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Levenhuk.com » Good to Know » Levenhuk Ra R80 ED Doublet Carbon OTA Review

Levenhuk Ra R80 ED Doublet Carbon OTA Review

There is an unusual model in Levenhuk’s semi-apochromat series that attracted my attention immediately. It’s a compact refractor telescope with 80-mm aperture, 500-mm focal length and a body made of high-quality carbon-fiber-reinforced polymer (or simply carbon). Actually, the body material is exactly what makes this model so special. The carbon body is less susceptible to deformation due to temperature changes, and it also reduces the telescope’s weight.

Let’s take a look at the telescope’s specifications:

Optical design refractor
Optics coating fully multi-coated
Optics material ED glass
Optical tube material carbon fiber
Objective lens diameter, mm 80
Focal length, mm 500
Focal ratio f/6.25
Eyepiece barrel diameter 2" (accepts 1.25"
accessories with an adapter)
Focuser 2" dual-speed Crayford
Optical tube dimensions, in 4.0x15.4
Optical tube weight, lbs 6.2
Tube-mount assembly system quick-release thumbscrew
Observed objects Solar System planets, star and globular clusters

What really caught my attention is the telescope’s compact size. Its optical tube’s length is only about 15 inches. Although the telescope’s objective lens is not large (80 mm), it is made of a special optics material. That is why the image quality is much better compared to regular (achromatic) refracting telescopes. That’s also why this model (semi-apochromat) is suited for astrophotography.

Let’s unpack the telescope. This model comes in an excellent case. A case like this securely protects a telescope from occasional mechanical shocks during storage and transportation. The case is filled with foam rubber, which tightly conforms to the optical tube’s shape, which in turn protects the optics from shaking. Remember that when transporting the refractor without proper protection like the one provided by this wonderful case, the objective may become a little warped.

I would say that this case is a work of packaging art. Its rounded corners don’t catch on your clothes and surrounding objects during transportation.

Case – secure protection of your telescope during storage and transportation. Due to tight foam rubber inside the case optics shaking is eliminated.

You can safely store the optical tube in this very case, but don’t forget to apply protective caps to prevent dust and moisture from getting inside.

Let’s set the tube on a mount. Here’s what Levenhuk Ra R80 ED Doublet Carbon OTA looks like with dew cap retracted (left photo).

As you can see, this optical tube is indeed short and compact. The carbon body also contributes to the telescope’s stylish look. I would give it an A+ for appearance. This model is a premium segment optical tube, so you can be sure that build quality is at the highest level.

Let’s extend the dew cap (right photo).

Levenhuk Ra R80 ED Doublet Carbon OTA with retracted dew cap.) Levenhuk Ra R80 ED Doublet Carbon OTA with extended dew cap.

The dew cap protects the objective from the dew drops and fogging up, so it’s a very important part of a telescope. It’s great that the dew cap of Levenhuk Ra R80 ED Doublet Carbon OTA is retractable; otherwise the tube wouldn’t be so compact.

The optical tube comes with a dual-speed focuser, which is a great advantage! A focuser like that allows you to achieve a lot more precise focusing as compared to regular focusers.

The focuser extends up to 3.15 inches, which allows you to use eyepieces with practically any possible focal lengths. For your convenience there is a scale on the focuser.

Dual-speed focuser of Levenhuk Ra R80 ED Doublet Carbon OTA. The convenient scale is applied to the focuser.

The kit of Levenhuk Ra R80 ED Doublet Carbon OTA includes 2” to 1.25” adapter, so you can use both 1.25” and 2” accessories like eyepieces or a diagonal mirror. Speaking of the diagonal mirror, it’s not included in the kit, but I strongly recommend purchasing one additionally for this telescope. Without a diagonal mirror you won’t be able to sit or stay comfortably during observations or astrophotography sessions when the telescope is pointed at or near the zenith.

Locking screws on the end of the focuser. They fix an eyepiece securely; you can be sure that it won’t fall out.

The kit includes 2” to 1.25” adapter. Trustworthy focuser screws.

Half an hour before beginning the observation, the protective cap should be removed from the focuser to let the telescope ‘cool down’. By the way, here we can witness one of the many advantages of the compact size – it only takes 20-30 minutes for Levenhuk Ra R80 ED Doublet Carbon OTA to get ready for observations; larger refractors usually need a full hour.

Getting ready for observations: remove the focuser cap. Removing the cap.

Inside the adapter there is a thin but sturdy liner made of copper. This liner compresses the eyepiece body like a collar when you tighten the thumbscrew.

Here’s what the adapter looks like when pulled out of the focuser (center photo).

The focuser also has a copper liner inside. The inner walls of the focuser’s tube are blackened to eliminate glare.

Copper liner inside the adapter. 2” to 1.25” adapter. Copper liner inside the focuser.

The focuser’s body is covered with an anodized finish, which looks impressive. There is a smaller fine focus knob on one side of the focuser. The larger knob, which is a coarse focus knob, allows you to focus the view faster but with less precision. For precise focusing, the fine focus knob should be used. Both knobs are comfortable to use and have fine ribbing, which provides for a comfortable grip.

Larger knobs are also rubberized.

Here’s the bottom view of the focuser. Note those two threaded holes on the pictures – they allow you to install focusing motor for automatic focusing.

The shiny focuser of Levenhuk Ra R80 ED Doublet Carbon OTA. Large knobs are rubberized. Bottom view of the focuser.

There is a knurled ring between the tube and the focuser. It allows you to rotate the focuser. All you need to do is release the ring and you can rotate the focuser. You might need to do this if one of the focuser’s knobs is pressed against something (for example, the mount), which makes using them uncomfortable.

It is really convenient that the focuser is designed as a separate block that can be rotated. Not every refractor can boast such a useful feature.

The screws on the focuser that seem to be useless at a quick glance don’t seem to hold anything. In reality, those screws are required to align the focuser to the objective’s optical axis.

These screws don’t need to be adjusted, because the focuser was already aligned during the manufacturing process.

Use this ring to rotate the focuser. The ring is comfortable to use. Here you can see the screws for aligning the focuser.

The bottom of the focuser holds yet another mysterious screw. This is a focuser tube locking screw. On my photo it faces upwards because I turned the focuser around its axis.

There are several ways to install the tube on a mount. I used a mounting plate from a camera tripod head. In this combination the second screw is used as a safety screw.

Focuser locking screw. Note that the focuser is turned around. Camera tripod head’s plate.

Let’s take a look at the main part of the optical tube – its objective lens. You can see that the objective’s rim reads the main specifications. You can also see thick multi-layer coating, which eliminates the loss of light on the air-to-glass boundary. That’s why the objective’s rim reads ‘fully multi-coated’. The objective lens is two-element: one of the elements is made of a special ED (extra-low dispersion) glass. The use of that glass is why the telescope produces high-quality images with minimum chromatic aberration.

Inside the tube: there are a number of diaphragms that cut off the glare, negatively impacting the view.

The inner walls of the dew cap are covered with velvet paper, which allows for a snug fit to the tube and prevents the cap from sliding off. You may think that it’s an unimportant detail, but that’s just because you have probably never tried to work with a refractor when the dew cap is constantly trying to slide off.

Fully multi-coated optics. Diaphragms inside the tube. The velvet paper on the inside of the dew cap.

A view through the optical tube without an eyepiece:

View without eyepiece.

Now we are gradually moving to testing. Earlier I described two threaded holes on the focuser, which may be useful for automatic focusing. Here’s one of the many possible options: a stepping motor is installed on the focuser’s fine focus knob. The rotation movements are transferred through the belt.

Installing the motor. The motor is installed on the focuser.

With the help of this combination I have performed the Roddier test.

The test results show that Levenhuk Ra R80 ED Doublet Carbon OTA features good image quality.

The Roddier test – great results! Some screenshots of the software I used for the test.

It cannot go unnoticed that the test image doesn’t form a perfect circle though; it’s more like a convex triangle. During visual tests the form of the test star also appeared more like a convex triangle with a circle around it. That tells us that there is some astigmatism and that the objective is over-compressed by its rim in some places. Luckily it can be fixed, meaning that this defect is not the fault of the objective itself.

Testing on Vega. 5x3 sec. batch, ISO 1600, Canon 50D:

Vega test.

You can see three pairs of rays, which indicates that the liners between the lens and the rim are a bit too wide.

Photo of a star field made with camera with crop sensor without flattener. 15x30 sec. batch, ISO 1600, Canon 50D. You can see that the matrix plane is not warped relative to the focuser, which is great. But you can also see the effect of residualchromatic aberration and the specific form of the stars mentioned earlier. When changing the format to 1200x800, it’s almost unnoticeable. As for the presence of chromatic aberration when it’s always like that – chromatic aberration is minimized compared to achromatic refractors with the same focal length, but it is still present; that’s why it’s called “residual”. Full apochromats provide images with no chromatic aberration at all, but they also form a higher price segment. As for working with this semi-apochromat, there is absolutely no discomfort during visual observations. Only with high magnification (160x) you may occasionally notice a star changing its form from round to triangular.

A star field.

The following images were taken in the red light-pollution zone. In such zones (the center of pretty much every city) visual observations are usually unsuccessful (excluding maybe lunar and planetary observations), but for astrophotography it’s not an obstacle! The telescope gains light from the bright objects pretty quickly.

Pleiades, an open star cluster. 15x30 sec. batch, ISO 3200, Canon 50D. Image processing: Photoshop, Iris.

Orion Nebula. 15x30 sec. batch, ISO 3200, Canon 50D. Image processing: Photoshop, Iris.

Pleiades. Orion Nebula.

Landscape and lunar astrophotography are also very interesting with this instrument.

Lunar astrophotography.

But what kind of visual observations can you perform with Levenhuk Ra R80 ED Doublet Carbon OTA? Because of the relatively small objective, the views of nebulas and galaxies won’t be as impressive as astrophotos; you will see just small hazy spots. On the other hand, this telescope is perfect for lunar and planetary (Jupiter, Saturn, Mars, Venus) observations due to the use of the ED glass. You can observe almost all star clusters (such beautiful astronomical objects!) and even bright globular clusters. There is also one very interesting for visual observations and imaging phenomena, of which not everybody knows - noctilucent clouds (also called night clouds). They can mostly be seen in summer at latitudes between 50° and 70°. Noctilucent clouds and their dynamics are of scientific interest, so you can even contribute to science by just taking pictures of these wonderful clouds!

Noctilucent clouds.

Summary. Levenhuk Ra R80 ED Doublet Carbon OTA is a good instrument. The build quality of this tube is at top level! The only blot on the landscape is a slight astigmatism of the objective. Despite this little flaw, you can successfully observe bright Messier objects, planets, the Moon, and make daytime and night landscape images. What I like most about this telescope is its light weight and compact size. It allows its owner to be light on their feet and have observations more often. You can take Levenhuk Ra R80 ED Doublet Carbon OTA with you on any trip. To become familiar with the starry sky, a camera tripod is enough, because the tube is really light you can safely use it. Later you can purchase a serious telescope mount. As compared to reflectors, the telescope “cools down” much faster – you won’t have to be tormented by waiting. As compared to a refractor with the same size and a body made of metal, this telescopes “cools down” faster as well (~10 minutes faster). Chromatic aberration is noticeable, but not critical. Levenhuk Ra R80 ED Doublet Carbon OTA is great for visual observations and also allows you to try your hand at astrophotography.