SIMPLE BUT PROFESSIONAL TELESCOPE FOR BEGINNER ASTRONOMERS

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Introduction: SIMPLE BUT PROFESSIONAL TELESCOPE FOR BEGINNER ASTRONOMERS

About: I'm a guy from Hungary. Musician, amateur astronomer, DIY-fan, airplane-fan, etc. My hobbies are important for me. In my home country the DIY-concept is an old tradition, so I became a fan in my early years.

SIMPLE BUT PROFESSIONAL TELESCOPE FOR BEGINNER ASTRONOMERS
Here is a really good, and very cheap DIY-telescope for beginner astronomers.
The budget is under 15 euros (or 16 $), you only have to spend a small money for the lenses, but this means that the image of your tiny scope will be an excellent, sharp, professional-like, so you are able to see the Jupiter and Venus as a globe, you can see the rings of Saturn, an hundreds of the craters and other surface object on the Moon using it, or, in clear weather maybe this scope can show even the four main (Galilean) moons of the Jupiter.

Step 1: THE PARAMETERS AND THE LENSES

The scope is a simple Kepler, its magnification is almost 20x, which is enough to start some astronomical stargazing. The image is shown upsidedown in it, so the terrestrial using is not recommended, but you should know, to "stand up" the image is necessary with plus lenses, but the quality of seen image is alvays poorer using extra optical elements. Astronomers don't mind the upsidedown, because they prefer the sharp, rich contrast images, and, in the space there is not any meanings of the earth-centered directions.
The lenses are the most important parts. Perhaps you would use simple eyeglass or acryl lenses laying over in the drawers or in forgotten boxes on the attic, but there are two important reason to avoid them. First you never know the exact focus, and rarely can find lenses with the optimal parameters for a good telescope. The other reason comes from the cruel facts of optics: simple lenses (like eyeglasses, glass or acrylic magnifiers) never can image an object in the focus without distortion.
There are two very serious problem with them: the spherical and the chromatic aberration, (and even one of these can totally ruin the image, but these distortions always exist in both). Well, that's why every trying to make scopes with eyeglasses or home magnifier glasses ends with a sad disappointment, when the beginners look through thein DIY scope to gaze a star or planet. The seen object in these scopes are fuzzy, rainbow-edged spots, which may be beautiful as disco light, but doesn't show any details on a celestial body. So I recommend you guys, when you decide to build this small scope, DON'T use simple lenses, but follow my instructions to get lens, and your scope will be a semi pro instrument for cheap.
The optimal lenses for a good telescope are achromats. This means these are planned with two, different material lenses, which have different refraction, well designed surface curves to fit each other, for the distortion-free imaging, and to neutralize the chromatic aberration. The entry level achromats are glued together (also known as 'glued achromats'), and have very clear and sharp image in a telescope. You should get these to build an excellent Kepler-scope.
But how to get them? Very easy, here is a site where you can find them (and others, too). You will need three lenses (originally it's enough to use only two ones, but this alignment is more professional). Two lenses are the same size, and the third is bigger. But now let's see the parts of a Kepler-scope, where I'll explain the whole project.

Step 2: THE KEPLER-TELESCOPE

This arrangement is a very old and very simple way to magnify distant objects. The parallel lightbeam from the object reaches a large diameter and relatively long focused collector lens, gets refracted and travels to the focus point, where gets into a small diameter, short focused lens, which magnifies the image. The large lens is the 'objective', the small is the 'eyepiece'. The focus lenght of the objectice and the eyepiece added together gives the total lenght of your telescope, the ratio of the lenses gives the magnification. But in this scope I planned a twist, because, if you put two similar achromatic lenses together as seen on the picture, you get a very good eyepiece with double magnification, named Ploessl-eyepiece. Thus we use 3 lenses with the following sort:

The objective - 5 eur
focus = 250 mm diameter = 30 mm
Art.Nr.: 569.OAL - this is the number you can identify the objectiv lens.
Here is its datasheet on the AstroMedia: http://astromedia.eu/Material-fuer-Selbermacher/O...
You have to get 1 of this lense for the objective.

The eyepiece - 4,6 eur.
focus = 26,5 mm diameter = 18,0 mm
Art.Nr.: 551.OAL - this is the number you can identify the eyepiece lenses.
Here is its datasheet on the AstroMedia: http://astromedia.eu/Material-fuer-Selbermacher/O...
You have to get 2 of them for the Ploessl-eyepiece. But one lens for a simple eyepiece with 10x magnification is also possible.

Step 3: MATERIALS AND TOOLS

Over the lenses, you will have to get some elements, but those are very common.

Let's see the materials:

The 3 achromat lenses, as explained above

A hoover tube, plastic or metal (26-27 cm lenght)

An old pen or some plastic tube (cca. 5-6 cm lenght)

2 bigger plastic bottle cap Black sheet (not glossy!)

Insulate tape

Some cardboard stripes in some mm-s to drive and keep the eyepiece tube.

And the tools:

Cutter or scissors

Glue tape, and some liquid glue

Step 4: ASSEMBLING OF THE MAIN TUBE

The tube of this telescope will be made of an old hoover tube. Its outer diameter is 30 mm, but it has a wider part at its end which inner diameter is a bit more than 30 mm. This is ideal for our small objective lens, and gives a short overrunning edge at the lens - this ring-like part doesn't let in the ambient light around the telescope.
With this ible I count with the mentioned lenses, but you can easily convert my sizes for other lenses, too. The lenght of main tube is the focus of the objective. In this case this size is 28 cm. The smaller tube (as seen on my drawing) is the eyepiece tube, it will slide when pushed-pulled in the main tube. And you have to cut a piece of foto cardboard, if you have, to cover the inner surcace of tubes, to avoid the unwanted reflections inside.

Take the plastic tube, cut it to the reqired lenght (27-28 cm), and roll around a black cardboard sheet, and put it into the tube in 20 cm lenght from the wide end. Now try your bigger lens into that end - it must be fit easy. If you done it well, you got a tube with black inner part.
Now take two bottle caps, and carefully cut their edge to get two plastic rings. These rings will support the lens without any gluing - you will have to cut a short piece from them to be able to roll them a smaller diameter when inserting. Push one of them into the wide end of the main tube, push it into the neck of the wide part, and be sure if it doesn't tilt inside. Now carefully put the big (30 mm diam.) lens out with its convex side to the sky, and push the other ring above it firmly. You can strenghten it with a small glue, but only the plastic ring, not the lens. If the lens is moving a bit inside, it's not a big problem. But never forget: the large lens must placed with its convex side to the sky. And with this operation you almost finished the assembling of the main tube.

Step 5: ASSEMBLING OF THE EYEPIECE TUBE (AND BAFFLES)

The eyepiece tube is different a bit. Find an old pen or any else plastic tube with cca. 20 mm inner diameter, and at least 5 cm lenght. Then take the two small lenses, set them face to face, as seen on my plan, with the convex sides towards each other. This is a very important part; the Ploessl-eyepieces are very efficient because of this trick. Let the distance between them 1-2 mm, not more.
Now try to roll this system into the insulating tape, but be careful, don't let the parts tilt or move. The axial symmetry is very important at this case. Roll the unit into the tape untin it fits into the eyepiece tube firmly, and set it into balanced position, because this unit must fit properly there, at the end of the smaller tube.

Optional baffles: If you want a professional edged eyepiece, then before the assembling the lenses cut a small disk from cardboard with the diameter of your lenses, and carefully cut out its inner part, to get a 2 mm, flat ring. The diameter of the inner hole must be cca. 12-14 mm. Make 4 baffles like this, and arrange them with the lenses as following: baffle - lens facing right - two baffles - lens facing left - baffle. This last baffle may have smaller inner diameter, cca. 10 mm. With this trick your viewing field will be reduced a bit, but its edge will be sharp. But the correct hole sizes must tried before the final assembling.
You may have small inconvience with the size of the inner ring of baffles, perhaps its not so elegant, because you will see all of your cutting errors magnified, but this is a little problem, and may be avoided, if you try the rings before fit them into the ploessl, or use a metal hole puncher set to cut industrial like holes. Here you should do some experiments to reach the best, but this part hasn't any influence to the imaging, only to the wieving area and its border. And try to find some proper size washer for screws what you can use. Be creative! I haven't made baffles in this scope, so my viewing field is fuzzy at the edges, anyway...

WITHOUT PLOESSL
If you want to spare money, you can build the scope with a simple eyepiece. In this case you should buy only one small lens (and spare cca. 5 euros). But then your magnification will be halved, about 10x. Even this magnification is enough to notice craters on the Moon, but the Jupiter and Saturn won't show details. If you use one eyepiece lens, its convex side should face to your eye.

Step 6: FINAL STEPS

Now you have almost finished the telescope, just only one small part is missing: to push and pull the eyepiece firmly but smoothly, you must glue 3 small stripes of some layers of cardboard into the free end of the main tube. Fold them in half, and put them in pointing the 'V'-shape to the end of the tube. When ready, carefully push the small tube into the large one, and try to sharpen the image. If you were succesful, you must see an upsidedown image in very good quality - with fuzzy viewing field edge, if there was not baffles, or with sharp edges, if there was.

If you can't find the sharp image moving the eyepiece tube, maybe your tube is too long or too short - in this case try to use some math: the focus of the objectiv is 25 cm, the ploessl is 1,4 cm, add them together, and measure the path of the light from lens to lens. Try to pull the objective out a bit (that's why you shouldn't glue it), or cut from the main tube at its eyepiece side, or try to use a longer eyepiece tube than the recommended 5-6 cm. When use the one lense eyepiece, remember that's focus is 2,6 cm.

Step 7: USING THE TELESCOPE

This scope (with the Ploessl-eyepiece) has serious magnification, so you will use it hardly with in hands. Place it on a camera tripod, to aim more easily, or lean your tube holding arm to the wall. But this optics worth for a tripod, because it is not easy to gaze the Jupiter satellites from hand. Look at the surface of Moon, it's amazing.
And, if you are an experience chasing guy, try to build this scope also with acrylic lenses, and notice the difference.

This scope - if you have done it accurately - is a very good small instrument for stargazers, and the only real difference from the serious observing refractors is its small objective diameter (and so its weak light gathering ability). If you want to build a valuable, serious observing scope up to 60-80x magnifications, the method is similar, but of course the price of a 60-70mm diameter achromatic objective is not five euros. But with a 70 mm scope you can observe a lot of objects which are invisible for the naked eye stargazers (globular clusters, bright galaxies, the rings of Saturn, details on Jupiter, and more...)

And some words at the end: Galilei's most sophisticated telescope was a poorer one than this. Smaller wieving angle, weaker optics. Be proud, if you could make it, and use it. And - perhaps some years later - you will buy (or build) a larger scope. I hope so:-)

2 People Made This Project!

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25 Discussions

1
rishabhsen
rishabhsen

Question 2 months ago

how can I get those lenses in India ?

0
isrhory
isrhory

5 months ago

Thank you for the guidance.
I have to say that the image is very disappointing. From looking at Venus I can only see the star-like shape a little bit bigger.
I don't know what is wrong, maybe the lens are defective?

IMG_20200506_204605.jpg
0
BigCthulhu
BigCthulhu

Reply 5 months ago

Hi!
Unfortunately Venus is the one of the hardest object to observe via scopes, and this is because of its very strong light. (I have to fight for it with even professional scopes.) Its light is so strong, you can't get normal image of it, unless you don't use some accesories. The most simple one is a cap on the objectiv lens with a small hole on its center. Decrease the aperture of the objejtive lens radically to get lesser light, don't be afraid, perhaps you must go down just 5-10 mm. The planet will be dimmer, so you can sharpen the image better with the focuser, and you can behold its phases like a miniature Moon. But with this method the resolution of the seen image will decrease too, but never mind, Venus never will show you any surface plus behind its homogen cloud layer.
The other method is some filter, which is able to decrease the light, and this is a better way to save the original resolution rate, but these filters are special and are not too cheap. Perhaps some old sunglesses will help, if you creative enough - put it after the eyepiece.
The most pro way is the polarization filter, which has option to change the "darkness" - you can make one using polarized 3D movie eyeglasses. Put two layer of its "glass" on each other, and as you set their position angle, the amount of the light will change it can absorb. This is can be put after the eyepiece.

0
isrhory
isrhory

Reply 5 months ago

Thank you Cthulhu for the informative suggestions.
But maybe I didn't explain my problem right.
Even when I look on close objects like red light antennas I get very fuzzy spot instead of circle, like I get from a simple ocular I have.
I think it is something about the optics that
Causing the problem.
Maybe I put them in wrong orientation or bit tilted?
Or the two lens of the eyepiece are not on the right proximity
Or the lenses are defective.
BTW, I've got the objective with sort of glue spots so I cleaned it with cotton swab and alcohol. I hope it didn't damage the coating.
What do you advice?

0
BigCthulhu
BigCthulhu

Reply 5 months ago

Ah, I see...
The possible causes of these erratic phenomenons are:

1. Yes, really, the unauthorized cleaning may cause this, but alcohol never does any damage when you use the swab carefully.
But the plastic lenses may be damaged by alcohol, if it is not pure, or has any other ingredient (f.e.: some sort of
diluents, paint thinner or benzol...) These materials solves the plastic. If your lenses are made of glass, and are coated
optics, the coating is very damageable by rubbing. But the fuzzy spot made the optics with damaged surface is not so likely.

2. Tilted optics. This may cause a very typical error; the lights sources are oval, the image is unsharp at the side. But some small tilted position with a longer focal lenght is not so visible.

3. The orientation. This is a more difficult possibility; If you have a Fraunhofer-achromat (Two part of the lens, with a very thin air-space between them), NEVER take them apart! The original position of the parts is the only correct position, meaning even the rotating of them! I've seen some wrong assembled objectives with terrible image, while using its the original position the image should have been correct, sharp and anastigmatic and achromatic. So NEVER take apart any two or three parts optics!

4. Close object. This is not important, the distance is not problem, because the image is always in the same virtual area in
the eyepiece. If you can't recognize the correct shape of a ligth source via the scope, there is a serious projection error inside.
As I mean, your scope has this serious problem; and this depends on the objective. IF this is a plastic or single glass version, the problem is common: the projection is poor because of the material of the lens. The visible image is colorized at the edges, the smaller bright objects are fuzzy, the sharpening is not possible. You can moderate this with a blende (a smaller free diameter, covering the objective lens with a cardboard lens cover, with a centered 1/2 diameter hole). This may decrease the errors, but the resolving capacity will be poor, too. The optimal solution is the exchange with a good achromat (the lens which is assembled by two parts with different refractive index.) The cheap one is an "achromat", this is often named "glued optics", because the parts are glued to each other. The image you can see with this is good enough for small scopes with long focal ratio (F8-f12). The better quality achromat is the mentioned Fraunhofer, with almost professional image, but it is not so cheap, and some frame or mounting is necessary for it.
When an objectiv is put into the tube in inverse position, the image may be wrong - check this, the (of course assembled)
objectiv must have a flatter and a more convex side; the convex side must looks towards the sky.
If your objective is the one of these better optics, and the visible objects are poor like you state, so you should test your eyepiece. The plastic lenses are unuseable for scoping, but even with the normal glass ones you may get negative experiences.
The better eyepiece is the following, if you can't try it, just take a look on it: there must be some color on the surface when you look at it from side. The blue is the common, the green is more sophisticated - so, if you look this color on an eyepiece, the image must be at least good using it. The plastic - as I mentioned - is good for the garbage, while the normal glass is perhaps good for a try.
On the eyepieces you can find markings, some of them: coated or (full) multi coated means these are good optics enough, the "Plössl", "Kellner", or "Barium" is the normal entry level, but these are widely useful ones. The "H" or "R" menas Huygens and Ramsden type eyepieces - perhaps here you can find better ones, but these systems are very anachronistic, old stuff.

Well, shortly: with plastic lenses don't wait any valuable images, and you get almost the same with the normal glass
accessories. If so, try to swap to an achromat (see before).
If the optics is an achromat, check it, if it's a Fraunfofer, and it in its correct position, and was never unassembled, or check the eyepiece.

Fhtang:-)

0
isrhory
isrhory

Reply 4 months ago

Thank you very much for your help and patience!
Just for clarification. I used just the same optics as you suggested in the article, that is all achromats from Astromedia, the objective 569AOL and the two small lenses forming the plossl eyepiece, 551AOL. I didn't take anything apart.
I meant that maybe I put the two 551AOL in wrong proximity. You said to put them 1 or 2mm apart but it is hard to precise so maybe that's the problem.
Maybe to put them in 0mm distance between each other is a better solution?
The antenna I mentioned is 500 meters away so I think it is a bit similar to distant start. I attached a picture of it as seen from my telescope.
Looking forward for you help!
Best Regards

IMG-20200516-WA0003.jpeg
0
BigCthulhu
BigCthulhu

Reply 4 months ago

Yes, all is clear:-)
Sorry, I was perhaps too detailed before, I didn't know you have made it with the recommended lenses.
To tell the truth, I'm not sure I know why your scope is so erratic; and, what a coincidence, yesterday I used just this scope I've builded when I wrote this issue above, and - as always - I wondered, how perfect image this small and simple scope has with these achromatic lenses. (Before, in my childhood I'd made a lot of scopes like this, but using simple lenses instead of achromats, and those images were terrible...)
So, it must produce good and sharp projection, and I don't have too much ideas, what goes wrong. Some additional advice, I can recall:
1. the two smaller lenses in the Ploessl eyepiece must be arranged with the convex sides towards each other. Never mind the small airspace between them; 1-2 mms are not important, with this modification only your magnification will change, but only with some percent with the sum focal lenght of the eyepiece. If you put them close, you get the half of their single focal lenght, and this method is OK.
2. Avoid tilting the lenses (the large and the two smaller ones). The optical axis must be in line with the center of the lenses and the whole tube.
3. The objective lens must be arranged with its convex side towards the sky. These are the most important rules to get clear and sharp images with a Ploessl and an achromatic objective.
4. And... there is something what may cause this error; if the inner surface of the tube is glossy or reflecting the inner light cone from the objective to the eyepiece. Roll a black photo cardboard or some other rough and dark sheet, and put in into the tube to cover its inner wall, or simply paint it black inside with mat black.
5. Try to observe dimmer stars and sharpen the focus on them. If the image is pinhole-like, small and sharp, then your optics is OK. Maybe the "red antenna" is too bright to get sharp image - just like Venus, I told you before. And try to observe Moon - it must be seen covered with craters and hills. The full Moon is not so spectacular throught telescopes, but today, tomorrow and after you can catch her all night long before she gets full:-)
If even the Moon is fuzzy or has some halo around, the problem is with your optics...
Try these, and don't give up! If you have experiences, share them with me here, I hope your scope will be functional soon.

0
Fr33spirit3d
Fr33spirit3d

6 months ago

Nice! I'm interested in making a decent telescope. I'd really like to just change out the lenses in a cheapo scope I got for Christmas. It's so lousy the moon isn't even visible through it..except for light.. Everything is just a fuzzy light..thats IF I'm able to even get it pointed at something! I've noticed the rainbow colors too..I just saw something about that.."chromatic aberrations", but I can't recall what causes it..

Anyway, do you think it would work to measure the size of the objective lens and switch it out with a better quality one and fit an eyepiece (made from 2 lenses like you talked about) to the eyepiece part..or would the length between the lenses be wrong?

0
BigCthulhu
BigCthulhu

Reply 6 months ago

Sorry, Frr33spirit3d, I've replied for you that long issue, but I located wrong place:-)

0
BigCthulhu
BigCthulhu

Reply 5 months ago

... so, I send you my answer here:

Sorry for delaying, now I have some time to answer:-)
That effect you
observe is both the spheric and chromatic aberration; I explain it
above, just in some words, this is generally for the shape and the
material of the objectiv lens. Never use plastic lenses - I think your
scope's is made of plastic, or perhaps simple glass. With these type of
lenses you never get normal, non-aberrated image from celestial objects.
If you can't get enjoyable wiev even of Moon, that lenses are really
low cost ones.
Change the objective lenses (the larger one towards
the sky) with an achromatic one (two components, green or blue surface
when look at it from sides), the important part is the diameter (to fit
it to the place of the old lens), and focus. The larger the focus, the
bigger the magnification. But never forget the focal point must be
inside the original tube to reach it with the eyepiece. The focal lenght
is measureable if you aim to a far light source (2-300 meters) and find
the smallest size spot projecting its image. Compare the focal lenght
this way, and measure the tube lenght, because the effective tube lenght
will be added the focal lenght of the obj. and the eyepiece (for ex.:
500mm plus 10mm).
This is the objective. The eyepiece is the other
part - I recommend you to try it with the new objeective lens, this
usually must be enough in the first round to get clearer images. If not,
try to make a ploessl-eyepiece (see above), and never forget: use at
least achromats for the enjoyable vision on the sky.
Fhtang:-)

0
shinojfez
shinojfez

Question 10 months ago on Step 7

If we use an objective lense of 70mm diameter and 800-900mm focal length, what should be the specifications of eyepiece lense to be used?

0
BigCthulhu
BigCthulhu

Reply 5 months ago

The eyepiece can be the same, the magnification will be higher, using the common formula:
Magn=Focal lenght of Objective / focal lenght of Eyepiece
With this objective lens your scope will be a good accessory for stargazing!
Fhtang:-)

0
mohanbhai
mohanbhai

4 years ago

nice .....interested to make telescope

i want to calculate the magnification of my telescope

so,

is there any formula to calculate magnification of telescope using diameter or focal length of both the lense.sorry if my english is bad i dont know much english :-)

0
BigCthulhu
BigCthulhu

Reply 6 months ago

Sorry for delaying, now I have some time to answer:-)
That effect you observe is both the spheric and chromatic aberration; I explain it above, just in some words, this is generally for the shape and the material of the objectiv lens. Never use plastic lenses - I think your scope's is made of plastic, or perhaps simple glass. With these type of lenses you never get normal, non-aberrated image from celestial objects. If you can't get enjoyable wiev even of Moon, that lenses are really low cost ones.
Change the objective lenses (the larger one towards the sky) with an achromatic one (two components, green or blue surface when look at it from sides), the important part is the diameter (to fit it to the place of the old lens), and focus. The larger the focus, the bigger the magnification. But never forget the focal point must be inside the original tube to reach it with the eyepiece. The focal lenght is measureable if you aim to a far light source (2-300 meters) and find the smallest size spot projecting its image. Compare the focal lenght this way, and measure the tube lenght, because the effective tube lenght will be added the focal lenght of the obj. and the eyepiece (for ex.: 500mm plus 10mm).
This is the objective. The eyepiece is the other part - I recommend you to try it with the new objeective lens, this usually must be enough in the first round to get clearer images. If not, try to make a ploessl-eyepiece (see above), and never forget: use at least achromats for the enjoyable vision on the sky.
Fhtang:-)

0
shinojfez
shinojfez

Reply 10 months ago

magnification = (Objective lense focal length)/(eyepiece lense focal length)

0
BigCthulhu
BigCthulhu

Reply 4 years ago

Hi, mohanbhai! The formula is simple: if you know the focal lenght of the objective lens (the bigger one toward the sky) and the eyepiece (at your eye when observing) you should do a simple distraction: F obj / F epc = Magn.

The diameters are not so interesting when counting magnifications, but the diameter of the objective lens determines the resolution of your scope - the bigger diameter increases the resolution and light gathering ability with a quadrant ratio (sorry, I'm not a native in English, too:-)) - that means the 2x diameter gives 4x resolution and light gathering. The magnification depends only on the focal lenght of the obj. and the eyepiece with their ratio in a telescope.

If you have a telescope that you want to determine, and there is not any given value on its case or body about the focal lenghts, you can use the "poor man's way" to get the magnification: look in the scope, and find an object to estimate the field of view; a roof with tiles, a distant fence, a brickwall, or any multiplicated object which is repeated periodically. Now count or estimate the number of the parts (bricks, tiles, fence rods, etc.), which are seen at the diameter of your field of angle, and turn your scope, look in it from the larger objective lens, to see a small light circle with a very small image at the end of it. Now you should estimate again the number of the parts, (the bricks or tiles), in this circle.

This is the all, the ratio of the two numbers gives the magnification: for example you can see 32 fence rods or roof tiles in the scope at the diameter line of the f.o.v., and 3 rods looking from the other side, then your scope has cca. 10x magnification. For a more exact result try to use a stativ or tripod to avoid the errors causing the hand holding moves.

Fhtang!

0
Mokso
Mokso

1 year ago

Szia. Az oldalon az 551OAL lencse sajnos elfogyott és nem is tudni hogy mikor lesz nekik legközelebb. Se az angol, se a német oldalon. Van más méretű lencse amivel esetleg helyettesíthetem? Vagy az 551 OAL-re hogyan keressek rá neten, hogy más oldalról meg tudjam rendelni? Nagyon szépen köszönöm ha időt szánsz a válaszra és brutál jó a poszt! Köszönöm! :)

0
BigCthulhu
BigCthulhu

Reply 1 year ago

Bocs, nem igazán néztem mostanában, mert egy idő óta idióta robotposztok és hülye fantomfelhasználók jönnek csak inboxba, és kicsit ráuntam, hogy mások idétlenségeit kerülgessem, de írtam neked vissza, itt is megadom az elérhetőségemet: blasius@tabulatura.hu, illetve www.scordatura.hu (itt is van mailcím, de a gmail-es postafiók rendre spamnek nézi a válaszaimat, inkább a blasiusra jelenkezz be.)
A lencsére van megoldás. Menjünk át privátba.

0
SharanC2
SharanC2

Question 2 years ago

Can we see planets?

1
Salamyman
Salamyman

2 years ago

you say the objective has focus = 250 mm, but on the website it ways 280 - which one is correct? 250 or 280?