collimationm

[peterpan3494]

hi all

i wonder if someone can help me out with some info

as some of you will know i have a Helios scope

and i think i need to set the lens up

have looked on you tube about setting these up and they are saying about a small circle on the main lens

(sorry still new and not sure of proper name )

now my lens does not have this circle to set the mirrors up with

so how do i set these up

also looking at buying a collimation eyepiece but not sure where or what kind

many thanks for reading

pete

[Peter Drew]

Hello Pete.

The small circle referred to is usually a ring placed at the centre of the main mirror, this is an aid to collimation when using a laser collimator tool. If your mirror does not have one it's a case of judging where the centre is. There are several types of laser for this purpose available from the leading astro outlets, it's important to purchase an adjustable one as they are not always collimated (lined up) themselves. You will be able to get plenty of help through this forum if you have any difficulties. .

[umadog]

There are a variety of tools and they don't all measure the same things. Tools for centring the secondary mirror as viewed from the focuser don't require a centre spot on the primary mirror. However, as far as I know, all the tools used to align your optics (axial alignment) will require a centre spot. Note that lasers also require a centre spot and are not intrinsically more accurate than other tools. They can, however, be more convenient. Their disadvantage is that they themselves need to be collimated and they can go out of collimation if you're not careful. Passive tools, such as Chehires or auto-collimators, don't go out of collimation. These passive tools can be super-accurate of they are well made. Lasers naturally work well in the dark. The other tools also work in the dark if you clip a light onto your spider.

This is probably way more detail than you want, but these links on Cloudy Nights cover the topic in great detail:

Telescope Reviews: The Best of Reflectors

If you go to the third link and scroll down, you will see a table listing a variety of different collimation tools and which misalignment errors they measure. You only need to measure and correct two of those errors to have a collimated Newtonian. You will need to read all of the information in these threads if you want to understand what those errors are. The bottom line is that a sight-tube Cheshire combination tool is sufficient.

If you are needing apply a centre spot, I would strongly recommend the spot and template kit from Catseye (CATSEYE TEMPLATES & CENTER SPOTS). The site has frames, so this link takes you to the home page: CATSEYE Collimation Main Page Frameset File The Catseye template will allow you to place your spot with sub-millimetre accuracy. The Catseye spots come in a variety of shapes and are highly reflective. They are a big improvement over the standard white "ring-binder." The kit will only set you back around a tenner.

[DOBBY]

If all else fails... there is a 'South Coast Observers' in the Community..Social Groups..at the top of this page...pop along to one of their observing meets...they'll be happy to help you..