Questions tagged [telescope]

Questions related to the physical instruments for astronomical observations.

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6 votes
2 answers
191 views

Does a star shaped mirror present problems either optically, or in signal processing over a more nearly circular mirror?

Pure speculation about a future replacement for the JWST that I almost certainly won't live to see. The JWST's mirror (and then some) would fit unfolded and flat into the Starship's 8m diameter ...
2 votes
1 answer
958 views

How does eyepiece exit pupil diameter affect image clarity and viewing experience?

This answer to Not Able to View Objects with Barlow Lens includes a calculation of exit pupil diameter as a way to address the limits of useful magnification when observing planets with a small ...
4 votes
0 answers
48 views

How does SDSS estimate photometric redshift of sources?

I'm looking through the data in SDSS DR 12: ...
6 votes
2 answers
918 views

How do you clean a foggy or dirty eyepiece of a telescope?

I'm wondering what the procedure would be to clean the eyepiece of a telescope when it looks foggy or there's dirt either on the outside or inside it. I can get rid of loose dirt with a camel hair ...
6 votes
2 answers
2k views

Would alcohol wiping damage multi-coated eyepiece coating? How else can I take COVID precautions on the eyepiece?

My small group of friends will be wearing masks. But could COVID-19 be spread by eyes/eyelashes touching the eyepiece? If so, what precautions should I take? I have a small Starblast scope with an ...
9 votes
2 answers
2k views

Is it possible to observe strong gravitational lensing with amateur telescopes?

Strong gravitational lens systems like the Cosmic Horseshoe have been imaged by scientific space telescopes, but have any amateur astronomers accomplished this? Or are amateur/small ground based ...
4 votes
0 answers
142 views

Telescope's eyepieces got blurry over time [closed]

Right at the beginning: This is not a duplicate of questions involving blurry images through their eyepieces. I only get blurry images for 2 of my 3 eyepieces so it's not the telescope's fault and in ...
2 votes
1 answer
162 views

Where can I find data on SDSS filter profiles?

I've seen lots of filter throughput curves for the SDSS, such as this one: from the SDSS camera page, but I'd really like to produce my own from the data. Is the filter response data per wavelength ...
6 votes
2 answers
465 views

Do we know at which angle the Event Horizon Telescope will look at the accretion disk of Sagittarius A*?

Do we know at which angle the Event Horizon Telescope will look at the accretion disk of Sagittarius A*? Additionally, would it matter if we are exactly in the plane with the accretion disk, i.e. ...
1 vote
1 answer
156 views

Can the Celestron Powerseeker 127EQ observe the moon during day time?

I am able to find the moon with the finder scope during the day. However, when I use my 20mm lense, it seems like I am unable to focus the moon at all. Is there a fix to this?
3 votes
2 answers
1k views

Focus Problems when using Barlow 3x or 4mm lens

So I just recently bought a Celestron Powerseeker 127EQ 12.7 cm f/7.87 Cassegrain telescope and I inserted a 20mm eyepiece and the telescope with the Moon. That eyepiece seems to work fine, but when I ...
4 votes
2 answers
455 views

Why are photos from telescope stretched at their edges?

You may know the issue that photos from (at least some) telescopes are stretched at the edges, so that the star locations do not fit compared to if this location would be on the center of the photo. ...
1 vote
0 answers
455 views

Why does my 10mm eyepiece produce blurry images?

I own a tabletop Sky-Watcher Heritage 130mm tabletop Dobsonian with a f/5 130mm aperture and 630mm focal length. 25mm wide-field eyepiece and a 10mm narrow-angle eyepiece. Last night I took it out to ...
1 vote
0 answers
46 views

uvotdetect sometimes doesn't make valid .fits files for DS9 to read (Swift UVOT, Heasoft)

I have downloaded galactic center sky images from the Swift database (https://www.swift.ac.uk/swift_live/index.php#doSimpleSearch.php?catname=swiftmastr&searchpos=galactic+center&searchrad=10&...
4 votes
3 answers
1k views

How to choose eyepieces and other accessories for a Celestron 70mm f/5.7 portable refractor?

I have a Celestron Specialty Series Travel Scope 70mm refractor which came with 10mm (40x) and 20mm (20x) eyepieces. Specifications: Focal ratio: f/5.71 Optical Design: Refractor Aperture (mm): 70 mm ...
3 votes
0 answers
59 views

Metric to estimate measuring accuracy

I need help/suggestions on which metric/approach to use. I am trying to estimate pointing precision by measuring the offset of the experimentally measured values from the real, theoretical values, ...
2 votes
1 answer
691 views

How far can the best telescope see in outer space from Earth?

I was wondering what is the farthest the best optical telescope can see into outer space from Earth. What causes them to see so far?
9 votes
1 answer
422 views

How to determine the scale on astronomical images?

I've always been amazed at the many beautiful images of objects in the night sky. The Andromeda galaxy is a superb example. But it was only a few years ago that I discovered that Andromeda in those ...
6 votes
2 answers
255 views

JWST mirrors each can be "positioned in tip, tilt, piston, horizontal & vertical decentering and clocking". What does this mean?

This interesting paper by Robert Warden refers to each mirror segment on JWST as having six actuators providing six degrees of freedom in positioning (plus one more to tweak the curvature). These ...
10 votes
2 answers
2k views

What (actually) is the " deprojected half-light radius" of this almost-all-dark-matter Galaxy?

The recent news of the Ultra Diffuse Galaxy (UDG) Dragonfly 44 is an excellent example of what could be termed 'observe different' thinking. The dragonfly telescope is noted not for the size of its ...
7 votes
0 answers
317 views

How are the aberrations seen in early JWST images corrected?

I found this image on space.com and it can also be found in NASA's JWST blog. This is one step in the process of aligning the 18 mirrors on JWST. A single relatively-isolated star has been selected. ...
3 votes
2 answers
137 views

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 ...
2 votes
1 answer
4k views

Camera adaptor won't focus [duplicate]

I'm trying to use my DSLR camera (Canon EOS-40D) with my kids' Celestron First Scope. I bought a 3x Celestron 1.25" barlow, Celestron 1.25" T-adaptor, and the Canon ring. These things all ...
7 votes
1 answer
565 views

What does par. lines mean in relation to a telescope aperture in 19th century German astronomical publications?

I am trying to understand what is meant by par. lines in an 1867 article "The Aberration of the fixed stars after the wave theory" by Prof. W. Klinkerfues of Royal Astronomy Works of ...
1 vote
0 answers
59 views

Is it possible to observe the full Moon using this telescope?

I'm trying to solve this task: For amateur observations, a small telescope with a lens focal length of 120 cm was brought to the Byurakan Astrophysical Observatory. If this telescope is directed ...
0 votes
0 answers
139 views

How exactly does NEOSTEL's fly's eye telescope's secondary mirror array split the primary beam among sixteen cameras?

Wikipedia's NEOSTEL says: The Near Earth Object Survey TELescope (NEOSTEL - also known as "Flyeye") is an astronomical survey and early-warning system for detecting near-Earth objects sized ...
2 votes
0 answers
186 views

Can JWST be damaged by looking at a bright star?

Can JWST be damaged by looking at a bright star? The Sun as well as particularily bright solar-system objects like Jupiter, Venus or the Moon not meant with this question.
5 votes
1 answer
121 views

Why orient a refracting telescope to the North?

I'm a french Guide of french military heritage. I have to prepare visit about "L'observatoire de la Marine, moulins du faouëdic" (Former windmill which served as an astronomical and ...
1 vote
0 answers
621 views

How to find the aFOV of a eyepiece?

How do I find the apparent field of view (aFOV) of a eyepiece using simple math (if possible)? I need the aFOV to give as a value to Stellarium’s custom eyepiece I found a Q&A about this subject ...
5 votes
2 answers
170 views

How do telescopes avoid blurry images?

Telescopes rotate with the Earth. If a telescope isn't fixed on something like the North Star then everything in its field of view is moving pretty rapidly, yet photos from these devices are crystal ...
2 votes
1 answer
102 views

Benefits to adding a 32mm Pössl to my Celestron AstroMaster 130EQ's eyepieces?

I am getting a Celestron AstroMaster 130EQ soon. I have heard that its eyepieces aren't the best, so I am considering a 32mm Pössl. For such a choice, what would be the arguments for and against? How ...
4 votes
1 answer
179 views

Hoping to do some viewing and astrophotography with a large-ish Dobsonian and a DLSR, is this scheme workable?

I haven't put a camera behind a telescope since the lunar eclipse of 1975 except for a few experiments with a cell phone held behind a pair of binoculars. I want the occasional thrill of using a ...
2 votes
1 answer
81 views

Is it possible to take the same images in HST palette as the optic telescope but with radio telescope?

Is it possible to detect signal from SII, H$\alpha$, OIII using radio telescope and make the similar images as optic telescope? If no, can we use the different elements to take signal? What minimal ...
1 vote
2 answers
98 views

How much magnification would I get by this Dall-Kirkham telescope?

I'd like to know how much magnification I would get by this telescope. The main specs are as follows: Focal length: 2563 mm Focal ratio: F/7.2 Number of lenses: 2 Optical diameter of Primary mirror: ...
3 votes
1 answer
142 views

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 ...
6 votes
3 answers
2k views

Trouble Seeing Distant Planets Such as Jupiter and Uranus

I am a beginner and I am using a Celestron AstroMaster 114 telescope. Whenever I try to view distant planets such as Jupiter I am presented with a black circle that has black lines leading from it. In ...
1 vote
0 answers
96 views

Maximum number of pixels across a synthesized beam in an ALMA image?

I have some ALMA data, from which I have created images using the TCLEAN task in CASA. I understand that with this type of data, it is necessary to have at least 2 pixels across the FWHM of the ...
6 votes
2 answers
194 views

Will the James Webb Space Telescope need re-alignment of primary mirror segments?

I couldn't find an answer to this question. James Webb Space Telescope will align primary mirror segments and secondary mirror in space. Question is whether these will need re-alignment during the ...
2 votes
1 answer
80 views

How much do collimation and viewing conditions affect magnification and viewing?

Before I start this post, I'd first like to make clear that this account is an alternate of my SovereignInquiry account--at the moment, accessing this account is much more convenient, so if things I ...
1 vote
1 answer
399 views

The most precise way to point the true north

Since all of my telescopes have equatorial mount and It needs to be placed with respect to North direction, what is the best way to point the North. Expecting answers that doesn't suggests methods ...
4 votes
2 answers
1k views

How does making a refracting telescope very long reduce the chromatic aberration of an uncorrected lens?

Below are two cropped views of "Johannes Hevelius's 8 inch telescope with an open work wood and wire "tube" that had a focal length of 150 feet to limit chromatic aberration." from ...
1 vote
1 answer
135 views

Can I use an achromatic focal reducer to reduce chromatic aberration?

I am using 75/1000 Plano convex lens to build telescope. Can I use an achromatic focal reducer to reduce chromatic aberration?
1 vote
1 answer
252 views

Can I use 75mm Plano convex lens to build telescope [closed]

I want to see Jupiter with moon. So am planning to build telescope. Can I use 75mm Plano convex lens with 1000mm focal length?
3 votes
2 answers
1k views

Will these simple 2 convex lens arrangement telescope see the moon clearly?

Hi readers, I am planning to build my telescope. Does this very simple 2 convex lens arrangement even possible to observe the moon clearly with high magnification? I am planning to buy 5 cm diameter ...
4 votes
2 answers
147 views

New to Astrophotography

I just had a quick question on my telescope I recently purchased. I have a Canon Rebel XTi and I paired that with the William Optics Guide Star 61 Guidescope. The Specs on the Scope are: Guide Scope ...
3 votes
1 answer
364 views

Not getting quality images in telescope

I have a Newtonian telescope (Celestron 130 eq) with 5.2 inch (~132 mm) aperture with 650 mm focal length, Spherical mirror. And having 4mm, 10mm, 12.5mm, 20mm,20mm (erecting eyepiece), a 3x and 1.5x ...
8 votes
1 answer
714 views

When might Rowan-Robinson's planet be discovered or disproved?

A month ago Michael Rowan-Robinson discovered three dots on old images of the sky which may or may not be an undiscovered planet (that's not identical to Brown's and Batigyn's hypothetical planet). I ...
7 votes
3 answers
708 views

What range of exit pupils work for observing the full moon?

I'm observing the full moon, from a major city, with heavy light pollution and dust. The objective size is fixed, for this comparison, something between 4 and 6 inches. The question is about the ...
1 vote
1 answer
245 views

Which one is better for both the beginner dad and the 7-yr old? Sky-Watcher 130P or Celestron StarSense Explorer 114AZ

I am looking for a beginner scope for myself and my 7-yr old. She has been asking for a telescope for some time but I don't know how immersed she would be, once bought. So, I want something which can ...
10 votes
4 answers
3k views

Why do satellites appear as streaks in telescope images?

Can you explain me in simple words why the satellite in this telescope image appears as a streak? The exposure time is 1 second.

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