Instructions for manufacturing and assembling refracting telescopes – Ursa Major 60F900 version
After many years of research and improvement, we would like to show you how to make a simple refractor telescope in minutes from the available materials at a much cheaper cost than traditional commercial refractors with an equivalent configuration. This version is called Ursa Major – the Ursa Major/Great Bear constellation, you name it “his sister” Be Bear it’s OK. But first, let’s learn the working principle of a refracting telescope!
I. Operating principle
The refracting telescope of the Kepler type is composed of 2 main parts: 1 converging lens with long focal length f1 (objective lens – lens facing the observed object) and 1 converging lens with short focal length f2 (eyepiece – where the lens is placed ‘eye). The O1 lens has the effect of creating a real image of the object (like a camera lens), the O2 eyepiece acts as a magnifying glass to magnify this image. Here are some formulas to remember:
Magnification
Distance between objective and eyepiece when observing celestial bodies or very distant objects (infinity)
Distance between objective and eyepiece when observing objects at close range (d < 50 m)
Note: When observing closely, the distance between the objective and the eyepiece is always greater than when observing celestial bodies or very distant objects.
II. Materials.
1. 60F900 achromatic objective with holder
Learn more about achromatic objectives:
https://deepsky2000.net/forum/showt…kinh-tieu-sac-
You can order here:
https://deepsky2000.net/cuahang/pro…m-ga-vat-kinh/
2. Eyepiece
Learn more about eyepiece types:
https://deepsky2000.net/forum/showt…i-kinh-Phan-I-
https://deepsky2000.net/forum/showt…-kinh-Phan-II-
You can order here:
https://deepsky2000.net/cuahang/dan…i-kinh-barlow/
3. D60 sharpener
Used to change the distance between the objective and eyepiece.
You can order here:
https://deepsky2000.net/cuahang/pro…chinh-net-d60/
4. 90 degree diagonal mirror 1.25″
Essentially a flat mirror that makes it easier to observe celestial objects above.
You can order here:
https://deepsky2000.net/cuahang/pro…-doi-goc-1-25/
In addition, you can also buy a complete set of components here to make a 60F900 refracting telescope at a preferential price:
https://deepsky2000.net/cuahang/product/bo-kit-60f900/
5. 1 piece of u.PVC Φ60 pipe approximately 1 m long
6. 1 straight connector (ferrule) u.PVC Φ60
7. 1 u.PVC 75-60 step-down connector
8. 1 piece of u.PVC Φ75 pipe about 10 cm long
9. Foam tape
You can find the above materials at electrical and hardware stores.
10. Bracket
You can order here:
https://deepsky2000.net/cuahang/dan…bam-nhat-dong/
III. Manufacturing and assembly
Step 1:
Wrap a layer of foam tape around the lens and insert it into the Φ75 tube as shown below, being careful to face the longer end of the lens outward.
2nd step:
Install the Φ75 pipe section into the 75-60 step change connector in the direction shown below. The Φ75 tube section has the effect of preventing unwanted light from entering the telescope.
Step 3:
Insert the focuser into the straight Φ60 connector.
Step 4:
First install the lens and focuser into the Φ60 tube, then measure the maximum and minimum length of the entire lens assembly. Then apply the formula from Section I to calculate the amount of Φ60 pipe to cut. Refer to plastic pipe cutting techniques here:
https://deepsky2000.net/forum/showt…ll=1#post22183
DV:
To be able to use a 4 mm eyepiece to observe celestial objects, the distance between the objective and the eyepiece must reach:
To be able to use a 20 mm eyepiece to observe objects 30 m away, the distance between the objective and the eyepiece must reach:
Note the distance between the objective and the eyepiece calculated based on the path of the light ray, corresponding to the distance from the objective to the center of the diagonal mirror + the distance from the center of the diagonal mirror to the eyepiece.
Step 5:
Finally, install the focuser and objective lens into the Φ60 tube, then install the eyepiece into the focuser. The body of the telescope is therefore finished.
Step 6:
You can further perfect the glasses by adding positioning glass, anti-reflective paint inside the glass and anti-glare lenses, decorative paint outside the glass…:
https://deepsky2000.net/forum/showt…ll=1#post22222
Step 7:
Attach the base to the glass:
https://deepsky2000.net/forum/showt…tu-che&p=23320
IV. Observation of practice
First, practice removing and assembling the glasses and using the stand to become proficient, then practice observing ground targets. Note that due to the optical properties of glass, the image will be upside down, top to bottom, left to right, which can be a bit distracting when observing geology, but observing celestial objects is carefree.
When you’re ready, let’s conquer the Moon first! Observing the crescent moon will be more impressive than the full moon because you will then be able to clearly see the craters at the edge of the crescent. Then try to conquer planets as well as weak celestial bodies. To locate celestial objects in the sky, you can use Stellarium star chart software for computers, Sky Map for Android, and Star Chart for iOS.
Instructions for use of Stellarium – Starry sky simulation software:
https://deepsky2000.net/forum/showt…p-bau-troi-sao
Attention: Absolute ARE NOT Observe the Sun directly with the naked eye or through telescopes or binoculars without a specialized filter! Failure to follow safety precautions may result in eye damage or permanent blindness.
If you want to take photos with glasses, you can purchase accessories here:
https://deepsky2000.net/cuahang/dan…anh-thien-van/
I hope that you who love astronomy can successfully make your own refracting telescope, Ursa Major 60F900 version.“authentic” Follow the instructions above!
Nguyen Tung Lam
Hanoi Amateur Astronomy Association – HAS
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