AstroNotes 2018 February Vol: 57 issue 02

Editor’s Message . Ottawa Skies . Maven . National Update . Getting Started in Astro-Imaging . Monthly Challenge . AstroNotes Bookshelf . Announcements . Member News . Next Meeting . Centre Information

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AstroNotes

The Newsletter of the Ottawa Centre, RASC

Volume 57 - No 2 - February 2018

 

Editor’s Message

 

At the February 2, 2018 our meeting chair, Kelly Jordan, announced that this would be her last meeting as meeting chair. She leaves later this month for a year of travel abroad.

Kelly was our meeting chair for a little over a year and did a fabulous job. She brought in a great selection of speakers to keep us both informed and entertained. She did much to encourage younger people to get involved with our greying group. She created a Youth Award that was handed out for the first time this year at the Annual Dinner. Attendance by younger people at our monthly meetings has increased very nicely over the last year. Young people are becoming more involved, like Danel Polyakov, 14 years old, who not only gave a presentation at a recent meeting but has also written a feature article for this month’s issue.

Kelly, we will miss you and thank you for gracing us with your leadership these past 14 months.

In this issue I am reintroducing an item that used to be a part of the monthly meetings that I enjoyed a lot. It is the monthly challenge. There will be a lunar challenge and a deep sky challenge. Each will have a small scope/beginner challenge and a large scope/intermediate/advanced element to it. I encourage everyone to try these challenges and submit your sketches or photos of your results so that we can share them at the meetings and/or reproduce them here in AstroNotes.

Astrophotography is a popular and challenging part of our favorite pastime. Paul Klauninger has agreed to provide us with the written version of the Imager’s Corner presentations that he, Eric and Taras have been presenting over the past few months. The first installment is in this month’s issue with more to follow over the coming year.

Enjoy.

Gordon Webster

astronotes@ottawa.rasc.ca

Ottawa Skies for February 2018

By

Dave Chisholm

There is no full Moon in February. The next one is March 2.

Mercury is not visible this month.

Venus is visible all month just after sunset.

Mars is visible in the early morning.

Jupiter is visible in the early morning.

Saturn is visible in the early morning all month.

Uranus is visible in the early evening all month.

Neptune is visible in the early evening for the first half of the month.

The best viewing date for the International Space Station is February 10. It rises in the WNW (299 degrees) at 18:10:07, reaches maximum in the NNE (29 degrees) at 18:13:24 and sets in the ESE (118 degrees) at 18:16:39.


MAVEN- Mars Atmosphere and Volatiles EvolutioN orbiter

By Danel Polyakov

Four billion years ago a beautiful blue marble, covered with oceans of crystal blue water, landmarks, snow and maybe even life could be seen in the sky. But I am not talking about Earth, I’m taking about a different planet. A planet that looks nothing like that today. I’m taking about Mars, the red old planet that’s covered with rust. But how did this occur? How did a planet so beautiful turn so old that it’s literally covered with rust?

NASA’s 2013 space probe was launched from Florida on November 18. An Atlas V rocket was carrying MAVEN, which is designed to study the Martian atmosphere while orbiting the planet. MAVEN’s mission is to determine how the planet’s atmosphere and water, which used to be substantial, were lost over time.

MAVEN has four specific objectives. Two of these are: 1) to determine what changes the loss of volatiles to space from the Martian atmosphere has played through time, and 2) to determine the current state of the upper atmosphere, ionosphere and the atmosphere’s interaction with the solar winds.

Let’s start with the first of these.

From my introduction you could visualize Mars as a blue planet, a planet full of oceans and rain. However, something changed, something that transformed the beautiful planet Mars into the planet we see today. Unlike Earth, Mars doesn’t have a strong magnetosphere. In fact, it doesn’t have a magnetosphere at all. But it did once. After what is believed to be a period in which Mars’ core cooled, it lost its magnetosphere. This left the Martian atmosphere open to the solar winds and radiation. When the sun was young, it was much more active, and its solar winds struck Mars at the extremely high speed of 500,000 meters per second.

Today Mars is losing about 100 grams of its atmosphere per second (Earth is losing 3kg/s). However, a couple billions of years ago, Mars lost much more of its atmosphere, 100-1,000kg/s. This was a huge rate, especially for a planet so small. But how and why did Mars lose so much more atmosphere? Where did it all go?

Here’s where MAVEN comes in. One of MAVEN’s components is the Neutral Gas and Ion Mass Spectrometer (NGIMS) which does exactly what its name suggests. The MAVEN scientists thought of a way to see how much of the Martian atmosphere was lost to space. This is done by calculating two different isotopes of Argon in the Martian atmosphere using the NGIMS. They used Argon-36 and Argon-38. Argon, being a noble gas, doesn’t chemically react with other materials. Hence, the only way it can be lost is to solar winds. Argon-36 is lighter then Argon-38 and stays in the upper atmosphere, open to the solar winds, while Argon-38 stays closer to the surface of the planet. After calculating the amount of Argon-36 compared to Argon-38 in the Martian atmosphere, we can determine that Mars has lost over 70% percent of its Argon to space. NASA can then use those numbers to identify how much of other gases have been lost to space, such as Carbon-dioxide, which is crucial for life and heat. All those numbers together can help us understand what Mars was like billions of years ago.

So back to the question, what has the loss of all those volatiles changed?

As the solar winds strip the volatiles away from Mars, the atmosphere starts to lose heat faster, cooling down the planet. Also, as gases such as water vapor and carbon dioxide start to get lost to space, Mars start to lose resources (e.g. water). The more gases lost to space, the lower the atmospheric pressure becomes, allowing water to boil off at less than 0C (at 600Pa). The water vapor would then be broken down, by radiation in the atmosphere, into its basic element (hydrogen and oxygen), which then would easily be swept away to space by the solar winds. As those conditions kept on getting harsher, the chances of water and life on the surface grew dimmer and dimmer.

MAVEN’s second objective is to determine the current state of the upper atmosphere, ionosphere, and the atmosphere’s interactions with the solar winds. MAVEN has taken the measurement of gas lost to space today. Three of these were Carbon (left), Oxygen (middle) and Hydrogen (right):

Hydrogen, being the lightest element, tends to rise far up into the atmosphere where it can easily get stripped away to space, forever lost to the planet. It was once believed that the amount of gas lost to space from Mars was constant throughout the year. But recent MAVEN observations have shown that the atmosphere loses over 10 times more gas when Mars is closest to the sun, then when it is furthest away, helping prove that the main factor for atmospheric loss is the sun.

In October of 2014, while the Siding Spring comet missed Mars by 130,000km, MAVEN’s NGIMS detected metal ions in the Martian atmosphere. That was a really big surprise for NASA, since there is only one way to get metal ions into the atmosphere: from the constant contact of small meteorites with the atmosphere. As meteorites burn up, charged particles in the atmosphere rip electrons away from metal atoms, turning them into positively charged ions. And since Mars doesn’t have earth’s strong magnetosphere to protect the planet from the solar winds, NASA didn’t think that these ions would stick around. Three years of MAVEN’s observations has confirmed that the number of ions escaping the planet has remained constant. Since the Martian atmosphere today is too weak to get any new metal ions, this proves that the atmosphere hasn’t always what it is today. However, this is a relatively unimportant part, since this fact has already been proven. The important thing to note is that before MAVEN detected those ions, the dynamics of the Martian upper atmosphere were pretty much invisible. The techniques refined though MAVEN are now being applied to help us understand other phenomenon.


National Update

The Calgary GA

Edited by Douglas Fleming

This year’s General Assembly of the RASC celebrates the 100-year anniversary of the Society and the 60-year anniversary of the Calgary Centre. Should be exciting!

The assembly will be held from Thursday, June 28, 2018 to Tuesday, July 3, 2018 on the campus of the University of Calgary, just 10 kilometers north-west of the city center.

Events include:

  • First Nations welcome

  • Featured speakers:

    • Dr. Robert Thirsk,

    • Dr. Fereshteh Rajabi,

    • Emily Lakdawalla and

    • Dr. Tanya Harrison

  • National Council Meeting

  • Alan Dyer Deep Space Photography Workshop

  • Tour of Cross Conservation Area: Canada’s first Nocturnal Preserve

  • Stampede Breakfast

  • Paper & Poster Presentations

  • RASC General Meeting

  • 150th Presentations

  • Awards Banquet

  • BBQ at the University of Calgary Rothney Observatory

  • Optional Tours of the Drumheller Badlands, the KT Boundary, Royal Tyrell Museum of Palaeontology, the Vulcan Trek Centre, the Mars Analog Centre and the Columbia Icefields

Calgary Centre has put together a promotional video that highlights Assembly venues and some of the attractions in and around the Calgary region.

https://www.youtube.com/watch?v=0NagIn2eKX8

Conference details:

http://rasc.ca/ga2018

Cost per person is $235

Accommodations at Hotel Alma http://www.hotelalma.ca


Getting Started in Astro-imaging

By Paul Klauninger

I have been involved in astro-imaging for over 30 years, and as such, have watched its evolution from the film era to modern-day digital imaging. The changes have been nothing short of monumental. I am frequently asked about getting into imaging the night sky and find that the common perception is that this is a very involved and expensive interest. The reality is that yes, it certainly can be. But there is also a great variation in the effort and expense involved, depending on what type of images one wants to capture. If your goal is to create an image where the Orion Nebula or the Andromeda Galaxy fills the screen, then the equipment to accomplish this can indeed get quite pricey. And, like any fine skill, there is a learning curve and a time commitment involved to capture and process such images. But there are other forms of astro-imaging that can also produce spectacular results and that offer a much gentler (and far less expensive) entry path into this fascinating pursuit.

To this end, last year I began a series of talks at our monthly meetings aimed at introducing members to basic astrophotography, using equipment that many already possess. Our AstroNotes editor, Gordon Webster, felt that this would be useful information to make available beyond our meetings and so here I provide a summary. My approach here is to assume nothing except an interest in learning astro-imaging and then to start with the basics.

Today’s DSLR and mirrorless cameras with interchangeable lenses are best for getting started in night sky shooting. These allow for full manual control and can produce excellent imagery. As with all good photography beyond cell phone selfies, the key is to get to know your camera’s capabilities. This is particularly important in astro-imaging, since you’re dealing with mostly dim targets under a dark sky. As such, many of the automatic and pre-programmed modes and functions cannot be effectively used. You must know how to operate your camera manually and easily change its settings. Trying to figure out how to alter ISO speeds or lens aperture settings in the dark and cold of a winter’s night is not the way to go! Read your user’s guide, experiment, and learn before venturing out into the field.

Basic astro-imaging involves setting up your camera on a tripod, aiming and focusing the scene, and clicking the shutter. Sounds simple, but there are numerous caveats and “gotcha’s”. Let’s look at the equipment to find some of the hidden gremlins.

  • The first is your tripod. This should be sturdy enough to solidly support your camera and heaviest lens. It also requires a ball head or pan-and-tilt head mount to attach and aim the camera. A low-end flimsy tripod can be very frustrating, as it can make precise aiming difficult and will likely allow the camera to jiggle even in a light breeze.

  • The second is focusing. This is the most common source of spoiled imagery, so it is a crucial point to master. You must focus the lens manually since auto-focusing is virtually useless in the night sky. In the days of film imaging, one could usually set most manually focused lenses to the infinity stop and be assured of a reasonably good focus. Not so today, where auto-focus lenses can typically rotate beyond the infinity mark. These cameras are built this way for a number of reasons, such as reducing strain on the auto-focus motors, accommodating variable focus points on zoom lenses, and allowing for thermal expansion.

Set the focusing mode switch on your lens to Manual. I then suggest using the live-view function available on most current DSLRs. Set a rough focus using the infinity mark and then aim at a bright star (dimmer stars often won’t be visible). Engage the live view and then centre the zoom field-of-view rectangle on the star. Magnify the live view (typically 5X or 10X). Slowly turn the lens focus ring to make the star image as small as possible. You will see that the star becomes brighter as you do so. This is the sweet spot. Adjust the focus back and forth through this sweet spot a few times to get a feel for where it occurs and how finely you need to adjust the lens to get to it. When the star is as tight and bright as you can get it, disengage the live view. There are a couple of caveats here. Note that if you are shooting on a night where the temperature will vary a lot (or when bringing a warm camera out into the cold), the change in temperature can alter your focus over time. You should check the focus multiple times during your session. Also, if you are using a zoom lens that uses a sliding barrel to set the zoom level, be aware that as you aim upwards, the barrel can move downwards and spoil your focus. A piece of masking tape between the lower edge of the sliding barrel and the fixed portion of the lens body can help prevent the barrel from sliding once you’ve achieved a proper focus.

  • Clicking the shutter must be done without touching the camera, otherwise you risk blurring your image. You can use a simple remote trigger or cable release, or even your camera’s internal timer. Some DSLRs also have a built-in Wi-Fi capability that allows you to trigger the exposure using a cell phone or tablet. However, if you’re thinking of doing time lapse imaging, an intervalometer is your best bet, and after-market vendors often sell these for far less than those available from your camera’s manufacturer.

  • A dew control system is also highly recommended. In our climate, the evening air, especially in spring and autumn, is often quite damp and lenses can become covered in dew very quickly. Frost can be problematic in the winter. Carefully cleaning the lens if this happens can help temporarily, but the dew will return in short order. And if you’re shooting a time lapse, having to stop to clean the lens will likely ruin the sequence. Your best bet is to install a dew strap near the front of the lens. This is essentially a heating element that supplies a very gentle heat to the lens to ward off dew. It is typically attached to a controller unit that can turn the strap power off and on as well as regulate the degree of heating. The straps and regulator are available from suppliers of astronomy gear. They are usually powered by a portable 12-volt power supply, available at stores such as Canadian Tire. A typical setup is shown below.

  • Finally, make sure your camera battery is fully charged before starting a session. Having a spare battery is also a wise idea, especially if you’re planning to do some shooting away from home.

So, once you’ve learned how to control your camera manually and have obtained the other bits and pieces of gear you need, it’s time to head out and shoot some pictures. You might want to try this from your backyard first before packing up the car for an all-nighter at some remote dark sky location. This will allow you to more easily experiment, practice your technique, and identify any problems with your equipment.

As a logical initial exercise, try the following, a form of astro-imaging that will be the basis for shooting subjects later on such as auroras, meteor showers, satellites tracks, and most nightscape time lapse sequences.

  1. Wait for a clear, moonless night and plan on spending an hour or more outside to allow for ample experimentation. Dress accordingly, since bugs or cold evenings can really temper your enthusiasm!

  2. Set up your equipment using a wide-angle lens with a focal length in the 8 to 35 mm range. Since these lenses cover a large swath of sky, they allow you to expose for a longer period of time than telephoto lenses before the trailing of stars due to the Earth’s rotation becomes obvious (unless of course, that’s the effect you’re trying to record).

There are three settings you can control that will determine the overall brightness of your image: the lens aperture setting, the camera ISO value, and the exposure length. These can all be independently adjusted. Each affects the final image in its own way.

  1. Set the lens aperture to fully open (its lowest “F” value), since you usually want as much light as possible to reach your camera. Closing the aperture slightly (e.g. one position from being fully open) prevents light from the very edge of your lens from reaching your sensor and can thereby sharpen the appearance of stars near the perimeter of an image. However, you might require a longer exposure time or higher ISO value to compensate for the associated loss in brightness. Experiment!

  2. Set the ISO level. Higher values increase the sensitivity of the camera’s sensor and so allow you to capture fainter light. However, higher settings also result in increased “noise” in your image. Fairly high values are generally required for astro-imaging. Use a value of ISO 1000 as a starting point.

  3. Set the exposure length. This can vary substantially and is affected by a number of factors external to your camera, such as your location, the quality of the sky, and the nature of your subject (what it is you’re trying to record). For your initial experiments, start with an exposure length of 10 seconds and increase the time from there, perhaps to as long as 5 minutes. You may need to reduce the ISO and/or aperture settings if such a long exposure is too much for your site. Set the length using the M (manual) setting on the camera. This typically allows you to specify durations from a tiny fraction of a second up to 30 seconds. The B (bulb) setting allows you to shoot arbitrary lengths beyond 30 seconds.
    These three settings work together to create your final image. You should experiment with various combinations to determine the best results. And note that your location plays a huge role in this. Shooting from a suburban backyard will give you vastly different results than under a dark rural sky. Your images can be overwhelmed by city light pollution in a very short time, whereas the same settings might give you an image that is actually too dark when obtained out in the country. The key is to experiment with your equipment to learn what it is capable of. Keeping a log book of your tests will accelerate your learning since it will be easier for you to identify what works and what doesn’t.

  4. Aim at a dark, unobstructed spot in the sky, away from any nearby ambient light sources such as street or house lights. Aiming at Polaris as an initial target can be quite interesting because it will let you easily see the effect of altering the exposure length on the trailing of the stars. Due to the Earth’s rotation, all stars in the northern hemisphere appear to move in concentric circles around Polaris. The longer your exposure length is, the longer the arcs that the stars describe around Polaris will be. Polaris is also bright enough to appear in the live view of some DSLR cameras and if so, can be used for focusing. For follow up nights, try shooting other sky regions (especially those areas containing some portion of the Milky Way) to see how these differ from shooting Polaris.

  5. Focus your camera as described earlier. If Polaris doesn’t appear in your live view, first use a brighter star for focusing and then switch your aim to the Polaris area. Be careful not to jostle the focus when changing your aim.

  6. Shoot a series of images with various combinations of lens aperture settings, ISO values, and exposure lengths. Keep track of what you’ve done in your log book so you don’t wind up having to repeat setting combinations.

  7. Review the images on your camera display to determine what seems to work best. You should also probably check the brightness setting of your camera’s display. Since most pictures are taken during the daytime, this is often set to be quite bright so that you can see the image properly in daylight. For nighttime use, you’ll probably want to lower the display’s brightness.

    If your camera displays an image histogram (most do), then this can be a valuable aid in determining a good combination of exposure settings. The histogram is a graphical view of the brightness range within the image. The horizontal axis represents the variation in brightness values, with the darkest pixels to the left and the lightest pixels to the right. The vertical axis represents the relative number of pixels at a particular brightness value: the higher the plot, the more numerous are the pixels at that particular brightness value.

    The histogram of most astronomical images resembles a steep mountain peak that tends to be closer to the left side of the graph than to the right. Translated, this shows you that the majority of the pixels are dark (due to the background sky) and only a small fraction that are bright (due to the stars and other objects in the scene such as meteors, auroras, and so forth). This is what you would expect. So if your “mountain peak” is at the centre or to the right side of the histogram, then you are over-exposing the image. The background sky will look too bright and washed out. Conversely, if the peak is hard over to the left side (or worse: the left portion of the peak is cut off), then you’re under-exposing and the sky will look very dark or black. You’ll also wind up losing brightness in the fainter stars and the objects of interest. Your background sky should be reasonably dark, but certainly not jet-black.

  8. Once you have adequately familiarized yourself with your equipment and completed this exercise a few times at home, consider repeating it at a location with a darker sky, such as FLO or the Lennox-Addington dark sky site. You’ll likely be amazed at the difference such a site makes for your images.

In follow-up articles to this one, I’ll examine various aspects of astro equipment, imaging techniques, target types, time lapse sequences, and processing techniques.

In the meantime … clear skies and good shooting!


NEW FEATURE:

Monthly Challenge Objects

February Lunar Challenge

For the first lunar challenge, I wasn't sure how difficult to make it, so I thought maybe we could start with the largest crater on the moon. Can you name it? Can you find it? Even an 80mm scope will do it.

February Deep Sky Challenge

NGC 1924 - The Orion Galaxy

We have all seen the Orion Nebula but who has seen the Orion Galaxy? Who even knew that there were galaxies in Orion? It turns out there are a lot of them. NGC 1924is a barred spiral galaxy, discovered by William Herschel in 1785. It lies 2 degrees west of M42. It is about midway between two 9th magnitude stars in a northwest to southeast line of stars. It is a 13.3 magnitude galaxy, so you can see it in an 8 inch (and maybe even a 6 inch) scope. However, you might want to use as much aperture as you can manage. Happy hunting! Please, let me know how you make out.


AstroNotes Bookshelf

Estelle’s Pick for January

Higher than Everest

An Adventurer’s Guide to the Solar System

By Paul Hodge


Announcements

  • The next members Star Party at the FLO is Saturday, February 20 with a thin crescent Moon that sets at 7:31PM

  • Winter Star Party List – FLO

  • March 17 - new moon - wear green and we will hunt for green stars and little green men

  • April 14 - waning crescent

  • Website and Email Addresses

    • The Centre is in the final stages of getting rid of its old web site, mailing lists and email addresses. The old ones can be identified by the ottawa-rasc.ca (dash) format while the new ones have the ottawa.rasc.ca (dot) format.
      The following email addresses should now be used:

president@ottawa.rasc.ca

meetingchair@ottawa.rasc.ca

webmaster@ottawa.rasc.ca

treasurer@ottawa.rasc.ca

secretary@ottawa.rasc.ca

astronotes@ottawa.rasc.ca

flo@ottawa.rasc.ca

contact@ottawa.rasc.ca

Each of these email address is automatically forwarded to the appropriate person. The old dash addresses will be disabled very soon.

Chris Teron, Secretary


Member News

Our Star Party Coordinator, Paul Sadler, recently sent out the following request for feedback on this year’s public star parties. In case you have not yet responded, the following is reprinted as a reminder.

I'm the Star Party Coordinator for 2018, and with input from various people, I have done up two surveys to solicit views from members about our approach to star parties.

The first survey asks you questions about our general approach to star parties (locations, logistics, themes) and can be found at:

http://polywogg.ca/rasc-ottawa-survey-2018-1-approach-to-star-parties/

The second survey is more precise about the actual dates for the star parties this year, soliciting views on individual weekends to target each month. It can be found at:

http://polywogg.ca/rasc-ottawa-survey-2018-2-timing-of-star-parties/

Both surveys are quite short -- there's a maximum of ten questions on the freebie version of Survey Monkey -- and will be open for voting / input for the month of February.

Tell me what you want to see different or the same in our scheduling of the star parties...

Paul

Next Meeting

7:30 PM Friday March 2, 2018 at the Canada Aviation and Space Museum (directions). Note there is a $3 parking fee for museum parking. The meeting runs until 9:30 pm.

PLUS: all our regular meeting features: Ottawa Skies, 10-minute Astronomy, Observer Reports, and of course, the beloved Door Prize!

All RASC monthly meetings are free and open to members and non-members alike. Refreshments will be available and this will be a wonderful opportunity to meet new friends who share a common interest and chat in a relaxed, stimulating and fun environment.  Please join us!


Centre Information

General enquiries: contact@ottawa.rasc.ca

To subscribe (or unsubscribe) to our members-only discussion list (rascottawa@googlegroups.com ) please contact secretary@ottawa.rasc.ca .

The Ottawa Centre 2018 Council

President: Tim Cole (president@ottawa.rasc.ca)
Vice President: Mike Moghadam
Secretary: Chris Teron (secretary@ottawa.rasc.ca)
Treasurer: Oscar Echeverri (treasurer@ottawa.rasc.ca)
Centre Meeting Chair: Oscar Echeverri (meetingchair@ottawa.rasc.ca)
Councilors: Carmen Rush, Gerry Shewan, Jim Sofia
National Council Representatives: Robert Dick, Karen Finstad
Past President: Gordon Webster

2018 Appointed Positions

Membership: Art Fraser
Star Parties: Paul Sadler
Fred Lossing Observatory: David Lauzon & Rick Scholes (flo@ottawa.rasc.ca)
Light Pollution Abatement: OPEN
Public Outreach Coordinator OPEN
Hospitality: Art & Anne Fraser
Stan Mott Astronomy Library: Estelle Rother
Ted Bean Telescope Library: Darren Weatherall
Webmaster: Mick Wilson (webmaster@ottawa.rasc.ca)
AstroNotes Editors: Gordon Webster & Douglas Fleming (astronotes@ottawa.rasc.ca)