Cheshire Collimator advice

[BlueBird]

Hi,
I am looking for advice in purchasing a good cheshire collimator.
2 items available at Bintel:
1/ Bintel chesire
2/ Orion collimatoing tool.

any thoughts?

The tool will be used in a 76mm reflector and a 200 mm reflector.

Thanks Marty.

[erick (Eric)]

My experience:- I asked at Bintel for the Bintel Cheshire. I was advised not to buy it but rather the Orion Collimating tool, which I did. (The staff members were quite convinced the Bintel tool was of unsatisfactory performance.) I have to admit, however, that I have never really made much sense of the view through that tool. I never put it in until I was collimated with the laser or barlowed laser and the Orion tool seemed to say it was spot on. However, recently, I was able to put a different Cheshire tool into my scope and the difference was significant. I could understand what I was looking at and crosshairs were in much better focus. I was told that Cheshire was from Andrews Communications. I've just looked at their site and it must be this one:- "Collimation eyepiece, Cheshire Newtonian type, Skywatcher brand" - $49. I look forward to hearing other comments.

[rmcpb (Rob)]

Make sure the cheshire eyepiece you get is a LONG one. If it is too short like my original one you cannot see the hairline cross well enough to use the thing. I have the Orion one now and its worth the extra $20 over the short one.

[Kokatha man]

rmcpb - are your comments at variance with Erick's? I thought he was saying that he found the Orion tool less useable than the one he used recently, that he thought came from Andrews Comm....(Erick, were you referring to what is generally called the orion collimator/sight tube ?)

Bintel recently gave me the same comments re the chesire they stocked - they've slashed its price but think it's an inferior device and not worth buying (how's that for product un-endorsement!)

Personally, I'm sick and tired of "collimating" my newt with a modified film canister!!!???!!! (I use the word "collimate" very loosely, even though I think I've achieved marvellous results with this crude device in the short time I've had my 10" dob.)

Bintel tell me (constantly) that their next shipment is imminent: I'd be very interested to hear some views on the qualities/effectiveness of collimators that are currently available have read - I'm also waiting for a laser job but understand they are best for fine-tuning collimation.

On another note, what's your take on the Round Table Platforms rmcpb? - I'm awaiting delivery in a few weeks of one myself.....regards, Kkm.

[erick (Eric)]

With regard to Bintel, yes, that was my experience.

The Orion collimating tool is a combined sight tube/Cheshire.

I can only say that the person with the Andrews' Cheshire looked through the Orion and said it didn't look very good, then brought out his Andrews Cheshire (which wasn't as long as the Orion as I recall), and we both agreed it provided a much better view.

However, I'm quite willing to accept that there is something wrong with my eyes

[rmcpb (Rob)]

I just happen to like the longer tube as it lets me see the crosshairs clearer. However, I only use the Cheshire intermittently as I use the laser collimator for the checks before observing. The Cheshire is mainly used for centring the secondary and to check the overall collimation occasionally.

[Starkler (Geoff)]

Originally Posted by rmcpb

I just happen to like the longer tube as it lets me see the crosshairs clearer.

The function of the crosshairs is to help get the secondary correctly aligned and a longer one is going to do this more accurately.

[ausastronomer (John Bambury)]

Originally Posted by erick

My experience:- I asked at Bintel for the Bintel Cheshire. I was advised not to buy it but rather the Orion Collimating tool, which I did. (The staff members were quite convinced the Bintel tool was of unsatisfactory performance.)

Hi Erick,

The staff at Bintel are correct. The Orion Collimating tool is a great device, only bettered by specialist "optical" collimating devices like the Catseye and the Tectron Tools, which are infinitely more expensive.

Originally Posted by erick

I have to admit, however, that I have never really made much sense of the view through that tool. I never put it in until I was collimated with the laser or barlowed laser and the Orion tool seemed to say it was spot on. However, recently, I was able to put a different Cheshire tool into my scope and the difference was significant. I could understand what I was looking at and crosshairs were in much better focus.I was told that Cheshire was from Andrews Communications. I've just looked at their site and it must be this one:- "Collimation eyepiece, Cheshire Newtonian type, Skywatcher brand" - $49. I look forward to hearing other comments.

Nooooooooooooooooooooooooooooooo !!!!!!!!!!!!

The Skywatcher combination cheshire is of clearly inferior quality to the Orion tool, which is Japanese made. The tolerances and machining on the Skywatcher tool are average at best and it will never be as accurate as the Orion tool, primarily because it will have a fractionally different orientation each time it is put into the focuser. In addition the Andrews tool is shorter and you also lose accuarcy as the tube length gets shorter. I have owned the Orion and also own the Tectron Tools, which are superb.

Persevere with the Orion tool, it is a very good unit. It just takes a little getting used to with all those reflections going on. That all comes with experience. You are driving a Ferrari and you are still on P-plates, pretty soon it will all "click" and you will get the gearchanges right

Cheers,
John B

[ausastronomer (John Bambury)]

Originally Posted by erick

I can only say that the person with the Andrews' Cheshire looked through the Orion and said it didn't look very good, then brought out his Andrews Cheshire (which wasn't as long as the Orion as I recall), and we both agreed it provided a much better view.

However, I'm quite willing to accept that there is something wrong with my eyes

Try staying back from the orion tool a little more. I bet you are getting your eye to close to it. Nothing wrong with your eyes, it's your technique.

Cheers,
John B

[erick (Eric)]

Thanks John, I would not be surprised at all that it is my technique. I've done some more reading ( http://www.propermotion.com/jwreed/A...te/Chesire.htm ) to properly understand what I am trying to achieve with the Orion tool and I believe I now do understand, particularly the role of the reflecting surface on the Cheshire. The instructions that came with it weren't crystal clear to me. I'll re-read them tonight and I will probably now understand them as well .

With my 8" f6, the laser collimation has always been so quick and apparently successful, I haven't worried about anything else (apart from initial sight tube checking). With the new 12" f5, I'd better improve my capability! Eric

[erick (Eric)]

Originally Posted by ausastronomer

Nooooooooooooooooooooooooooooooo !!!!!!!!!!!!

Well, that's a pretty definitive comment!

[Cluster]

Originally Posted by erick

I was told that Cheshire was from Andrews Communications. I've just looked at their site and it must be this one:- "Collimation eyepiece, Cheshire Newtonian type, Skywatcher brand" - $49. I look forward to hearing other comments.

I bought my first real scope last week (GSO 6" reflector) and found collimating to be tedious, so I decided to buy some tools from Andrew's. Not having used anything before I grabbed both the $49 GSO laser collimater and the $49 Cheshire Newtonian, Skywatcher brand. I didn't know which I'd like better and find more useful (some tutorials recommend against using lasers for the secondary, others say it's fine).

The GSO laser is a nice piece of work and despite having a rather broad laser beam, collimated my telescope easily.

I honestly felt ripped off when I opened the Cheshire's box. It looks extremely cheap (all plastic), the rubber around the top is uneven, there is no sighting cross and the silver reflecting surface looks like it was sprayed on using $2 spray cans. A used film canister would be as useful and infinitely cheaper. $49? no way.

I expected a sighting cross and I guess my inexperience showed. The GSO laser is so easy to use for both the secondary and primary that honestly I don't know why anyone would use something else.

Anyway, that's my experience :-)

[Kokatha man]

Hi cluster, I reckon you're right about that Andrews chesire - they actually put one in with a parcel they sent me yesterday: could have been accidental but I reckon they're trying to get rid of them - I took one look at it after thinking I'd got a lucky dip and thought "nah - I'll stick with the film canister for now....!"

Pity you had to pay for yours - want another to keep it company?

[Geoff45 (Geoff)]

Originally Posted by Cluster

The GSO laser is so easy to use for both the secondary and primary that honestly I don't know why anyone would use something else.

Anyway, that's my experience :-)

Because a cheshire is more accurate and a barlowed laser (google this) is even better. A straight laser relies on the laser spot hitting the centre spot of the mirror exactly. If you are 2 mm off, then your error at the eyepiece is 4mm--way too much for an f5 Newt. See the very informative article here originally published in Sky and Telescope, which also describes the barlowed laser. For mine, the BL is the easiest and most accurate way too go, but a Cheshire comes pretty close (I use the Orion and find it's OK).
Geoff

[GeoffW1 (Geoff)]

Originally Posted by ghsmith45

For mine, the BL is the easiest and most accurate way too go, but a Cheshire comes pretty close Geoff

Hi,

Another Geoff chiming in here, I have both these gadgets, and use both, and agree wholeheartedly.

I have to be careful here because I recently got involved in some depressingly acrimonious exchanges (all very unnecessary) through wanting to stick to my guns, but I think that there is a LOT of variability in this:

- Dobs respond better to some techniques than others, do you think?
- Some Dobs (from what I read) are more sensitive than others, is this true?
- Some of us place more importance in certain collimation areas than others

How many think N O Carlin is the final authority for collimating Dobs (I think myself it is hard to fault him) ?

Cheers

[ausastronomer (John Bambury)]

Originally Posted by Cluster

The GSO laser is so easy to use for both the secondary and primary that honestly I don't know why anyone would use something else.

Anyway, that's my experience :-)

Well the GSO laser might be very easy to use but unfortunately life isn't that easy

You cannot properly collimate a telescope from scratch, with just a laser only. The laser cannot help with setting the secondary distance from the primary mirror. You can only do this with a sight tube or if you're good, eyeball it. Unfortunately things get worse, if the secondary/primary distance is not correct it is still possible to adjust the tilt of both mirrors and get the laser striking back perfectly upon itself, thus making the telescope appear properly collimated, when in fact it is not. Whilst the laser would show the telescope as collimated in this situation, a sight tube or star test on both sides of focus would show it to not be collimated. A laser is only useful to adjust the "TILT" of both the primary and secondary mirrors once the secondary is properly positioned in terms of its distance from the primary and in its rotation.

Once you have the telescope properly collimated a laser does an excellent job of adjusting the tilt of the mirrors. The barlowed laser method is only useful for adjusting the tilt of the primary mirror.

The best test as to whether your scope is properly collimated, is to check it with a bright star. I always do this several times during the night as the mirror cools, or shifts slightly with sling movement. A defocused star image on either side of focus contains an enormous amount of information about the scopes collimation and its optical quality. I don't need to go into all that here as Dick Suiter wrote an entire book on it. In very very simple terms follow whats bellow:

Use an eyepiece giving 10X to 15X per inch of aperture, if seeing will allow, less power if not.

Defocus the same distance both sides of focus until you get a diffraction pattern showing "rings". The diffraction rings should appear "PERFECTLY CIRCULAR" and not egg shaped. The secondary shadow should be perfectly centered in the diffraction rings on both sides of focus. If the secondary shadow position in the diffraction pattern appears to change from one side of focus to the other, the secondary position is incorrect in its distance from the primary. In other words, it is not properly aligned with the focuser.

Cheers
John B

[ausastronomer (John Bambury)]

Originally Posted by GeoffW1

Hi,

How many think N O Carlin is the final authority for collimating Dobs (I think myself it is hard to fault him) ?

Cheers

He is obviously a person very skilled in optical theory and the properties of light. So far as being an authority on collimating a telescope, he is an authority to people who need some assistance in collimating a telescope and in many cases don't properly understand it. A lot of experienced observers still do it the same way they did it, long before Nils Olif came along with his S & T article, me included. I am sure my telescope was properly collimated before that article came along.

Vic Menard, who is still around and a Cloudy Nights contributor, wrote a lot of articles and a book on collimation, before Nils Olif found his red laser. I doubt that Vic Menard needs to use a barlowed laser to collimate his telescope.

Come to think of it. I doubt Isaac Newton ever had a laser; and he obviously figured out how to collimate his telescope

Nils Olif's barlowed laser method is very good for quickly checking the tilt of the primary mirror, once you have everything else properly aligned. Keep in mind that's all the barlowed laser method is good for. Does it do this single job any better or more accurately than can be achieved with other methods? The answer is no.

Cheers,
John B

[GeoffW1 (Geoff)]

Originally Posted by ausastronomer

he is an authority to people who need some assistance in collimating a telescope and in many cases don't properly understand it. Cheers,
John B

Well, that's poor old Nils put in his place!

More seriously. you don't think then that he can lay claim to some small incremental improvements over his forerunners?

Cheers

[BlueBird]

Thanks All who have contibuted.

I personally have not been able to get good results from using my film canister, and wanted to get an improved technique and tool, or is it an improved tool and technique.

From the discussion and 2 web addresses a site tube is an important first step.

The Orion combitation site tube and cheshire collinator is what I will be looking for.

Thank you all. Marty.

[ausastronomer (John Bambury)]

Originally Posted by GeoffW1

More seriously. you don't think then that he can lay claim to some small incremental improvements over his forerunners?

Cheers

The answer is probably yes; and I don't mean to be denigrating to him.

But I truly don't believe its heading things down the right path, in terms of properly educating new astronomers in how to set up their equipment. Collimating a telescope and setting it up properly is all part of the learning curve. By leapfrogging, a lot of beginners miss vital parts of that learning curve and don't ever understand the processes and theory behind proper optical alignment of all the components, namely, focuser, secondary mirror, primary mirror and the many different ways each of these components can be adjusted and the effect of those different adjustments. In my opinion it is somewhat akin to putting a 16 yr old in a new Ferrari before you have taught him how to change gears.

How do people who only use a laser or barlowed laser go when they drop the laser on the ground and break it, as they get it out of the car, prior to collimating the telescope? Do they pack up and go home for the night without observing, or just observe for the night with a poorly collimated telescope?

Use it as a means to save time once you know how to collimate a telescope, but don't leapfrog the steps in the learning curve along the way.

Cheers,
John B