Fascinated by astrophotography, I have been planning of setting up a better equipment for astro imaging. Making and procuring the required items one by one. Last month I got a Canon DSLR EOS 1200D and doing some experiments to get familiar with. the camera had come with 18-55 lens kit alone and shooting the moon with that did not produce good images. I need 55-200 zoom lens at least for better images and planning to procure one. Meanwhile I just tried making a telephoto lens found in the net using a simple plano convex lens with focal length of 200mm and diameter of 50mm and using some PVC tubings.
The T ring for Canon EOS and T adapter for 1.25" eyepiece were purchased from online stores. The other items used are:
1. Plano convex Lens f =200mm, d=50mm
2. 40mm thick wall PVC tube (wall thickness 4 mm)
3. 32 mm PVC tube
4. 50mm PVC Coupler
5. 50mm PVC tube
6. 50-32 PVC Reducer
7. M 5X10 Screws
8. Spray Paint Black Flat (Matt)
Using these items , I had made a telephoto lens as shown in the figure above. The lens is bought from a stationary shop. Two rings of 10,15mm were cut from 50mm PVC tube and used as stoppers for the lens. The 50-32 reducer was cut to 15mm length to reduce weight. the 32mm PVC tube must protrude for about 60mm from the reducer which slides inside the 40mm PVC tube. The inside diameter of the 40mm tube is about 32mm. Two holes of 4.2mm were drilled at 15mm from either end and M5 threads were made using hand tap. These are for M5 screws to stop the tubes at required focal point. I had used an 1.25" thread-in yellow filter to the T adapter to prevent entry of dust inside the camera. Both the inside and outside of the entire assembly is spray painted with black flat (matt finish) to minimize internal reflections and to improve contrast. As the lens is a single element, the images are rich of chromatic aberration but still the result is amusing. To get better images, the lens must be replace with achromatic lens of same diameter and focal length which is available on line. Objective lens of old binoculars may also be used provided the diameter is 50mm else suitable adapters to be made. Here are some of the photos shot with this lens.
