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Wednesday October 18th 2017

‘Astronomy on a Budget’

Observing Tips for Beginners

 

Amateur AstronomersAmateur astronomers have to face some challenges with equipment, weather and environment during their stargazing sessions. The tips listed below help to overcome some initial hurdles and make the celestial night show even more exciting. If you have further tips, please contact us. We will be glad to share them with our fellow amateur astronomers.

Finder Alignment

Some telescopes come with finderscope others with red dot finder. Either way, the finders need to be perfectly aligned with the telescope axis. Alignment can be carried out during the day. Point your telescope at a stationary object far away. A chimney, an antenna mast or a mountain peak will serve well. Move the telescope so that the object is exactly in the middle of the eyepiece view. Lock the telescope in that position: Re-check if the object is still in the middle of the view. A adjust the finderscope / red-dot-finder by turning the adjustment screws so that the cross hair / red dot is exactly on the object. Do not compromise. Time spent for propper aligning means less time searching objects and more time observing fascinating objects.

Finding Objects with Finderscope / Red Dot Finder

I look for objects with both eyes open, one directly aimed at the object, the other through the finder. One has to get used to this way but once acquainted with it, objects are found much easier. Using the finder view with two eyes provides not only a small cutout of the sky but you can see a large part of it.

Magnification

Most telescopes come with one or two eyepieces. If you have more than one, start your search for objects always with your lowest magnification (the eyepiece with the largest focal length). The longer the EP focal length, the wider the field of view and the easier it is finding objects. Once the object is centered in the eyepiece, you can increase magnification with shorter focal length eyepieces.

Stay Warm

Besides setting the equipment up, stargazing is really not a very physical activity. Due to the excitement about celestial objects it is ofter forgotten that our body can loose temperature – quite quickly that is. Make sure to wear sufficient layers of clothes to keep you comfortably warm. The winter, nights in the desert or at high altitude remind us permanently to stay warm, but it can become very cold during a night after a nice, warm day in Spring or Fall. Check the weather forecast for the night. Take particularly windchill factors in account and dress accordingly.

Dew

How does dew form? The dew point is the point at which the air is saturated with water vapor. Warmer air is able to absorb more water vapor than colder air. If the air it cools down, excess water vapor has to go somewhere. On a greater scale, it will rain, on a smaller scale, exposed objects get wet.  Whenever air cools down our equipment cools down as well and the exposed surfaces radiate excess heat. As this happen, moisture condenses at a greater rate than that at which it can evaporate, resulting in the formation of water droplets.

Moist lenses disturb the view significantly. Because they have their mirror deep down in the tube, Newtonian telescopes are relatively save, but all other types of telescopes, including binoculars are unfortunately susceptible to dew. A simple but a little bit cumbersome trick is to point the telescope downwards between observing sessions. When pointing it down, it is more difficult for the radiated heat to escape, and lenses will keep their temperature longer; and with that, they stay longer moist free.

Another defense against dew are large(r) dew shields. Most telescopes come with some dew protection but these shields are often far to small. Larger dew caps are available for every telescope but they can be be made easily with readily available material. Dew shields delay dewing, unfortunately, they cannot prevent it completely.

When the telescope gets moist, take utmost care when de-fogging the lenses. Best is not to touch the lenses at all, especially when they are coated. A fan is often the preferred option. If you have to use a cloth, take a very soft one. Do not rub, only dab the lens to make sure the lens coating is not damaged during cleaning.

Heating telescopes with special telescope heating bands is most convenient. These dew heaters keep the telescope just a bit warmer than the air temperature and with that, preventing dewing and moist surfaces. Heating bands need however a 12 V power source, and they can draw quite some current.

If you bring telescopes from the cold into the warm, lenses will moist almost immediately. Do not put the protection caps on right away, wait until the lenses are completely moist free.

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Astro-Imaging for $100

Astrophotography on a Budget - Orion Image captured with Canon SX120 (10 exposures, 4 seconds each, ISO400)
Constellation Orion - Image captured with Canon SX120 (10 exposures, 4 seconds each, ISO400)

Is is possible to make astro-images with entry level digital point-and-shoot cameras?

The answer to that question is a reluctant “somewhat”. With a basic camera it is indeed possible to shoot decent astro-images but the objects are rather limited: the moon and star constellations. 

It is not about pixels

Basic astrophotography is not about Mega-pixels. Good images can be taken with cameras of 4 MP, or even less.  What is important are three vital camera features, without them astrophotography will become a gamble. These features are:

  • Manual focus
  • Capability to preset exposure time (Tv)
  • Capability to delay exposures. 

Another component is of great importance: a solid tripod. The magic word here is “solid”.

Manual Focus

Manual focus is important because of the way cameras perform auto focus. Some compare contrast changes. Sharp images have more pronounced contrast changes between adjacent pixels, unsharp images deliver more gradual changes. Other cameras compare bit patterns in specials sensors (phase detection). The patterns are shifted when the image is out of focus.

Either way, both methods are not really helpful when imaging a quasi black dark sky. Furthermore, if there is any contour visible in the image (f.e. a tree in the foreground), automatic focus will jump right at it, putting the  actual celestial object out of focus. Astrophotography objects need to be focused manually to infinite.

Manual Time Setting (Tv)

Moon
Moon – Image taken with Canon SX120, post-processed with GIMP

Time setting is important because the amount of light gathered by the CCD is only a tiny fragment compared to that of daylight images. This means, the exposure time need to be long. Typical exposure times for imaging stars are between 1 second and 30 seconds.

Tripod – Solid

A solid tripod will keep the exposing camera steady in position. With long exposure images, any vibration will be clearly visible in the images. The camera has to be absolutely still.  For noise reduction purposes we need to take a series of at least 10 images, ideally 30-50. More on this subject later.

Exposure Delay

Even if the camera is firmly mounted on a tripod, pushing the exposure button will cause slight vibrations. The result is star streaks in the image. Exposure delay prevents this effects. Many cameras have a built in 2 seconds or 10 seconds delay. When the button is pushed, there are still initial vibrations, but the delay allows mount and camera to stabilize. The result will be significantly sharper images.

Zoom – Better Not

Some cameras have a zoom feature. Unless you are shooting the relatively bright moon with a very short exposure time – just forget the zoom feature of the camera. Why? Because the Earth rotates. This will show badly in the images in form of elongated stars. Please try to follow the short calculation below – it is indeed eyeopening.

The earth rotates once in 24hours, one rotation equals 360 degrees. That means, in one hour the rotation angle is 360/24=15 degrees, and in one minute it is 15/60 = 0.25 degrees, right?  A quarter of a degree does not sound a lot.

True, but… Lets say we want to expose a the constellation Orion for 12 seconds. The angle the earth moves during this period is 0.25/5=0.05 degrees. A 10x zoom would increase the apparent angle by the same factor of 10. Within 12 seconds the image would shift by 0.5 degree.

One might think, that still seems negligible. Does it really have an effect?  – Yes it does, and very much so. Picture the moon. The angle of the moon is, well, 0.5 degrees. That’s right, within 12 seconds exposure using 10x zoom, stars in our image would become as long as the diameter of the moon is; definitely not what we are looking for.

So, how are images with a high power telescopes possible?

Astrophotography with high power telescopes requires special mounts; they are called German Equatorial Mounts (GEM). These mounts have gear and electronically controlled motors that move the telescope exactly so that it perfectly compensates for the Earth’s rotation.  You have probably guessed it: these mounts are rather expensive. Price depends on their carrying capability and accuracy. Entry level models that can be used for basic astrophotography start at about $500  ($300 used), and with growing demands, mounts can reach quickly true astronomical prices.  

First Photos

Preparations:

  • Make sure the battery is fully charged and the memory card offers enough space.
  • Reduce the brightness of the camera display to minimum. This helps to keep / maintain the night vision.
  • Mount the camera on the tripod.

 Shooting:

  • Choose your object
  • If possible set your camera to the highest ISO speed.
  • Manually focus to infinity.
  • Set exposure delay to 2 (or more) seconds.
  • Set exposure time (Tv) to 5 sec.
  • Take your first test shot. You can see if the object is framed right and the image is in focus.
  • You might need to play with ISO speed and exposure time to optimize image exposure.
  • Once done and you are satisfied, take a series of at least 10 images of your object (recommended 30-50). 

Note: photos of stars look always quite dark in the camera monitor. It is often advised to increase the brightness of the image later during post processing.  

Post processing (very basic):

This following description is for images with stars (not applicable for moon shots).

  • Load your images to your computer and inspect every single image
  • Sort out wiggly images, and such that have unwanted artifacts like plane or satellite trails
  • Stack the remaining images with DeepSkyStacker (DSS) – setting: average
  • Once DSS has created an image, optimize it with the build-in post processing tool

The advantage of stacking a series of astro-images (rather than using just one image), is that the noise portion will be significantly reduced, and the lunimance and saturation of the actual objects (stars) are emphasized. Since we are working usually with high ISO speeds, noise is much more present in astro-images than it is in daylight images.  

Further reading

  • Catching the Light – Great site on Astrophotography with a DLSR by Jerry Lodriguss. Noise reduction in astronomy images

Coming soon:

  • Deep Sky Stacker tutorial
  • GIMP tutorial
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Getting Started

So you think you are interested in amateur astronomy. Well, you are not alone. Every one of us who has become “hooked” on our hobby started out right where you are now. Hopefully we can get you started in such a way that you will find our hobby interesting and rewarding.

Most beginners get involved in amateur astronomy because they have looked up at the majestic night sky and found it fascinating. We have all marveled at the beautiful images from the Hubble Space Telescope. Just remember, if you expect to see images like those from Hubble, you are going to be deeply disappointed. After all, if we amateurs could see “stuff” just like Hubble, NASA would never have spent billions of dollars putting the observatory into orbit.

First of all, and this is extremely important:

DO NOT GO OUT AND BUY A TELESCOPE UNTIL YOU ARE ABSOLUTELY SURE YOU KNOW WHAT YOU WANT/NEED.

There are lots of telescopes out there and some are total junk. So do not go out and make a major purchase that could very well disappoint you once you gain additional experience.

If you have not already done so, stretch out in a lawn chair and look up at the night sky. You will be amazed what you can see on a clear dark night just by “looking up”. Most people have binoculars so try using them from the lawn chair, you will see even more. Just scan the sky and look for areas of interest. The moon is visible almost every clear night of the year. Look along the “terminator”, the region between the light and dark parts of the moon. This is where you will find the most visible detail. Light pollution (along with clouds) is the biggest adversary for observers. If you live in an area where there is a lot of light pollution, try going out into the country where the sky is much darker. State Parks are a great place to view the night sky and you will see a lot more.

Skymap.com - free monthly skymaps with explanation of interesting objectsAs you gain observing experience you will want to learn more about “what’s up” in tonight’s sky. Most people know about constellations, but which ones are currently visible? Will I even recognize them if I see them? What are the names of the bright stars that I can see? Are any of the planets visible tonight? Are there any Deep Sky Objects (DSO’s) that I can see? To answer these questions, and many more, you will need a roadmap of the sky. These roadmaps are called sky charts and planetariums. A simple free version of a sky chart is available online at http://skymaps.com/.

Have you ever wondered how a telescope works? Is it just plain old magic? Nope, there is a real reason that we can see all of those objects in space that are so very far away. If you would like to know more, take a look at http://science.howstuffworks.com/telescope.htm. This site does a great job of introducing the beginner to the kinds of telescopes that exist and how they work.

Find an astronomy club in your neighborhood and visit them at their public nights and star parties. You will meet great people who are glad to talk with you about astronomy and equipment, and will be glad to show you celestial objects with their telescopes.

Once you have attended some astronomy events you will discover that there is a lot more to amateur astronomy than you ever thought possible. You may have even found out that your real area of interest is not what you thought it was. Hopefully you have had the opportunity to view through various types of telescopes (and other observing tools) that are available. You may have even decided what type of telescope best fits your interests. You have been introduced to a whole new vocabulary of names and terms. You have found additional sources of information including books, the Internet, monthly publications and computer software (just to name a few) that will allow you to continue to learn about your new hobby.

Yet you have just scratched the surface. Amateur astronomy is a lifelong pursuit and the only regret that many of us “old timers” have is that we did not start it early enough in our lives. For many, amateur astronomy is a family happening. Regardless, now is the time for you to really get started.

Posted with friendly permission of : Indiana Astronomical Society
Source: http://www.iasindy.org/astronomy101.php

 

Further Information:

  • Sky & Telescope Guide: Getting Started in Astronomy for Northern Hemisphere or Southern Hemisphere. Great free pdf guide from Sky & Telescope. It offers valuable tips and advise for astronomy beginners, and it comes with bi-monthly star charts as well as a map of the moon.

 

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A Telescope for under $100

Refractor 70mm on alt-azimuth mount
Refractor 70mm on alt-azimuth mount

This article is for people who are in the market for their first telescope – but have only a very limited budget (say $100) at their disposal. Some amateur astronomers will say spending $100 on a telescope is wasted money, simply because there is no great telescope for that amount. Good optics is expensive, but not everyone has hundreds of dollars to spend and there are indeed some decent telescopes that are fun and do not break the bank. A tight budget should never prevent anyone to start a fascinating hobby. 

Telescopes are available in three basic types: refractors, reflectors and catadioptrics and they come with different mounts. An Astronomy Source article “Introduction to Telescopes” in coming soon. The link from souledout.org  provides also a nice overview on telescope types.   

What can you see with a beginners telescope?

Quite a lot. I heard people complaining that the view through their basic telescope did not reveal bright and colorful images. Well, do not expect Hubble quality images with a $100 telescope. Suitable objects for these telescopes are the moon, the bright planets Jupiter and Saturn, some of the brighter deep space objects, and stars. Observe  Andromeda Galaxy (M31) or Orion Nebula (M42), you can also see the famous Hercules Cluster (M13). Stars shine in different colors due to their different temperatures and consistence, and there are many exciting double or ever multiple star  systems to watch. Did you know that Polaris, the North Star,  is actually a 3-star system? 

When looking for a budget telescope, keep in mind:

  • Do not consider department store telescopes that come with a ton of accessories, parts and pieces, and promise magnifications of whopping 500x or even more. These items are usually toys. There is nothing wrong with toys, but really, don’t expect clear images or lasting fun and excitement with those. What you can expect is inferior optics a lot of plastic parts that will break soon.
  • Glass lenses. Plastic lenses simply do not deliver the view quality of well polished and adjusted glass lenses.

New versus used

  • Telescopes can last very long if they are treated well. Used scopes are often available for half the price of a new one and many astronomers choose to buy used, simply because they want more: for the same money they get a much better (used) telescope, offering better images.
  • Be very careful buying a telescope at a yard sale. You may get lucky and find the deal of the century. More likely is however that the item is in a bad shape, because it has been neglected over years.
  • However, used equipment sold by serious amateur astronomers is usually in pretty good condition. True astronomers care about their equipment. A good source buying used telescopes and accessories is www.cloudynights.com. Check their classifieds and see what it offered here. Sellers describe their items in detail and provide usually very reliable information about the condition of their goods. Look for other dedicated astronomy sites that offer classifieds.
  • If you decide to buy used, you should wait – and be quick. This sounds like a paradoxon, but you should watch the classifieds for a while to get a feeling about a fair market price of  the the item you have in mind. When you see the right one, be quick to get it. Good items are often sold within a couple of hours. 

Further items for amateur astronomers:

  • Planisphere. Easy to operate map like device, that shows you where stars, constellations and planets are – all year long.
  • Red Flashlight. Eyes adapt to the dark, this is called night vision. Night vision takes a while, about 15-30 minutes, but allows to see much more and much fainter objects in the dark. Exposure to bright light, with the exception of red, erases light vision immediately and it takes another 15-30 minutes.
  • A good  astronomy book about telescopes and star watching gives helpful hints for the beginner and advanced astronomer.

Conclusion

Beginning astronomy is the start of a great, very exciting and fun hobby. A simple 70mm or 80mm refractor on alt-azimuth mount is probably the best choice as starter telescope for around $100. These telescopes are very easy to set up and simple to operate – just point and see the universe.   

 Further reading


  

 

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Helio Now

Solar Dynamics Observatory

Solar Dynamics Observatory 2017-10-18T12:47:08Z
Observatory: SDO
Instrument: AIA
Detector: AIA
Measurement: 171

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