As I'm waiting for a delivery (3-4 weeks) from Astrosystems I would like to add to my parcel an Autocollimator, but can't choose which one.
My choice is between the 1.25" Autocollimator at $45 or the 2" for $89. What are the practical benefits if any for choosing the 2".
I have noticed the "Catseye" people don't do a 1.25" but do recommend the Astrosystems 1.25" for those who want one.
I have read that the autocollimator is far more accurate than any laser as it uses multiple reflections. Now as most focusers have some sort of slop when fitting any tool to it, will this same slop have the same detrimental effect on the autocollimator as it does on the laser.
As the autocollimator is far more accurate will this slop have less negative effect on the final setting.
Thanks
Richard
Last edited by richardda1st; 25-09-2010 at 09:44 PM.
As I'm waiting for a delivery (3-4 weeks) from Astrosystems I would like to add to my parcel an Autocollimator, but can't choose which one.
My choice is between the 1.25" Autocollimator at $45 or the 2" for $89. What are the practical benefits if any for choosing the 2".
I have noticed the "Catseye" people don't do a 1.25" but do recommend the Astrosystems 1.25" for those who want one.
I have read that the autocollimator is far more accurate than any laser as it uses multiple reflections. Now as most focusers have some sort of slop when fitting any tool to it, will this same slop have the same detrimental effect on the autocollimator as it does on the laser.
As the autocollimator is far more accurate will this slop have less negative effect on the final setting.
Thanks
Richard
go for the 2inch its got a bigger image and i suggest that you change the colour of the round centre marker on your primary from a white one to a orange coloured one as it will be easier to see the multiple reflections and make them merge into one "donut" .the amount of adjustment to achieve this one donut is very little and bobs knobs are a big aid.
go for the 2inch its got a bigger image and i suggest that you change the colour of the round centre marker on your primary from a white one to a orange coloured one as it will be easier to see the multiple reflections and make them merge into one "donut" .the amount of adjustment to achieve this one donut is very little and bobs knobs are a big aid.
I assume you use the 2" yourself. If you don't mind me asking, what brand is yours. Any comment on the quality of the Astrosystems autocollimator.
I assume you use the 2" yourself. If you don't mind me asking, what brand is yours. Any comment on the quality of the Astrosystems autocollimator.
Thanks
Richard
hi Richard, i actaully own two astrosystem 2 inch barlowed laser collimators ,one orion laser collimator 1.1/4 inch and the usual collection of sight tubes and cheschires,,,,,,the auto collimator is the astrosystem 2 inch model.i have used the 1.1/4 inch astrosystem model as well but i found the two inch diameter gave better reflection due to its size.which ever collimator i use the final stage of collimation is using the auto collimator ,you will be surprised how much fine tuning is still involved....the unit is very well made the mirror is first surface ...hope that helps you
Yes, it all helps.
I have been using an orion delux laser, which was okay sort of, until I tried to improve on it's own collimation, fixed it sort of, but it needs adjusting all the time, it's battery runs out by the time I get it close.
It will be nice to have a tool that doesn't need a battery.
Yes, it all helps.
I have been using an orion delux laser, which was okay sort of, until I tried to improve on it's own collimation, fixed it sort of, but it needs adjusting all the time, it's battery runs out by the time I get it close.
It will be nice to have a tool that doesn't need a battery.
Thanks again
Richard
you will find that its best used in the day time or at twilight
Richard,
The main advantage of the 2" over the 1.25" is providing a larger view to detect where all the reflections are. When your scope is somewhat miscollimated, reflections will unstack and many of these reflections will get out-of-view with the 1.25" autocollimator which makes it harder to stack them.
A 2" autocollimator does NOT make reflections brighter.
I do recommend using a 2" autocollimator over 1.25" given the focuser supports it.
As far as which 2" autocollimator to purchase, there are few things to keep in mind:
1- Reflectivity of the mirror. You need to be able to see the 4th reflection of the center spot. If you can’t then the autocollimator will not provide the desired accuracy.
2- Flatness of the mirror. If reflections change shape compared to the original center spot then the autocollimator is somewhat useless.
3- Mechanical accuracy if the autocollimator. To test it, rotate the autocollimator in the focuser without tightening any of the focuser’s set screws. Evaluate how well reflections maintain their positions. Little jittering is OK but if reflections shift their positions noticeably then the autocollimator is somewhat useless.
Based on my experience, only the Catseye autocollimator passes on all above items. My Astrosystem autocollimator passed item # 2 but it did not do as well on items # 1 & 3.
In the USA, the difference in price between a 2” Catseye autocollimator and a 2” Astrosystem is only $11 (referring to only the single pupil autocollimator) which is a little extra to pay to get a much better tool. But, I do not know what the difference would be in Australia.
One more thing. The autocollimator theory explanation in the Astrosystems website and documentation is incorrect and their procedure is incomplete and somewhat incorrect. The proper procedure to use an autocollimator is explained in the Catseye website.
Jason
Thanks for you comments Jason. Your avatar tweeeeked some of my meurons and sent me back to the net.
From the catseye web page it appears that there is no shipping charge, so the price difference is as you say, must check, (no additional shipping from atsrosystem for me).
I do assume that the Astrosystems units will also be of good quality (but I do make an ass of myself on a regular basis). I appreciate your comments regarding the Astrosystems AC and will keep them in mind.
Richard
ps I'm confused as to weather you can use the AC in the dark, I have assssumed that all you need to do is shine a light down the tube.
Last edited by richardda1st; 28-09-2010 at 07:30 PM.
So an autocollimator will still possibly show significant miscollimation after the use of a decent barlowed laser collimator? So it would be worthwhile to get one as a finishing touch?
So an autocollimator will still possibly show significant miscollimation after the use of a decent barlowed laser collimator? So it would be worthwhile to get one as a finishing touch?
It all comes down to tool quality and knowledge.
For example, a quality barlowed laser tool used correctly will yield better results than an average autocollimator used incorrectly.
For example, Astrosystem autocollimator instructions are incomplete and will not get you the best results even if a perfect autocollimator is used. Their instructions ask the user to adjust the secondary mirror until all reflections converge and the background darkens. But that is insufficient. Just check the attached photos. As you can see, reflections seem to have converged and the background is darkened but collimation is way off for two while the third is OK. Astrosystems instructions are akin to asking someone to keep adjusting the secondary mirror until the laser beam retraces its path but that is not enough since the laser beam can retrace its path even when it strikes the primary mirror few inches off center.
Interestingly, Nils Olof Carlin and Vic Menard published enough information explaining the theory and the proper instructions to use single-pupil autocollimators several years ago yet Astrosystems did not make any effort to update and correct their instructions.
Back to the 1.25" versus 2" autocollimators, the attached photo shows the image off a 1.25" Astrosystem autocollimator versus a 2" Catseye autocollimator.
Yes well I'm definately going for the 2", thanks Jason & qld. The larger target area shown in those pics will be worth the extra few dollars.
I have just been offered a test run using the 2" catseye, so I'll wait till then.
Richard
ps. I hope I'm not the only one who finds all the different combinations and naming style on the catseye page very confusing.
ps. I hope I'm not the only one who finds all the different combinations and naming style on the catseye page very confusing
No, I find them confusing too, Richard.
Can anyone tell me if using a Catseye whether it's necessary to replace your primary centre spot with one of theirs, or will it work with the standard spot that the scope came with?
Can anyone tell me if using a Catseye whether it's necessary to replace your primary centre spot with one of theirs, or will it work with the standard spot that the scope came with?
Thanks,
Not necessary to replace your center spot but the cateye triangular shape helps to point to the collimation screws to tweak. They actually have a new profile now which is even better for superimposition of the spots and works well with the double pupil A/C.
Yes well I'm definately going for the 2", thanks Jason & qld. The larger target area shown in those pics will be worth the extra few dollars.
I have just been offered a test run using the 2" catseye, so I'll wait till then.
Richard
ps. I hope I'm not the only one who finds all the different combinations and naming style on the catseye page very confusing.
You need the sight tube (TELECAT XL) to center your secondary under the focuser.
Then the cheshire (BLACKCAT XL) to align the primary.
Then the auto-colimator (INFINITY XL/K) to tweak the secondary orientation and tilt.
Of course it is an iterative process. Read thorougly the link to the PDF Jason posted and have a look at Vic Menard's primary offset technique. It's important to understand why it works.
For those who are interested to understand the autocollimator in details, you can read my thread at cloudynights http://www.cloudynights.com/ubbthrea.../o/all/fpart/1
Read at least the first page of the thread
Bear in mind that understanding the details included in the first page of the above thread is NOT a requirement to use the autocollimator.
Jason
I have read a few articles & forum posts regarding the autocollimator, I'm convinced that the AC is the best tool to use at the moment. I understand the basic concept but for the fine detail that Jason has explained is not so easy.
I assume (ass again) all will fall into place once I get my hands on one of these tools.
Richard
ps. Thanks Neil I'm glad I'm not alone in my confusion.