8
The Essential Journal for Amateur Astronomers Around the World! Issue 82 Spring 2014 $6.50 US Amateur Astronomy Magazine Remembering John Dobson Mel Bartels recounts his personal interaction with this inspiring amateur astronomy legend Binocular Summation Part II - Arne Otte does comparative analysis. How much can you see with two mirrors and two eyes versus one? Observing Deep Dky Treasures Looking South Touring The Trumpler Classes Sunspots Amateur Astronomy Visits Ewen Whitaker -The Man who named the Moon Star Party Calendar Uncle Rod’s Cracker Barrel Image Gallery Shorts From Down Under Working with Photoshop Layer Masks - How to Get the Most Out of Your Data The Grind: A Mirror Maker’s Journal of inspiration and perspiration

Amateur Astronomy - rspec-astro.com · Astronomy for a while, I am not the worldes most serious amateur astronomer. Oh, I am serious about having fun with astronomy, mucha-chos. And

  • Upload
    others

  • View
    0

  • Download
    0

Embed Size (px)

Citation preview

Page 1: Amateur Astronomy - rspec-astro.com · Astronomy for a while, I am not the worldes most serious amateur astronomer. Oh, I am serious about having fun with astronomy, mucha-chos. And

The Essent ia l Journal for Amateur Astronomers Around the World!

Issue 82Spring 2014 $6.50 US

AmateurAstronomy

Maga z i n e

Remembering John DobsonMel Bartels recounts his personal interactionwith this inspiring amateur astronomy legend

Binocular Summation Part II - Arne Otte does comparativeanalysis. How much can you see withtwo mirrors and two eyes versus one?

ObservingDeep Dky TreasuresLooking SouthTouring The Trumpler ClassesSunspots

Amateur Astronomy Visits EwenWhitaker -The Man who namedthe Moon

Star Party CalendarUncle Rod’s Cracker BarrelImage GalleryShorts From Down Under

Working with PhotoshopLayer Masks - How to Getthe Most Out of Your Data

The Grind: A Mirror Maker’s Journal of inspiration and perspiration

Page 2: Amateur Astronomy - rspec-astro.com · Astronomy for a while, I am not the worldes most serious amateur astronomer. Oh, I am serious about having fun with astronomy, mucha-chos. And

40 www.AmateurAstronomy.com Spring 2014 Issue # 82

Unk Takes the Fingerprintsof the Stars

As y’all have no doubt gathered ifyou’ve met me, or even if you have justbeen reading my column in AmateurAstronomy for a while, I am not theworld’s most serious amateurastronomer. Oh, I am serious abouthaving fun with astronomy, mucha-chos. And I am serious about showingother people how to have fun in ouravocation. But doing Real Science aspart of my amateur astronomy career?No. Not until lately, anyhow.

I am an astronomy educator at a uni-versity, but I’ve kept that part of myinvolvement in the science more or lessseparate from the amateur side of life.When I’m wearing my amateur hat, Ijust like looking at pretty stuff and tak-ing pictures of pretty stuff. As an ama-teur, I approach astronomy as a

descriptive discipline, like the zoolo-gists of old who spent all their time col-lecting butterflies. The serious stuff isfor the classroom.

That’s just changed a little bit. Idon’t think I will suddenly and com-pletely stop being that most amateur ofamateurs when I am out on the observ-ing field hanging with my buddies andoohing and ahhing over M13, but, as Iwrote here not long ago, change issometimes good in astronomy. Doingdifferent things is the way to avoidburnout.

So it was that when I got an emailfrom Tom Field, author of the RSpecspectroscopy software asking me if I’dlike to try his program and RobinLeadbeater’s Star Analyser diffractiongrating, to try my hand at taking stellarspectra, I didn’t say “no.” It actuallysounded like fun. I’ve long been inter-ested in stellar evolution and spectral

classification, and have been teachingthe basics of those things for going ontwo decades. Emailing with Mr. Tom, itdawned on me I had never got out andtaken stellar spectra of my own withmy own telescope. Maybe it was timeto get a little more hands on.

Not that I wasn’t skittish about mak-ing it all work. A look at Tom’s RSpecwebsite, “Real Time Spectroscopy,”(http://www.rspec-astro.com/) cluedme in that this was one powerful pro-gram. Reading there, and looking at theposts on the RSpec Yahoogrouprevealed people are doing stuff like tak-ing the spectra of quasars and demon-strating their redshifts with the aid ofthe software. Unk? About as far as I’vegone is showing undergraduates how touse a simple spectrometer to look at theemission spectra given off by dischargetubes in a warm, quiet classroom.

Uncle Rod’s Cracker BarrelArticle and images by Rod Mollise

Page 3: Amateur Astronomy - rspec-astro.com · Astronomy for a while, I am not the worldes most serious amateur astronomer. Oh, I am serious about having fun with astronomy, mucha-chos. And

Spring 2014 Issue # 82 www.AmateurAstronomy.com 41

Mr. Field, however, assured me Icould do it, gave me instructions fordownloading the program from hiswebsite, and got the grating, a 100-linejob (http://www.rspec-astro.com/star-analyser/), on its way to me. I hoped hewas correct, because I suddenly foundmyself getting right excited about tak-ing stellar spectra.

When I got Tom’s program down-loaded and installed, I was relieved tofind that while it was obviously verycapable and featured a ton of options,

it was also amazingly user friendly. Itsinterface is very well designed, and itwas easy for me to figure out basicoperation of the software. That was thegood. The bad, as you might expect,was that the weather took a turn for theworse as soon as the Star Analyser 100grating arrived.

Luckily, Mr. Field had sent me asample image of Vega and its spectrumto play with, so I was able to sit downand get acquainted with the programindoors. RSpec was resoundingly easy

to use in Chaos Manor South’s diningroom, but I suspected it would be a dif-ferent story out on a dark field in themiddle of the night when I began tak-ing my own spectra. Before I couldeven think about doing that, though, Ihad to decide which camera to usewith the Star Analyser and RSpec.

What I had on hand was an SBIGST2000 CCD, a Mallincam Xtreme, acouple of Canon DSLRs, a webcam-like ZWO ASI120MC planetary cam-era, and my old Meade color DSI. Tom

The Star Analyser 100 1.25” f i l ter cel l and looking through the cel l at the grat ing and spectra

of the Star Capella

Page 4: Amateur Astronomy - rspec-astro.com · Astronomy for a while, I am not the worldes most serious amateur astronomer. Oh, I am serious about having fun with astronomy, mucha-chos. And

42 www.AmateurAstronomy.com Spring 2014 Issue # 82

suggested the Mallincam might be agood place to start, but I demurred. I’dhave had to involve a frame-grabberand software to convert the Xtreme’sanalog video to digital form. As for thestill CCDs and the DSLRs? I thoughtany of them might be a bit of a handfulin the beginning. Well, what about thatZWO? People are using them foreverything from the Moon and planets,to hydrogen alpha imaging of the Sun,to deep sky astrophotography. Whywouldn’t it work as a spectrograph?(If’n you are new to this stuff, a spec-trograph is an instrument that takesimages, spectrograms, of spectra, thepretty rainbows.)

It appeared it would work withRSpec—the program recognized thecamera/driver, anyway. As soon as Iplugged it into the PC, RSpec’s videomodule began displaying video, andindicated it was ready to record.

When I finally got clear skies on aclear but cold January Friday, I loadedup the telescope, mount, camera, andlaptop and headed for our club dark C-8 Rear cell setup with flip mirror

The RSpec Display

Page 5: Amateur Astronomy - rspec-astro.com · Astronomy for a while, I am not the worldes most serious amateur astronomer. Oh, I am serious about having fun with astronomy, mucha-chos. And

Spring 2014 Issue # 82 www.AmateurAstronomy.com 43

site. Which scope? My most used SCT,a Celestron Edge 800, “Mrs. EmmaPeel.” As long as your telescope canachieve focus with a camera, it willprobably work with RSpec and the StarAnalyser grating, but my sense is thatmore focal length is probably betterthan less for this application. Themount was my Celestron VX GEM,which is light and easy to tote aroundand has great tracking and go-to.

The sky was almost 100% cloud-free when I pulled onto the club field,which was a good thing for observing,if not such a good thing for comfort. Iglanced down at the temperature dis-play on the dashboard of the truck. 39Falready and the Sun wasn’t even downyet. Bundled up in my heaviest coat,the one that allowed me to surviveBath, Maine one winter, I got to workassembling the telescope, mount, andcamera.

The setup on the SCT’s rear cell wasthe almost the same as what I use forlunar and planetary imaging: Meadeflip mirror screwed onto the rear port,12mm reticle eyepiece in its focuser,and the ZWO in the camera port. TheStar Analyser grating, which comes in astandard 1.25-inch filter cell, wasscrewed onto the camera’s 1.25-inchnosepiece. The only difference frommy planetary rig was that the camera

went directly into the flip mirror with-out a Barlow. I figgered a smidge over2000mm would be enough focal lengthfor spectroscopy.

Why did I use the flip mirror? TheZWO’s chip is small, 1/3-inch, andeven without a Barlow and with accu-rate go-to, I thought the flipper wouldmake star centering easier. With the flipmirror in place, I flip the mirror down,center the target in its eyepiece, flip themirror up, and the object is guaranteedto be in the field of the camera. In addi-tion, the flip mirror is set so what’s infocus in its eyepiece is in focus in thecamera with maybe just a little fine-tuning required.

Alright, time to get to work. TomField suggests starting with Vega oranother bright star of spectral type A(y’all still remember “Oh Be A Fine

Girl Kiss Me,” I hope). When you arecalibrating your spectra later, you willneed to find the star’s h-beta line, andthat is strong and obvious in A stars,and especially in bright Vega. Alas,Alpha Lyrae was within 10-degrees ofthe western horizon, and given the see-ing—even higher altitude stars weretwinkling like crazy—was a no-go.What then? Rigel was perfectly placedin the east. It’s a B type star, not an A,and the Balmer lines are not as promi-nent in its spectrum, but I reckoned itwould do.

The most surprising thing? Despitethe cold and my relative inexperiencewith RSpec, I had no trouble getting thestar onscreen. Centered Rigel in the ret-icle eyepiece. Flipped the mirror up.Lit-off RSpec, hit the Live Video tab,and there was Rigel. What was reallycool, though, y’all? In the main display

Video of Rigel

Rigel

Page 6: Amateur Astronomy - rspec-astro.com · Astronomy for a while, I am not the worldes most serious amateur astronomer. Oh, I am serious about having fun with astronomy, mucha-chos. And

44 www.AmateurAstronomy.com Spring 2014 Issue # 82

area of the program, I was seeing thegraph of the star’s spectrum—live. So,that’s why Tom calls his program“Real Time Spectroscopy.”

It was far too cold to make me wantto play with Rigel’s spectrum out onthe field, so I recorded it for later pro-cessing. One thing was obvious with-out processing of any kind; the graphwas showing plenty of the dips thatrepresent absorption lines. It was clearthe simple rig was picking up a fairamount of detail in the star’s spectrum.

Before mashing RSpec’s recordbutton on, I centered the star a littlebetter on the program’s video displayand placed it within the two movablebars that are used to bin the image forthe best image scale. I positioned Rigelon the left and its rainbow on the rightusing the program’s rotate tool slider(star on left and spectrum on right isthe normal format for spectroscopicimages, and that’s the way your starsand spectra need to be for RSpec towork right).

I fired off 15-seconds of video ofRigel, took another sequence as“insurance,” and began ponderingwhat else to shoot. Alnitak was nearby,and while it’s even hotter than Rigeland has even less prominent Balmerlines, I went for it anyway. I followedup with a cooler star, Capella, since itwas bright and nearby, and finally gotan A star with Sirius, a natural, though

he was low in the sky and hoppingaround like mad in the poor seeing. Ihoped RSpec’s image-averaging fea-ture could fix that.

What then? It was now truly, nofooling, honest-to-god c-o-l-d. I’dchugged about half a Monster EnergyDrink earlier, and had set it aside whileI was doing my spectroscopy. I wentback to it now and was not exactly sur-prised to find what was in the can wasa Monster slushy. Chaos ManorSouth’s warm den was sounding betterand better. Especially when the nextcold front began to push in at mid-evening. Ice was forming on my equip-ment cases, scope, and me. Time toload up and skedaddle.

Back at home at Chaos ManorSouth with the gear unloaded, I washappy to be out of the cold and sipping“sarsaparilla.” Scanning the cablechannels revealed Friday night TV is awasteland, with nothing at all on 300plus freaking channels. I settled foranother amazing (uh-huh) episode ofFinding Bigfoot and was soon snooz-ing in my chair.

Come Saturday morning I wasready to start on what I figgered wouldbe the real work of spectrometry withRSpec, processing the sequences I’dtaken. First, however, I needed someinstructions. RSpec really doesn't haveany yet. Mr. Field has writing a manu-

al on his to-do list, but tells Unk thatthus far he’s been too busy getting theprogram working as well as possible toget to that. In lieu of a manual, there isa series of excellent instructionalvideos on the web you can access fromwithin the program. I watched thevideos and made up my own shorthandlist of instructions on how to calibratespectra.

When RSpec is running, you openyour video file, and once more rotatethe image with the slider control tillthe star is on the left and the spectrumon the right (RSpec records raw video,so your rotation of the star in livemode is not preserved). When that’sdone, you again position the star andspectrum inside the two mouse-mov-able bars on the video display for cor-rect image scaling. If the graph isn'tmoving around too much, you can justpause it, scroll through it with a sliderto pick out a particularly nice frame,and proceed to calibration. If it isjumping around due to seeing, youmight want to click the “average” boxto steady it down a bit before choosinga frame and beginning calibration.

Calibration is the heart of your task.You've got a spectrogram of your star,a graph showing dips that representabsorption lines. However, the X-axisof the graph is in pixels, notangstroms, and is useless for figuringout which lines are which, which lines

Sirius

Page 7: Amateur Astronomy - rspec-astro.com · Astronomy for a while, I am not the worldes most serious amateur astronomer. Oh, I am serious about having fun with astronomy, mucha-chos. And

Spring 2014 Issue # 82 www.AmateurAstronomy.com 45

represent which elements, that is. Youfix that by calibrating your spectro-gram, changing those pixels toangstroms (or nanometers if’n you pre-fer).

Despite my fears, calibration turnedout to be easy. Step one is to open thecalibration window, natch. You thenclick on the peak in the graph formedby the star’s image, the big spike on thegraph on the left. Next, and a littletrickier, you have to click on the dip onthe star’s spectrum that represents thehydrogen beta absorption line. That isnot difficult if your star has a prominentline at the h- beta wavelength. WhileRigel didn't show as prominent a line asVega would have, it wasn’t too hard topick out the h-beta absorption line.How do you know which dip in yourgraph is the one for the h-beta line? Itshould be the first big valley to the leftof the spectrum’s peak. Calibrationdone, click “apply” to get to themoment of truth.

To find out if you did good nor not,you mash the “elements” button in thetoolbar up top (three vertical lines). In

the window that appears, select“Hydrogen Balmer Series.” That makesvertical lines representing the good oldBalmer lines appear overlaid on yourspectrogram (the graph). Does thehydrogen beta line (you can run yourmouse over the lines to identify them)pass through the dip you identified asthe hydrogen beta line on the graph?Do the other Balmer Series lines coin-cide with dips on the graph? If so, youare in like Flynn.

My results? Purty good. Maybe notperfect, but purty good, though some ofmy dips didn't quite line up perfectlywith the superimposed lines. I suspectthat was mostly due to seeing. Unk’sfumble-fingeredness in clicking in theright spots on the graph was also nodoubt responsible for some of the error.

What next? Once you’re calibrated,you can go on to identify the other linesin your spectrogram. RSpec provideslibraries of professional spectra forcomparison purposes as well as a selec-tion of elements (the vertical overlaidlines) in addition to the Balmer Series.Your finished spectra, which RSpec

calls “Profiles,” can be saved, export-ed, and printed.

What you do with your profiles afteryou have them is up to you. It’s fun justto be able to see for yourself how spec-troscopy works, and to marvel at thefact that you can see what the stars aremade of using your little telescope.There are also opportunities for ama-teur spectroscopists to contribute to sci-ence. Amateur spectra of transient phe-nomena like novae and comets can beparticularly important, since the prossometimes don’t have time to getdata—or enough data—during thosefleeting events.

To say I was thrilled with my resultswith this incredible program and grat-ing would be an understatement,muchachos. I was frankly dumbfound-ed by how well and easily RSpec andthe Star Analyser worked. Will this leadto Uncle Rod becoming more science-centered in his amateur astronomy?Well, I wouldn’t say that, but I will sayI am having a wonderful time takingthe fingerprints of the stars.

BUY beautiful Hubble NASA high qualityastronomy space pictures, posters, slides,and backlit transparencies from outerspace programs and spacecraft missions tothe Moon, Mars, Jupiter, Saturn, and pho-tos of the Earth from space.

Page 8: Amateur Astronomy - rspec-astro.com · Astronomy for a while, I am not the worldes most serious amateur astronomer. Oh, I am serious about having fun with astronomy, mucha-chos. And

Spring 2014 Issue # 8276 www.AmateurAstronomy.com