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5answers
3k views

Recommended first accessories for starblast 4.5

My son got an orion starblast 4.5 for Christmas. It comes with orion explorer II 17mm and 6mm eyepieces. We are looking at some additional accessories and wondering what you would recommend as "first ...
2
votes
2answers
103 views

Is it possible to build an optical system that increases the perceived surface brightness?

So is it possbile to build a system from lenses and mirrors that can make faint gas nebulas brighter or can be used as nightvision? If you increase the size of the aperture of a telescope it will ...
2
votes
1answer
354 views

How to measure the altitude of an object in the sky?

If I use a telescope to observe a plane in the sky, how can I find the altitude of the plane(altitude of the plane with respect to the ground)?
2
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2answers
56 views

Why don't reflector telescopes place their reflectors at an angle?

To avoid placing a secondary mirror in front of the objective mirror, why not tilt the objective and design the eyepiece in such a way that comatic aberration is minimized?
2
votes
1answer
603 views

Keplerian Telescope Exit Pupil Location - Whats the Basis for It's Formula?

For a simple two lens Keplerian telescope, this is the formula for the location of the exit pupil: $$z'=\frac{f_2}{f_1}(f_1+f_2)$$ Where $z'$ is the distance to the exit pupil location (i.e. eye ...
2
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2answers
132 views

WHY is a Refracting telescope image distance $S'=-\infty$?

In the above slide, it says that "Eyepiece '2' makes the image distance $S'$ approach $-\infty$." However, What I don't understand is that if I place my eye right at the Eyepiece 2, then I would see ...
2
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1answer
24 views

What was the most distant supernova spotted by a amateur astronomer until today?

What type of commercial amateur telescope and what method (difference imaging,...) did he use for identifying the supernova?
2
votes
2answers
316 views

How to calculate error of parallax and sextant based navigation?

First of all, why wasn't the sextant ever used for land navigation? The horizon is easier to see at sea, but land based sextants could be used in conjunction with artificial horizons (as at sea when ...
2
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0answers
59 views

need data-point: count rate of APD (avalanche photo-diode) for specific aperture and stellar magnitude

I hope lab / experimental physics is fair game for this web-site. If not, sorry! I'm designing a sensor system to perform specialized [astronomy and space-sciences] experiments, and need a "reality ...
1
vote
3answers
80 views

Why do telescopes move synchronously?

Here's a very nice video (see it in HD) of timelapses captured at the atacama desert. In the beginning of the video you can see that 4 telescopes move synchronously. Could anyone explain why? I always ...
1
vote
1answer
2k views

How long does it take for pictures by Hubble to arrive on Earth?

Recently, there was news that Hubble took a high definition picture of the Andromeda galaxy. I wanted to know how long does a high definition picture from Hubble takes to arrive on Earth; if at all ...
1
vote
1answer
31 views

What is meant by the point-source response of eye or telescope?

I have heard that a source is called unresolved if it is much smaller in angular size than the point-source response of the eye or telescope observing it. What is the meaning of point-source response ...
1
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2answers
2k views

What is the highest useful magnification todays largest telescopes can offer?

I know that the maximum (useful) magnification is limited by the diffraction limit, but I was not able to find numbers for the highest useful magnification factors using modern large telescopes. How ...
1
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2answers
1k views

How to Ray Trace Chief and Marginal Rays in Thin Lens Systems

Looking at the below images, the chief and marginal ray appear to be modeled just fine. But, those lines don't seem to conform to the rules typically used in thin lens ray traces. An example of ...
1
vote
1answer
63 views

Data/signal from a black hole to observe a singularity

I wonder if a situation is possible where, we measure some signal/property concerning a black hole. Supposing the measurement we make with some telescope, gets us the Fourier transform coefficients of ...
1
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1answer
474 views

CCD's and the photoelectric effect

Do charge coupled devices as found in telescopes use the photoelectric effect if not what eles librates the electons. Also what is charge intergration in reation to CCD's.
1
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1answer
207 views

Distance at which a 300m asteroid is visible

Using the best available telescopes, and assuming a typical albedo of 10%, at what distance can a 300m asteroid be seen (well enough to start plotting its course) in 1) visible and 2) infrared ...
1
vote
1answer
74 views

What is the limit of the deep field exploration?

The deep field exploration is quite fascinating, first the Hubble Deep Field (HDF) showing a small piece of the Univers one billion year after the Big-Bang, next the Hubble Ultra-Deep Field (HUDF), ...
1
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1answer
111 views

Non-discoveries by the Kepler space telescope: exomoons, co-orbital planets, trojans

I am just reading the review article Advances in exoplanet science from Kepler (arxiv preprint: http://arxiv.org/abs/1409.1595), and I found a remarkable paragraph (last paragraph in section "...
1
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1answer
213 views

Does sign convention in geometric optics fail to explain the cases of image formation by virtual objects?

Here is an example of Cassegrain telescope: Parallel rays from a distant object get reflected by the concave mirror forming an image at its focus behind the convex mirror. This image acts as a virtual ...
1
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2answers
92 views

Any projects to build a telescope in space?

Like in the title. With E-ELT we are pushing the limit of what we can build on the ground. With JWST we are pushing the limit of what can we launch into space. So instead, why don't we launch tools ...
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0answers
74 views

World's Largest Radio Telesope : How accurately does it need to be figured?

In Guizhou Province, China, the worlds largest radio telescope is almost complete, measuring 500 metres across. I am aware that todays largest optical telescope require very accurate figuring and ...
1
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0answers
48 views

Telescopes and faster than light travel [closed]

If sometime in the future we master faster than light travel, could we solve past crimes by warping to a place in space where the light from Earth is just arriving from that time period and using a ...
1
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0answers
31 views

Wavelength limited resolution

I've read through answers to similar questions, and I haven't been able to find a satisfying answer. I've heard it said that in order to make out something, you need to use light with a wavelength at ...
1
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0answers
41 views

Given a focal length and an aperture of the telescope, what is its field of view?

While I know FOV of scope is equal to FOV of eyepiece divided by magnification. How can one find FOV given only the focal length and aperture of the telescope?
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0answers
23 views

Is there a limit to telescope resolution? [duplicate]

Could a strong enough telescope read a newspaper on a planet 1400 light years away, or is there a theoretical limit to the resolution of magnification?
1
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3answers
47 views

About light nature [closed]

I have some particular questions about the nature of light...cause all I know from all sources is that it is a wave and a particle and stuffs, but if light "COMES" from all directions, and is in every ...
1
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0answers
195 views

What prevents Digital interferometry in an optical telescope array?

I understand it is common to combine an array of radio telescopes in to a single instrument using interferometry. This has the photon collecting area of the combined radio telescopes but an aperture (...
1
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0answers
118 views

If we increase the aperture of a telescope and decrease its magnification, can it be harmful to the eyes?

The full moon is the brightest object in the night sky. I believe that if we increase the aperture of the objective, and decrease the magnification of the telescope, it might concentrate a dangerous ...
1
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0answers
55 views

When viewed from a telescope, does an object get more magnified if its angular diameter is increased?

and if yes, how can the diameter be increased? Lets say I want to view saturn from a small telescope. Increasing the angular diameter will give a better magnification if the answer to the above ...
0
votes
1answer
240 views

Resolving power of ultra-telescopes [duplicate]

Assuming we could create and orbit optical telescopes of arbitrary size, perhaps starting with (say) inflatables or active membrane of 100m diameter what kind of resolution in imaging extra-solar ...
0
votes
3answers
2k views

What can be seen with a 114mm Aperture 675x Zoom Telescope?

I choose to post this question on the physics exchange seeing there would be a bigger audience for answers than the astronomy exchange still in BETA. But i'm looking to buy a telescope and was ...
0
votes
1answer
155 views

Detecting molecules in space?

http://www.forbes.com/sites/alexknapp/2012/02/24/nasa-detects-solid-buckyballs-in-space/ I refer to the above article, which mentions that buckyballs "far smaller than the width of a hair" were ...
0
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2answers
1k views

Do I need to focus the telescope?

I purchased a 90x refractor telescope with below configuration. Objective: 50mm diameter with 360mm focal length 2 Eye pieces: 6mm, 20mm (10-1/ 8" scope) 1.5x erecting eye piece It measures 13- 5/...
0
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2answers
73 views

What is the maximum of information in a beam of light?

If I look at the space I can see the Andromeda Galaxy as a small dot in the sky. If I look through a telescope, I can see the spiral shape. If the saw right through a huge telescope, I could see a ...
0
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2answers
159 views

Can I use one convex lens to create a telescope?

Is it possible to create a telescope with only one convex lens? Specifically, is the image I drew below possible? (This was supposed to be rotated 90 degrees counterclockwise.) In this picture, ...
0
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0answers
29 views

Blurry image in a Celestron 8SE

We have a Celestron 8SE. Last night we were looking at the quarter moon. The moon was in focus. We switched viewers & 2nd viewer only saw a blurry white blob, not the surface of the moon. When ...
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1answer
48 views

Calculating the diameter of Jupiter through an image

I took an image of Jupiter through my 8" Dobsonian Telescope, attaching a DSLR and a 1.25" Barlow Lens where the eyepiece goes, as shown in this video: https://www.youtube.com/watch?v=reFxoF3XoaU ...
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0answers
283 views

What is the physical meaning of magnifying power of a telescope?

So the following question was given in the JEE Mains 2016 conducted throughout India on 3rd April. An observer looks at a distant tree of height 10 m with a telescope of magnifying power of 20. To ...
0
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0answers
31 views

I have a fits file. I need to find the brightest pixel?

When I use astropy.fits to read the data of the fits file, I get a numpy array of values of shape(64,32,32). I am not able to understand what does this array contain. Ofcourse they are not RGB values ...
0
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1answer
51 views

How can one tell how much light is blocked by a secondary mirror in a reflecting telescope?

I've been reading about reflecting telescopes and I understand how the secondary mirror doesn't cause any obstruction to the image itself, but I've read that it does dim the image by blocking the ...
0
votes
1answer
57 views

Using wormholes to see out of the visible universe

As is commonly known, using our telescopes, we can only see so much of the universe because of its faster than light expansion. However, although under normal circumstances it is impossible to see ...
0
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0answers
39 views

Refracting telescope image formation

I'm having some trouble understanding how a refracting telescope forms a magnified image for an object that is not assumed to be infinitely far away. I drew this ray diagram: And as you can see, a ...
0
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0answers
35 views

Why we see a distant object more closer from us with a telescope?

The side magnification in the image obtained by a telescope its always less than 1, then, Why we see a distant object more closer from us?
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0answers
44 views

Magnification: Microscopes Telescopes

What is the difference between the way a microscope magnifies say a star and a telescope say a cell? Why is it, that the eyepiece of a telescope magnifies stronger when it is smaller and with a ...
0
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0answers
21 views

Is image scale the same as focal length?

I am supposed to show using a diagram how image scale is related to focal length. But my formula for image scale is $$\text{image scale} = \frac{y}{\theta} = F$$ where $y$ is the image size on the ...
-1
votes
2answers
140 views

Telescope “blue book” [closed]

I have a telescope that I may be in the market to sell in the near future and am wondering if there is a good source to find its value in the used market. Although it's never been out of the box, it ...
-1
votes
2answers
5k views

Celestron NexStar 6 SE vs. Orion XT8 [closed]

I'm interested in purchasing a new telescope and have narrowed it down to the NexStar 6 SE vs. the Orion XT8. I'd like to be able to get into astrophotography and read that having the Go-To (auto-...