My Second Telescope: the Leavitt
After building the Hadley, I wanted something more. There were a few ways to take better astrophotos: aim properly, collect more light, motorize a mount to follow earth’s rotation, or build a bigger telescope to collect more light. I chose to build a bigger telescope.
The Leavitt is the product of a year of work. This telescope is an 8" diameter f/4.5, with a focal length of 48.5". Its 3-pole design makes for easy adjustment of focal length to accomodate a camera fits into a car and weighs less than 20 pounds.
The mirror is an 8" diameter f/4.5, with a focal length of 89.5". I polished and parabolized it myself from January 2024 to August 2024. Its short focal length means the telescope’s views are less magnified and therefore brighter, perfect for deep sky objects. It has also given me great views of Mars, Jupiter, and Saturn.
The body
For the body, I used the existing Leavitt 3D printed telescope design. It uses three 0.5" aluminum rods and 3D printed parts. Each circle is split into three sections joined by screws to fit onto a standard smaller-than-8" print bed. It took two 1kg filaments of PLA, and since .
I designed a few of my own replacement parts. The original mirror cell (the part that holds and tilts the primary mirror) held the mirror in place with glue on three points, but that glue may slightly deform a mirror by a few nanometers. Since my mirror turned out to be accurate to within 1/20th of a wavelength, instead of glue I designed a mirror cell that encloses the mirror in plastic using three spokes with built-in clips stopping the mirror from falling out.
The mirror mount is an all-new design inspired by the Hill Mount I made for the smaller Hadley telescope. I don’t have access to woodworking tools, so I took a page from the mount I designed for my Hadley and designed a 3D printed truss structure. The telescope’s width is more than the size of my 3D printer’s bed, so I had to design it with a front crossbar.
Compared to the Hadley’s Hill Mount, which is 2.5’ tall, my Leavitt mount is 3’ tall. Because the Leavitt’s mirror has a longer focal length, its telescope tube is longer, so I thought the extra height was needed to stop the tube from hitting the ground when aimed upwards. However, I didn’t account for the extra weight of the mirror, which made the telescope tube bottom-heavy and moved the pivot point closer to the mirror. That meant that the extra height worked against the mount and made it more prone to tipping over. It works, but the design could be made more stable someday.
The mirror
I didn’t buy this telescope’s mirror - instead, I manufactured it myself. Amateur mirror making has a long history, and there are textbooks published a hundred years ago that document processes that still works to this day. This was my first time polishing a mirror, and I’m very proud of the end result: a parabolic surface accurate to within 1/20th of a wavelength of visible light - 25 nanometers or so. I worked on this mirror from January 2024 to August 2024, and first light was in December 2024, just in time to see the Mars conjunction.
For more, see my page on mirror grinding, or check out the blog posts I made along the way.