AstroSystems Autocollimator - 1.25" or 2"

[richardda1st]

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

[qld]

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.

[richardda1st]

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

[qld]

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

[richardda1st]

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

[qld]

you will find that its best used in the day time or at twilight

[Jason D]

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

[richardda1st]

Thanks for you comments Jason. Your avatar tweeeeked some of my meurons and sent me back to the net.:lol:
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.:confused2:

[Jason D]

I do it all the time. I use one of these small clip-on LEDs which I clip either to the OTA rim or to one of the spider vanes. It works great.

Jason

[JethroB76]

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?

[Jason D]

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.

Jason

Proper instructions are in http://www.catseyecollimation.com/INFINITY%20XL%20Use%20&%20Care%20-%20R2.pdf

[Jason D]

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.

[richardda1st]

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.:confused2:

[erick]

Richard

Have you read the various Cloudy Nights threads on collimation and tools?

[NeilW]

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?

Thanks,

[multiweb]

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.

[multiweb]

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.

[Jason D]

For those who are interested to understand the autocollimator in details, you can read my thread at cloudynights
http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Board/reflectors/Number/3532750/page/0/view/collapsed/sb/7/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

[richardda1st]

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.:thumbsup:

Richard

ps. Thanks Neil I'm glad I'm not alone in my confusion.:confused2::confused2:

Some web pages are just not as easy as others.

[Jason D]

It is called the HotSpot

[Jason D]

Hi Richard,
Make sure to report back when you experiment with your new autocollimator.
I assume you got the Astrosystem 2" autocollimator.
Jason

[erick]

I have a 2" cheshire and a 2" two pupil autocollimator arriving shortly from Catseye. Richard and I live fairly close so we can experiment and learn together on our scopes. :thumbsup: (I've already fitted a hotspot to my 12" f5 mirror.)

[ericc]

Hi all,Jason makes mention of a small clip on led-- for illumination of the catseye triangle at night.
Has anyone got a picture or any info on this beast(as it sounds like it would be alot better than what Im using at the moment--a torch)?
Ta--Eric

[Jason D]

Hello Eric,
Attachment photo is what I used for some time. I am currently evaluating a significantly better and robust clip-on light. Stay tuned.
Jason

[ericc]

mmmmmmm--I like the look of that one Jason-------------and yep,im all eyes and ears for the next model.
Thanx for the feedback.

[JethroB76]

I had a clip-on light like that from a $2 shop. You will many such options if you look in those kinds of shops. $10 would probably get you 2 or 3 that would last you for years.

[richardda1st]

Would appreciate more appraisals on astrosystems 2" auto collimator from those who use them.

[erick]

You'll find that clip-on for about $3.99 in the corridors of your Coles or Woolies. Be careful, the socket can easily fall out of the ball joint with a knock. I have a couple I painted red and use to iluminate eyepiece cases. I finally superglued the socket into the ball joint at the right angle.

[multiweb]

Watching this space with interest. I have one of those clip-ons (white light) but I find that if the light is too bright the whole stack of 'Hotspots' gets lost in the stray light. Wondering if a narrrow beam limited only to light up the hotspot area only is preferable?

[richardda1st]

BUMP :shrug:

Ps. Shipping for the catseye 2" ac is $38.00 US

[JethroB76]

That's a ridiculous price. Does it arrive at your place before they send it, or what..

[catseyeman]

This "ridiculous" price which does seem high at first glance by the uniformed is for USPS Priority International Mail service which is actually the lowest cost "insurable" venue for International Shipments. There is a standard $7 adder for packaging materials and labor over and above what the postal service charges me. If the customer agrees to waiver their right for a refund or credit should the merchandise be damaged or lost in transit, then there IS a USPS 1st-class International Mail option for packages weighing 2 lbs or less. If this is of interest by anyone, contact me for a quote.

Regards,

Jim Fly
CATSEYE Collimation
www.catseyecollimation.com (http://www.catseyecollimation.com)

[JethroB76]

It may have read that I was having ago at Catseye, but that wasn't my intention. I am fully aware that most, if not all the cost, likely stems from how much the provider charges you. I was comparing it to my experience of the price of insured shipping of heavier, more expensive EPs and like out of the US.
So it was meant very much as a dig at the postal service's charges. Unfortunately, there has to be a base charge for a given parcel so it may not seem equitable for a light weight package compared to a heavier one.

While we are on the topic of postage..when I add an item to my cart on the website and go to checkout, the estimated postage to Aus is $0.00. Does this get updated later in the checkout process, or do you send a separate invoice for postage?

[catseyeman]

For International shipping, you can order one of 2 ways:

1) Order directly off the website using the PayPal "add-to-cart" feature at which time you will not be charged for shipping. When I receive the order, I will determine the total shipping charge (USPS Priority International Mail cost + $7 materials & processing) for the weight and insured value and reply with a request for the balance due and a direct PayPal link for the payment.

2) Send me an email indicating your product selection(s) and I will return a delivered price quote (USPS Priority International Mail cost + $7 materials & processing) and a direct PayPal link for a 1-time submission of the funds.

If a customer requests 1st-class shipping (for the reduced rate), a waiver of credit or refund due for damaged or lost merchandise is required via email prior to shipping.

Regards,

Jim Fly
CATSEYE Collimation

[JethroB76]

Cool. Thanks for that..hmm now what to get

[erick]

Pay insurance for your peace of mind. I had an order coming from the US for just under $1000 and didn't have insurance :screwy: Both I and the supplier had an uncomfortable few weeks when it vanished. (My guess is that it spent several weeks in customs while they waited to see if anything further arrived from the supplier for me, pushing the lost over the $1000 GST exempt level). Arrived finally and we both exhaled!

[Jason D]

Jim sent me a new product to evaluate for him. It is a clip-on with bright and narrow RED LED.

http://www.catseyecollimation.com/cliplights.html

I was pleased with it -- Definitely superior to my original cheaper plastic clip-on in terms of usability and durability.

[Sentinel]

I can recommend the INFINITY XL autocollimator and the service of Jim Fly.

I don't use the autocollimator much but it an excellent tool to use to get the secondary alignment correct.

The CatsEye collimation system is excellent value and while I have a Glatter Collimator, I would be more than happy with the CatsEye system as my primary tool for collimation.

[richardda1st]

Yes every one agrees that the catseye is a quality item.:thumbsup:
The catseye Infinity XL will cost me $138 US delivered.
The catseye Infinity XLK will cost me $167 US delivered.

The Astrosystem 2" AC will cost me $89 US (no extra delivery cost as I can add it to a current order).:)

But it appears that there's not many members using the Astrosystems AC to add some more comments.:confused2:

[Jason D]

I am interested to hear from Astrosystem 2" autocollimator owners about how well the center spot reflections maintain their positions when the autocollimator is rotated freely in the drawtube.

You might be interested in this recent thread at CN

http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/3903990/page/0/view/collapsed/sb/5/o/all/fpart/1/vc/1

Jason

[richardda1st]

Hi Jason.
The inaccuracy of the Astrosystem as compared to the laser in your CN post is a very useful comparison and informative statement.

You state that, "Had your autocollimator been a laser collimator, it would have traced a circle with 1.25mm (10mm/8) radius on the primary mirror".

But, can you please explain, if the circle would have a 1.25mm radius, what does the (10mm/8) represent?

Thanks
Richard

[Jason D]

Refer to attachment.
Assuming we have an autocollimator where the mirror is not perfectly squared to the barrel. When we stack reflections P & 2, the autocollimator axis (same as focuser axis in this case) will point off-center. If we insert a quality laser collimator, the beam will strike the primary mirror off-center as shown.
Now let us rotate the autocollimator 180 degrees. Reflections P & 2 will unstack. The distance between them is 8X the axial error. We can estimate the distance between reflections P and 2 then divide the distance by 8.
In the link I provided, I estimated the distance between reflection P and 2 to be around 10mm after the 180 degree rotation. Dividing the distance by 8 will give me the true error. 10mm/8 = 1.25mm
Jason

[richardda1st]

Okay so your estimate of 10mm (which you say is accurate:confused2:) divided by 8 passes = laser scribing a circle on the primary of a 1.25mm radius. Is that right?

Q 1. Is that a severe enough error for an autocollimator to negate the benefits?

Q 2. Wouldn't most lasers and or laser+focuser give errors of at least that?

Thanks for your time.:D

Richard

[Jason D]

Refer to the photo in this post
http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/3903990/page/0/view/collapsed/sb/5/o/all/fpart/2/vc/1#3906061
The 10mm estimate is the distance between reflections P & 2 which is an accurate estimation. The triangle spot perforation diameter is known to be 6mm. If you reference it, then you can estimate the distance between reflections P & 2 centers to be around 10mm.

The 8X is not because of 8 passes. In fact, Reflection 2 is only 5 passes. The 8X math is kind of complicated but it is a true statement.


Q 1. Is that a severe enough error for an autocollimator to negate the benefits?

Yes, because an average quality laser collimator can do better.

Q 2. Wouldn't most lasers and or laser+focuser give errors of at least that?

Yes. That is why autocollimators better be of superb quality to improve collimation above and beyond what other tools are capable of delivering.

Jason

[richardda1st]

Thanks for clearing that up for me Jason.:thumbsup:

Looking forward to Erick's call to try out his catseye tools.

Cheers
Richard

ps re the clip on light. Wouldn't a diffuse light be better than a spotlight which may be to bright to look at.

[richardda1st]

Just to keep it fair.;)
Lets not get into a brand name war please.:screwy:

------------------------------------------------------------------------------

Hello Richard,
We have been making collimation tools including the Laser, lightpipe/sightube and autocollimator for over 20 years. It is unfortunate that there is a lot of conflicting information out there about their use. Our Autocollimator is adjusted with an optical set-up having a 100' path. All others are just assembled mechanically and machine tolerances determine the accuracy. We adjust the tilt of the cap which holds the mirror to align the autocollimator, therefore the cap is not perpendicular to the body, so when the autocollimator is placed in the drawtube it is not inserted with the expectation the cap will be flush with the drawtube. Persons trying to force the cap flush with the drawtube has been one source of calling our tools "inaccurate". The three items in Jasons note are all incorrect in some way. First it is not necessary to see the fourth reflection, although you usually can. This level of collimation accuracy exceeds the ability of a telescopes structure to hold accurately. You will notice everyone talking about tool accuracy with no mention of the telescopes ability to hold it. What most assume or don't want to admit is that most production telescopes won't hold the single pass accuracy achieved by a laser or Cheshire (lightPipe). If you can percieve any movement of the laser spot within the center spot of the primary (1/2 pass) or on the bottom of the tool at the focuser (1 pass) when moving the telescope up and down then there is little need to waste time on using an autocollimator.

Item 2, flatness of the mirror is not critical, it is the center of the reflected spot that is being lined up so slight deviations in the appearance of the image have no affect.

Item 3 He is confusing the test for a laser which can be evaluated by rotating in the focuser. Doing this with an autocollimator cannot be done without tipping the autocollimator and seeing some movement since it only takes 1-2 thousandths of clearance between the two to show it.

I wrote the instructions and stand by them, they have been evaluated for over 20 years by thousands of customers. There seem to efforts by some manufacturers to keep collimation difficult and muddy the information water to get customers to buy their tools out of frustration.

As far as our tools accuracy, it is interesting that we have never gotten a autocollimator returned that did not test accurate. Our experience is that many have some difficulty learing the tool or don't care to take the extra time needed and rather than admit this go to the fallback "innacurate tool" defense.

We stand behind our product with a money back guarantee and complete customer support.

Randy Cunningham
-------------------------------------------------------------------------------------------
Hi Richard,
Adding the thread is fine. I'm just trying to figure a way to dispel a lot of misconceptions that sadly, seem to be coming from manufacturers as a ploy to sell their products. I'm not saying it is across the board and some is obviously unintentional. There is one other option I haven't mentioned, that is using a laser or a Cheshire (Lightpipe) to get basic collimation and then use the star test for fine collimation. It is as accurate as an autocollimator and costs nothing and can be done at night, unlike the autocollimator. You have no doubt noticed that all the finer collimation methods are not intuitive like the Laser or Cheshire and have a learning curve.

Randy Cunningham
-----------------------------------------------------------------------------------


As for my decision:

As others have said, the Catseye tools (thanks Erick for the trial run) are very impressive tools, quality and accuracy.

The ac is to fiddly for me, and as Randy points out many scopes including mine will not be able to hold this very accurate fine tuning as I noticed during the trial run, so it's not worth all the fuss. Brilliant for quality scops.

I'v decided to get myself a good 2" barlow laser. I think I was told to do just that by Mr.47TUC back at the Snake valley camp earlier this year, why don't I listen?:P

Thanks one and all.
Richard

[multiweb]

I don't understand that bit. :shrug: In my experience a tilted mirror is a problem. I have experienced this on an A/C with an SCT. Very hard to iterate towards a finer alignment if your A/C mirror is not square. Unless I'm missing something?

[Jason D]

It seems that some have misinterpreted my posts as an attempt to push for a competing product. I find that to be unfortunate and insulting. I am not a vendor nor am I affiliated with any vendor. I never made a single penny from my involvement with astronomy. I am an engineer who loves and enjoys solving challenging technical problems. I was intrigued by the autocollimator reflections. I have viewed it as a challenging mathematical problem to solve. I developed a ray trace simulator to understand how reflections are formed and their characteristics. I spent a significant amount of time understanding the intricacies of the autocollimator and unraveling more of its secrets. Catseye encouraged me to proceed and adopted several of my innovations.

http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/3532750/page/0/view/collapsed/sb/7/o/all/fpart/1 (http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/3532750/page/0/view/collapsed/sb/7/o/all/fpart/1)

If a hypothetical laser collimator vendor attempts to sell a laser collimator that when rotated traces a circle with 1.3mm radius at a distance of 1500mm, will that vendor win good reviews? The 1.3mm radius represents an error of 3 arc-minutes which is the accuracy guaranteed for Astrosystems autocollimators.

If someone has a laser collimator that hardly traces a circle at a distance of 1500mm then how will an autocollimator with 3 arc-minutes error introduce additional accuracy? Additional accuracy implies using a tool with higher quality and higher sensitivity. Using a tool with lower quality will make things worse – not better.

Randy’s attempt to discredit the rotation test is unfounded. What is the point for someone to get out of his/her way to stack all center spot reflections then see them noticeably unstack when the autocollimator is rotated 180 degrees? I have already covered the math behind assessing the autocollimator mirror error with the rotation test. It is a valid method to assess the quality of an autocollimator.

Randy’s statement about mirror flatness being unimportant is also unfounded. A closed light path needs a flat autocollimator mirror. Without it, the background of the autocollimator will be semi-dark. This is a true statement because each part of the autocollimator mirror is contributing to the enclosed light path. Besides, why should anyone assume if a mirror is not precisely flat off-center to be flat at the center? I believe it is fair to assume the mirror will have the same good or bad quality throughout its surface.

Randy’s statement about discrediting the importance of the 4th reflection is a clear example that he does not understand the autocollimator. If I understood him correctly, he is stating that the 4th reflection is the most sensitive reflection and that ultra sensitivity is an over-kill for most scopes. He missed the whole point about the 4th reflection. First, the 4th reflection is NOT more sensitive than the other reflections. In fact, the 3rd reflection is 2X more sensitive than the 4th reflection. The math behind reflections bouncing back and forth between a concaved mirror and a flat mirror is complex and unintuitive. The importance of the 4th reflection is to use it for secondary mirror alignment. Each reflection measures a different error: 2nd reflection measures how close is the focuser axis to the COC point (Center of Curvature). 3rd reflection measures how parallel the autocollimator mirror is to the focal plane. 4th reflection measures how close is the focuser axis to the primary mirror center.

I disagree with the statement that quality and accurate collimation tools are a waste of money with scopes that flex and can’t maintain collimation for two reasons: First, the quality collimation tools will place collimation at the center of the “sweet spot.” This is the small area where collimation is considered excellent. Any minor movement of the scope will move collimation but will keep it within that “sweet spot.” In case someone swings their OTA significantly and the scope gets slightly out-of-collimation then it is up to the owner. If the owner is doing planetary observation and would like to ensure the scope is perfectly collimated at a given AZ/ALT setting, then the owner will have the option to do so using quality and sensitive collimation tools.

I am not the first one to unravel the autocollimator secrets. I only unraveled additional secrets. Nils Olof Carlin (barlowed laser inventor) was the first to analyze the autocollimator mathematically. Vic Menard used Nils Olof analysis to devise an excellent procedure to use the autocollimator starting with a technique he called CDP (Carefully Decollimated Primary). CDP uses the 4th reflection which Randy felt was unimportant. Nils Olof’s and Vic’s contributions have been published on the web for many years – even before I got into this hobby. Catseye took that work and productized it. I am still dumbfounded to why Astrosystems is still publishing outdated and inaccurate procedure and inaccurate description of the autocollimator theory.

http://web.telia.com/~u41105032/Acoll/Acoll.htm (http://web.telia.com/~u41105032/Acoll/Acoll.htm)
http://homepage.mac.com/vicmenard/telescopes/NPaddend.html (http://homepage.mac.com/vicmenard/telescopes/NPaddend.html)
http://www.catseyecollimation.com/vicsCDP.html (http://www.catseyecollimation.com/vicsCDP.html)

My critisim of the Astrosystems autocollimator should not be misinterpreted as a criticism of their other products or their business practices. I have nothing against Astrosytems. I am only criticizing the quality and documentation of a single product.

I stand behind every statement I made in this thread.

Everyone is free to do whatever they want with their money and purchase any product they desire. After all, amateur astronomy is only a hobby.

Jason