cheshire collimator

[asimov]

Hi all.

The question I have for you all is: Do I REALLY need a cheshire to collimate correctly???

I guess you could say I'm from the 'old school' because I firmly believe you dont need to purchase a collimating device to do the job. I have both a reflector & a refractor, & here is my 'technique'

For the reflector, I just look down the draw-tube, get EVERY circle concentric with every other circle. Plunk the film canister with the peep-hole in the draw-tube, [which gives you more precision]keep adjusting until again..every circle is concentric with all other circles. Then take it out and star test..adjust the primary IF it needs it till all the diffraction rings are concentric. [The diagonal off-set is achieved automatically by doing the star-test collimation]

For the refractor, I take the EP out, keep the cover on over the objective...look down the draw-tube with some light behind you [such as a fluro or even a white wall that is illuminated with a decent bright light] You will see..in my case 4 round ghost-like reflections...adjust the primary till the reflections overlap, one on top of the other. Again, adjust things until all circles you see are concentric with one another...in my case, I needed to re-position the focuser assembly till it was 'square on'. I took it out for a star-test & the result was a perfect concentricity of all diffraction rings.

Now after saying all that...theres a little niggling doubt/thought in the back of my mind saying........." sorry, but it CANT be collimated correctly because you did NOT use a cheshire!!"

I posed this exact same question on the cloudy nights forum & general concensus being.. " yeah yeah, but it's EASIER with a cheshire!!"

OK, it maybe easier.....I'm not sure what I'm trying to say here!..
Ummm...is my star-test lying to me & it's not collimated CORRECTLY? IF this is the case, I WILL purchase a cheshire! As far as I know, a star-test is the defyning/correct/best way to collimate.

Thought/opinions/comments people?

Asimov










:confuse3: :confused: :confused: :confused:

[ving]

it makes it easier.
but if you can do it properly without then there no reason to buy one :)

but at under $30 it not exactly a big purchse to make you collimation easier is it?

in the end its what you want that counts :)

[atalas]

Hi Asimov

I can't see how collimating with the star test will give you secondary offset!but I can see how It gives you good main mirror collimation.
If you don't believe that your peep hole is not doing a good job just stick a cheshire in the focuser and then you will be a believer!


Louie:whistle:

[asimov]

The cheapest cheshire I can find is 70 bucks! Mind telling me about the 'under 30 buck one' ?

[atalas]

ANDREWS COMMUNICATIONS SYSTEMS !

Louie:)

[slice of heaven]

Im also from the old school asimov and use the same technique but that doesnt mean its perfect. For visual I find it good enough, though I will admit a good tool/tools will make it easier and eliminate that nagging doubt. I will eventually purchase the tools but it wont simply be a cheshire. I'd rather jump to the top of the tree in regards to collimating if I am going to purchase tools for the job. Good collimation can be achieved, with the sight tube and a good understanding of the steps involved.

[asimov]

Andrews do not mention a cheshire in their telescope accessory list....only the laser

[atalas]

He has got them asimov ring him!


Louie:)

[ving]

just call me when you need a fr.....


1800 ANDREWS :P

I bought mine from there so I know he has em and they are cheap :D

[asimov]

Much obliged Louie! Oh, & you were right...a star test collimation does NOT automatically off-set the diagonal mirror! he he! [but u already knew that]

Asimov

[Starkler]

A cheshire makes it easy to get it accurate enough that you dont need to tweak on a star test.
As you have a driven mount, star test tweaking would be a lot easier. For us dob owners, stars just wont stay put for us and some form of collimation tool is very desireable.

[asimov]

Hi Geoff...That's interesting, so a star test IS accurate enough.

Incidentally, My mount is not driven [as yet] After 30 years of collimating this way, one gets pretty good/quick getting to those collimating screws!

[RAJAH235]

Hi asimov. The main reason that I have a Cheshire is that, after I have done any maintenance or repairs to my t'scope that required the removal of the main cell/2ndary etc, I can check the collimation very SLOWLY/ACCURATELY, using the Cheshire while indoors.(warm & dry). Final 'Star testing' is then done later.(COLD & damp). :P
Regards, L. :D

[seeker372011]

Ok you have me convinced I am buying a Cheshire from Andrews on Monday...I belonged to the Asimov school of thought, but now I am going to come over to the dark side

actually Mike (iceman) showed me his Cheshire up at Kulnora and I have been thinking its an essential..and at below 30 dollars...

[RAJAH235]

Right Ving, How're we splitting the spotters fee?:P:P :D L.

[seeker372011]

what's that 3 cents each?

[RAJAH235]

Now you all know, we're not THAT cheap! We work on a fixed contract.:P :D L.

[asimov]

You guys had me going for awhile! Hats off to ya!

I'm staying at the old school! I cant warrant buying a cheshire, I dont care how cheap they are....After 30 yrs. I reckon Iv'e developed skills good enough to collimate without a bloody cheshire. It's called 'KNOW YOUR INSTRUMENT'

No disrespect to the people that *think* they need all this collimating stuff. I'll put the money I save into another EP.

And while I'm on the subject of the 'old school' another thing I refuse to conform to is stacking images. It's 1 raw image with a CHEAP KODAK digital camera for this lil' black duck.

I do get carried away, dont I ?? he he!

This post ain't sposed to be taken seriously.....god knows I'm gigglin' while I'm typing it!

Regards to everyone here,

Asimov

[asimov]

DONT do it Seekeerrrr!

[seeker372011]

too late...in my hot little hands..now I belong to the dark side

[asimov]

Let me know weather u get better views after using, ok? :)

[iceman]

Yeh looking forward to seeing the results seeker.. you should also check your secondary and primary for pinching, as I said in your image thread.

I've used the film canister, but then I bought the cheshire, and it IS easier with the cheshire, and probably gets me much more accurate results without the need to star test. Like Laurie, the star test is the final final test and minor tweak if needed.

[frogman]

Put my order in for a tube AND A laser with Lee today.

[slice of heaven]

Now thats a better option froggy, 2 tools

[frogman]

working it out ..... the tube is good...to a point...
the way i see it collimation is like woodwork.
the tube is a coarse sandpaper
and the laser is the final wetanddry.

[BC]

Hi there,

While I'm on the telescope hunt, I'm checking out the collimator thing. It all sounds like the Cheshire is the go, and is only $29. When I spoke with the "other" shop, they wanted to sell me a laser unit for $75. My assumption was that the expensive laser unit would be better, but then I read somewhere "use the laser to get close but use a Cheshire to fine tune". This makes the laser sound rather useless, and I should only spend $29. Is this the go?

[ving]

its what I did... works fine for me :)
the laser is prolly more expensive because of the technology in it