introdution to astro photography

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INTRODUCTION TO ASTRO-PHOTOGRAPHY Stillwater Stargazers March 2016 By Mark Casazza

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Page 1: Introdution to astro photography

INTRODUCTION TO ASTRO-

PHOTOGRAPHY

Stillwater StargazersMarch 2016

ByMark Casazza

Page 2: Introdution to astro photography

Agenda Basic concepts Cost from $5 to $50,000+ Planning Capturing Processing

StackingDevelopingPrinting

Page 3: Introdution to astro photography

Basic Concepts

Page 4: Introdution to astro photography

Basic Concepts Taking a picture of the dark

High ISO (gain) – adds noiseLong exposures – adds noiseVery dim objects – signal strength ~ noise level

This is a battle against noiseLots of pictures – coax the signal from the noiseCool the electronics – minimize the noiseCalibration frames – subtract the noise

Page 5: Introdution to astro photography

Why Raw and not JPG Compression

Small deviations are lost in compressionThis is your data being destroyed!

14 bits vs. 8 bits16384 shades vs. 256 shadesYour data: 800 to 1600 vs. 12 to 25 shades64x more data!

Page 6: Introdution to astro photography

Equipment Cost

Page 7: Introdution to astro photography

This doesn’t have to be expensive The $3.95 budget

Modern Android 5 (Lollipop) cell phone○ http://www.camerafv5.com/pages/manual-cam

era-controls-table.phpFV-5 software – $3.95Deep Sky Stacker – FreeComputer to process – Okay so you need

one of these too.

Page 8: Introdution to astro photography

FV-5 cell shot Camera: LG-H815 Exposure: 30 sec F/1.8 ISO-2700 http://a.disquscdn.com/uploads/

mediaembed/images/2914/3911/original.jpg

Page 9: Introdution to astro photography

But you can go nuts

http://downthewormhole.blogspot.com/2011/05/das-planewave.html

Page 10: Introdution to astro photography

What Serious Investment Buys

Page 11: Introdution to astro photography

What was that? Planewave 12.5” CDK: $12,500 Apogee U16: $17,500 Paramount Me: $15,000 Optec 3” focuser: $900 Filter wheel & filters: $1,000 Pick off mirror Guide scope Motorized focus

Page 12: Introdution to astro photography

My Rig Mount: Orion EQ-G Primary Scope: Explore Scientific ES ED 127 Primary Camera: Full Spectrum Canon Ti1 Guide Scope: Orion “Short Tube 80” Guide Camera: Meade DSI Pro Focuser: Rigel n-step with USB and temp Image Capture: Backyard EOS

Test driving Sequence Generator Pro Computer: eBay Dell Laptop

Page 13: Introdution to astro photography

My Rig

Page 14: Introdution to astro photography

My Dark Sky Setup

Page 15: Introdution to astro photography

Session Planning

Page 16: Introdution to astro photography

Planning – What to shoot What is your field of view?

Sensor size (Canon T1i is 22.3mm X 14.9mm)Focal Length of lens or scope (952mm)FOV = sensor/focal length * 57.3

○ 22.3/952*57.3=1.3 X 14.9/952*57.3=0.9Look for objects that fill up at least 40% of the field

What is up tonight? How late do you plan to stay up? Where are you?

Page 17: Introdution to astro photography

Software Tools Spreadsheet with NGC/IC

My creation - I can provide Sky Tools 3 ($100 or $125) TonightsSky.com (shameless plug)

Page 18: Introdution to astro photography

Sky Tools 3

Page 19: Introdution to astro photography

Other Planning to Consider Object surface brightness and your SQM Weather

http://forecast.weather.gov/MapClick.php?w0=t&w1=td&w2=wc&w3=sfcwind&w3u=1&w4=sky&w5=pop&w6=rh&w7=rain&w8=thunder&w9=snow&w10=fzg&w11=sleet&w12=fog&w13u=0&w16u=1&w17u=1&AheadHour=48&FcstType=graphical&textField1=40.437&textField2=-84.3797&site=all&unit=0&dd=&bw=&BackDay.x=72&BackDay.y=11&BackDay=0

http://clearoutside.com/forecast/40.44/-84.38?view=current http://www.cleardarksky.com/c/NwBrmnOHkey.html?1 http://www.accuweather.com/en/us/coudersport-pa/16915/astronomy-weather/335322

Local Obstructions & Lights Guide star

For advanced folks who use a pick off mirror○ Sky X helps with this○ CDC to a much lesser extent

Page 20: Introdution to astro photography

NWS Hourly Forecast

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ClearOutside.com

Page 22: Introdution to astro photography

ClearOutside.com

Page 23: Introdution to astro photography

ClearDarkSky.com Get email alerts from

ClearSkyAlarmClock.com

Page 24: Introdution to astro photography

AccuWeather.com They provide an Astronomy summary

Page 25: Introdution to astro photography

Image Capture / Acquisition

Page 26: Introdution to astro photography

Basic Steps Normal Scope Setup For equatorial mounts

Rough Polar Align with polar scopeDrift align – This is essential for longer exposures

Sync Scope to ComputerI use plate solving

Focus on bright starBahitnov Mask

Frame Target Fine Focus Start guiding (if you are auto guiding)

Page 27: Introdution to astro photography

Bahtinov Mask Usage Place mask over

primary Take picture Adjust focus Repeat until all lines

meet in center

Page 28: Introdution to astro photography

Calculating exposure Take a sample shot Inspect histogram

You want the left side to be away from the left wall, but not too much

If you have a tool to do spot histograms check galaxy & nebula core for over exposure○ Backyard EOS has this

You may have to shoot several exposures (M42) Check focus & remove Bahitnov mask

Page 29: Introdution to astro photography

Take pictures Take as many pictures as you can

30 to 50 exposures is where you start to have limited returns

1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024○ You half the noise with every doubling

To Dither or not to DitherDithering is jogging the scope a small bit between

shotsCauses hot pixels to move around relative to the starsDither!

Page 30: Introdution to astro photography

They Don’t Look Great at First

Page 31: Introdution to astro photography

Software Came with the camera – Free Backyard EOS - $50 Astro Photography Tool - ~$21 ** Sequence Generator pro - $100 ** Images Plus - $240 ** Nebulosity - $95 CCD Auto Pilot - $100 to $300 **** Provides auto focus capabilities

Page 32: Introdution to astro photography

Special Hardware Bahitnov mask Guide scope and camera

Or pick off mirror and camera Guide-able mount

Computer control ST4 port (with ST4 guide camera)

(Modified) DSLR camera or CCD cameraDLSR camera adapter

Filter wheel (if using a monochrome camera) Specialty Camera Reducer/Corrector/Field Flattener Laptop

Page 33: Introdution to astro photography

Flats – take at least 30 Before you move the camera, you need

to take flats Flats are pictures of an evenly

illuminated sceneDawn skyT-shirtLight box

This captures any vignetting and dust in your system

Page 34: Introdution to astro photography

Darks – take at least 30 If it gets cloudy or your object sets and

you can keep your equipment out take darks

Darks are equal length exposures at the same temperature with the lens cap on

You can also build a dark library This captures the “exposure noise”

Page 35: Introdution to astro photography

Bias frames – take at least 30 You can take these any time Take the shortest possible exposure with

the lens cap on This captures the “read noise” of the

chip

Page 36: Introdution to astro photography

Image Processing - Stacking

Page 37: Introdution to astro photography

Stacking The goal of stacking is to take every frame, line up the

stars and combine them into a single shot. This will:Drive out noiseCreate more “bits” of dynamic rangeDSLR’s start with 14 bits, after ~10 sub-frames you can have a

true 32-bit floating point intensity value. Inspect all frames for exceptional frames that will mess

things upSome programs auto score shots for focus

○ Nebulosity○ FITS Image Grader (by Main Sequence)

Combine all the lights, darks, bias, and flat frames Each program has a different process, learn yours, try the

options

Page 38: Introdution to astro photography

Theory Bias represents the read noise

Subtract from the flat or light frame Darks represent the exposure noise

Subtract from the light frame Flats show vingetting and dust motes

Apply to light frame

Page 39: Introdution to astro photography

Software Deep Sky Stacker – Free Nebulosity - $95 Images Plus - $240 CCD Stack - $200 Pix Insight - $230 Euros ($250)

Page 40: Introdution to astro photography

Image Processing - Stretching

Page 41: Introdution to astro photography

What is non-linear stretching 90% of your data occupies

10% or less of the “data space” The goal is to get this to cover

25% or more of the “data space” without blowing out the bright areas

Each image needs different treatment

Orig Targ0 0

10 10

15 23

20 36

25 49

30 62

35 75

40 80

50 87

60 93

70 99

80 105

90 110

125 130

150 150

250 250

Page 42: Introdution to astro photography

Digital Development This is an astro-photo specific process to

bring out dynamic range into a visible space Software

Nebulosity – $95Images Plus - $20Pix Insight - $250Star Tools – 60 AUD ($45)CCD Stack - $200

Page 43: Introdution to astro photography

Other special issues Gradients & Vignetting

Amp glowLens/Scope vignettingSky glow (even and uneven)

NoiseThe whole process is a battle against noise

Exaggerated colors / saturationReal colors are not as saturated as we like to see in our

pictures○ Stars broadcast every wave length (blackbody)○ Nebula radiate specific frequencies or reflect blackbody

Color alignmentEach color focuses slightly differently

Page 44: Introdution to astro photography

Simulators Black Body

http://phet.colorado.edu/sims/blackbody-spectrum/blackbody-spectrum_en.html

How eye sees colorhttp://phet.colorado.edu/sims/html/color-visi

on/latest/color-vision_en.html

Page 45: Introdution to astro photography

General Purpose tools Photoshop / Lightroom

Expensive!Very powerfulFull 16 bit supportLimited 32 bit support

GimpFreeSimilar features to PhotoshopFull 8 bit supportLimited 16 and 32 bit support

More options on the Mac

Page 46: Introdution to astro photography

My Generic Workflow Pre-process in Nebulosity Initial stretch and enhance in Star Tools

StretchCropBinHRD, Contrast, etc.ColorDe-noise

Final tweaking in PhotoshopFinal stretchFinal color saturation

Page 47: Introdution to astro photography

Software to consider Sky Tools 3 - ($100 or $125) Backyard EOS - $50 Astro Photography Tool - ~$21 Sequence Generator pro - $100 Images Plus - $240 Nebulosity - $95 CCD Auto Pilot - $100 to $300 Deep Sky Stacker – Free CCD Stack - $200 Pix Insight - $230 Euros ($250) Nebulosity – $95 Star Tools – 60 AUD ($45) Photoshop or Lightroom – Expensive! Gimp - Free

Page 48: Introdution to astro photography

Future topic Image Acquisition

Camera selectionTelescope/lens selectionGuidingFrame, focus & exposureCapture software

Page 49: Introdution to astro photography

Future topic Basics of Image processing

Calibration frames (darks, flats, & bias)StretchingColor correctionColor saturationSoftware suggestionsLive demo using tools costing under $50

Page 50: Introdution to astro photography

Future topic Free and Inexpensive AP software

Deep Sky StackerAstro Photo Tool (free version)Sequence Generator (free version)GimpCDCBackyard EOS

Page 51: Introdution to astro photography

Future topic Photoshop tricks & tips

Works with Gimp tooLevels & CurvesLayers & MasksScreen Mask Invert to pull out dim detailBlock Method for more color saturationLab color by channel curve for color

saturation