Barlows & Collimators?

[ballaratdragons]

Hi all,

It's question time. :P
Both Mombat and I need to know the same things.

Never having used either a Barlow or a collimator we need to know which is better.

<b>Barlow 2x:</b> Question - Short or long? and whats the difference?

<b>Collimator:</b> Laser or Cheshire? and whats the difference. I know one has a laser, but how does the Cheshire work?

We would both appreciate any help.

[Striker]

I wrote this reply just so you got the email to check the response Ken.....sorry.....bit bored tonight....lol

Tonyhttp://www.users.on.net/~striker/laser.gifKen

[ballaratdragons]

Yeah, I been counting the cricket sounds myself to this question.

I must have upset a lot of people.

Half the people in here know the answers.

[RAJAH235]

Hi Ken and Mombat, All I can say is that I have the Meade #140 Barlow which is a long series. It is a top performer as far as I'm concerned.
The cheshire E/P,(about $60), has a large hole(25mm) in the side near the top and an eliptical alum. reflector inside,set at 45deg, with a 10mm hole in it. There is a 2mm hole in the top face which you look thru. By shining a torch into the side, you can see ALL the reflections. If your t'scope is correctly collimated, then your eye ends up in the CENTRE OF ALL THE CONCENTRIC CIRCLES.(with a little bit of 2ndary offset).
eg. Like a dart board.
As for the laser coll., they are prone to going out of collimation themselves. (Don't drop). They work by projecting the beam onto all the surfaces and finally disappearing up itself! If it doesn't, your t'scope isn't collimated. Not sure of pricing.
Cheshire can be dropped,(done), stood on,(done), and generally knocked around, but don't do this with a laser.
Maybe the others can comment on the diff. between long and short barlows, and their prefs. I never bothered. I looked for the most efficient and L.proof.
HTH. Regards, L. :thumbsup:
ps. I think the short tube is mainly used on t'scopes with limited focuser travel.

[ballaratdragons]

Thanks Laurie.

Do you have to look through a Cheshire or can you see it from the back end of the scope?

[RAJAH235]

What sort of t'scope?????? You've got a DOB. You look thru the 2mm hole in the cheshire(1.25 inch diam), which is in the focuser.

[ballaratdragons]

My 12" Dobber and Mombat is getting a 10" Dobber.

In other words I can't sit down the back end and adjust it looking up at the cheshire. Bummer.

[RAJAH235]

Ken, how do you expect to see the mirrors and your eyeball if you are at the base of the t'scope? You put the cheshire into the focuser tube, you look thru the 2mm hole in the top of the cheshire. Then you shine a torch,RED LED, into the large hole in the side. This illuminates the mirrors so that you can see where your eye is. If it ain't in the centre of the dartboard (concentric circles), then your t'scope ain't collimated!(with a little bit of 2ndary offset). Check this link.:thumbsup:http://skyandtelescope.com/printable/howto/scopes/article_790.asp

[Starkler]

You cant go wrong with a cheshire.
Its very easy to go wrong with a laser. In fact its pretty hard to be sure with a laser that everything IS right.

Id post a few usefull links but ive lost all that for now as my pc has died and im on a laptop :(

Bintel has the Orion Shorty plus for $150 I think, which is a highly recommended one and identical to the Celestron Ultima which carries typical Celestron pricing if you know what i mean .

[ballaratdragons]

Thanks Laurie and Geoff.

I thought that a Cheshire might possibly work like the laser one where you can stay at the bottom of the scope and see into the side of the laser tube.

Looks like I'll have to go Cheshire and just keep moving up and down the scope.

I already have a film canister sight tube, I just want to get it more accurate.

Thanks guys

[Starkler]

Ken the ultimate measure of collimation is a star test.
How well does the film cannister go in that regard ?

[RAJAH235]

Ken, It is easier if you get someone to do the adjusting for you, whilst you look at your mirrors/eyeball! You'll be there ALL night, if you do it yourself. Only minor adjustments are usually necessary. When you get to star test it, you definitely need 2. YOU have to keep moving the t'scope to keep the star in the centre of the field, while the adjustment is made! The reason I say this is, If the mirror is moved too far and the image moves off the axis, you will find it hard to get it back again without a drastic realignment. Please use 2 people. Your child can twiddle the coll. screws. :prey:

[ballaratdragons]

Geoff,

I have not had clear skies in a week now. I'm still waiting to do a star test.

I just keep trying to collimate to perfection while waiting for some sky, and getting frustrated!

I know that I could spend weeks collimating, and it will alter soon as I carry the scope outside, but it's good practice. But would like to know the right tool to speed up collimating outside once the scope is set up.

Don't think we have clear skies for a while yet.

[Starkler]

agh trying to collimate a dob with a star test alone isnt an easy thing to do.
I meant use your tools to collimate then verify its accuracy later on a star test.

[ballaratdragons]

Thanks Laurie,

Great idea. Kids or Missus (Cheryl). I did try a quick star test when I first got the scope. Bloody star had moved every time I got back up to the EP. lol

The trip from the bottom of a 12" to the EP is a long one. You need a packed lunch for each journey.

[ballaratdragons]

Thats o.k. Geoff I knew what you meant.

I wouldn't dare attempt to collimate by star test.

[RAJAH235]

Ken, did you try the link??????
L.

[ballaratdragons]

Yes Laurie thanks.

I also printed that one off for a friend up the road a few days ago.

I must have not read all of it. I will re-read it in bed tonight.

[RAJAH235]

Ken, your collimation shouldn't change just by moving the t'scope outside. I transport mine in the car like many others and my collimation doesn't change. It's a DOB, with a steel tube isn't it?
My Meade's got a SONAR TUBE. ie; CARDBOARD.

[ballaratdragons]

Yep, steel tube!

It probably doesn't move but I would like to know that I can collimate quickly should I need to out in the dark.

The quick star test I did when I first got mine showed a set of perfect rings but because of the wind the image looked like it was boiling (air currents in the tube). I am eager to test it on a still night.

[ving]

andrews sell a cheshire for $45.
I have a GSO 2x barlow... dont know if its long or short.

but go the cheshire. its dead easy to use :)
now unsubscribe to this thread or I'll spam it :P

[wavelandscott]

I'd encourage the chesire over the laser...no need for power and no moving parts...it is dead simple and very solid...I have the Orion Chesire and it looks and feels nearly indestructable.

I've not had much experience with Barlows...

I have a 2.5X Powermate...it is a glorious piece of work...but, I can not say that it is truly better or worse than other Barlows available as I have not compared it side by side with anything else...it does however work a treat!

There were some good threads on CN (Cloudy Nights) discussing the pros and cons of "shorty vs regular" Barlows...

[ballaratdragons]

Thanks all. Consensus rules. I'll get the Cheshire. Mombat probably will too.(?)

I just found out today why I could not get the scope to collimate exact!

The focuser was not perpendicular to the focal plane. 0.5mm of plastic laminate under the lower side and all fixed.

I gave it a daylight test.

WOW! what an improvement. I can focus perfectly on every strand of a cobweb on a small fence post 1 kilometre away. And that is even through heat haze using a 9mm Plossl.

Can't wait to do a real star test tonight, weather is finally starting to look good for tonight.

[jackenau]

Keep me informed Ken, will probably influence a decision I have to make.

The other Ken or another Ken

[Mombat]

Yeh i think i'll get the cheshire too thank guys

Looks like you'll get fine whether to test it out on tonight ken.

Perfect to see jupiter and the moon hey!!

[RAJAH235]

Ken, I had a similar prob. with my cardboard Meade. The UWA 14mm was too heavy for it, (distance from tube was large), and as such the focuser,(orig. rack & pinion), compressed the tube slightly, putting it all out of line. A small piece of packing under the lower mounting solved the alignment prob.
Star images are pinpoints. When you do your star test, pick a mag 3 or 4 star. All the best. :thumbsup:
Just the facts m'am.

[ballaratdragons]

Yep, occultation should be good.

and I just spent the last 20 minutes painting out the street light in front of my property with black paint. Hope it makes a big difference.

Last night I noticed we seem to have grown some new street lights in our little town. We had 4. Gonna go for a drive later and have a count of the new ones.

[janoskiss]

Ken, You should check out the barlowed laser method of collimation too. (google for "barlowed laser").

[ving]

hey mombat, where in the southern highlands are you?

[Vermin]

Apparently if you aim a red laser pointer at the daylight sensor on top of the lamp you can get it to turn off. A $5 pointer mounted on a small camera tripod and an O-ring to hold the power button on should do it.

[ballaratdragons]

Might have to try that one Tom, thanks.

I'll get up the ladder or use the binocs tommorrow and see if I can find the daylight photo cell.

Just been out and had a look at the paint job. Those Mercury Vapours are damn bright. I put 2 very heavy coats of black on it and it looks like it has a fine layer of dust on it!

Has cut the brightness back about 30% though.

I'll check again in about half an hour when it is very dark.

[ballaratdragons]

Pitch black sky now.

Paint has cut back the street light by under 10%. Damn.

Looks like the red laser is the go.

Tried a star test but atmosphere is 'yuk' (technical term for terrible). All the Stars are twinkling at present. 40 million tiny scratches in my glasses are helping either!

[iceman]

lol the locals won't need to look to far to find the culprit :D

[ballaratdragons]

Only got one neighbour (I offered him a lookie through my scope but said the light makes it hard to see anything) and he finally renegged and said I could paint it out. lol

[Vermin]

You could also try and *paint* the light with a 303 :)

But seriously I heard about the red laser pointer method on SAA (science.astro.amateur), and many people reported success with it.