Observing with both eyes open through large, comfortable, binoculars at bright star clusters such as the double cluster in Perseus is truly awe inspiring. Binocular vision for these type of objects is so much more satisfying than squinting through even a rich field telescope. However there are several issues that need to be overcome when observing through binoculars. Hand holding even a pair of 7X50s is quite tiring and the images are never completely satisfactory due to the difficulty of holding them steady with the neck craned back. Image stabilized binoculars would certainly improve the steadiness of the image but with the trade off of significant cost and increased weight. Standard, reasonable priced, binoculars, even those advertised for astronomy, use "straight through" prisms which means craning the neck backwards when viewing the sky, especially when viewing anywhere close to the zenith. Even using a robust tripod with a parallelogram mount does not really help with neck strain unless you add a lounge chair which leads to a very cumbersome operation when you want to rotate the set up to view a different azimuth. Overcoming the problem of neck strain and image stability has led to all sorts of different solutions being built for observing with astronomical binoculars. A quick search on the internet of "lawn chair with astronomical binoculars" and then clicking on "22 best astronomical binocular images" on Pinterest shows many of the gadgets and different ideas that have been tried over the years.
This leads to the first requirement for comfortable astronomical binoculars, i.e., they should ideally have eyepieces at 90 or at least 45 degrees from their line of sight. Eyepieces set at 45 degrees start to become more awkward at anything over 60 degrees of elevation but are more comfortable for horizontal bird spotting and are a practical compromise. Binoculars with angled eyepieces do exist commercially but they tend to be expensive and heavy thus requiring a heavy duty mount which adds significantly to their overall cost and a decrease in their portability. The simplest solution to this problem can be side by side, rich field telescopes with mirror diagonals , or erecting Amici prisms and indeed this is a solution providing you keep the objective size at or below around 50 mm. However, 50 mm objectives cannot bring out the true magnificence of most of the celestial objects so larger objectives are highly desirable, but of course with that comes more cost, more weight and less portability.
This website describes the design of several styles of astronomical binoculars, which from now on will be called Binoscopes or Binocular Telescopes which is the more common term when two astronomical telescopes are combined into one instrument. Each design emphasizes comfort in observing and portability and, as will be explained later, each design has certain advantages and disadvantages. There are several crucial design aspects that astronomical binoscopes must try to optimize, i.e., ease of collimation of each optical path, a means to change the inter-eye distance, a means to merge the left and right images so that the brain perceives one combined image, ease of focusing each eyepiece and ease of observing the sky with minimum neck strain. How these design requirements are addressed in each style of Binocular Telescope is described.
Select from the menu bar above to find out how to build:
1) 50mm Binocular Telescope which weigh less than 2 pounds with 45 or 90 degree angled eyepieces. This design can be mounted on a standard ball head photo tripod and used with magnifications from 6X to 60X although it is normally used at a magnification of 9X with a 6 degree field of view. If you intend to use these primarily for astronomy then the 90 degree angled eyepieces are the most comfortable. If they will be used for day time and night time then you might prefer the 45 degree angled eyepieces. If you already have a 3D printer they are inexpensive to build with a total cost of around $120. This design is a great way to begin if you are starting out on a hobby of astronomy since it will eliminate many of the frustrations that can arise with small, inexpensive telescopes on wobbly mounts with too narrow field of view. It is designed to be used with a smart phone, running an astronomy planetarium app which greatly adds to the pleasure of learning the constellations and appreciating the many wonders of the night sky.
2) 114mm F8 Dual Newtonian, Offset Stacked, Binoscope. This binoscope is inexpensive (<$400) and provides great views of the moon, planets, globular and open star clusters and the brighter galaxies. It is compact and light ( 6Kg/13 lbs) and can be used with magnifications from 28X to 200X. Merging of the left and right eye images and changing the inter pupil distance (IPD) can all be performed while viewing. It is the best "all rounder" design for casual backyard astronomy and from a dark site it can show all the Messier Objects and much more. (Work in progress but quite a lot already documented)
3) 150mm F5 Dual Newtonian, Offset Stacked, Binoscope. This binoscope is primarily designed to be used at low magnifications between 23X to 37X for wide field, large exit pupil, bright views of Deep Sky Objects (DSOs), preferably at a dark site. It is very light (5Kg/11 lbs), compact, relatively inexpensive at $450 and the left and right images can be merged while viewing but the IPD is a separate adjustment which takes a few minutes and thus is not ideal for showing the view to a long line of people at a star party. (Documentation not started)
4) 80mm F7.5 Dual Refractor Binoscope. This binoscope (with 90 degree eyepieces) is primarily designed for portability so that it can be brought on a plane as hand luggage when travelling to dark sky sites. It only weighs 2.5Kg (5.5 lbs) and costs ~$300 with eyepieces, and can be used with an inexpensive, light, ($65, and 2.8 lbs) photo tripod. It is still a great "all rounder" binoscope that can provide very satisfying views of many of the brighter DSOs, the craters on the moon, follow the movement of the 4 main moons of Jupiter and show Saturn's rings, It provides "correct view" images, making star hopping more straight forward. It works well for terrestrial use and is just like using high performance, regular, binoculars, albeit with 90 degree angled eyepieces. This binoscope is best used with 20mm, wide field eyepieces (68 degrees AFOV) which give 30X magnification and a 2.3 degree true field of view. However, it can be used for higher magnification where one of the telescopes is kept at 30X to act as a finder scope and the other one used with the 20mm eyepiece and 3X barlow to give 90X. ( Photos but documentation not started, yet, but very soon)
5) 80mm F5 Dual Refractor Binoscope using two 80mm Meade Adventure Scopes
6) 70mm F5.7 Dual Refractor Binoscope using two 70mm Celestron Travel Scopes
7) The key part for making the 3 refractor binoscopes above is an inexpensive ($30), and practical, 3D printed erecting mirror system based on the Matsumoto EMS invention of 1982. (documentation started)
8) A light weight Alt-Azimuth Dobsonian mount that can be used for all the binoscopes with just minor modifications in the number or height of the altitude bearing arms and the spread of the legs. This mount is easy to build and uses easy to find parts from Amazon and Lowes Hardware. The stiction and friction of the azimuth bearing are practically the same as the "ATM Classic" of Ebony Star formica on white teflon but uses readily available teflon furniture sliders on the "rough" side of a 2mm thick ABS plastic sheet. The build takes about a day with simple tools and cost less than $100. (Documentation 100% complete for the 114mm Binoscope option, photos for the 150mm and refractor binoscope options)
9) Description of Tri-Finder : a unique celestial object finding system,
For all of these designs you will need a good 3D printer, preferably one with 300mmX300mm build plate. The one used here is the Creality CR-10. All the printing is done directly on glass with a coating of Aquanet hair spray. This arrangement works perfectly with no adhesion or removal issues.
This leads to the first requirement for comfortable astronomical binoculars, i.e., they should ideally have eyepieces at 90 or at least 45 degrees from their line of sight. Eyepieces set at 45 degrees start to become more awkward at anything over 60 degrees of elevation but are more comfortable for horizontal bird spotting and are a practical compromise. Binoculars with angled eyepieces do exist commercially but they tend to be expensive and heavy thus requiring a heavy duty mount which adds significantly to their overall cost and a decrease in their portability. The simplest solution to this problem can be side by side, rich field telescopes with mirror diagonals , or erecting Amici prisms and indeed this is a solution providing you keep the objective size at or below around 50 mm. However, 50 mm objectives cannot bring out the true magnificence of most of the celestial objects so larger objectives are highly desirable, but of course with that comes more cost, more weight and less portability.
This website describes the design of several styles of astronomical binoculars, which from now on will be called Binoscopes or Binocular Telescopes which is the more common term when two astronomical telescopes are combined into one instrument. Each design emphasizes comfort in observing and portability and, as will be explained later, each design has certain advantages and disadvantages. There are several crucial design aspects that astronomical binoscopes must try to optimize, i.e., ease of collimation of each optical path, a means to change the inter-eye distance, a means to merge the left and right images so that the brain perceives one combined image, ease of focusing each eyepiece and ease of observing the sky with minimum neck strain. How these design requirements are addressed in each style of Binocular Telescope is described.
Select from the menu bar above to find out how to build:
1) 50mm Binocular Telescope which weigh less than 2 pounds with 45 or 90 degree angled eyepieces. This design can be mounted on a standard ball head photo tripod and used with magnifications from 6X to 60X although it is normally used at a magnification of 9X with a 6 degree field of view. If you intend to use these primarily for astronomy then the 90 degree angled eyepieces are the most comfortable. If they will be used for day time and night time then you might prefer the 45 degree angled eyepieces. If you already have a 3D printer they are inexpensive to build with a total cost of around $120. This design is a great way to begin if you are starting out on a hobby of astronomy since it will eliminate many of the frustrations that can arise with small, inexpensive telescopes on wobbly mounts with too narrow field of view. It is designed to be used with a smart phone, running an astronomy planetarium app which greatly adds to the pleasure of learning the constellations and appreciating the many wonders of the night sky.
2) 114mm F8 Dual Newtonian, Offset Stacked, Binoscope. This binoscope is inexpensive (<$400) and provides great views of the moon, planets, globular and open star clusters and the brighter galaxies. It is compact and light ( 6Kg/13 lbs) and can be used with magnifications from 28X to 200X. Merging of the left and right eye images and changing the inter pupil distance (IPD) can all be performed while viewing. It is the best "all rounder" design for casual backyard astronomy and from a dark site it can show all the Messier Objects and much more. (Work in progress but quite a lot already documented)
3) 150mm F5 Dual Newtonian, Offset Stacked, Binoscope. This binoscope is primarily designed to be used at low magnifications between 23X to 37X for wide field, large exit pupil, bright views of Deep Sky Objects (DSOs), preferably at a dark site. It is very light (5Kg/11 lbs), compact, relatively inexpensive at $450 and the left and right images can be merged while viewing but the IPD is a separate adjustment which takes a few minutes and thus is not ideal for showing the view to a long line of people at a star party. (Documentation not started)
4) 80mm F7.5 Dual Refractor Binoscope. This binoscope (with 90 degree eyepieces) is primarily designed for portability so that it can be brought on a plane as hand luggage when travelling to dark sky sites. It only weighs 2.5Kg (5.5 lbs) and costs ~$300 with eyepieces, and can be used with an inexpensive, light, ($65, and 2.8 lbs) photo tripod. It is still a great "all rounder" binoscope that can provide very satisfying views of many of the brighter DSOs, the craters on the moon, follow the movement of the 4 main moons of Jupiter and show Saturn's rings, It provides "correct view" images, making star hopping more straight forward. It works well for terrestrial use and is just like using high performance, regular, binoculars, albeit with 90 degree angled eyepieces. This binoscope is best used with 20mm, wide field eyepieces (68 degrees AFOV) which give 30X magnification and a 2.3 degree true field of view. However, it can be used for higher magnification where one of the telescopes is kept at 30X to act as a finder scope and the other one used with the 20mm eyepiece and 3X barlow to give 90X. ( Photos but documentation not started, yet, but very soon)
5) 80mm F5 Dual Refractor Binoscope using two 80mm Meade Adventure Scopes
6) 70mm F5.7 Dual Refractor Binoscope using two 70mm Celestron Travel Scopes
7) The key part for making the 3 refractor binoscopes above is an inexpensive ($30), and practical, 3D printed erecting mirror system based on the Matsumoto EMS invention of 1982. (documentation started)
8) A light weight Alt-Azimuth Dobsonian mount that can be used for all the binoscopes with just minor modifications in the number or height of the altitude bearing arms and the spread of the legs. This mount is easy to build and uses easy to find parts from Amazon and Lowes Hardware. The stiction and friction of the azimuth bearing are practically the same as the "ATM Classic" of Ebony Star formica on white teflon but uses readily available teflon furniture sliders on the "rough" side of a 2mm thick ABS plastic sheet. The build takes about a day with simple tools and cost less than $100. (Documentation 100% complete for the 114mm Binoscope option, photos for the 150mm and refractor binoscope options)
9) Description of Tri-Finder : a unique celestial object finding system,
For all of these designs you will need a good 3D printer, preferably one with 300mmX300mm build plate. The one used here is the Creality CR-10. All the printing is done directly on glass with a coating of Aquanet hair spray. This arrangement works perfectly with no adhesion or removal issues.
If interested in any of these designs please contact me at:
astronomybinoculars@petertinkerer.com
astronomybinoculars@petertinkerer.com
