# Tag Info

18

A contrast stretch reveals stars down to magnitude 4 or 5. The stars you asked about are Deneb (center) and Vega (bottom). The constellation in the center and below is Cygnus; we also see Cepheus at upper right and part of Draco at lower right. The stars appear as blobs 10-12 arcminutes wide due to several factors: Rotation around the north celestial pole, ...

16

You cannot gauge the redshift of a galaxy by looking at a false colour image. The images taken through different filters are stacked and colourised to suit. You can say that the blue galaxies are indeed bluer than the red galaxies, but there is no absolute scale with which to judge redshift by eye. Secondly, there is no detail in the NASA web page, but the ...

15

Yes. The estimates are that LSST will produce about 10 million alerts per night (LSST Alert Distribution presentation) which will be at least a factor of 5x greater than the amount coming from ZTF currently. ZTF is an approximately 10% scale model of what the LSST alert stream will look as there is about 5x fewer alerts and the alert packets contain about 50-...

9

Let me see if I can explain the main aim and accomplishment of this work. First off: the picture you're puzzling over is a "luminance RGB" image, in which the bright regions are represented by color (a sort of pseudo-true color using near-infrared images), with the second faintest parts represented with black and the very faintest parts with white. The ...

8

The Failures of High Magnification Higher magnification doesn't help you observe deep sky objects better. Deep sky objects unlike stars are extended objects. They subtend a finite solid angle on you. This ensures that the surface brightness(brightness per unit solid angle) of extended objects remains constant. Hence, a higher magnification would not make it ...

8

When you plug the lead researcher's name into Arxiv, the first search result is The missing light of the Hubble Ultra Deep Field. 3 main steps: Creation of sky flat fields for the four filters. This process is fully described in Sect. 2.4. – Creation of a catalogue of all WFC3/IR datasets that may affect our mosaics (including calibration ...

7

It's very unlikely that large optical telescopes will ever be built on the Moon, because the Moon is almost the worst possible place to build them. (The surfaces any of the planets other than Earth are worse.) It has no particular advantages over orbit and costs a lot more to build there. The Moon looked like a good location when observatory technology ...

7

Yes, of course. Many, many examples. Telescopes work in the infrared, far-infrared and there are even samples of galaxies that are selected on the basis of their mm emission. The most distant galaxies detected now have redshifts of 7 or more. This means the wavelength of their light has been stretched by a factor $1+z$ - i.e. by a factor of 8. Thus light in ...

7

It all comes down to the brightness of objects (not their size). For all intents and purposes we can assume that the most distant galaxies and the small, but much closer, objects in the Oort clouds are unresolved point sources.The Oort cloud objects are too faint to see, with JWST, but it should be able to see bright galaxies and quasars even at 13 billion ...

6

The "stair-step" pattern visible in the first image is characteristic of the the Hubble's Wide Field and Planetary Camera 2 (WFPC2). This pattern is created by the arrangement of the four CCD chips. This image shows how the three larger "wide field" chips and the smaller, single "planetary camera" chip are arranged to create the pattern. The bottom picture ...

6

There are two factors here. First, to construct an image such as this, several optical filters are used, and then these are then merged to give an image. The colours that you see are therefore not the "true" colours (they couldn't be, the light you see is far too faint for the human eye) but are chosen to bring out details in the image. A galaxy that is ...

6

What causes these asteroid trails to be so strangely shaped and repeated? The linked image is a composite of several long duration exposures captured by the Hubble Advanced Camera for Surveys of the same region of the distant sky. Each individual exposure was about ~2200 seconds long. Nearby objects such as asteroids would have been subject to the proper ...

5

Nearby galaxies are seen in their old age. Distant galaxies are, on average, the same age as the local ones. But due to the finite speed of light, the farther you look, the younger you observe them. That means that the most distant galaxies are observed in their infancy, and they look much different from the old ones. Galaxy evolution This is one reason to ...

5

Collisions between a rogue brown dwarf and any other star would be very rare because the space between them is so vast. I don't want to say it'd never happen, but it would be a rare event. It's much more common for two stars that are already in the same system to collide by spiraling into each other, usually by tidal decay. A collision with a brown ...

4

It depends. The Barlow is usually a cheap shortcut for avoiding to buy an expensive short focal length eyepiece. Also you need Barlows and high magnification usually only for small objects. For example the ring nebula (M57) is pretty tiny, and might benefit. Your telescope is still rather wide field, so getting high magnifications might be neccessary to ...

4

Barnard 68 is the first thing that comes to mind for me, it is a little over 10' across and is opaque in the visible spectrum. I'm sure there could be something much larger out there, but like I said, this was the first to come to mind.

4

There are actually quite a few examples of this. A particularly nice one, where you can see star-forming substructure within the distant, lensed galaxy (the extended, vertical "snake" structure just right of center), is this HST image: This is another HST-based example, in which the same background galaxy is lensed multiple times (indicated by white ovals) ...

4

Those targets are good choices for beginners at the right times of year. However, in June M42 is a daytime object, and M31 rises in the wee hours, leaving only M13 and Albireo in the evening. Other good summer targets include: M8, the Lagoon Nebula M11, the Wild Duck Cluster M57, the Ring Nebula Precise polar alignment is only required if you plan to take ...

3

At the f-number you have used, you'd already expect to get weird images. In astronomy we usually use $f=\infty$, but this is of course only relevant for extended objects, not point like sources. But with $f/2$ it's impossible to say whether it's extended or not. Still I'd say this is probably starlight, as also the fainter objects in your field seem to ...

3

Although you have not given any information about your telescope, the Orion nebula is easy to see with almost any telescope, even under urban light polluted skies. Surface brightness is almost always greater (ie fainter) than magnitude - so for example the total magnitude of the Orion nebula is about 4 (from memory) but you say surface brightness of 13. ...

3

Use the Optical Spectra Query Form. You'll want to set PRIMTARGET to "GALAXY". Here's the list of possible parameters it can return http://skyserver.sdss3.org/dr10/en/help/docs/QS_UserGuide.aspx#Spectroscopy. Note, there is a query limit of 500,000 rows, so you'll have to break up the query since you'll have more spectra than that.

3

If you have a Laptop or Notebook you can download one of several planetarium programs like Stellarium or Cartes du Ciel. They will display large areas of the sky that will help orient you initially. Zoom the computer view to match the view in your finder then zoom in again and get a view on the laptop that is close to the view in your eyepiece. Compare the ...

3

The asteroids leave corkscrew shaped trails which are interrupted by not recording when the Earth passes through the field of view. The corkscrew shape echoes the path of the telescope moving around the Earth as the Earth moves around the Sun. The straighter trails you are familiar with are merely zoomed-out versions of the same -- asteroid hunting needs ...

3

The AT60ED is a nice small refractor. However, its objective lens simply projects an image at the focal plane. Adding a field flattener mimimizes curvature that degrades sharpness at the edges of the image. The flattener requires a specific back-focus, or distance (about 57 mm for the AT60 FF) between its (T2, 42 mm thread) flange and the image plane where ...

3

I don't think there is a "recommended" FL for DSO observation. If you only observe visually, the eyepieces you use are just as important und the magnification depends on them. If you are concerned about the field-of-view you will get from these telescopes, I recommend checking out FOV calculator tools such as astronomy.tools. There you can enter ...

3

There isn't really a "best" focal length because it depends on the object you might want to observe. Angular Size The Ring Nebula (Messier 57) is only about 1.4' across. Meanwhile there are larger objects such as the Andromeda Galaxy (Messier 31) -- that's about 3° across (and a pair of binoculars may work better than a telescope because too much ...

2

Yes, there are quite a lot of them, but ISS is by far the brightest. The other satellites can be visible with magnitude fainter than 3. "Can be" means in dusk/dawn, when the satellite is in the sunlight.

2

The Sloan Digital Sky Survey has saturation limits at around 13th or 14th magnitude. You are looking at $\phi$ 1 Cancri, which is a 6th magnitude star. It is hardly surprising that SDSS fails to morphologically classify it correctly. No idea what your second question is about. You have given a link which has a latitude and longitude in the url. Longitude ...

2

As it stands I think the answer is no. The most luminous object in the (observable) universe is probably hidden behind many magnitudes of dust extinction. There are lots of faint, infrared-detected objects that may be extremely luminous galaxies in the early universe (and indeed some have turned out to be) but it is difficult to get their redshifts, so it is ...

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