Show HN: Curiosity – DIY 6″ Newtonian Reflector Telescope

A DIY Newtonian reflector telescope with dobsonian mount. A fun to do hobby project taking us closer to the moon and beyond. A lot of plans ahead on how to make it much better and portable but this was the first time me and my friend implemented or rather bui…

Madhav on Computer M & Swarup on Computer S. Both, looking at their reddit feeds and getting awed by the pictures of Moon, Jupiter, Saturn, Orion Nebulae and what not, clicked by people all around the world. Us discussing, HOW MUCH DOES A DECENT TELESCOPE COST? Well, it does cost a lot (*a lot is definitely subjective). Living in bengaluru, India where the current period of months(October to March) aids us to stargaze with the most beautiful clear skies.

Something had to be done, so we jumped on searching our reddit feeds and cloudy nights to get an understanding on what people have accomplisheed, I came across this book called “Build Your Own Telescope by Richard Berry (1985)”, which communicated in a very interesting way. The initial thought following the book was to build a 4" telescope but eventually we jumped onto a 6" Newtonian Reflector with Dobsonian Mount.

Hence, the name of our telescope "CURIOSITY". The image shown below is the most essential and the easiest calculation that one has to look for while building a newtonian reflector telescope. In our case, for the distance between the diagonal mirror and the primary mirror, we did not strictly adhere to the +1", rather we subtracted it i.e., our final equation looked like F-T-H-1". This was done because of the focuser size.

The calculation looks like Q. Why did we go for a 190mm inner diameter of tube? A. After referring a lot of sources over the internet and also during the assembly process of the telescope, it is advised to maintain an offset of ≥ 20mm from the size of primary mirror i.e., for a 6" or 150mm primary mirror size, 150 + (2*20) = 190mm should be the minimum inner diameter of your PVC tube. The following images are snippets of our design from Fusion 360 software which supports student licences, though some limitations, but does fulfill our job.

We were lucky enough to have access to a really big wooden router at our lab's facility. To make our life easier and pace up the process, we decided to utilize the capability of the wooden router for contour cuts of our desired profiles for telescope components. This section highlights all the information that we came across to deepen our understanding pre-during and post assembly of the telescope.

The aim is to put up information that will be helpful as and when we get to learn about something new. Happy Learning! The property of an optical system that tells you how much brighter things will appera than what the human eye can see. In our case, our primary mirror has a diameter of 150mm and considering if the average human eye lens has a diameter of 6mm in darkness, how much more light will the mirror gather than the human eye?

Answer: $$LGP = frac{150^2}{6^2} = 625$$ so 625 times more light. The telescope has much larger aperturer than the eye and allows more light which means even stars too faint to be detected by the eye can easily be brightened by the telescope so that they are easy to detect and study. Diffraction: Bending of light near the edges of an obstacle similar to how water spreads out into waves when an obstruction is present in front of it.

More on diffraction in telescope can be found >> Diffraction in Astronomy Airy Disk: A very bright, circular spot of light formed in the center of image which together with the series of concentric rings around is called Airy Pattern. The first classic mount for any budding amateur astronomer that only requires screws, glue, plywood and that's it. The name coming from a renowned amateur astronomer "John Dobson" is best known for promoting awareness regarding astronomy to the common people and thus guiding everyone with low cost & quick mount newtonian reflector telescope.

>> Telescope Building with John Dobson, a must watch video series on building a dobsonian mount. When you don't want to move your telescope manually, you opt for an equatorial mount which is designed to follow the track the movement of the objects in the night sky. Comparing with a dobsonian mount, equatorial mount offers more sturdy and expensive mount. The motorized tracking of equatorial mount whose axis align with the earth's rotational axis.

The electronics involved gives the opportunity to the user to play around with the overall navigation of the deep sky objects.

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