Return to the Cloudy Nights Telescope Reviews home pageAstronomics discounts for Cloudy Nights members
· Get a Cloudy Nights T-Shirt · Submit a Review / Article

Click here if you are having trouble logging into the forums

Privacy Policy | Please read our Terms of Service | Signup and Troubleshooting FAQ | Problems? PM a Red or a Green Gu… uh, User

Equipment Discussions >> Reflectors

Pages: << 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | (show all)
Jason D
Postmaster
*****

Reged: 10/21/06

Loc: California
Re: Concise thread about autocollimators+improveme new [Re: rlmxracer]
      #5629593 - 01/18/13 10:04 AM

Quote:

What am I doing wrong?



It does not sound you are doing anything wrong. Based on your steps, collimation should be close enough to see the center spot reflections via the autocollimator pupil. I assisted few members in other forums who own the same brand – Farpoint autocollimator s. They reported when conducted the 180 degrees rotation test, the center spot reflections moved significantly. This is an indication the autocollimator mirror is not precisely squared with its case. Since you have the same brand, it could be the reason why you can't see the reflections. According to the same members, the Farpoint mirror was placed on cork pads which apparently shifted and caused the mirror to tip slightly on one side. They took their autocollimators apart and adjusted the cork pads placement. According to them, that improved the tool but they still noticed a large center spot reflections shift when conducted the 180 degrees rotation test. I do not know if your Farpoint autocollimator has the same issues.

The 180 degree rotation test does NOT apply to reflection P since it is the only reflection that does not reflect off the autocollimator mirror. It is best to reference reflection 2 for this test.

Jason


Post Extras: Print Post   Remind Me!   Notify Moderator  
rlmxracer
sage
*****

Reged: 11/09/11

Loc: Motocross Mecca , CA
Re: Concise thread about autocollimators+improveme new [Re: Jason D]
      #5629716 - 01/18/13 11:11 AM

Thanks for the quick reply Jason, I'll give the AC a 180 turn and see if that changes anything. Another possible issue that I forgot to mention is the Farpoint cheshire seems to have a very loose fit in my focuser. I cant tell if this is causing it to shift when I snug up the brass compression ring to hold it. Thanks Rob.

Edited by rlmxracer (01/18/13 11:28 AM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
Jason D
Postmaster
*****

Reged: 10/21/06

Loc: California
Re: Concise thread about autocollimators+improveme new [Re: rlmxracer]
      #5629775 - 01/18/13 11:38 AM

Cheshire loose fit has no impact since the cheshire is only sensitive to the primary mirror alignment -- as in your case. On the other hand, the sight-tube/cheshire combo is senstive to the loose fit.

Post Extras: Print Post   Remind Me!   Notify Moderator  
rlmxracer
sage
*****

Reged: 11/09/11

Loc: Motocross Mecca , CA
Re: Concise thread about autocollimators+improveme new [Re: Jason D]
      #5629852 - 01/18/13 12:16 PM

Ok good. I have placed a lap of scotch tape around my combo tool to make for a mor precise fit in the 1.25 to 2" adapter. When I remove and replace the combo tool and adapter the crosshairs remain aligned with the center spot so that seems good. You were right (as usual)the Farpoint AC I purchased was poorly made. the mirror is glued to a thin plexiglass disk and sandwiched in between the cap and body of the AC with the small cork pices there to keep it from rattling around. My AC mirror was glued off center on the plexi disk and the hole in the center of it has small chips in the mirror. I did the 180 deg turn you suggested and I can see half of one of the centerspot reflections, but thats it.
So it looks like at this point the best I can do is use my combo tool to align the secondary and the 2" cheshire for the primary. I'm kind of bummed cause I'm going out to the desert for the weekend and was hoping for the best collimation I've had yet. At least it will be close. Rob


Post Extras: Print Post   Remind Me!   Notify Moderator  
Jason D
Postmaster
*****

Reged: 10/21/06

Loc: California
Re: Concise thread about autocollimators+improveme new [Re: rlmxracer]
      #5629951 - 01/18/13 01:31 PM

Quote:

You were right (as usual)the Farpoint AC I purchased was poorly made. the mirror is glued to a thin plexiglass disk and sandwiched in between the cap and body of the AC with the small cork pices there to keep it from rattling around



Squaring the AC mirror to its case is critical. Without precise squaring, the AC will not be useful. I do not see how Farpoint design can achieve and maintain this a critical alignment.

I need to clarify that some jittery movement of reflection 2 with respect to reflection P when conducting the 180 degree rotation test is OK since this test is highly sensitive. However, dramatic movement is unacceptable.

Jason


Post Extras: Print Post   Remind Me!   Notify Moderator  
rlmxracer
sage
*****

Reged: 11/09/11

Loc: Motocross Mecca , CA
Re: Concise thread about autocollimators+improveme new [Re: Jason D]
      #5630156 - 01/18/13 03:57 PM

Squaring the AC mirror to its case is critical. Without precise squaring, the AC will not be useful. I do not see how Farpoint design can achieve and maintain this a critical alignment.
That is why it is getting sent back on Monday. I'll be giving Jim Fly a call.
Jason do you think the Infinity XLK is a must have for my f4.9 dob or is it more aimed at the imaging crowd with their f3-4 newts? Thanks again Rob.


Post Extras: Print Post   Remind Me!   Notify Moderator  
howard929
Member
*****

Reged: 01/02/11

Loc: Low End of High Ground
Re: Concise thread about autocollimators+improveme new [Re: rlmxracer]
      #5630179 - 01/18/13 04:07 PM

Quote:


That is why it is getting sent back on Monday. I'll be giving Jim Fly a call.





Better yet, give Howie Glatter a call. His Blug/Tublug combined with his laser and barlow work exceedingly well any time of the day or night for an acceptable price.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Starman1
Vendor (EyepiecesEtc.com)
*****

Reged: 06/24/03

Loc: Los Angeles
Re: Concise thread about autocollimators+improveme new [Re: rlmxracer]
      #5630272 - 01/18/13 05:15 PM

Quote:

Squaring the AC mirror to its case is critical. Without precise squaring, the AC will not be useful. I do not see how Farpoint design can achieve and maintain this a critical alignment.
That is why it is getting sent back on Monday. I'll be giving Jim Fly a call.
Jason do you think the Infinity XLK is a must have for my f4.9 dob or is it more aimed at the imaging crowd with their f3-4 newts? Thanks again Rob.



My dob is f/5, and no matter how meticulous I am at using a sight tube and cheshire, I always find a residual error when I go to the AC. And, no matter how meticulous I am with the center pupil of the AC, I always find a trace of residual error in the lateral pupil of the XLK autocollimator.

Now, when sight tube, cheshire, and both pupils of the AC agree, you're dead on.

Where this is a little more important is if you use a coma corrector like the Paracorr (I do), the tolerances for misalignment get significantly tighter, and the AC becomes a more important tool.

And if you're going to get a Catseye AC, you might as well get the XLK version and really dial it in.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Starman1
Vendor (EyepiecesEtc.com)
*****

Reged: 06/24/03

Loc: Los Angeles
Re: Concise thread about autocollimators+improveme new [Re: howard929]
      #5630285 - 01/18/13 05:26 PM

Quote:

Quote:


That is why it is getting sent back on Monday. I'll be giving Jim Fly a call.





Better yet, give Howie Glatter a call. His Blug/Tublug combined with his laser and barlow work exceedingly well any time of the day or night for an acceptable price.



Agreed, but the Catseye autocollimator makes a very useful tool to eliminate residual errors left by the Glatter tools as well.
A sight tube and cheshire, or a good laser and barlowed laser tool (like the Blug or Tublug from Howie Glatter) will get you 98% of the way, but only a good autocollimator will get that last 2% of residual errors.

As an example of what I mean, I have moved many scopes up and down through their altitude movements without seeing changes in collimation in the sight tube and cheshire. But it is a VERY rare scope that can move up and down over a wide range without seeing collimation changes in an autocollimator--it's just that sensitive. As my scope cools, even differential contraction of the aluminum poles changes collimation in the AC until the scope gets near the ambient temperature.

Which not only means the Catseye AC is a great tool for dialing in collimation close enough for the pickiest observer with a coma corrector, it is also a great tool to help track down sources of collimation changes in the scope, some of which will be easily correctable (like stronger springs on a primary mirror or tighter spider vanes) and some of which may require some more elaborate changes to the scope (like larger diameter poles, or a change of spider or a change of pole attachment pieces).

But, when you're done, you'll have a scope that is not only collimated to much tighter tolerances, but also one that will hold that collimation in use.

Here's a collimation tutorial you might find useful.
http://www.cloudynights.com/item.php?item_id=2677


Post Extras: Print Post   Remind Me!   Notify Moderator  
Jason D
Postmaster
*****

Reged: 10/21/06

Loc: California
Re: Concise thread about autocollimators+improveme new [Re: rlmxracer]
      #5630463 - 01/18/13 07:29 PM

Quote:

Jason do you think the Infinity XLK is a must have for my f4.9 dob or is it more aimed at the imaging crowd with their f3-4 newts? Thanks again Rob.




Let me put it this way:


1) Will the combination of XLK and Blackcat along with a well-centered Hotspot give the best axial alignment?

I would say yes.


2) Will the additional accuracy be visible at the eyepiece visually?

That depends on many factors such as seeing conditions, scope mechanical stability, optics quality, thermal stability, experience level of the observer, and whether a paracorr is used or not.


3) Should those with f4.9 get an XLK?

Everyone needs to do their own research and decide. For example, read Don’s response above. Don is an experienced observer who researched and made his decision to get the XLK. In my case, I am a collimation perfectionist and I will not be happy until my XLK-C agrees with the Blackcat and my HG laser tools – but that is just me. Here is my philosophy: I like to perfect all conditions within my control that impacts the quality of my views. That will leave the largest error margin for all other conditions beyond my control.

It is wonderful when everything comes together. Last night I observed Ganymede shadow transitioning across Jupiter. Seeing was great and I perfected collimation. I was able to push my 10” reflector up to 500X. Not only I saw both Ganymede and its shadow as discs but I was flabbergasted when the shadow gradually became elongated with the major axis point in Jupiter's pole direction towards the end of the transition. Moments like this in good seeing condition makes you appreciate both the premium optics and good collimation .

Jason


Post Extras: Print Post   Remind Me!   Notify Moderator  
Chucky
sage
*****

Reged: 04/16/10

Loc: Dublin, Ohio
Re: Concise thread about autocollimators+improveme new [Re: Jason D]
      #5631120 - 01/19/13 07:37 AM

<< As my scope cools, even differential contraction of the aluminum poles changes collimation in the AC until the scope gets near the ambient temperature. >>

As a scope is a living and breathing collection of parts....constantly expanding, contracting, bending, twisting (even if only a tad), I sometimes wonder if anguishing about the last 1 or 2 percent of collimation is worth the worry or effort with an AC. But of course it is.....as it never hurts to always start from the best precision one can obtain (especially with fast scopes)....much like getting the best initial alignment with digital setting circles!


Post Extras: Print Post   Remind Me!   Notify Moderator  
howard929
Member
*****

Reged: 01/02/11

Loc: Low End of High Ground
Re: Concise thread about autocollimators+improveme [Re: Chucky]
      #5631470 - 01/19/13 12:22 PM

Any method of collimation that results in 800x views is more then good enough for me to consider as a viable option. And there is one among us who does that after using the Glatter system. Besides, here in the wild foot hills of Long Island I'm more concerned about what's sneaking up on me in the dark then I am about that last 1 or 2 percent you speak of.

Post Extras: Print Post   Remind Me!   Notify Moderator  
memoryman
member


Reged: 03/27/11

Loc: UK
Re: Concise thread about autocollimators+improvements new [Re: EdTheEdge]
      #5768486 - 03/31/13 10:34 AM

I concur with EdTheEdge, excellent in depth article, but I'll have to revisit many times before I fully understand it all!!
P.S. Is the CAM amendment absolutely necessary and if so is it available?


Post Extras: Print Post   Remind Me!   Notify Moderator  
Jason D
Postmaster
*****

Reged: 10/21/06

Loc: California
Re: Concise thread about autocollimators+improvements new [Re: memoryman]
      #5768625 - 03/31/13 11:39 AM

Quote:

P.S. Is the CAM amendment absolutely necessary and if so is it available?




A CAM adds little value when getting a combination of a Blackcat XL cheshire and an Infinity XLK autocollimator.
The CAM will eliminate the need for the Blackcat XL cheshire; however, it might not be as intuitive to use and will require some practice.
Jim Fly from Catseye has been offering the CAM as a special order.

Jason


Post Extras: Print Post   Remind Me!   Notify Moderator  
davidpitre
Post Laureate
*****

Reged: 05/10/05

Loc: Central Texas
Re: Concise thread about autocollimators+improveme new [Re: Starman1]
      #5768666 - 03/31/13 12:03 PM

Quote:

But it is a VERY rare scope that can move up and down over a wide range without seeing collimation changes in an autocollimator




This is a good point and often missed. I have yet to see a newtonian that can swing from 20 to 90 degrees without images moving in the autocollimator. In the vast majority of scopes I've seen, secondary shift can be seen with a laser as the scope moves in altitude, many times with as little as 30-40 degrees tilt of the telescope. In my mind this puts confidence in good collimation in a different perspective.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Pages: << 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | (show all)


Extra information
18 registered and 26 anonymous users are browsing this forum.

Moderator:  ausastronomer, Phillip Creed, JayinUT, okieav8r 

Print Thread

Forum Permissions
      You cannot start new topics
      You cannot reply to topics
      HTML is disabled
      UBBCode is enabled


Thread views: 45610

Jump to

CN Forums Home


Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics