Questions tagged [newtonian-telescope]
Questions about reflecting telescopes using a concave primary mirror and a flat diagonal secondary mirror.
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Is it possible to estimate where the coma-free zone is based on the secondary mirror reflection seen through a collimation eyepiece?
If I understand correctly, the whole point of collimation is to make the coma-free zone at the center of the image at the image plane. I would like to understand how accurate the collimation needs to ...
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Is there a reflecting telescope like as a Newtonian telescope but with a negative lens before the diagonal mirror?
A Cassegrain reflecting telescope contains a negative optical element between the main mirror and its focus. This increases it's focal length.
Is there a reflecting telescope like as a Newtonian ...
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Getting good images only when I cover the part of telescope opening
I have recently built a 4.5inch reflector telescope. The primary mirror is of 900mm focal length. The issue is, when I try to observe Saturn I am not getting good images. It looks like kind of double ...
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Is my TAL-1 telescope too old to be useful
I have a TAL-1 4.3” Newtonian reflector. It is old, gifted to me by my dad and was gifted to him many years ago.
Last year I spent some time cleaning it, calibrating and getting it in a good state. It ...
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Need help in choosing a used telescope for a beginning observer [closed]
I am a beginner when it comes to telescopes and have been doing research online for a week with which one to buy. At the moment I’m interested in a pre-owned telescope. My priority is planets but also ...
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How to locate M13, Ring Nebula?
This is a bit last minute. I'm leaving shortly to go camping and expect to have dark skies. I watched NASA What's Up June 2020 which suggested checking out M13 (for which it gave pretty good ...
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Using setting circles on a German Equatorial mount
Recently I have been working on equatorial grid system consisting of the right ascension and declination coordinates. Even after understanding the concept behind those coordinates, I am puzzled by the ...
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Is there any specific way to record observations on any celestial object while looking through a telescope? [closed]
Which aspects or factors do I take into consideration while I record observations on any celestial object?
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Is a mirror cell only necessary for collimation?
I'm building a truss Newtonian, and I'm planning on achieving collimation using turnbuckle-style trusses, as demonstrated in this thread. If I'm collimating this way, is there any reason to support ...
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Improving portability of truss Newtonian
I'm designing a 10in f/6 truss Newtonian as a sort of big travel scope; something that I can break down into parts to fit in a backpack or similar but will still give me decent angular resolution. In ...
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Could someone explain what is wrong with my telescope, and what should I be able to see with it?
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 ...
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Betelgeuse appears in a rainbow of colors through a Newtonian telescope
My husband and I are complete amateurs. Tonight was only our second night using our new Orion XT6 Dobsonian telescope. Betelgeuse looked very clear, bright red. However, when we pointed the telescope ...
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What is the difference between a Cassegrain telescope and a Gregorian one? Which one is better?
Of the three giant (or 'Extremely Large') new telescopes being built, the Thirty-Meter (TMT), the the Giant Magellan (GMT) and the Extremely Large Telescope (ELT), only the Magellan, from what I ...
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Not able to get Perfect Focus with DSLR and Newtonian
When using DSLR with Newtonian (130mm/1000mm), I am not able to get perfect focus.
However, when I use an eyepiece, I am able to get crystal clear views. So, I think collimation is okay.
The focusing ...
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How to estimate my eyepiece FOV?
As a follow-on to my question about seeing Jupiter and Saturn at the same time in my scope, I'd like to ask how I might determine the Field of View (FOV) of my eyepieces. More specifically, I'd like ...
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Sky-Watcher Dobsonian 16 Inch Synscan Go-To [closed]
What is the best way to buy Dobsonian telescope 16‘? Where can I buy it new or used? What I will need to have in advance? Which negative sides it has? Please, share any information you have about this ...
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Is there a good replacement finder scope for the Celestron 127EQ?
I've had a Celestron 127EQ for a couple years now and have only used it a couple times.
One of the reasons I haven't gotten much use out of it is that when I do use it I spend all of my time aligning ...
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Help stabilizing telescope
First time astronomer here... (pardon any less than accurate terminology)
My son received a secondhand telescope, a Celestron Powerseeker 114AZ.
Last night I calibrated the Starpointer, and was able ...
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What are these three black cap-like pieces?
My son received a secondhand telescope for his birthday. It is a Celestron Powerseeker 114AZ.
I found these three black cap-like pieces separate from other parts. I can’t find what they are or what ...
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Focusing issues
I have an 8 inch Skywatcher scope. I have collimated it with a laser collimator but when I tried to study the moon I got just a bright ball and on stars I could see nothing. My lens are a super 10 mm, ...
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How does diffraction occur in a reflecting telescope?
It's understandable how diffraction occurs in refracting telescopes, because the lens itself is a small aperture for light to pass through.
But what about reflecting telescopes? Since light is ...
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Why are Cassegrain telescopes shorter than Newtonian reflecting telescopes?
Many websites say this is because the effective focal length of the objective is increased by making the secondary mirror convex. This allows a Cassegrain telescope to be shorter than a similarly ...
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Best telescope for astronomy
I am interested in buying a telescope and I would like to use it to look at like galaxies and nebulas.
Right now I'm looking at a 130 mm fast (f/5) Newtonian that comes with two eyepieces of 10 and ...
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Is moisture harmful to a Newtonian Reflector?
It is often cold outside, especially in the evening. So when I take my Newtonian Reflector back in my house, it starts condense.
Can the water destroy my telescope? or the mirrors? Do I have to clean ...
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Did Edmund Scientific 4¼ inch Newtonians have 90° prisms as secondary mirrors in the 1970's?
I mentioned my old telescope's secondary mirror in this answer (stiffness) but I'm not certain I am remembering correctly. My first telescope was a Edmund Scientific 4¼ inch Newtonian reflector. This ...
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Custom telescope
I am currently trying to make a Keplerian telescope from "scratch" with plano-convex lenses bought online.
I have found my objective and eyepiece lenses. I'm just not sure if they will suffice to ...
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Under what situations can an aperture mask improve the resolution of a small/medium amateur telescope? Is this demonstrable mathematically?
@antlersoft's answer describes some of the challenges to seeing any details in the small disk of Mars in small amateur telescopes. In the case of reflecting telescopes, it mentions the use of either ...
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I need help getting mars to look like a circle
I am having a lot of trouble getting a sharp image in my telescope. It is a skywatcher with a focal length of 1200mm and a diameter of 254mm. I have a laser colimater that I got for Christmas, so I ...
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Advice on first Telescope (refractor vs reflector), Barlow lens
I am planning on buying my first telescope. I am getting an 80mm refractor and a 114mm reflector for the same price range. Which would be a better option? Further, would a Barlow lens solve the ...
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Mars looks like a blur
I took my telescope out tonight (I am new, just got the telescope a few days ago, it's my first one) and I was observing Mars, however all I see is just an bright orange circle, with no surface detail,...
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What's the difference between a Newtonian telescope and a regular telescope
So, recently I was shopping for telescopes and I decided on the following telescope:
https://www.amazon.com/Celestron-21049-127EQ-PowerSeeker-Telescope/dp/B0007UQNKY/
I had exactly $180 to spend, ...
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About bigger resolution of telescopes [closed]
Any idea about the design of new better telescope having small length of diameter and having more resolving power.
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Newtonian reflector collimation question
After an initial collimation, I took my scope (150mm/750mm) out for a star test. While I could see concentric circles when the bright star is at the centre of the video, when the star is on the side ...
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Using setting circle for Right Ascension
I'm a little bit confused about the setting circle of my EQ5 mount. Basically, I'm trying to find M42 nebula using Sirius star as reference. So, considere that I did the following steps:
...
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Collimating with a home-made collimation cap
I've made a home-made collimation cap and am trying to use the procedure linked to in another answer.
However, I've run into two issues right off the bat. In this picture from the linked page, it ...
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Retrofitting a DSLR camera to a super-cheap Tasco reflector telescope
I was given a 1995 vintage Tasco "302003" Newtonian telescope recently and have had some exciting success with it. I have managed to view the Moon in beautiful detail and also had my first glimpse of ...
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My homemade telescope
My telescope is blurry and I am not sure why I used a 254mm primary mirror f/5 with a secondary mirror at 62.5 and I also used a 32mm eye piece I know if I stand back 20cm from eyepiece I see a clear ...
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Cannot calibrate “upgraded starpointer finderscope” for Celestron AstroMaster 114EQ
My wife just bought me an AstroMaster 114EQ which came with an "upgraded starpointer finderscope" -- it looks different than the one depicted in that link. I have tried following the instructions in ...
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Laser Collimator For Dobsonian vs Newtonian
Will a laser collimator like the Gosky 1.25 Metal Laser Collimator, https://www.amazon.com/gp/product/B01M4IVUYG/ref=crt_ewc_title_dp_1?ie=UTF8&psc=1&smid=AHQ6VCR020F8X, work for a dobsonian ...
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Does making a ground based telescope larger always give you a better resolution?? why?? or why not? [closed]
i just don't really understand this topic.
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Why does any planet look like a (not so) big white ball through my telescope?
I have a 130mm (5") diameter Newtonian reflector with a 650mm focal length (f/5). I have collimated my telescope already but when I'm looking at Mars or Jupiter (not a star I'm sure), all I see is a ...
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Dish antenna as parabolic mirror for OPTICAL telescope?
Can I use a chrome painted dish TV antenna as a parabolic reflector for my optical telescope? Given that glass mirrors are quite expensive, I am thinking of using a Dish TV antenna and coating its ...
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How much of a difference do good lenses make?
I recently purchased a Celestron PowerSeeker 114EQ and with it I got three lenses (which I assume are low quality), a 4mm, a 20mm and a 3 x Barlow.
I can get pretty decent views of the moon but a ...
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Telescope collimation issue
Recently, I purchased a Chinese 8 inch reflector telescope from local store. When I observing stars and planets I've been having trouble getting really sharp image from this telescope. I observe Venus ...
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How do I remove fungus from a telescope mirror?
I use a Celestron NexStar 130SLT Azimuthal Newtonian Reflector. I noticed that recently, due to the wet season, some tiny spots of what appears to be fungus have appeared.
Having taking appropriate ...
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Why does the focal length of a telescope have an effect on the magnification?
I previously asked that
Is the angular resolution of a telescope irrespective of used eye-piece?
I learned that the resolution is fixed when the light enters the telescope, and that the eye-piece ...
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Is the angular resolution of a telescope irrespective of used eye-piece?
Suppose a telescope has aperture $D = 20$ cm. The angular resolution of such telescope, according to the Rayleigh criterion (if I have understood it correctly), is given by
$$\theta = 1.22\cdot\frac{...
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How to view Jupiter with 4.5" Newtonian Reflector
I have a 4.5" Newtonian Reflector and I took a look at Jupiter the other night.
I was able to get a reasonably sharp view of it and see a number of it's moons, but I was unable to see any surface ...
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Difficulties in finding Jupiter
I am new to astronomy. Jupiter is now visible to the naked eye but I have difficulties in locating it with my (new Newtonian reflector) telescope. The lowest magnification I have is 36X, which I guess ...
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Working with high-magnification eye-pieces
My telescope (Newtonian reflector) has a focal length of 900 mm. So, using a 25 mm eye-piece, I get 900 mm / 25 mm = 36X magnification. Using a 10 mm eye-piece, the magnification would be 90X.
My ...
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