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In January of 2016, I received my first telescope, through Astronomers Without Borders. It was and is my first telescope: an AWB 130 Newtonian tabletop telescope with a 650mm focal length and a 130mm aperture. I am completely new to telescopes and have no experience whatsoever with astrophotography.

Please try to forgive my unprofessional description!

After some attempts, my telescope fell into disuse, and now, finally, I am getting back to it. The telescope came with a 10mm and 25mm eyepiece. The moon's diameter is .52 degrees as viewed from Earth, and a 10mm eyepiece. Supposedly, I should be able to frame the entire face of the moon with little room to spare using the 10mm eyepiece. However, I often found that the moon appeared rather small in the 10mm; if I changed the focus to try to zoom in and get more detail, the image became too blurry. The 25mm seems to make things sharper, but its wider field of view means less magnification and consequently, less detail.

Two days ago on Thanksgiving, my family and I were exiting the movie theater (we had gone to see King Richard at 3:15 in the afternoon) around six pm. I noticed a very bright star, and another relatively bright one close to it. I went home and quickly used two astronomy apps to identify them--and I realized that they were Jupiter and Saturn. Most of the planets were above the horizon that night, but with my telescope, I didn't expect to see anything much brighter than Jupiter. So, I pulled out my telescope, went out onto my porch, and pointed my telescope at Jupiter.

And all I saw was a bright, white dot with three or four other dots forming a line across it.

The best I've observed in terms of celestial detail is the moon, and I previously hadn't gotten much detail out of Earth's closest satellite. When I pointed my telescope at something other than the moon, the best I usually got was an unidentifiable dot. So, I was almost pleasantly surprised that I was seeing this much "detail." I presumed I was looking at Jupiter and four of its moons in orbit. Again, I tried to zoom in, but I only saw a large, circular patch of light with a smaller ring inside it. The ring was probably from a ring on the primary mirror inside the telescope.

If I was looking at Jupiter, shouldn't I have at least gotten a look at its color?

In an attempt to problem solve, I collimated my telescope yesterday, and I'm planning on taking it outside once again tonight. I also visited numerous websites and saw that with a telescope like mine, I should be able to observe Mars, Jupiter, and Saturn in detail, as well as some of their moons.

Do I need more powerful eyepieces? Am I doing something wrong? Please help me out!

*Update: Last night, I took my telescope out onto the porch again, and using JohnHoltz's suggestion, I located a bright object close to the horizon. To my surprise, I saw something that looked like the moon, but was much smaller. I used an astronomy app to confirm that I had indeed seen Venus in one of its phases! That was perhaps the most success I had had in seeing a celestial object other than the moon. I had to leave the telescope for a moment, and then I couldn't find it again, but I believe I've made progress.

However, I pointed my telescope at Jupiter a few minutes later, and all I could see was something that looked like a bright star. Perhaps I couldn't attain higher magnification because there might have been a slight haze in the sky.

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    $\begingroup$ You've already accepted an answer, so I won't bother writing another one, but here are some useful links for you: FoV calculator so you can preview what you should be able to see with a given telescope+eyepiece combination. OneSky Newtonian - the biggest resource of information about your telescope: over 5000 posts from people who own it. Regarding Jupiter - buy a 2x Barlow lens to use with your 10mm eyepiece. If that works then buy a ~5mm eyepiece. $\endgroup$
    – Aaron F
    Nov 30 '21 at 15:58
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    $\begingroup$ Thank you! These tips will be very helpful! $\endgroup$ Nov 30 '21 at 16:15
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Welcome to the wonderful world of visual astronomy!

The first thing I would like to point out is that, when you are talking about “zooming in,” you’re actually adjusting focus—placing the eyepiece exactly in the right point of focus of the telescope’s main mirror. The “smaller ring” you see, presumably dark, is the shadow of the secondary mirror, when out of focus. Now, the positioning of the eyepiece must be very precise; in the case of your telescope, it’s something like 1/100 mm (1/2500 in), maybe even less. So you need to go very gently with the focusing knob (which I guess you had been calling the “zooming” knob up to now). Basically, you need to turn it until the image is “as small as possible, and as bright as possible,” as I was told when I began in astronomy myself, many years ago.

The second thing is how to calculate magnification. It is simply the focal length of the telescope itself divided by that of the eyepiece. With this 650 mm telescope, the 25 mm eyepiece will magnify 26× and the 10 mm, 65×. The higher the magnification, the bigger optical defects become, which explains why the image is sharper with the 25 mm—but smaller when in focus.

What are those optical defects? Well, for one, the optical surface of the mirror is never perfect, just as good as the manufacturer can make it. Obviously, very expensive instruments have more careful manufacturers, but that doesn’t mean the AWB telescope was made by a “bad” manufacturer (if I remember well, they’re done by Explore Scientific, which is respected and respectable).

But there is an optical defect on which you can have an influence: it’s called collimation. It simply consists of aligning perfectly the optical axis of the mirrors among themselves, as well as with that of the eyepiece. Here is not the place to teach you how to do it, but you can certainly find excellent tutorials on YouTube about it. Basically, you have a few bolts/screws behind the main mirror and maybe also near the smaller mirror in front of the telescope tube. These bolts/screws must be very slowly and very gently turned while looking through the eyepiece and adjusting them until you get the best image possible.

When the collimation is not done properly (and it can change for a variety of reasons, notably vibrations [e.g., induced by moving the instrument] and even temperature variations), images become blurred, and those of stars may appear “comet-like.”

Start with this, and should you have any more questions, well, you have already come to the right place!

Cheers!

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  • $\begingroup$ First of all, the circle I saw is more likely to be the "doughnut circle" on the primary mirror; I'm not sure what it's for, but I can see it when I look into the telescope at the primary mirror. Second, What do you mean by "the positioning" of the eyepiece? Third, when I "refocus" so that the image I get looks clear, it's just a small, bright, white dot. Any time I try to get better detail, the image is too blurry. This question partially answers my question. $\endgroup$ Nov 27 '21 at 23:36
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    $\begingroup$ "1/100 mm (1/250 in)" -- those two measurements differ by a factor of 10 -- which is correct? $\endgroup$
    – nanoman
    Nov 28 '21 at 4:26
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    $\begingroup$ Oops! Forgot a zero! 1/2500 in. Sorry! $\endgroup$ Nov 28 '21 at 21:57
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    $\begingroup$ @SovereignInquiry: Yes, the image is supposed to be a small, bright, white dot indeed. As for the “donut circle” of the primary mirror, it’s used for alignment with a collimating laser, and no, it is not what you see when you defocus; it really is the secondary mirror’s shadow. As for the positioning, I meant when you refocus: it changes the position of the eyepiece ever so slightly. $\endgroup$ Nov 28 '21 at 22:01
  • $\begingroup$ @PierrePaquette If all I'm supposed to see is a small white dot, then what is the point of the telescope, and why do other people claim that they can see planets in detail with telescopes of the same size? $\endgroup$ Nov 29 '21 at 14:08
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I suggest you take your scope out during the day and look at the most distant object on land (or sea) that you can see: a building, tower, or tree. Start with the 25 mm eyepiece and turn the focus knob. There is only one position where the object is clear. Any view will be more blurry on any other position.

With the object in focus, change to the 10 mm eyepiece. Chances are the object will not be in focus. Rotate the kobs until the object is as sharp as possible in the 10 mm eyepiece.

The behavior is the same when looking at the sky. There is one position of the focus knob for each eyepiece where the image is in focus and sharp.

Start with the 25 mm eyepiece since it is easier to align on an object. When it is centered, you can switch to the higher power 10 mm eyepiece.

The Moon should fill most of the view. Jupiter will be a small disk with darker cloud bands (stripes) across the middle. Otherwise the colors are subtle and hard to see in your small scope and skill level. Saturn's rings will be visible. Stars will remain a pinpoint when everything is aligned and working properly.

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    $\begingroup$ Please, do not look at the Sun during the day! That is extraordinarily dangerous to your vision. Be also careful of Sun reflections on shiny objects, such as windows or cars. I personally would only point a telescope during the day at a nature scene, no artificial objects, with the Sun behind me. $\endgroup$
    – dotancohen
    Nov 28 '21 at 10:26
  • $\begingroup$ @dotancohen, very good warning! $\endgroup$ Nov 28 '21 at 22:56
  • $\begingroup$ Just a note, if you look at something too far away you may not be able to get a sharp picture. I had a Newtonian I was trying to do some astrophotography with with bad results and when I pointed it at a mountain ~50km away during the day time there was way too much atmospheric distortion for anything to look sharp and focused at any setting. $\endgroup$
    – Michael
    Nov 29 '21 at 15:00
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Even if your telescope is correctly set up, its short focal length of 650mm is not ideal for observing details of the moon and planets. You should get one or two more eyepieces with a shorter focal length. I would get a 6mm and 4mm, which would give you magnifications of about 110x and 160x respectively. See here for some decent budget priced models https://agenaastro.com/gso-6mm-plossl-eyepiece.html
https://agenaastro.com/gso-4mm-plossl-eyepiece.html

Anyway, you made an error in your calculation: the diameter of the moon is 0.5 degrees but the field of the eyepiece itself is 45 degrees so you would need a 90x magnification (45/0.5) for the moon to completely fill the field. Your 10mm eyepiece gives only a magnification of 65x though, so it fills only about 70% of the radial diameter of the field of view. You need at least a 6mm eyepiece for the moon to fill the field of view (the eyepieces I suggested above have actually a slightly wider field of view (52 deg) but a 6mmm would do this here as well; and with the 4mm you would even only have about half the surface of the moon in view).

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    $\begingroup$ Although with such short-focal eyepieces, the magnification level becomes so high that it approaches the diffraction limit of the main mirror, so it’s tricky… $\endgroup$ Nov 28 '21 at 22:02
  • $\begingroup$ @PierrePaquette That's kind of the point - use the entire telescope to its max. And also to build an understanding of the tools. $\endgroup$
    – dotancohen
    Nov 29 '21 at 6:04
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    $\begingroup$ @PierrePaquette The diffraction limit of a telescope with 5 inch diameter is about 1 arcsecond. You won't really notice this even at 160x magnification, especially not for moon or planet observations. I wouldn't go much higher though, also because telescope vibrations would get annoying. $\endgroup$
    – Thomas
    Nov 29 '21 at 8:28
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    $\begingroup$ I fail to see how more magnification is the right answer in this contest. It's a tabletop telescope, is probably wobbly and is hard to know how good the quality of such a system is (my guess is, pretty low). I would guess that at higher magnification it will be almost impossible to keep the objects in the field of view and to focus them. $\endgroup$
    – pygri
    Nov 29 '21 at 15:58
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    $\begingroup$ @pygri The OP is apparently unhappy with the magnification, and getting 1 or 2 new eyepieces would be the obvious way to address this problem. The review in the following link reports actually good results for this particular scope even for magnification 200x and above theopportuneastronomer.com/equipment/telescopes/… $\endgroup$
    – Thomas
    Nov 29 '21 at 20:57

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