How To Build A Powerful Telescope?

Building approaches

• first, let's begin by stating that building a telescope will not be cheaper than buying an equivalent sized telescope unless you already have most of the material on hand.
• second there are two primary ways of building a telescope. one is to make your own optics, which requires grinding your own primary mirror, the other is buying pre-made mirrors and building a telescope around them.
• the former will teach you everything you wanted to know about optic design, fabrication, and testing.
• the latter is much easier to do and less labor intensive.
• while you won't save any money building over buying, it is a very rewarding endeavor and you will learn a lot about your scope and how it works.
• in the end you will have something one of a kind that no one else has.
• i would say this is generally correct, until you get into big apertures. you can save huge $$$$ building your own big aperture structures.

Aperture and large-scale builds

• it depends what you mean by “large” and your level of diy/engineering skill.
• amateur telescope builders have traditionally made 6″ and 8″ reflecting telescopes with reasonable prospects of success, and there are books and websites which tell you how to do it.
• (if you just want to visually tour the sky - look at planets etc. - these telescopes are good enough.)
• keen builders might tackle a 12″ as a second project and one has heard of 24″ mirrors - though then you are into fairly major engineering for a sufficiently robust and stiff telescope structure and mounting, if the the optics are to be given the chance they deserve to work.
• (you are also probably going to be making yourself a mirror grinding machine the relieve the tedious physical work of grinding.)
• you don’t make instruments of this scale (24″) just to eyeball pretty objects in the sky: you are probably aiming at some serious astronomical work, even as an amateur.
• hence you will also be spending money on instruments to attach to the telescope (a good astronomical camera, an astronomical filter set and so on).
• it’s getting expensive - but it is still attempted and achieved by the really keen.
• 36″ telescopes and larger tend to be bespoke professional instruments mounted and housed to support professional research, so perhaps feeding a spectrograph.
• serious and expensive engineering is involved.

Dobsonian telescope

• dobsonian telescopes are a common diy effort.
• a 6-8” would be a good first effort for you to get your feet wet...
• many of the parts can be made with common lumber, or 3d printed.
• you’ll have to source certain things like the mirrors and likely the focuser, etc from manufacturers...
• then if you have success, and you want to go further, you can really go nuts and build a big boy.

Dobsonian mount and optical tube

build a dobsonian telescope

introduction

• our dobsonian sits in the garden at dusk cooling down for the nights observing.
• the yellow optical tube assembly is a 6-inch f/7.5 newtonian.
• the plywood dobsonian mount is simple to build and very functional.
• the scope was entered in the optical and mechanical competitions.
• it won aninnovative component award for the adjustable cradle design.
• the optical judges told me on their second visit i had the best collimated scope and the easiest to point and hold dobsonian mount on the filed that night - so if you have any doubts about the curved vane spider or mount design, rest assured they work well.

reference material & resources

• anatomy of a newtonian optical tube
• anatomy of a dobsonian
• obtaining materials
• shopping for lumber & hardware
• shopping for telescope parts
• selecting plywood for your dob
• rustproof hardware
• sawing, shaping, drilling & sanding
• the basics of making plywood parts.
• newt-web newtonian telescope design

Refractor telescope materials

• gather all your materials.
• you'll need a piece of corrugated paper that is about 24 inches in length (this is a ridge material, easily available from paper stores or craft stores).
• you'll need two magnifying glasses that are not the same size.
• you will also need strong glue, scissors, and a pencil.
• if the magnifying glasses are the same size, the telescope won't work.

Magnifying glass telescope steps

1. hold one magnifying glass (the bigger one) between you and the paper.
2. place the second magnifying glass between your eye and the first magnifying glass.
3. move the second glass forward or backward until the print comes into sharp focus.
4. you will notice that the print appears larger and upside down.
5. wrap the paper around one of the magnifying glasses.
6. measure along the edge of the paper from the first mark.
7. you will need to measure about 1 1/2 inches from the mark.
8. this will create the extra length to glue around the magnifying glass.
9. cut down the marked line on the paper to the other side.
10. you should be cutting across the width of it (don't cut lengthwise).
11. the paper should be about 24 inches in length on one side.
12. cut a slot in the cardboard tube near the front opening about an inch (2.5 cm) away.
13. do not cut all the way through the tube.
14. the slot should be able to hold the large magnifying glass.
15. cut a second slot in the tube the same distance from the first slot as was written down between the two glasses.
16. this is where the second magnifying glass will go.
17. place the two magnifying glasses in their slots (big one at front, little one at back) and tape them in with the duct tape.
18. leave about 0.5 - 1 inch (1 - 2 cm) of tube behind the small magnifying glass and cut off any excess tube remaining.
19. glue first length of paper around one of the magnifying glasses.
20. you'll need to glue the edges of the paper together as well, since you've left about 1 1/2 inches of paper.
21. make the second magnifying glass tube.
22. this one will need to be slightly bigger than the first one.
23. not too much bigger, only so that the first will fit into the second one.
24. slot the 1st tube into the 2nd.

Mailing tube telescope steps

1. gather materials.
2. cut the outer tube in half.
3. you'll need both sections, but the inner tube will act to space them out.
4. the lenses will go in either section of the outer tube.
5. cut 2 pieces from the inner tube of the mailing tube.
6. the spacers hold the second lens in place at the end of the outer section of the mailing tube.
7. make eye-hole in mailing tube cap.
8. drill holes on the outside of the large tube.
9. you'll need to make the holes where the lens is going to be placed in the outer tube, because the holes allow you to put glue into the inner part of the tube.
10. near the end of the inner tube is the best place, about an inch in.
11. you'll also need to the make holes at the end of the outer tube for the eyepiece and the cap.
12. glue eyepiece lens against removable cap.
13. the eyepiece lens is the plano-concave lens and the flat side needs to be against the cap.
14. you'll glue through the holes you made and turn the lens to spread the glue.
15. press tube against lens until the glue is dry.
16. cut off closed end of outer tube.
17. insert first spacer into outer tube.
18. the spacer will need to lie flat on the inside of the outer tube to hold the concave-convex lens in place.
19. you'll need to drill the holes and put the glue in like you did with the eyepiece.
20. insert lens and second spacer.
21. you'll need to make the holes, put the glue in and spread it around.
22. press firmly until the glue has dried.
23. insert inner tube into outer tube.
24. you can slide the pieces as necessary to get the right focus.

Small refractor telescope

• it is possible to make your own homemade telescope with a few basic materials.
• and once the diy project is completed, you'll have your very own telescope with which to observe the stars and planets.
• the good thing about building a small refractor telescope is that they're light and portable, making them idea for taking to dark-sky sites.
• what’s more, their optics need little or no adjustment so they are ideal scopes if you’re a beginner.

1. identify the principal focus of your lens with wooden stands and some card on which to project an image of a distant object
2. measure its focal length
3. use this measurement with the plans in our pdf instructions to work out the tube length
4. carefully cut the main tube with a suitable saw
5. wrapping a sheet of paper around the tube is a good way to mark a straight line
6. take care here; perhaps get someone to help hold it
7. cut a second piece and split it lengthways
8. cut three lengths of 43mm pipe to make the sliding focuser
9. split the shorter sections and remove a strip from one so it fits inside the larger piece (a couple of matchstick spacers help the eyepiece fit snugly); the other will stretch to fit around the outside
10. draw round the inside of the main tube on a suitable piece of wood
11. cut out with a coping saw for a tight fit in the tube
12. mark the central hole by drawing round the assembled focuser, then drill and cut out the hole for the focuser tube
13. paint the inside of the tube and dew shield black with paint
14. apply some mastic glue around the focuser and between the wooden end and the main tube when assembling
15. decide what packing is needed for the objective to fit tightly inside the tube
16. cut a ring of plywood or make three packing strips and position these between the objective and the inside of the tube
17. push into position with a little tape or mastic glue
18. fit the dew shield and cover gaps with tape

Focus, magnification, and brightness

the eyepiece also has a focal length.

the view through the eyepiece comes into sharp focus when the focal point of the objective lens and the focal point of the eyepiece exactly coincide.

the purpose of having a draw-tube is to allow the position of the eyepiece to be moved until its focal plane coincides with the focal plane of the objective lens.

at that position the telescope will be sharply focused.

the increase in magnification of the terrestrial telescope depends upon the ratio of the distance ‘v’ to distance ‘u’.

if ‘u’ and ‘v’ are identical then the increase in magnification is x 1 i.e. the overall magnification is not changed by the presence of the relay lens.

if, as in diagram 2, the value of length ‘v’ is double that of length ‘u’ then the increase in magnification is length ‘v’ ÷ length ‘u’ which gives a result of x 2 i.e. the magnification produced by the telescope has been doubled by moving the relay lens a small distance towards the objective lens of the telescope.

in any telescope, the brightness of the view through that telescope will depend upon the magnification.

as you increase the magnification of the telescope the brightness of the image will diminish in proportion to the square of the magnification increase.

double the magnification, and the brightness will diminish by a factor of four;

triple the magnification and the brightness will diminish by a factor of nine.

Safety and lens notes

• take note that the images may appear upside down.
• this type of telescope is really good for viewing the moon.
• the images will be upside down, since astronomers don't care about up and down in space (there is no up or down in space, after all).
• since this is about 9x you should be able to see the moon's surface really well and even saturn's rings.
• anything else will be too far away for your telescope.
• you can increase the magnification power of the lenses, and also add a third or fourth lens.
• you should not look at the sun with a telescope, even for a second, as this could cause permanent blindness.
• make sure you get the right lenses for the second telescope, since the wrong lenses will mean you won't get to see anything.
• do not look directly at the sun or any other bright objects using telescope, it may damage your eyes.
• be careful not to drop the magnifying glass, it breaks easily.