I introduction to most of the concepts of astro photography that you can use with whatever you vae.

1. GHAAS Imagers
March 2021
By
Mark Casazza

2. Orion from Mountain Top
 This 213 6-second shots @ 1600 f/3.5 28mm

3. Agenda
 Basic concepts
 Minimum equipment
 Planning
 Capturing
 Processing
 Stacking
 Developing
 Printing

5. Basic Concepts
 Taking a picture of the dark
 High ISO (gain) – adds noise
 Long exposures – adds noise
 Very dim objects – signal strength ~ noise level
 This is a battle against noise
 Lots of pictures – coax the signal from the noise
 Cool the electronics – minimize the noise
 Calibration frames – subtract the noise
 Need uncompressed data
 Don’t have a DSLR or astro-camera, don’t fret

6. Why Raw and not JPG
 Compression
 Small deviations are lost in compression
 This is your data being destroyed!
 14 bits vs. 8 bits
 16384 shades vs. 256 shades
 Your data: 800 to 1600 vs. 12 to 25 shades
 64x more data!

7. Three Types of Astrophotography
 Easy – Star Trails, Moon
 Moderate – Meteor showers
 Challenging –
 Deep Sky
○ This will be my focus; I will explain the others as I go
 Planetary
○ We will cover this at another time. It is arguably the most difficult type

9. This doesn’t have to be expensive
 The $3.95 budget
 Modern iPhone or Android cell phone – 3.95
○ http://www.camerafv5.com/
 ProCamera for the iPhone – $8.99
○ https://www.procamera-app.com/en/
 Deep Sky Stacker – Free
 Gimp 2.10 – Free
 Computer to process
○ Okay, so you need a computer
 Stable place and way to set the phone/camera

10. 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

11. Other non-DSLR options
 Canon Point and shoot cameras
 CHDK $0.00
 http://chdk.wikia.com/wiki/CHDK
 Android Phone
 Manual Camera $4.99
 FV-5 $3.95
 A Better Camera $0.99
 iPhone
 Pro Camera $8.99
 Pro Cam $7.99

12. Optimal Minimal Equipment
 Rock solid tripod
 Consider sandbags to hold it still
 Prime lens vs. zoom lens
 The less glass the better, each surface is an opportunity for light loss and
reflections. Prime.
 Focal ratio
 The faster the lens the better, but…
○ Some lens have distortions when wide open
○ Astrophotography will expose them
 Remote or timed trigger
 Even better, lock the shutter open
 Bahtinov mask (focusing tool)

14. Planning – What to Shoot
 What is your field of view?
 Sensor size (Canon T1i is 22.3mm X 14.9mm)
 Focal Length of lens (35mm)
 FOV = sensor/focal length * 57.3
○ 22.3/35*57.3=13.6 X 14.9/35*57.3=24.4
 Look for objects that fill up at least 40% of the field
○ Moon is 0.5 (would require 380mm to use 40%)
 What is up tonight?
 Summer favorite is the Milky Way
 Winter favorite is Orion
 The Moon is harder than you think

15. Don’t Forget to Check the Weather
 http://clearoutside.com/forecast

17. ClearDarkSky.com
 Get email alerts from
 ClearSkyAlarmClock.com

19. Basic Steps
 Acclimate the camera to the environment
 Leave camera outside 30 minutes prior to use
 Focus – This is a lot harder than you think!!!
 The longer your focal length the harder to focus
 Set exposure
 Frame
 Shoot, take lots of shots. Over 100. Really!
 If it is cold outside put the camera in a zip lock back before
you bring it in.

20. Focus – Bahtinov Mask Usage
 Place mask over lens
 Take picture
 Adjust focus
 Repeat until all lines meet in
center
Search for “Bahtinov Mask dslr” on Amazon

21. Exposure Time & ISO
 Your camera is stationary the sky is not!
 “Sky Speed” varies
 https://www.lonelyspeck.com/advanced-astrophotography-shutter-
time-calculator/
 35MM lens on a T1i at
○ Declination 0: 8 seconds
○ Declination 70: 17 seconds
 For star trails ignore this time
 You want the maximum ISO before insane noise
 For the T1i this is 1600
 Newer cameras can go higher

22. What is Declination
 Declination is the number of degrees the center of the shot
is from the celestial equator.
 Polaris is at 90
 Simple enough?
 Not sure, use 0

23. Star Trails - Calculating exposure
 Carefully remove the Bahtinov mask
 Take a sample shot
 Inspect histogram
 You want the left side to be away from the left wall, but not too much
○ Left peak is the sky’s brightness
 If you have another peak on the right avoid it hitting the far right
○ Right peak is any large foreground object

24. Frame the Object
 Carefully remove the Bahtinov mask
 Remember, the sky is moving
 Objects move around the North Star
 For most directions this is East to West
 West of the North Star (south to north)
 East of the North Star (north to south)
 North of the North Star (west to east)
 Set up so your target moves through the frame

25. Frame the Object
 Remember the sky is moving
 Objects move around the North Star
 Set up so your target moves through the frame
N
W
E
S
W
E

26. Take Pictures – Lots of
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
 20 second exposures
 35mm lens has is 34 by 24
 It takes 96 minutes for the sky to rotate 24
 30 minutes @ 20 seconds = 90 shots
 Big or empty SD card and strong battery help
 Optional AC adapter or 12V converter is helpful

27. They Don’t Look Great at First

28. But wait, there is an image there!

29. Darks Frames – Take at Least 30
 If it gets cloudy or your object sets, & 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”
 These are important but optional

30. 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
 These are helpful and optional

31. Flat Frames – Take at Least
30
 Without touching the focus
 Take a picture of an evenly illuminated field
 A grey card can work here
 Try to get a similar histogram to your images
 Need varies depending on vignetting of the image from
“nice to have” to essential
 Generally, these are essential

32. Pre-Processing Math
 Pre-processing is applying darks, flats, and bias to the
individual images before stacking
 Light - bias - (dark - bias)  (flat - bias) = Frame
 If you skip this step and just stack lights, 

34. Essential 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 noise
 Create more “bits” of dynamic range
 DSLR’s start with 14 bits, after ~10 sub-frames you can have a true
32-bit floating point intensity value.
 Inspect all frames for bad ones
 Combine all the lights, darks, bias, and flats
 Each program has a different process, learn yours, try the
options
 For star trails you just stack without aligning on stars

35. Stacking Software
https://nightskypix.com/astrophotography-stacking-software/
 Sequator – Free – Windows
 Deep Sky Stacker – Free – Windows
 Autostakkert! – Free – Windows
 Lynkeos – Free – Mac OS X
 SiriL – Free – Windows, Mac OS X, Linux
 More if you want a commercial product

37. 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 75% or more
of the “data space” without blowing out the
bright areas
 Each image needs different treatment
Orig Targ
0 0
5 60
10 110
15 150
20 180
25 195
50 210
75 215
100 220
125 225
150 230
175 235
200 240
225 245
250 250
0
50
100
150
200
250
0 50 100 150 200 250

38. Digital Development & More
 This is an astro-photo specific process to bring out dynamic
range into a visible space
 You can do this yourself with levels and curves
 Or buy special software $$ Star Tools, PixInsight, Nebulosity
 There are many other tricks!
○ If you are interested, watch this video
Requires PhotoShop, maybe Lightroom or Gimp 2.10
○ http://www.astronomersdoitinthedark.com/dslr_llrgb_tutorial.php

39. Other Special Issues
 Gradients & Vignetting
 Amp glow
 Lens/Scope vignetting
 Sky glow (even and uneven)
 Noise removal
 The whole process is a battle against noise
 Exaggerated colors / saturation
 Real colors are not as saturated as many like
 Color alignment
 Each color focuses slightly differently
 Highlight the nebula, surpass the stars

40. Commercial Software under $100
 Backyard EOS or Backyard
Nikon – $50
 Image acquisition for DSLRs
 Star Tools – 60 AUD ($45)
 Digital development
 Color correction
 Noise removal
 Many other processing tricks
 Nebulosity – $95
 Image acquisition - CCD
 Stacking
 Digital development
 Luminar AI - $99
 Image processing
 Astro Photography Tool (APT) -
$22
 Image acquisition
 Computer focusing!
 Plate solving via PS2 or Astro Tortilla
(Both Free)

41. So, You Have a Tracking Mount!
 Alt-Az mounts
 Allow longer exposures, but not multiple minutes
 Equatorial mounts
 Anything from an EQ-1 to a Paramount
 Polar alignment is essential for good performance
 Cable management is essential for your sanity
 Long focal length = Very difficult
 Short focal length = Relatively easy
 Start short with experience go long

42. Cable Management

43. Accurate Polar Alignment
 PoleMaster – Neat piece of unnecessary equipment
 Assumes your mount’s case in plumb
 PHD2 offers a drift align process that is
 Easy (once you understand it)
 Accurate (to arc-seconds of accuracy)
 https://openphdguiding.org/PHD2_Drift_Alignment.pdf
 Steps
 Rough align on Polaris
 Perform Drift Align in PHD2
 Stop when you are satisfied, don’t go crazy!
○ I generally settle for 5 arc minutes or less error

44. Long exposures
 Most good equatorial mounts can support a 3-minute
exposure without guiding depending on your focal length
 Your mileage will vary
 Guiding is essential for longer exposures
 Short focal length 10mm to 400mm
○ Optional, but will improve images
 Mid range focal length 400mm to 2000mm
○ Essential beyond 2 to 4 minutes – Guide scope
 Long focal length 2000mm+
○ Essential period – Consider a pick off mirror

45. What is Guiding?
 While your main camera takes a long exposure
 A guide camera is taking short pictures
 A computer is interpreting the picture
 The computer is sending commands to the mount to correct for any
tracking errors
 PHD2 is the primary guiding software
 Despite its name “Press Here Dummy” it is rather complex to
properly configure.
 At longer focal lengths a guide scope has too much flexure;
you need to use a pick off mirror

46. With and Without Guiding