Category Archives: Trivia

Hunting Comets and other faint objects in not-dark skies

Posted on by
8

AirGlow Comet [5_070386]

one hour payday loans

It turns out the much hyped PanSTARRS C/2011L4 Comet is not living up to the hype. Unfortunately failure to meet the over exhuberant expectations  is common since predicting brightness and visibility of an object like a comet is a difficult science. In fact, it’s part science, part black art and part good guessing – mostly the latter.

The photo above was taken on March 12 when the moon and PanSTARRS nestled closely together. The close quarters made finding the comet much easier despite the bands of clouds passing by.  The strategy for finding the comet in that case was simple: use a telephoto lens, put the moon at the right edge of the photo and take different exposures periodically and at different settings (e.g. +2, 0, and -2 stops). Then hunt for smudges.

The IDEAL telephoto lens would be one that was a few angular degrees wider than the difference between the moon’s position and the comet’s position. How to determine the position of each is discussed in the last section below. Figuring out the angular view of your lens is easy using online tools like this one from Tawbaware, makers of Image Stacker (like that program!). If you know the field of view at your minimum and maximum zoom, you can use that information to your advantage.

Finding the Comet with a Nearby Moon

The point at the moon strategy made finding the comet easy because:

  1. There is no way you’d be able to see the comet if you were not able to find the much brighter moon nearby.
  2. On that one night, the comet and the moon were within 4 degrees of one another.  That’s quite close.

I know some people tried to find the comet using wide angle lenses. That strategy might work, but the comet is such a tiny thing and it’s visibility is so tenuous based on the atmosphere, light pollution, and sky brightness that you may only realize – as many did – that you captured the comet after carefully inspecting your photos at home.

Contrails and Comet Tails [B_050938]

The truth is you are unlikely to see PanSTARRS by eye or in your camera’s view finder unless your conditions are nearly ideal.  Hopefully ISON which is coming in December will be brighter and better.

Finding the Comet when the Moon is Farther Away

The following night, both the comet and the moon had moved relative to the sky. On March 13, the moon was 12.5 degrees above the comet and about 4 degrees farther west (again, how I knew this is coming in just a minute).  So one simple strategy for finding the comet would be to zoom your telephoto lens so that it has a field of view of about 14 to 15 degrees in the long direction which for me, is 80 millimeters focal length on a 1.6 crop factor camera.

On a tripod with the camera in portrait orientation adjust the view so that the the moon is in the upper left of the frame. Shoot bracketed shots. Check the lower right corner of each one for the tell-tale comet smudge.  Keep readjusting the view so the moon remains in the upper left for each shot. Zoom out a little bit too, in case your geometry is a little off. Eventually as it gets dark enough or the sky clear enough you should find it.

In fact the way I found the comet last night without using my camera but by using my telescope. The program Clinometer (on my iPhone) measures angles. I sighted the moon with my 8″ Dobsonian telescope and measured the angle along the telescope barrel using the inclinometer program. I then lowered the altitude (elevation angle) of the telescope by 12 degrees to match the altitude of the comet. Then I slowly rotated the telescope northward until I found the comet.  It wasn’t easy from my urban location, but it wasn’t impossible either.  By the time I was able to find the comet it was only about 6 degrees high in the sky – that’s way too low if you have trees, hills, and houses nearby to deal with.  In theory, this strategy would work with a telephoto lens or with binoculars, however, binoculars need to be steady and where I spied from last night had streetlights in the distance and the flare and glare from those streetlights made finding the faint comet nigh impossible.

What if there is no Moon to Find the Comet With?

Unfortunately starting on March 14th, the moon will be quite far from the comet, so the opposite strategy is required:  Use a landmark in a known direction as the starting point and look “upward” from the horizon.  In other words, zoom your telephoto lens so that the field of view covers the angle from the horizon to the comets altitude (angle) above the horizon.  Don’t forget that as the earth spins this angle changes every minute! Orient you camera in landscape mode and point it as close as you can to the correct direction (azimuth). Look along the top of the frame to see if you’ve captured the comet.

IMG_1622.PNG

SpyGlass’s view shows the direction the camera is facing (Azimuth) and the elevation angle (Altitude)

But what direction should you point your lens or telescope? Use a compass application or actual compass. BEWARE however as the compass applications have lots of gotchas and are only accurate to about 5-10 degrees.  And if you aren’t sure how to use a real compass your local magnetic declination might bite you. Better would be a GPS with a built-in calibrate-able compass.  And perhaps even better still would be to use an application like TPE (which I discuss in my Catching the Moon Webinars) to calculate the correct azimuth from the location you plan to stand.  An application that might help a lot is “SpyGlass”
however don’t forget that I found the directional accuracy of my iPhone and iPad to be pretty poor.  Being off by 5 degrees may mean looking in the wrong place.

How Do I Know the Altitude and Azimuth for the Comet?

Stellarium_MoonMarch14

Unfortunately, that’s a tough one.  I use the free program Stellarium. I then added the comet to the “Solar System Data Base” (search around on the web and you’ll find instructions). I selected my viewing location, dialed in the time, did a search for good ‘ol C/2011 L4 and let it tell me the azimuth and altitude.

PanStarrs_March14

Above I’ve dialed up the time and clicked the moon. The highlighted line shows me the azimuth (direction) and altitude (angle above the horizon) for the moon which at that time are 264 degrees or just a little south of west, and 30.5 degrees high.  Clicking on the comet shows 272 degrees – a tiny bit north of west and 9.5 degrees.  So now we know that the comet will be 8 degrees north and 21 degrees south of the moon – and that won’t change significantly for the rest of the night.

Since we also know the direction for the comet is about due west at this time, we can apply the telephoto-lens horizon trick I described earlier.

Another way you can find the azimuth and altitude is by checking my animation HERE – note that the animation is correct for San Francisco  (and most places nearby).  There is also a table of the azimuth and elevation in the text of the Flickr post.

 

By the way, one way to find the right spot on the horizon is to use the sunset location as a guide.

CometIllustration

Now Open: The Store

Posted on by
Reply

So many of our students at our webinars and workshops as well as our website visitors ask us about our Notes, Instructional Videos and Photoshop additions that it was time to make it possible to deliver them.  So we created a digital store integrated with this blog.  In fact, we’ve only had the store open for two weeks and already we have a clear bestseller:

Advanced Stacking Action Bundle
Advanced Stacking Action Bundle
Includes the easy to install Advanced Photoshop action, a 2 hour video on creating star trails, notes (PDF) on creating star trails and practice files. Compatible with Photoshop CS4, CS5 and CS6. NOT Compatible with Photoshop Elements, Lightroom or earlier versions of Photoshop.
Price: $31.95

Making It So

But making it so was not a straight line path from where we were to where we wanted to go. We toyed with a variety of things to create a store. Using PayPal buttons directly – simple and maddeningly painful at the same time, using ZenCart, and looking at a few others solutions.

Ultimately we wanted something relatively simple. Something that could handle a small, but growing array of products – all digital, and that would be relatively easy to integrate into the BLOG without breaking off limbs or snapping frazzled nerves. We settled on WP E-Store. It’s neither flawless nor as spectacularly simple to get working as we would want it to be, but it is well featured and well supported.

I should probably make a note that I, Steven, am capable of twiddling with HTML, circumspect of all CSS (because I’ve never found it to be pleasant to deal with), able to write JavaScript and PHP when needed – but prefer not to. If none of that makes sense to you, that might be fine unless you decide to embark on creating a store because I’ve already learned that I have needed all those skills in some form already.

We want a store secure against theft, hacks and intrusion, that is easy to use and easy to configure. We also want to offer discounts to people who attend our Webinars and Workshops as well as repeat customers. Using PayPal directly proved unmanageable. Our store also needs to manage the digital content that gets created on an almost daily basis. We had no expectation or illusion that we would sell prints or images through this store. In fact, Steven has a well featured means for selling hard goods through ZenFolio. Interestingly most Steven’s print sales occur in the United Kingdom – likely because they see Steven’s images in the Royal Observatory. ZenFolio is great for selling prints and mounted images – even iPhone cases!

WP eStore

What we like about WP eStore is that it does handle the key things we want: digital sales through PayPal (and credit cards), and secure encrypted links for digital goods and a nice simple interface for our clients and customers.

What WP eStore lacks, however are a number of things including a simple way to process refunds (always a painful thing through PayPal), more configurability of the display of products and the shopping cart and a few gotchas in the way you configure products. For example, with WP eStore you can specify a “thumbnail” image for a product – but by default the thumbnail will be clickable and go to the thumbnail image. That’s completely silly.

Of course since we purchased WP eStore we’ve also noticed a lot of other competitors, including WooCommerce which looks snazzy, but it appears you get nickeled and dimed to death to get all the pieces together.

Biggest Obstacle

The biggest impediment to our eStore is our theme.  Theme? Yes, the page layouts are controlled by a WordPress theme. Unfortunately the theme we like is not as customizable as we’d like. That spiffy graphic at the top, for example clutters up the store so we are planning to either switch themes or hack up the Twenty-Ten theme we are using.

What is Ahead?

One day we hope to also offer free and paid Webinar registration through the store. And perhaps even workshops, too. Meanwhile the place to find webinars and workshops is either at:

Still reading. Perhaps you just arrived at the best part… a discount coupon good for 20% off of everything in the store:    WELCOME

Oh, and if you would like to see if a Webinar will work for you and your set up, you can join a FREE webinar to kick the tires on March 12, 2013. We hope to see you there!

Untimely Battery Death: How to Avoid It.

Posted on by
9

As a night photographer I’m a proponent of the philosophy of “carry a big battery” and you’ll never miss that shot.  However I learned a hard lesson about my corral of batteries that I feel I must pass on before you too shriek in terror when you find your once reliable battery has met an untimely (and inconveniently timed) demise.

Lithium Batteries are Greatly Disturbed By Heat

This was the lesson I learned the hard way. I had a stable of five fully charged batteries ranging in size from 1800 milliamp hours all the way up to 8,000 milliamp hours. I kept them in a shaded part of my car through some summer days in the San Francisco Bay area.  And that was how I learned that Lithium + Fully Charged + Heat = premature death.  The two low capacity batteries previously allowed me two and a half hours worth of continuous night exposure. Now they each last about 12 and 15 minutes.  The three HUGE batteries that could easily power my camera all night long for continuous exposures now have about the same life in them as my regular 2000 mA hr batteries – that is, about 1/3 as long as they used to last.

I learned why my brutish batteries became so feeble at Battery University.  In a nutshell I discovered that storing batteries cool (less the 86 F) and at 40% charge is the most effective at prolonging their life.  What I do now is keep all of my batteries in a separate pouch which I take with me into my office or home – even if I leave my camera equipment in the car.

I’d like to heed the 40% storage method – but not all of my chargers accurately tell the battery capacity. And worse, when I’m running out for a night of exposures, I usually don’t have an extra hour or two to fully charge my workhorses.

And yes, repeated discharge and recharge of those batteries will diminish their life, but NOT as fast as fully loaded batteries baking at a mild 90 degrees or more.

 

Astronomy Photographer of the Year: 2012 Edition

Posted on by
3

The Royal Observatory, Greenwich has just announced the winners, runner ups and highly commended entries for this year’s contest.

You can watch two of the judges discuss this years winners and runners up.

The entire list can be seen on the Royal Museum’s winners page here and in person at an exhibit. Below are those that I really liked – displayed with permission, of course.

M51_The Whirlpool Galaxy


M51 – The Whirlpool Galaxy
Martin Pugh garnered top prize for this amazing photo taken over 8 hours in the Sierra (Astrophotography by Martin Pugh)

Simeis 147 Supernova Remnant

Simeis 147 Supernova Remnant

by Rogelio Bernal Andreo (DeepSkyColors.com)

Like me, Rogelio is a San Francisco Bay Area resident. Obviously Mr. Andreo has mad skills and dedication to astrophotography. See his portfolio for more work.

Lost in Yosemite [C_033706] Runner Up - Astronomy Photographer of the Year, 2012

Lost in Yosemite
by Steven Christenson


It would seem that Rogelio and I are linked somehow. We both won in our categories in 2010, and we both were runner’s up in 2012. Above is my runner-up shot. Click the picture and read the story about the lost hikers we met on our night hike up Half Dome.

You can view a slides show of all the photos submitted to the contest here. Warning: There are a LOT of them – 688 in the over teen category (I’d call it adult, but that word seems to have a different connotation).

Why your Streak is (probably) NOT a Meteor

Posted on by
33

Satellite or Meteor? [C_061879] So you took our advice or perhaps the advice of someone more clever than us and have captured a streaking bit of flaming cosmic stuff that some people call shooting stars. We do not want to rain on your parade, but let’s first get something straight: that flaming streak is more properly called a METEOR.  If it hit the ground, it’s a meteorITE.  If it in fact struck YOU, well you’re a lucky one!  No one in recorded history has ever been directly struck by a meteor EVER. We know what you’re thinking (really, we do). You’re thinking, but dudes: “What about the German boy who was hit in the hand, or the lady who had one bounce off her furniture and hit her in the leg or the man who suffered a broken finger when one crashed through his windshield and bounced off his steering wheel.” Sorry those were METEORITES apparently you weren’t paying attention when we explained the difference between meteors and meteorites.  Did anyone ever find a meteor on the ground? NO THEY DIDN’T… they found a meteorITE. Are we harping? Sorry.

Here is the sad news. You probably DID NOT catch a meteor (or meteorite) in your photo. Terribly sorry to tell you that. Go ahead, bring the photo and plop it in front of us. Claim what you want… but we are skeptics. Below are some things to rule out before we will conclude you have indeed caught a meteor.

Why Are We Such “Meteor Haters”

Hey, don’t put words in our mouth. We LOVE meteors. We just don’t believe you caught one. And here is why.

  1. Meteors move VERY, VERY fast across the sky and therefore across your image.
  2. Only exceptionally bright meteors throw out enough light in their rapid transit to even  register on your sensor or film.
  3. Just because you SAW a meteor occur in the direction your camera was pointing when  it was taking a picture doesn’t mean it registered.
  4. And it probably wasn’t a meteor.
  5. Besides, we think you’re wrong. So there.

Ok, so we admit to being a bit sour about it. After all, collectively we have shot about 20,000 (TWENTY THOUSAND) frames trying to catch meteors. And how many did we get? About 100.  We didn’t get so few just because we suck at it.

Below the Belt [5_020853] CARMAic Visitor from Cygnus [5_034154]
Dew Drop In [C_019416] Chiplet [C_034134]

Perseus slays Little Bear, oh my! [B_032691]

Of those 100, about 20 are readily noticeable. Of those 20, perhaps 10 are well captured. And of those 10, sigh, only a few really stand out.   But perhaps we should admit that we – like you – didn’t make all of those attempts under the best conditions. No, Like you, we took most of our shots when there was moonlight, light pollution, streetlights, and other impediments and the result was as you see at the left here: the meteor is almost impossible to see.  Like you we’ve SEEN a lot of meteors. And like you, most of the time the meteor we saw was regrettably not where we had pointed our cameras.  It’s a game of (very low) odds, after all.

Why You Didn’t Catch a Meteor (or maybe you DID!)

So many times we have seen people post their “brilliant meteor shot”. Almost exactly as many times we noticed one or more of the following:

  1. There are tell-tale flashing white, green or red lights. The tale those lights are telling is “aircraft” but the gleeful meteor hunters have their fingers in their ears.  Look closely at your shot to see.
  2. The streak bends or changes direction and the curvature is not due to field warp (as with e.g. a fish-eye lens). Sorry, but only airplanes curve like that.
  3. The shot immediately before or the shot immediately after the prize has the continuation of the streak. There is a 0.000008% chance of capturing a single meteor that spans more than one frame.
  4. The shot was at low ISO (less than 400), a high f/stop (anything above f/4), a narrow field of view or for a very long time. For a meteor to register you’d need a super slow flaming fireball of a meteor. If in fact you got one, well good for you and we are jealous.
  5. After ruling out aircraft, most people fail to rule out the next most obvious possibilities: satellites, flare and moths.   Yep, moths or any other bug that might fly through a source of illumination. We’re pretty sure you’ll be able to tell if it was a firefly though. Satellites are a little sneakier. They can – and do appear, move through the sky and disappear.  And they can fade in and out, too.

Satellites

There are MANY satellites in the sky. So many that we catch them ALL the time.  About every shot that doesn’t have a stinkin’ airplane seems to have a bloomin’ satellite in it.  Most satellites are quite dim and you don’t see them easily with the naked eye, however there are a few bright ones and one family of satellites that is EXTREMELY bright for a brief time.  We’ll get to that in a minute.

Meteors and Meteorites Have A Signature

Star Man and Perseus [C_059960-1]

Perseid Meteor, Milky Way and Galen’s Arch, Alabama Hills, Lone Pine, California, August, 2012

Most meteor streaks have the following things in common:

  • They brighten rapidly and dim a bit more slowly.
  • They are asymmetric (the brightening phase and dimming phase rarely look exactly alike)
  • Because of the two things above, meteors streaks rarely, VERY rarely have nice round ends – generally one or both ends are tapered.
  • Often meteors are colored!  The Perseids, for example, are often green, the Orionids are often yellow.

Perseid meteor traveling from the lower left to upper right. Note the changes in brightness and color

About those Bright Satellites

Satellites seem to wink in and wink out because they are illuminated by sunlight.  You’ll rarely ever see a satellite at the midnight hour because the earth blocks sunlight from striking the satellite. However for as much as 3 or 4 hours after sunset or before sunrise (and more at other elevations), a satellite may move quickly and stealthily out of the earth’s shadow into a place where it can be seen clearly against the dark sky.  Or it might do the opposite: streak across the sky and then wink out when it enters the earth’s shadow. But there is one spectacularly bright satellite. Sorry did we say one, we meant 90 of them!  The family of satellites named Iridium. The name Iridium refers to the planned 77 communication satellites – the atomic number for Iridium is, 77.  The Iridium satellites exist to service those big, bulky sat phones – about the only option you’ve got if you need phone service in the Bering Sea or on an ice shelf in Antarctica.

Satellite Flash (Iridium) [5_033852-4br]

Iridium and “Flares”

Because the Iridium satellites are highly polished, and because each of those 90 objects are circling the earth every 100 minutes or so at a relatively low orbit, it’s not at all unlikely that one will reflect the light of the sun toward you! If you happen to be in just the right spot the brightness is extreme.  How extreme? Astronomers use a stellar magnitude scale. On this scale the smaller the number, the brighter. The stars in the Big Dipper are around 3, the brightest star, Sirius, is -1.46; Venus, the brightest planet at its shiniest is -4.6 and the brightest Iridium flares are -9!  What this means is: Iridium flares can be 100 times brighter than Venus or about 2,000 times brighter than the brightest stars!

Iridium satellites move swiftly but nowhere near as fast as meteors so they are far more likely to leave a mark in your photo than a meteor. Iridium flares behave very predictably. They start dim, slowly grow brighter and then slowly fade all the while that they transit the sky. If you want to mess with someone, use an Iridium sighting tool, figure out when and where to look in the sky and tell people nearby: “I have this sense… that something strange is about to happen… right … up … there”.  If you time it well people will be so amazed they may fall down and worship you. Time it wrong and they will laugh. Either way it’s great fun.  [NOTE: That link will only work in MILPITAS, CA - you need to use your GPS location].

The thing is, however that your camera doesn’t know when the grand entrance is going to happen and it will dutifully record the event while you’re busy chatting with your fellow night denizens.

Meteor Radiant Point (Delta Aquarid Meteor Shower)
Unfortunately we ran out of space before we got a chance to explain to you that even your correctly identified meteor is probably incorrectly identified as a “Perseid Meteor”.

In summary, we TOLD YOU you didn’t catch a meteor!

But if you think you did and are willing to stand some public humiliation at being proved wrong, please post ONE alleged meteor shot below in the comments.  Please also give us the date, time, timezone and GPS location so we can make sure it wasn’t an Iridium Flare. Wait, why make us do that… do it yourself!

Oh, one last thing… did you find this article interesting? Amusing? Alienating as hell?  Please share it!