How do I collimate my Newtonian telescope – aligning the mirrors in daylight?

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For a refractive telescope, Collimation is crucial. Collimation enables you to get the best out of your Telescope.

The Newtonian Telescope is designed to eliminate aberrations. Despite this feature, poor Collimation may cause aberrations and distortions.

You need to tune your Telescope to maintains its integrity. You may have heard that Collimation is a difficult and challenging task. But we beg to differ.

Let us show you how Collimation is a speedy and straightforward technique. We before we get to that, let’s discuss a bit more about the Newtonian Telescope.

What is a Newtonian Reflector telescope?

The Newtonian reflector is an archetypal mirror-based Telescope. Its basic principle is simple yet creative.

The Telescope first took form 1668. Its creator, Isaac Newton, was inspired by the original mirror-based Telescope. His take was to add a flat deflecting mirror inside the Telescope’s tube.

The Telescope was invented when there still so much to discover. Interestingly, the Telescope’s design is still as readily used and applied.

The history behind Newtonian Telescope?

In the 16th century, refractive telescopes exhibited chromatic aberrations. A Refractive telescope used lenses that bend light waves. This creates a hitch with colored wavelengths that passed through the glass.

Upon viewing objects through the Telescope, the lens exhibited colored fringes. There was also a problem with distortion.

This is what makes the Newtonian Telescope so unique. The Telescope has zero lenses.

It was Newton’s idea to omit the lenses. He figured it is best to remove the component causing aberrations.

He replaced the lenses with mirrors. The mirrors he used were made with a blend of copper and iron.

How does Newtonian Telescope work?

Replacement of Lenses with Mirrors in telescopes was a quantum leap. The chromatic aberration became non-existent.

The Newtonian Telescope has a primary mirror in its tube. This mirror reflected the light into the Telescope.

A secondary mirror was placed in the focal path of the primary one. This directed the image to the eyepiece of the Telescope.

It is easy to infer that the secondary mirror blocks a part of the image. But that is not what happens. The secondary mirror is so tiny that there is zero blockage.

What is Collimation in a telescope?

In brevity, Collimation is the process of aligning telescopic optics. There are two essential alignments for the Collimation of Newtonian Telescope.

The secondary mirror is adjusted to achieve a Focuser Axis alignment. Next, the primary mirror needs adjustment for the primary axis.

Both the mirrors should be aligned so that the image is of the best quality. The shorter the focal ratio, the higher is the need for Collimation.

Collimation misunderstood as an incubus task. In reality, it is simple to collimate a Newtonian Telescope.

How to collimate a Newtonian- aligning the mirrors in daylight?

There are two types of Collimation applicable to Newtonian Telescopes. One is performed without the help of any equipment. While the other requires collimation tools for proper alignment.

Both methods offer accurate results. It is up to you to collimate with or without a collimation tool.

Considerations to make before collimating a Newtonian Telescope.

Here are a few precautions that you need to practice before collimating the Newtonian Telescope

Always place the Telescope in a horizontal position.
Avoid performing any task in front of the Telescope. If any objects slide to the primary mirror, it might break.
Never point the Telescope in the direction of the sun.
Collimate your Telescope indoors.

Collimating the Newtonian Telescope

Collimating the Telescope without a tool is a cost-effective process. The task requires a lot of virtual observation.

You will need a hex key, screwdriver, collimation cap, and white paper. The collimation cap has a hole in the centre and an interior reflective surface.

Secondary Mirror Alignment

Despite the name, it is crucial to align the secondary mirror first. Remove the cap from the focuser and the dust cap from Telescope.

Place a sheet of white paper below the secondary mirror. Ensure that you don’t touch the reflective surface of the mirror.

A bright background assists in better alignment. The mirror will appear prominently through the focuser.

Adjust the collimation cap on the focuser and peek through the hole. You might see some decentred reflections. This is not a roadblock, as we are yet to align the primary mirror.

Locate the mirror keeping it relative to the focuser. You’ll see a centred image of the primary mirror through the secondary one.

If you don’t see a centred image, adjust the screws of the secondary mirror. A screwdriver comes in handy while loosening or tightening the screws.

Make sure you are not manipulating the screws of the secondary mirror’s support. The support keeps the mirror in the proper position.

Aligning the Primary mirror

Check for a small dot in the centre of the primary mirror. That dot/circle needs to be aligned. You must align it with the collimation cap’s reflection in the secondary mirror.

Adjust the knob until both the images are aligned. Once that is done, your Newtonian Telescope is perfectly aligned.

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