Collimation of an Alluna Ritchey-Chrétien telescope

This guide describes how to use your Alluna Ritchey Chrétien telescope in a few steps and
adjust it perfectly in a matter of minutes. Collimation is best carried out in daylight.

All telescopes are adjusted on the optical bench at the factory as well as possible. Should
nevertheless, after shipping and installation, a collimation be necessary, then definitely only to a very
small extent. Take care when turning the adjustment screws.


Takahashi ocular adjustment
Step 1

You require a Takahashi ocular adjustment and to connect to the telescope the adapter M100x1.
The Takahashi ocular adjustment and the appropriate adapter that fits all of our RC telescopes, can be purchased from us as accessories.

RC collimation adjustment Step 2

Connect the ocular adjustment with the M100x1 adapter

Telescope collimation Step 3

Then screw the adapter with the ocular adjustment on to the Alluna RC telescope M100x1 output. It is good to extend the output a little with the existing extension tubes.

RC telescope collimation Step 4

The ocular adjustment is now firmly attached to the telescope. The optical axis matches exactly the subsequent use of CCD camera eyepiece or other accessories! Nothing will shake; everything is fitting tightly! Now, the aperture of the telescope should be directed towards a bright wall or white paper. It is advantageous if the telescope points upwards during adjustment, but in no case downwards.

right telescope collimation Step 5

When looking through the ocular adjustment look with a misaligned system at the accompanying picture. This system we have misaligned strongly for the explanation. The goal is now to make all the visible rings concentric.
The ocular adjustment can be moved a bit back and forth. This can precisely be focused on the individual visible rings.

Alluna-Optics adjustment

Secondary mirror holder

Step 6

There are three adjusting screws and three lock screws for the primary mirror and the secondary mirror.


Collimation Ritchey Chretien telescope
Alluna optics
collimation Cassegrain telescope
Step 7

First, the secondary mirror is always adjusted.

Unscrew the three counter-open screws on the secondary mirror holder.

By turning the adjustment screws on the secondary mirror holder the smallest inner white point moves which is the marking that is on the secondary mirror. This must be accurately centred to the second inner white ring.

If the inner two white rings are centred on each other, the secondary mirror is adjusted already.

Do not forget to tighten the counter screws on the secondary mirror holder and
at the same time check the adjustment.

The locking screws do not need to be very tight. A light even tightening is sufficient.

Cassegrain adjustment Step 8

Second, the adjustment of the main mirror is carried out.

First, the three lock screws must be gently opened on the back plate.

Now you need, when looking through the Tak-Colli-Scope, to ensure that the broader black circle is positioned in the slightly narrower outer black circle.

Please compare the image on the left with image one above. If between the two circles a very thin white ring is seen uniformly, the primary mirror, and thus the whole RC system is fully adjusted.
The adjustment is correct now to 96 to 100%, all takes less than three minutes.

The image on the left shows an almost perfectly aligned Alluna RC. If you look closely the main mirror still should be a little "hint" to the bottom right - there the white line is quite a bit wider.

Please do not forget to tighten the lock screws of the primary mirror evenly (but not too tight!) while checking the adjustment with the Colli scope.

Adjustment on the stars
Step 9

Check collimation on the real star 

With the adjustment on the day the RC should already be very well adjusted. 

The control and perfection of collimation, you can perform at night on a defocused star.

It is best to use to your CCD camera on the telescope output. Then position a medium bright star in the centre. 
The star will then be defocused as far that you can see well the dark shadow of the secondary mirror in the star discs.

If everything is perfect the shadow should be exactly in the centre of the star disc. If not 
you can readjust a little. Here only the primary mirror is adjusted.

Please note that the star should always be in the middle of the image field.

Note: Through questions to us, we know that this manual is also used for adjusting Cassegrain and RC telescopes which are not used for Alluna Optics telescopes.
Often the results do not meet the expectations of the Tak-Collimations scope.

Please note that our RC telescopes are machined very precisely! This means that in Alluna Optics RC systems the primary mirror, the secondary mirror and the baffle tube and the spin is exactly centred on the axis in the OTA system. Mirror shifting of Alluna telescopes is virtually non-existent and the weak point of many telescopes is the focuser which we do not need. Alluna RC telescopes have a modern secondary mirror focusing. The Tak-Colli-Scope is firmly bolted to the telescope on the axis. Just like how the camera is positioned later.

In other Cassegrain and RC systems, these axes often do not match, are slanted or shift during load changes (mirror shifting). Often an existing focuser is shaky or askew on the back plate. An adjustment of the visible rings with the Tak-Collimations Scope rarely leads to success in these telescopes. Such telescopes you need to adjust more frequently and directly as possible to the star at the zenith or the main direction of observation used on the observation evening. 


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