Astronomy

Can I use an array of inexpensive cameras as an alternative to a telescope?

Can I use an array of inexpensive cameras as an alternative to a telescope?


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The link below describes how an array of inexpensive cameras can create very detailed images. Would this work for astronomy?

https://graphics.stanford.edu/papers/CameraArray/


Yes it would. However, it also depends on your definition of "Detail". For some, it's a tight shot where the whole frame is only a few dozen arcseconds wide, and others think of detail as being wide field, but also "deep" - or having a very high signal to noise ratio.

If you want wide field, and a high signal to noise ratio, then yes, a multi-camera array will work well, and you'd be able to accumulate a large number of high integration time images in a relatively short amount of time.

So here's a breakdown of what you and others who may not know need to know about deep sky astrophotography:

The main goal for all photos is to produce as visually pleasing image as possible. A single image taken of any target will accumulate light from many sources. The first, and obvious source is the light from whatever target you're trying to photograph. The second, less obvious source is light pollution from man-made sources, the moon, and natural sky glow. The third source is the electronic and thermal noise of the camera itself.

Technically, all of these sources are "signal" - however two of the three are unwanted, so we will call the light pollution signal and the camera signal 'noise'. Longer exposures produce more signal from what you want, but also more noise from what you don't want.

Luckilly, noise can be reduced by using several techniques in conjunction with each other. First, you need to take long photos. The signal will increase linearly with time. A 60s photo with a signal of "x" will have a tenth of the signal as a 600s photo. Noise, however, increases with the square root of the exposure. Using the same example, the 600s photo will have a signal to noise ratio that is about 3.2 (sqrt of 10) times better than the single 60s photo.

Increasing the Signal to noise ratio by taking longer exposures is the first step to producing 'detailed' wide field images. Camera noise can be further reduced by taking many images. An array of cameras makes this trivial. Two cameras will produce twice the images as one camera, and 10 cameras will produce 10 times the images as a single camera. That's obvious. Why does it matter?

When we stack images, the more we have, the better the stacking algorithms can preserve the signal we want to keep, and reduce the camera noise we don't. Once again, the signal to noise ratio mathematics work out the same as above. 1 image will have a certain signal to noise ratio, but 10 images will have a signal to noise ratio that can be about 3.2 times higher - because the total integration time has increased ten fold.

Of course, if you're stacking photos, you should be calibrating them as well (dark frames, bias frames, etc) - which really reduce the amount of noise per sub-frame. Because of this, your actual SNR boost by stacking should in theory be a lot higher than 3.2.

If photographed a target across 60 degrees of the sky (30 before meridian and 30 after) then you'd be able to acquire photos for 4 hours. One camera taking 10 minute photos would get 24 photos in the 4 hour period of time. If you had 5 cameras, you'd get 96 photos. 72 additional photos in the same amount of time is a lot of extra data to help reduce the noise, and really let the faint details stand out above the background - especially if all of your photos were well calibrated.


The 6 Best Digital Cameras Under $100 of 2021

Our editors independently research, test, and recommend the best products you can learn more about our review process here . We may receive commissions on purchases made from our chosen links.

Although smartphone cameras are getting better by the day, they still can’t match up to proper cameras when it comes to serious photography. This is primarily because real cameras offer a wide array of advanced features, such as bigger image sensors and long range optical zoom lenses. What’s more, the continued improvements in the world of technology have made these features more affordable than ever.

Even if you have a tight budget of just $100, there’s a diverse variety of cameras available in the market to choose from. These include point-and-shoot snappers such as Kodak’s PixPro FZ53, instant cameras with integrated printers like Polaroid’s Mint, and even compact action cameras like Canon’s Ivy Rec. That said, having these many choices can (and often does) get confusing, which is why we’ve rounded up some of the best digital cameras under $100 you can buy. Read all about them, and take your pick.


Affordable HD Binoculars | Under $300

ED glass in a binocular is imperative for the novice to advanced bird watcher, as they provide much more clarity than non-ED versions. The same goes for a hunter who needs to properly identify the age range of a deer, or be able to count the points on that buck they’ve been tracking out in the woods. Any serious wildlife viewer should have ED field glasses in their pack.

Bushnell

Bushnell Legend M-Series Ultra HD Binoculars

The Bushnell Legend line also goes into binoculars, and they make them extremely affordable. They are available in the standard 8否 and 10否, but are also offered in a more compact 10吕, 8吠, and 10吠 size. Not only are these affordable, but they offer the most bang for the buck in this under $300 price range.

Hawke Sport Optics

Hawke Sport Optics Sapphire ED Binoculars

Hawke Sport Optics was founded in the UK over 15 years ago, and the company established their US headquarters in Indiana in 2007. Their products are geared for the user with a budget, but they certainly make a product that will last for many years. They are the manufacturer with the most options in the affordable range we are discussing in this article. From the compact 8吕 Sapphire, to the 12吮 Endurance, Hawke has an amazing array of options in the sub $300 range!

Carson

Carson 3D Camo Binoculars

Carson offers their 3D line at a great price, and they are a very popular brand in birding circles. I personally own a Carson monocular that is used out on Disc Golf courses, and I am very pleased with the performance over the last few years. Their ED binoculars are just as impressive, and they are available in standard magnification and objective sizes, from 8x32mm to a 10x50mm.

Vanguard

Vanguard Endeavor Binoculars

Vanguard also continues their ED optic line into the binocular category. The Endeavor series is incredibly popular with our customers due to the cost and design aspects. All of the Endeavor models have an open style hinge, so the user get can a full grip on the barrels of the binocular. A big difference in the Vanguard design is that they add another hinge towards the front of the barrels, providing more stability for clearer viewing. The standard Endeavor models are under our $300 price point, and the Endeavor II models just over that price. They are also available in the most popular magnification and sizes of 8x32mm through 10x42mm.


Best Cameras for High-Resolution Planetary

High-resolution planetary photography records fine details on the Sun, Moon, and planets of the solar system. Planetary photography requires larger apertures to pick out tiny details on planets such as Jupiter and Mars, as well as small craters on the Moon and details in sunspots. These objects are bright, so exposure is not the problem, but good "seeing" or atmospheric steadiness is critical.

Cameras with small pixels and high frame rates that can output uncompressed high-bit raw video are the best. You don't need a large sensor for high-resolution planetary photography because the planets are small even when magnified to the correct sampling for the size of the pixels in the camera.

Certain DSLRs can also be used for high-resolution planetary imaging such as the Canon T2i (550D), 60D, and 60Da. These cameras have a special "Movie Crop Mode" that gives 1:1 pixel resolution at 640 x 480 pixels off the sensor at 60 frames per second, recording directly to the memory card in the camera, so you do not need a computer at the scope. Other cameras can be used, typically by capturing Live View at 5x magnification to get to 1:1 pixel resolution, but you must use a computer at the scope to use this trick.

The latest cameras with high-definition video might also be able to be used if a video mode can be found that outputs 1:1 pixel resolution that is not interpolated or decimated. Some of these cameras can also output raw, uncompressed video to an external recorder.

All of the images below were captured with DSLRs.


Imaging with a DSLR through the telescope

The principle of taking photographs through your telescope with your DSLR is quite simple: just use the telescope in place of the camera lens, and snap away. Simple! But as soon as you try it, you will start to discover the problems.

Attaching the camera

The simplest way is to use a T-adapter. Many modern telescopes have an eyepiece holder with an external thread which is the same as that adopted by Tamron many years ago when designing lenses to fit a wide variety of cameras. It is 42 mm in diameter but has a different thread from the old Pentax 42 mm lens fitting. You can get T-adapters for most DSLRs to fit this thread.

If your telescope doesn’t have this thread, you can get a 1¼-inch adapter with the thread.

You will need to rebalance the telescope once you have attached the camera. Meade ETX telescopes in particular cannot be balanced, the only alternative being to tighten up the declination clamp rather more than is wise. You can buy additional weights to fix to the ends of Schmidt-Cassegrains to help balance them. Don’t expect an axis clamp to be able to cope with the extra weight of your camera – it may work to start with, but you’ll cause additional wear on both the clamp and, more importantly, the motors, which will always be straining to move more weight than they were designed for.

Focusing

This is not as straightforward as you might wish. DLSRs invariably use autofocus, and lack the focusing aids of film SLR cameras. But your telescope has to be focused manually and judging when a star is in perfect focus can be tricky. You might even find that you can’t bring a star to focus at all, particularly with the cheaper Newtonians. The popular basic SkyWatcher 130, for example, doesn’t focus close enough to the mirror to achieve focus with a camera attached, though there is a version that does have the focusing range for photography.

If you can’t adjust the focus far enough out, you could add a short extension tube or a star diagonal, or if you are using a 1¼-inch adapter just don’t push the adapter right in but tighten up the thumbscrew to hold it in place. But if you can’t focus far enough in, all you can try is to use a Barlow lens in the system as well. This increases the effective focal length of the system, giving more magnified images, but it often allows you to focus.

If your camera has Live View (which shows the actual image seen through the system), use it to help you to focus. On many cameras, such as the Canon 40D, the maximum zoom of Live View has some interpolation and never appears as sharp as the final image so you still have to guess the exact focus point, but it is more precise than using the basic optical viewfinder.

Photographing through a telescope with the camera tethered to a computer.
Credit Robin Scagell/Galaxy

However, the best solution, if your camera manufacturer provides the software, is to shoot ‘tethered’ to a computer. This allows you to see the Live View image on the computer screen, but without any interpolation, so you can focus critically, but even if you don’t have Live View you can still take a shot and check the focus. Shooting tethered has other advantages: you fire the camera from the computer, so you won’t jog it, you may be able to operate the camera from indoors, and you have the whole storage capacity of the computer rather than just your memory card. The drawback is that it means yet another black wire to trip over in the dark, and of course you need the computer near the camera, which generally means using a laptop.

Otherwise, use a cable release to trigger your shots so as not to jog the camera when shooting. Some cameras use a conventional mechanical cable release, which is comparatively inexpensive, while others opt for their own electrical releases, which cost more. Alternatively, set the camera’s timer so that the shutter goes off either two or ten seconds after you press the shutter release, giving vibrations a chance to settle down.

Shooting

Now you are ready to start taking photos. But as you know, objects move through the field of view quickly unless your telescope is driven. In the case of non-driven telescopes, you will be restricted to the Moon and possibly Jupiter and Venus, which are sufficiently bright that you can give exposure times faster than about 1/100 second. But for longer exposures, the telescope must be motor driven, ideally on an equatorial mount. If you have an altazimuth, you’ll find that after a short time stars at the edge of the field of view will start to trail around the centre of the field of view – called field rotation. In this case you may be restricted to exposure times of just a few seconds.

Photograph of M57, the Ring Nebula, taken using an altazimuth mount with no periodic error correction.

This photo of the Ring Nebula, M57, was taken through a telescope on an altazimuth mount with no periodic error correction. The star trails are zigzags, and the image has rotated around the centre. It also shows vignetting – the cutoff of light at the edges of the frame by the camera adapter

Assuming that you have a driven equatorial mount, you will soon discover its limitations. A drive that keeps Jupiter, say, in the field of view for many minutes at a time for visual observing does not need to be very accurate. It will probably suffer from periodic error, which is a regular variation caused by errors in the machining and alignment of the worm and wheel drive mechanism. Typically, you will see a periodic movement of a few arc seconds every eight minutes or so. The other error is the polar alignment of the equatorial mount. If this is not spot on, stars will trail even in the absence of periodic error.

Periodic error correction (PEC) is provided by many mountings, but you need to follow a star for the duration of the periodic error, using an eyepiece with crosswires which itself is a considerable extra expense, correcting the error as you go. You may need to do this every night you observe, if the telescope is not left in situ during the day. Polar alignment is time-consuming and requires care, and is also lost unless you keep the mount in place. But you can get away without doing PEC every night, and with only good-enough polar alignment, by using an autoguider. But using an autoguiding system is a subject in itself and will not be covered here.

Other issues

As well as autoguiding, you may now need to tackle the other major issues of astrophotography – getting rid of light pollution on your images, and image processing to bring out the faint detail. These subjects will hopefully be the subject of further help files, not yet written!
Robin Scagell


Phased Array

Speeding up radio astronomy
Radio telescopes use specialised cameras, called receivers, to detect and amplify faint radio waves from space. Most of these cameras only see a small part of the sky at once, which makes surveying large parts of the sky a time-consuming process.

For more than a decade we’ve been developing receivers with a larger field-of-view, and these have been used on our own Parkes radio telescope as well as other world-leading instruments.

OUR RESPONSE

Phased array feeds – a radical new approach to radio astronomy
For our newest radio telescope, the Australian Square Kilometre Array Pathfinder – ASKAP, we’ve developed innovative ‘phased array feed’ receivers with a wide field-of-view. This is the first time that this type of technology has been used in radio astronomy.

Each phased array feed is made up of 188 individual receivers, positioned in a chequerboard-like arrangement. Alongside the receivers are low-noise amplifiers, which greatly enhance the weak radio wave signals received. These components are housed in a water-tight case mounted at the focal point above each of ASKAP’s antennas. Together with specialised digital systems developed for ASKAP, the phased array feeds create 36 separate (simultaneous) beams to give a field-of-view of 30 square degrees on the sky.

This pioneering technology will make ASKAP the fastest radio telescope in the world for surveying the sky, taking panoramic snapshots over 100 times the size of the full Moon.

First-generation phased array feeds have already been fitted to six of ASKAP’S 36 antennas and the early science results are outstanding. Second-generation phased array feeds, the result of a program to streamline their manufacture and make operational enhancements, are in the final stages of development and testing before full-scale production begins.

Along with colleagues in The Netherlands, Canada and the USA we’re also developing phased array feeds as rapid-imaging devices for potential use by the much larger Square Kilometre Array telescope, and for wider use throughout the world’s leading radio-astronomy observatories.

Phased array feed technology also has enormous potential outside astronomy. Much like our fast wireless LAN technology (which was developed from our expertise in radio astronomy and led to ‘WiFi’, the way most of us now access the internet without wires), phased array feeds could make a positive impact in a variety of alternative applications. For example, geophysics and medical physics could benefit from the rapid imaging made possible by phased array feeds.

Recognition of our phased array feed technology is building: it won Engineers Australia’s national Engineering Excellence Award in 2013, and was overall winner in The Australian Innovation Challenge in 2014.


Can I use an array of inexpensive cameras as an alternative to a telescope? - Astronomy

Photomultipliers (PMTs) are currently adopted for the photodetector plane of Imaging Atmospheric Cherenkov Telescopes (IACTs). Even though PMT quantum efficiency has improved impressively in the recent years, one of the main limitation for their application in the gamma-astronomy field — the impossibility to operate with moon light — still remains. As a matter of fact, the light excess would lead to significant and faster camera ageing. Solid state detectors, in particular Geiger-mode avalanche photo-diodes (G-APDs) represent a valuable alternative solution to overcome this limitation as demonstrated in the field by the FACT experiment (The First GAPD Cherenkov Telescope[2]). They can be regarded as a more promising long term approach, which can be easily adopted for the new generation of cameras and for the Cherenkov Telescope Array (CTA). We describe here the Photo-Detector Plane (PDP) of the camera for the 4 m Davies Cotton CTA Small Size Telescopes, for which large area G-APD coupled to non-imaging light concentrators are planned. The PDP includes 1296 photosensors, the biasing and pre-amplification stages, the control electronics as well as the mechanical support and the watertight enclosure. We developed with Hamamatsu a new large area hexagonally shaped G-APD with an area of 93.6 mm2. This G-APD is divided into 4 channels which will be summed after the pre-amplification stage to maintain an acceptable time characteristic of the signal. The characterization of this device for 50 jim and 100 jim micro-cell sizes will be discussed and compared to other non-custom photodetectors.


Contents

INAOE and UMass-Amherst signed the agreement to develop the Large Millimeter Telescope project on 17 November 1994, but construction of the telescope did not begin until 1998. [6] [7] The first observations were taken on June 2011 at 1.1 and 3 mm using the AzTEC camera and Redshift Search Receiver (RSR), respectively. [8] On May 2013, the Early Science phase began, producing over a dozen scientific articles. The official name of the LMT was changed to "Large Millimeter Telescope Alfonso Serrano" on 22 October 2012 in order to honor the initiator of the project, Alfonso Serrano Pérez-Grovas.

The set of LMT instrumentation is built by heterodyne receivers and broad-band continuum cameras, some of them still under development.

Hetherodyne receivers Edit

SEQUOIA operates in the range 85–116 GHz band using a cryogenic focal-plane array of 32 pixels arranged in dual-polarized 4×4 arrays feed by square horns separated by 2*f*λ. The arrays are cooled to 18K and use low-noise Indium Phosphide (InP) monolithic microwave integrated circuit (MMIC) preamplifiers designed at UMass to provide a characteristic receiver noise of 55K in the range 85–107 GHz, increasing to 90K at 116 GHz.

A novel MMIC-based receiver designed to maximize the instantaneous receiver bandwidth to cover the 90 GHz atmospheric window from 75 to 110 GHz in a single tuning. The receiver has four pixels arranged in a dual-beam and dual polarized configuration. Orthogonal polarizations are combined in waveguide-based orthomode transducers. Beam-switching at 1 kHz on the sky is achieved using a fast Faraday rotation polarization switch and a wire-grid to interchange the reflected and transmitted beams to each receiver. This ultra-wide-band receiver typically achieves noise temperatures < 50K between 75–110 GHz. The Redshift Search Receiver has exceptional baseline stability because it does not involve mechanical moving parts, therefore being well-suited to the detection of redshifted transitions of the CO ladder from star-forming galaxies at cosmological distances. An innovative wide-band analog autocorrelator system which covers the full 38 GHz with 31 MHz (100 km/s at 90 GHz) resolution serves as the backed spectrometer.

Broad-band continuum Edit

AzTEC millimeter camera developed to operate at 1.1mm. It is formed by a 144 silicon nitride micromesh bolometer array arranged in a compact hexagonal package and fed by an array of horns separated by 1.4 fλ. The detectors are cooled down to

250 mK inside a 3He closed-cycle cryostat, achieving a

3 mJy Hz-1/2 pixel sensibility. AzTEC field of view at the LMT is 2.4 arcminutes square and manages to take completely sampled images through telescope or reflecting secondary surface movements.

Future instruments Edit

TolTEC will be a high-speed, high-sensitivity polarimetry camera for the LMT. It will image the sky at three (1.1, 1.4 and 2.1 millimeter) bands at the same time. It is built using 7000 polarization-sensitive kinetic inductance detectors (KIDs), therefore each TolTEC observation will produce six images simultaneously, one at each band and each polarization. TolTEC's cases of study are: cosmology and physics of clusters, galactic evolution and star-formation along the history of the Universe, the relation between the star-forming process and the molecular clouds and small bodies of the Solar System.


Can I use an array of inexpensive cameras as an alternative to a telescope? - Astronomy

We constructed a 3.0 meter diameter f/1.5 Liquid Mirror Telescope (LMT) between 1990 and 1994 at the NASA Johnson Space Center, Houston, Texas. We have subsequently operated it since 1995 at the NASA Orbital Debris Observatory (NODO), Cloudcroft, NM. Employing an inexpensive rotating container of mercury as its primary parabolic mirror, the NASA LMT is a cost-effective alternative to telescopes utilizing glass mirrors. We detail criteria for mirror construction including environmental considerations via Hg vapor emission analysis. We describe performance optimization to the NODO site seeing limit of 0.8 arcseconds FWHM via analysis of perturbations to image quality from mirror angular velocity stability, dynamic balance, rotational axis tilt, and prime focus lateral and tilt displacements. We detail the behavior of the two prominent mirror surface wave phenomena-spiral and concentric forms. We demonstrate that the former probably results from vorticity in the air boundary layer above the mirror and show diffraction effects from the latter. We describe mirror stabilization in terms of boundary layer theory. The prime focus NASA-LMT utilizes corrective optics yielding a field of 46 arcminute diameter. Utilizing Micro-Channel-Plate (MCP) intensified video cameras we have obtained 750 hours of zenith staring orbital object event data with a limiting object diameter of approximately 1 cm at 1000 km altitude and 0.1 albedo. We have extended to 17.75 the lower magnitude limit of optical detections among the telescopes employed for orbital object surveys, further demonstrated the incompleteness of the SATCAT, and corroborated results of RADAR employed in orbital object detection. Utilizing CCDs we have conducted a 135 night broadband and multi-narrowband survey of 20 square degrees of sky at high galactic latitude down to a limiting magnitude of

22.0. The survey data will yield information on object morphology, spectral classifications, and large- scale structure to a redshift (z) of 0.5 with an accuracy of ∆z <= 0.02. Broadband images from this survey are presented, demonstrating that the NASA-LMT optical performance is comparable to conventional telescopes of equivalent size located at a similar site.


5 Telescope Photography Tips

No matter which method you choose, there are a few things to keep in mind when photographing through a telescope.

Minimum Focusing Distance

A camera lens cannot focus on an object that is closer than its minimum focusing distance. A small focal length lens (e.g. 50mm) can typically focus on objects closer than a lens with a larger focal length (e.g. 150mm). The smaller lens will be easier to use in conjunction with the telescope because you can put it closer to the eyepiece. If your lens has a macro setting, that will help reduce the minimum focusing distance as well.

Manual Focus

If your camera has manual focus, use it. This will help you get a sharper image through the telescope. Smaller lens cameras such as cell phones generally handle the autofocus fine. Larger lens cameras like DSLRs see a good bit of the area around the eyepiece and will have trouble using autofocus.

Shutter Shake

If your telescope is not a large heavy one, the shutter motion on your camera might cause shake while using the prime focus method. This can result in a blurry photo. You can minimize this with good support for the camera or by using a cable release or remote shutter button. You can also lower your ISO and increase the time the shutter is open so there is a more stable recording time to overpower the time it shakes.

The Moving Moon

The higher the magnification, the more apparent the movement of the moon will be in your photography. If you have a 1000mm telescope and a doubler on your camera, the moon motion could be apparent in just a few seconds. Experiment with exposure times to see what works best for your particular set-up.

Exposure

It is okay to underexpose the moon a bit. Even with the light lost through the telescope, the moon is so bright compared to the sky around it that the camera may overexpose the moon while it's trying to brighten the sky.