017 at 08:42, Jason D said:

B ) If you already own an XLKP autocollimator (the production/common version without an extended barrel), consider purchasing (if you do not already own one) a quality 2" extension to elevate the XLKP AC to bring the AC mirror within 1.25% of the focal plane. Use relative size and parallax between reflections P&2 as your guide to know if the AC mirror is within the desired range. Do your math before purchasing to ensure the extension has about the right height. I want to emphasize the word "QUALITY" extension. Do NOT use or purchase a poor quality 2" extension.

Sorry to jump in but I too own the 130pds and a quattro 8". After looking on google I still cannot find out how to work out the focal plane. If anyone has a link or equation I would appreciate it. I do only have the infinity xl.

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6 hours ago, richyrich_one said:

So we are back to the fact that standard Catseye autocollimators are not suitable for imaging reflectors. My opinion from the start. 

Why haven't the extended versions always been available? Is it coincidence that they have only become so since this thread? 

The visual autocollimator is adequate for imaging reflectors. I have already explained in earlier posts that the error is small. I also provided a technique in this thread to further reduce the small errors. Catseye instructions do call for the autocollimator mirror to be positioned at or near the focal plane. I am not into astro-imaging and I do not know how common for imagers to also own a 2" extension tube to be able to use their imaging reflectors for visual observation. If owning a 2" extension tube is common with imagers then the extension tube can be used to eliminate all errors -- assuming the extension tube is of good quality. The new product ensures the overall mechanical quality of the autocollimator is perfect.

Jason

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2 hours ago, spillage said:

Sorry to jump in but I too own the 130pds and a quattro 8". After looking on google I still cannot find out how to work out the focal plane. If anyone has a link or equation I would appreciate it. I do only have the infinity xl.

Are you asking about how to determine the height of the 2" extension tube that can be used with your autocollimator? 

Jason

 

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No equations are required. You need to figure out the approximate distance between the camera's sensor and the OTA. You will need a 2" extension tube that will position the AC mirror at approximately same distance. You will need to improvise to make these measurements. Placing the AC mirror exactly at the focal plane (where the camera sensor is positioned to obtain focus) is not essential. Being very close to the focal plane is good enough.

Jason

 

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