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Cheshire Schmeshire


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Hi all

I have been getting successful collimation (confirmed by someone very experienced) for a long time with my dobs and consider myself reasonably good at it based on my methods to date.

These have been :

1) Use of a (collimated) Laser, barlowed for the primary adjustment

2) Use of a home made collimation cap and a cheapo plastic Cheshire type collimator that came as a freebie with a previous scope (pics of both of these below).

I have grown to prefer option 2) above despite the back and forth required given the 1.6m focal length of my scopes. Using the cap I can clearly see the position of the secondary in relation to the drawtube (I use a small piece of card to block the primary reflection) and also the position of the reflected primary and all three clips, all evenly positioned in the round secondary.

I can also clearly see the black circular doughnut on the primary and encourage the dot (being the reflection of the peep hole in the collimator) into the centre of said doughnut - I'm collimated - at least good enough for visual and star tests confirm this.

However, the collimator I have is plastic and does not have the fancy crossed wires of a 'proper' Cheshire so I thought I'd buy one. I got the Astro Engineering one with an etched target also on the angled face of the tool and the build quality seems really good. The peep hole is a little larger than expected (4mm) but this seems to suggest it will act well as a sight tube too and replace both of my current tools. It has of course the 'posh' crossed wires.

BUT I cannot see the doughnut and dot very well at all and the current tools I have seem to be so much clearer and easier to use. Is the one I have bought unusual in that is has such thick cross wires (they do seem to be quite thick just under 1mm as far as I can see) and do I even need cross wires if I am getting good collimation without them? Maybe I am doing it all wrong but it seems to work for me and the results through the scope are excellent.

Can anyone advise if they have similar issues?? At the minute I am considering sending it back as I cannot see me using it.

Cheers

Shane :)

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The crossed wires are good oin a Cheshire as they can help. One way of approaching it is to get the cross wires over the donut for the secondary to prinmary alignment - then get the dot in the dounhut for the primary to secondary.

I cant say why your AE Cheshire is playing up - I assume you have decent light source down the front of the tube while using it. Also I assume you have the 'bright' face of the cheshire (ie the shiny bit) pointing at a light source as well.

I have a cheapie Cheshire - just your basic cheap and nasty one and it works fine. Oddly I am looking for a nicer one myself and had considered the AE one.

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The crossed wires are good oin a Cheshire as they can help. One way of approaching it is to get the cross wires over the donut for the secondary to prinmary alignment - then get the dot in the dounhut for the primary to secondary.

I cant say why your AE Cheshire is playing up - I assume you have decent light source down the front of the tube while using it. Also I assume you have the 'bright' face of the cheshire (ie the shiny bit) pointing at a light source as well.

I have a cheapie Cheshire - just your basic cheap and nasty one and it works fine. Oddly I am looking for a nicer one myself and had considered the AE one.

cheers AB, yeah I use the same methods as with my cheapie one as you describe. the view through them is chalk and cheese. maybe it's my eyes but I cannot clearly see beyond the cross 'hairs' to even see the doughnut and dot, although I can see it clearly on my cheapie one without any cross hairs.

maybe I should try and borrow another kind and see if it's for me or not. :)

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Shane - been there and done that !

I've tried 2 "posh" cheshire collimating eyepieces (with cross wires) and a couple of laser collimators, including the Baader. I still find my cheap plastic cheshire (just the same as yours) does the best job and is the easiest and most intuative to use.

Plus it works for refractors as well !.

I do still have a laser (which I've spent ages getting well collimated) but I only use that to adjust the secondary tilt - it's back to the cheapo plastic one for the primary adustments.

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well, this is good feedback - especially from John.

I have just been over to someone very experienced locally and he looked through it and said 'uuuughhh that's awful'.

needless to say it's going back and I might even sell my laser too as I seem to have settled on the 'cheapo Cheshire'.

it seems the only way to go better is to go for the catseye type stuff but I know little about that. I'll stick with what works for now :)

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Been there Shane - had two lasers and both were as much use as a chocolate teapot. The firts one was so miscollimated it was a waste of space, the 2nd one I collimated myself but aftre a few uses the power button broke and to be honest I had to check its collimation every time. A measuring tool thatv cant be trusted is no tool at all.

The Hotech laser was superb and gave good results and if I had a very long tube newt I'd get one.

I suppose I am going to end up coughing up for the Catseye Chesires in the end.

Edited by Astro_Baby
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