Recommend a collimation tool

[Kamikazer]

hi, guys

i need advice in selecting a collimation tool.

i believe i have quite a good of idea of what collimation is, but to make things clear, here is my understanding:

-secondary alignment does not require a really high degree of accuracy since it ultimately only affects how efficiently the lightcone is captured.

-i can easily machine a sight tube myself to centre my secondary, and use the primary mirror reflection to align it.

-i DONT THINK how accurately the focuser is squared to the optical axis is really important. it couples with secondary alignment to affect your illumination circle.

-collimation tools need to have a good tight fit with your focuser and concentricity is a big issue.

-primary mirror alignment is most important


there seems to be 2 popular tools for primary alignment:
auto collimators
-i understand they are very accurate, though i cant see how they work for secondary alignment
-how friendly are they for single person, work in the dark collimation?

laser collimators
-they may require collimation themselves
-more expensive
-45 degrees viewing port is good for single person, work in the dark.
(there seems to be a lot of post in cloudynights on the Blug but i dont understand where the black ring on the angled surface came from)


barrel formats
-if i primarily observe with 1.25" EP, should i get a 1.25" collimation tool?
-if i collimate using a 2" collimation tool, and use a 2" to 1.25" adapter with 1.25" EP, wont a 2" to 1.25" adapter introduce concentricity issues, effectively causing a miscollimation (for the 1.25" EP)?


so, i need a recommendation on which collimation tool, from which brand, and what are their pros and cons, and what look out for. (i know i am not being very clear, hope u understand what i mean)

i hope to keep my budget under $200 (not absolute)

thank you

[weixing]

Hi,

hi, guys

i need advice in selecting a collimation tool.

i believe i have quite a good of idea of what collimation is, but to make things clear, here is my understanding:

-secondary alignment does not require a really high degree of accuracy since it ultimately only affects how efficiently the lightcone is captured.

-i can easily machine a sight tube myself to centre my secondary, and use the primary mirror reflection to align it.

-i DONT THINK how accurately the focuser is squared to the optical axis is really important. it couples with secondary alignment to affect your illumination circle.

-collimation tools need to have a good tight fit with your focuser and concentricity is a big issue.

-primary mirror alignment is most important

Ideally, everything need to be as accurate as possible to get the best out of the scope, but in reality it's very hard to do that, so don't worry about it... just do the best you can and enjoy the scope. By the way, the focuser should be squared by the manufacturer... unless you remove the focuser.

laser collimators
-they may require collimation themselves

As long as you don't drop it, the collimation of the laser collimator will not be off (unless it's already off when you purchase it). Also, it's very hard to collimate a laser collimator yourself, so don't do it yourself.

-more expensive

Some non-laser collimator are more expensive than a laser collimator.

(there seems to be a lot of post in cloudynights on the Blug but i dont understand where the black ring on the angled surface came from)

You mean using a barlow laser collimator?? In this case, the black ring is the reflection of your primary mirror center spot marking if you use the common donut style center marking.

barrel formats
-if i primarily observe with 1.25" EP, should i get a 1.25" collimation tool?
-if i collimate using a 2" collimation tool, and use a 2" to 1.25" adapter with 1.25" EP, wont a 2" to 1.25" adapter introduce concentricity issues, effectively causing a miscollimation (for the 1.25" EP)?

The best is to use the barrel format that you use. If you use 2" eyepiece most of the time, then 2" collimator will be the best, but in reality a 2" collimator is quite expensive, so IMHO, 1.25" should be good enough.

By the way, IMHO, the easiest and fastest way to collimate in field is to use a laser collimator. They are quite a number of laser collimator out there and some of them are very good, but also very expensive.

Although scope collimation need to be spot on to get the most out of the scope, but in reality and practical usage, you might not be able to achieve that due to various reason especially for a dob. So, IMHO, before you decide which collimation tools to get, you must first determine whether your scope are able to hold the collimation well and your scope tolerance of mis-collimation.

Since you are using a F6 Newtonian and an Antares dual speed 2" crayford focuser, IMHO, you might not need those high-end collimation tools as collimation accuracy requirement for a F6 scope to perform well is not that high and also the play in the Antares dual speed 2" crayford focuser might always cause the collimation to be off a bit most of the time.

Anyway, for your budget and your F6 scope, IMHO, the Orion LaserMate Deluxe laser collimator should be good enough. Other better collimation tools will be way more expensive.

Just my S$0.02.

Happy collimating and have a nice day.

[Kamikazer]

hi,

how about a celestron cheshire eyepiece? i know how a cheshire works, so the question here is the one from celestron accurate? is its crosshair and pinhole well centred?

[Meng Lee]

Hi,

My personal view is

1) Use a laser collimator for initial alignment. The main advantage is that, you can collimate without running back and forth between the primary screws and the focuser.

2) Then do fine collimation using a star.

Oh, anyway, I got a laser collimator going at a reasonable price in the Buy and Sell subforum.

Meng Lee.

[Canopus Lim]

hi,

how about a celestron cheshire eyepiece? i know how a cheshire works, so the question here is the one from celestron accurate? is its crosshair and pinhole well centred?

Do note that cheshires are also not that accurate. The crosshairs sometimes are not even centred in the barrel and you would need perfect eyesight to use it since the pinhole is too small to use your spectacles to see through it. The biggest problem is using it at night as you need to shine a torch into the mirror and at the same time look through the pinhole and at the same time doing the trial and error adjustments of the primary mirror tilt.

The easiest, fastest and realiable (to f/5) way of collimating is to use the barlowed collimation technique. First use a normal 1.25 inch laser collimator to tilt the secondary mirror such that the laser spot is at the centre of the primary mirror (centre of the donut). It is best to use an adapter that is tight to your laser, to reduce the tilt of the beam.

Then using your own 1.25" barlow, attach the laser to it and having a pre-made white colour cover that has a hole (at the exact centre) to cover the front of the barlow lens. Turn on the laser and the laser beam will divert because of the barlow (it is a divergent lens), and a larger beam will fall onto the mirror and the shadow of the donut will be cast onto the white cover. Tilt the primary mirror such that the donut is centred to the laser aperture (the hole of the white cover). The biggest advantage of the barlowed technique is that it is unaffected by the laser tilt due to the adapter and the focuser. Do note that a lot of adapters are designed with very loose tolerance such that the laser is easily tilted and never centred due to the adapter. Using the barlow way effectively eliminates the main weakness of using a laser collimator, other than buying a 'knock out of collimation' collimator.

It may sound a few steps, but through practise, it routinely takes less than 5 min to do and has consistent results.

[Kamikazer]

hi guys,

thanks for the advice. i will get the 2"/ 1.25" Howie Glatter single beam Laser.