Embedded Files
The D114F900 telescope uses a 114 mm spherical mirror and diagonal mirror purchased (October 2024 dollars) from Amazon (or other sources). It's focal length is 900 mm.
The tube assembly and trunnions are a kit. They are simply screwed together with a couple of glue joints.
You can easily make the kit. While there are a lot of parts, each one of them can be 3D printed on a consumer-grade printer (these were printed on a Creality Ender-3 printer (October 2024 dollars)). You will need a KG of plastic filament (PLA, or preferred, PETG) - $15 at October 2024 prices (your choice of color, but black works well for telescopes). It WILL take some time to print all the parts, but the machine does all the work from the supplied data files (see below).
If you don't have (access to) a suitable 3D printer, ASEM has one members can check out and one of our members will train you to use it!
Part Files
Part Files
The file below contains all the STL files needed to print the telescope kit. Click on the arrow in the upper right corner to download the zip file.
In addition, you will need
six (6) #10-24 1/2" screws
four (4) 1/4-20 hex head bolts, 3 1/2 inches long for altitude bearings
six (6) #8 wood screws 2 " long for altitude bearings
E6000 glue
D114F900_files.zip
The mirror end is where the mirror cell mounts using the adjustable mounting holes. Note the female thread in the top for connecting to the next tube segment.
The mirror end is where the mirror cell mounts using the adjustable mounting holes. Note the female thread in the top for connecting to the next tube segment.
You will need five (5) of these wall segments. Note the male thread on the bottom and female thread on the top for connecting to the other pieces.
You will need five (5) of these wall segments. Note the male thread on the bottom and female thread on the top for connecting to the other pieces.
You will need one of these to act as the altitude bearing hub. Two trunnion extensions are glued using E6000 glue. There are alignment holes for screws to align the pieces properly and clamp the joint while the glue sets up.
You need two copies of the trunnion extensions which are glued to the main saddle using bolts in the alignment holes to assure correct alignment and to compress the joint while the glue sets.
You need two copies of the trunnion extensions which are glued to the main saddle using bolts in the alignment holes to assure correct alignment and to compress the joint while the glue sets.
The focuser block glues to the eyepiece saddle. The alignment holes are for bolts to compress the joint while the glue sets. Note there are no female threads in the top as this is the last piece of the tube assembly. There are three (3) tube segments between the eyepiece saddle and the main saddle.
The focuser block glues to the Eyepiece saddle. Alignment holes are for bolts to compress the joint while the glue sets up.
The focuser block glues to the Eyepiece saddle. Alignment holes are for bolts to compress the joint while the glue sets up.
The focuser screws into the focuser block to provide a focus control. An eyepiece is inserted into the focuser.
The focuser screws into the focuser block to provide a focus control. An eyepiece is inserted into the focuser.
The spider holds the diagonal mirror with just a dab of glue to keep it from falling out. It fits into the eyepiece saddle and the alignment holes will help to position it correctly.
The spider holds the diagonal mirror with just a dab of glue to keep it from falling out. It fits into the eyepiece saddle and the alignment holes will help to position it correctly.
The mirror plate holds the mirror with three (3) clips that attach with #10-24 screws. 1/4-20 2.5 inch hex head bolts fit into the plate before the mirror is installed for the collimation screws.
The mirror plate holds the mirror with three (3) clips that attach with #10-24 screws. 1/4-20 2.5 inch hex head bolts fit into the plate before the mirror is installed for the collimation screws.
The collimation bolts fit into the three holes with springs in between. The cell is attached to the mirror bottom using #10-24 screws into the threaded holes.
The collimation bolts fit into the three holes with springs in between. The cell is attached to the mirror bottom using #10-24 screws into the threaded holes.
You need three mirror clips which secure the mirror using #10-24 half inch screws through the threaded holes in the mirror plate.
You need three mirror clips which secure the mirror using #10-24 half inch screws through the threaded holes in the mirror plate.
Washers are needed under the three cell mounting screws to prevent interference with the collimation screws
Washers are needed under the three cell mounting screws to prevent interference with the collimation screws
Two sets of altitude bearings are needed to attach to the wood rocker box. Two (2) 1/4-20 3.5 inch hex head bolts are pushed through from the bottom of the bottom bearing before attaching to the wood rocker box with three #8-2in wood screws.
Two sets of altitude bearings are needed to attach to the wood rocker box. Two (2) 1/4-20 3.5 inch hex head bolts are pushed through from the bottom of the bottom bearing before attaching to the wood rocker box with three #8-2in wood screws.
A 1/4-20 nut will fit into the end of this knob with a dab of glue. You will need four (4) for the altitude bearings and three (3) for the mirror collimation bolts.
A 1/4-20 nut will fit into the end of this knob with a dab of glue. You will need four (4) for the altitude bearings and three (3) for the mirror collimation bolts.
The AstroHopper base is attached to the main saddle with glue or double sided tape to hold a smart phone for the AstroHopper app. Velcro strips on the base and the smart phone make for easy install and removal. Be sure the smart phone aligns with the axis of the tube.
The AstroHopper base is attached to the main saddle with glue or double sided tape to hold a smart phone for the AstroHopper app. Velcro strips on the base and the smart phone make for easy install and removal. Be sure the smart phone aligns with the axis of the tube.
This laser finder (follow link for stl files) attaches to the eyepiece saddle with glue or double sided tape.
This laser finder (follow link for stl files) attaches to the eyepiece saddle with glue or double sided tape.
Assembling the Optical Tube (OTA)
Assembling the Optical Tube (OTA)
The main components of the tube simply screw together (you might want to use a dab of glue on the threads for a permanent bond - maybe after testing everyting out), Start with the mirror end and attach two of the wall sections before attaching the main saddle. Three more wall sections lead up the eyepiece saddle. Glue the trunnion extensions onto the main saddle using E6000 glue and long screws through the alignment holes to get both sides even and compress the glue joints. Attach the focuser block to the eyepiece saddle in a similar manner.
The diagonal mirror is placed in the spider and held in place with just a dab of E6000 glue. The spider fits into the eyepiece saddle and is rotated to bend the focused beam out the focuser tube. It bottoms out against a shelf that should properly align it.
The 1/4-20 bolts are placed into the mirror plate before the mirror is set in place and secured with three mirror clips using 1/2 inch #10 24 screws in the threaded holes.
The springs are placed over the bolts and these are pushed through the holes in the mirror cell and secured by the knurled knob nuts.
The mirror assemblly is placed in the mirror end and fixed in place with three 1/2 inch #10-24 screws into the threaded holes in the mirror cell. Use the washers to keep the screw from interfering with the collimation bolts. Several hole combinations allow adjusting where the focal plane will fall in the focuser. Contrary to this view, I have found the third from the bottom position best for my eypieces.
The AstroHopper base is simply glued (or 2-sided taped) to the main trunion. It is designed to hold a retired smart phone along the axis of the telescope for use with the AstroHopper app. Velcro pads are probably the best way to attach the phone to the base. See using the telescope section below.
Alt-Az Mounting
Alt-Az Mounting
The mounting of the optical tube assembly (OTA) is by the Alt-Az system popularized by John Dobson. (If you don't know who John Dobson was, you really should explore this link!)It is easily constructed from one 24x48 piece of MDF (about $12 in 2024) and provides a stable base for using the telescope. The bane of most small, commercial telescopes is the mounting which almost always is 'wobbly' and hard to use and this one really works well.
The image to the left shows how the parts for the rocker box can be cut from a single 24x48 sheet. The .dxf file is available for use with a CNC router (which I have available at my local Maker Space. The legs are press fits into the bottom slots and are secured with a bit of wood glue ( I prefer Tight Bond III)
The pieces can, of course, be cut out with a saber saw and table saw (the circular bottom board is not used as a bearing). The holes are optional to save weight.
The pieces are assembled and glued together using a good wood glue (I prefer Tight Bond III). If you can't cut the slots for the legs, you can use the slot outlines to position wood screws through the bottom to secure the legs. I would use glue here too.
A coat of paint makes it look nice and will seal the MDF (if that is what you use). I prefer Krylon Hammered Black.
The lower altitude bearing is fitted with the two 1/4-20 bolts 3.5 inches long before being screwed on to the top of the legs using the #8 wood screws. It's always a good idea to drill pilot holes before inserting the wood screws to keep the material from splitting.
Using the D114F900 Telescope
Using the D114F900 Telescope
The telescope is a qualty beginners telescope. It is not a toy and can introduce the user to amateur stargazing. It is much more stable that typical commercial telescopes costing $200 or more. It will reveal myriads of details of the Lunar surface, show Saturn's rings, Jupiter's moons and bands and some deep sky objects (depending upon the light pollution of your observing site). It will help you decide if you want to get a larger telescope later.
You will need at least one eyepiece and I recommend the SVBONY 23 mm (for 39X) , and SVBONY 10 mm (for 90x) to start. They are not expensive and will show the capabilities of the telescope quite well.
Finding Sky Objects
Finding Sky Objects
The sky is a big place and your telecope field of view is small - with the SVBONY 23 mm eyepiece recommended above the field of view through the telescope is about 1.5 degrees (which is 3 times the size of a full Moon). You can sight along the edges of the telescope to get close to brighter objects but will still have to scan the telescope back and forth, up and down to put the object in the eyepiece. That's not too bad for this telescope. Think of searching a 10x10 degree patch of sky. Start at the lower left corner, pay attention to how wide your field of view is and move to the right 6 or 7 field widths. Then move the telesope up one field width and go back to the left for the same 6 or 7 widths and repeat. Practice makes perfect!
To get a lot closer with your first pointing effort, I recommend you buy a green laser pointer (shop around) and make the laser holder at this link.
Using whatever pointing technique you select you will be limited to objects you can see with your unaided eye. That's not too bad, though, you have the Moon, Venus, Jupiter, Saturn, the Andromeda galaxy, the Orion nebula, and lots of double and interesting stars.
To find fainter objects you will need a map (lots of them available in libraries, book stores and online) and learn to 'star hop.' Star hopping means locating bright stars you can find near to your target and then noticing fainter stars that you can 'hop' to until you are close to your target. I recommend SkyMaps which is a free downloadable and printable monthly sky map to get started. It will identify the naked-eye stars visible during the month it is designed for and has many suggestions for what to look for by naked-eye, binoculars and small telescopes.
Many telescopes have a smaller, finder telescope that will show you fainter stars but in a wider field than your main telescope. But I want to recommend a technology leap (my characterization) that will help you ...
AstroHopper
AstroHopper
AstroHopper is a free app that runs on almost any 'retired' smart phone. It doesn't care about Android, iPhone, or whatever as it runs in a browser on the phone. You can check out if it will work with your candidate phone by going to artyom-beilis.github.io/astrohopper.html (you don't need a telescope to check out the app) .
AstroHopper is a free app that runs on almost any 'retired' smart phone. It doesn't care about Android, iPhone, or whatever as it runs in a browser on the phone. You can check out if it will work with your candidate phone by going to artyom-beilis.github.io/astrohopper.html (you don't need a telescope to check out the app) .
To use, you attach it to the axis of the telescope such that the up-down orientation of the phone is aligned with the axis. The D114F900 telescope as a 3D printable bracket to mount the smartphone. Start the app and the screen will display a sky map showing you where it "thinks" the telescope is pointed. I say "thinks" because there are still some errors in the phone's sensors that need to be calibrated out. To do so, align the telescope with some bright star (you WILL need to learn at least some of them to be a successful star gazer), press the 'align' button on the display and then press the image of the star you have centered in the eyepiece. After a few seconds it will report 'aligned' and you are pretty good to go, at least for relatively nearby objects. You can search for your desired object and AstoHopper will indicate where you want to go. Arrows on the screen will direct you to go right-left and up-down as needed to get to your target. You may still have to scan an area around the starting position to center your target. If you move a large distance from the last alignment star, you will probably have to re-align on a new one closer to your desired target. But it works! and practice makes perfect!
To use, you attach it to the axis of the telescope such that the up-down orientation of the phone is aligned with the axis. The D114F900 telescope as a 3D printable bracket to mount the smartphone. Start the app and the screen will display a sky map showing you where it "thinks" the telescope is pointed. I say "thinks" because there are still some errors in the phone's sensors that need to be calibrated out. To do so, align the telescope with some bright star (you WILL need to learn at least some of them to be a successful star gazer), press the 'align' button on the display and then press the image of the star you have centered in the eyepiece. After a few seconds it will report 'aligned' and you are pretty good to go, at least for relatively nearby objects. You can search for your desired object and AstoHopper will indicate where you want to go. Arrows on the screen will direct you to go right-left and up-down as needed to get to your target. You may still have to scan an area around the starting position to center your target. If you move a large distance from the last alignment star, you will probably have to re-align on a new one closer to your desired target. But it works! and practice makes perfect!
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