Jump to content

NLCbanner2024.jpg.2478be509670e60c2d6efd04834b8b47.jpg

Collimation Cheshire or Laser?

aussi skywatcher

Recommended Posts

aussi skywatcher

aussi skywatcher

Posted
Posted

Hi Guys, what are your views on the above, laser or Cheshire type collimator's? I have used a Cheshire type found it ok but fiddly when working on your own (my scope is 1.2 mtrs long) plus not easy to use in low light/dark conditons. I like the idea of being able to use the laser type that reflects the beam back onto a "target" that can be seen from the rear of the scope are these any good, do they work as described? The one I am looking at is the orion model or similar (there seems to be a few that look the same but are badged under different names) I would value your views on this topic.

Cheers Aussie skywatcher :(

Link to comment
Share on other sites
steppenwolf

steppenwolf

Posted
Posted

Much debate on this subject but I like the laser collimator as it is intuitive to use and means that you can collimate a large 'scope on your own. There is one caveat though - you MUST use one that you can self collimate. I.E. you must be able to ascertain that the laser collimator itself is correctly collimated and to do this you need to make a jig to hold it so that it can be rotated and the effect of rotation viewed on a wall about 20 feet away. Any movement of the laser dot on the wall must be adjusted out. Here is a picture of my 'jig':-

post-13675-133877353491_thumb.jpg

Link to comment
Share on other sites
rusirius

rusirius

Posted
Posted

I have both a Cheshire and Baader laser and I use both. If the collimation is badly out then I use the cheshire, then I use the laser to check the final fine tuning. If its only slightly out, then I just use the laser to make a quick adjustment. I have found that laser and cheshire 'agree' when everything is aligned correctly and its usefull to be able to confirm alighment using two methods after a major adjustment.

Link to comment
Share on other sites
Merlin66

Merlin66

Posted
Posted

Caution guys.... he's using a 6" SCT.....

These are best collimated without the laser ( and even the Cheshire is of limited value)

The best, most reliable and probably easiest is to use a webcam in the focusser and point to a reasonably bright star just out of focus - you'll see the "doughnut" of the secondary in the main mirror; adjust the secondary until the central dark circle is smack in the centre of the brighter disk. Try this again but closer to focus ( ie smaller doughnut).

This will get you very close and final critical collimation should be done on a star image at focus.

Link to comment
Share on other sites
Jarndyce

Jarndyce

Posted
Posted

Thanks Merlin and AB.

I've read up on this method, and I've been told that accurate collimation can make all the difference on an SCT.

How often should I expect to collimate a 6" SCT?

I haven't got it yet - just learning as much as I can before it arrives!

Link to comment
Share on other sites
proflight2000

proflight2000

Posted
Posted

Just incase anyone is interested, collimating an actual laser is pretty simple. Arrange a jig as has been mentioned, then get yourself a sheet of A4 paper, place it on a wall or something where the laser can reach it whilst on the jig. Turn the laser on then mark with a pencil where the laser dot appears on the paper. Then go back to the laser and turn it 90 degrees, again go to the paper and mark where the laser dot appears. Do this for the whole 360 degree turn of the laser. Now look at the dot marks on the paper, a well collimated laser when turned through its 360 degree tube extent should have the dot in the same position on the paper throughout. If the dots you marked are all over the place then you need to collimate your laser, hth.

Link to comment
Share on other sites
rusirius

rusirius

Posted
Posted

Opening post was by aussi skywatcher but it was Jarndyce who was asking about the SCT. The Ops scope is "1.2 meters long" so its unlikely to be an SCT - unless its a very big one! (Astro_Baby, I think your original assumption is still correct). Merlin is probably right when it comes to collimating an SCT though. A Cheshire would be of limited use here and the star test method is probably the easiest and best. Never thought about using a webcam to check the results though...

Link to comment
Share on other sites
aussi skywatcher

aussi skywatcher

Posted
  • Author
Posted

HI again, thanks for the comments, perhaps I should have said in the first place my telescope is an 8inch Skywatcher Newtonian (dob mount). So far I have only had to make very small adjustments and the Cheshire has been fine but as I say its not easy when you are on your own, I guess I really just want to know how reliable the lasers are, if I bought one then I would probably use them inconjunctionwith other as a means of double checking (or am I becoming paranoid????????). Funds are limited and I have seen the Orion variety on special just now here in Oz hence my query, dont want to miss out on a good price if its worth having.

Cheers Aussie Skywatcher :(

Link to comment
Share on other sites
John

John

Posted
Posted

Save your money and stick with the Cheshire! It will give you as good or better collimation!

I agree - I had the Skywatcher 8" dobsonain which is an F/6 scope and I managed to keep it in good collimation using a simple plastic cheshire eyepiece. I've got a laser now that I've moved to an F/5 12" scope but TBH I find the non-laser cheshire just as good in that as well.

John

Link to comment
Share on other sites
Astro_Baby

Astro_Baby

Posted
Posted
I'm sure you're right - but why?

Don't know much about Maks, I'm afraid.

Its cos the Celestron 4SE has very fiddly collimation that involves taking the entire rear end of the scope off so you cant actually see what your doing as you do it. You have to remove the rear end of the scope which includes the focus tube, adjust the colimation on its primary miror and then reassemble and check if collimation is correct.

The manual says if the collimation has gone out send it back to the factory cos its tough to do. Personally I like a challenge so I'd do it at home.

With that said - by astro folklore maks should very seldom need collimating. We'll see on that. Never having owned one before its all a new thing for me.

Link to comment
Share on other sites
Whippy

Whippy

Posted
Posted
I'm sure you're right - but why?

Don't know much about Maks, I'm afraid.

Its cos the Celestron 4SE has very fiddly collimation that involves taking the entire rear end of the scope off so you cant actually see what your doing as you do it. You have to remove the rear end of the scope which includes the focus tube, adjust the colimation on its primary miror and then reassemble and check if collimation is correct.

The manual says if the collimation has gone out send it back to the factory cos its tough to do. Personally I like a challenge so I'd do it at home.

With that said - by astro folklore maks should very seldom need collimating. We'll see on that. Never having owned one before its all a new thing for me.

I'd be VERY careful about taking the back off of a Mak. The point about these scopes is that they're collimated, ready to go out of the box and they're not supposed to be mucked about with by the user. If it's out, then send it back. If you want a Mak-Cass that you can collimate, get a Rumak design one such as an Intes Micro model with an adjustable secondary like SCT's.

Anyways, I've found that my laser does it's job well enough but a star test is the best way to get the collimation spot on.

Tony..

Link to comment
Share on other sites
aussi skywatcher

aussi skywatcher

Posted
  • Author
Posted

Interesting discussion, thanks guys, I've looked at all the points of view here (and elsewhere) and pondered over them but in the end curiosity prevailed and I did buy a laser(the Orion). Played around with it today and I have to admit I am impressed with the simplicity of use. Lots of arguments were about the collimation of the collimator itself but these problems seem to be easily overcome if you think logically and don't assume that what you just bought is "perfect" but take the time to check and recheck what you are doing. After using the laser I slipped in the Cheshire and it agreed so now I am happy. Anyway thanks again for all you help. Clear Skies

Aussi Skywatcher

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

Go to topic listing

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.