Astrophotography on the Go: Using Short Exposures with Light Mounts

318 Pages·2015·8.98 MB·English

by  Joseph Ashley (auth.)

Joseph Ashley
Astro-
photography
on the Go
Using Short Exposures
with Light Mounts
The Patrick Moore
T he Patrick Moore Practical Astronomy Series
Series Editor
John Watson
M ore information about this series at h ttp://www.springer.com/series/3192
A strophotography
on the Go
U sing Short Exposures
with Light Mounts
Joseph Ashley
J oseph A shley
M arathon, G reece
I SSN 1431-9756 ISSN 2197-6562 (electronic)
ISBN 978-3-319-09830-2 ISBN 978-3-319-09831-9 (eBook)
D OI 10.1007/978-3-319-09831-9
S pringer Cham Heidelberg New York Dordrecht London
L ibrary of Congress Control Number: 2014947868
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C ontents
1 I ntroduction to Astrophotography on the Go ...................................... 1
1 .1 Introduction ...................................................................................... 1
1 .2 Technology Considerations .............................................................. 2
1 .3 Why Lightweight Mount Astrophotography? .................................. 4
1 .4 Why Is “Astrophotography on the Go” Important? ......................... 5
2 A Short Review of Astronomy Basics Related
to Astrophotography ............................................................................... 9
2 .1 Introduction .................................................................................... 9
2 .2 Celestial Coordinates ..................................................................... 1 0
2 .3 Distances in Space.......................................................................... 1 2
2 .4 Constellations ................................................................................. 1 3
2 .5 Telescopes ...................................................................................... 1 4
2 .6 Telescope Characteristics ............................................................... 1 8
2 .7 Telescope Mounts ........................................................................... 2 0
2 .8 Manmade Objects in the Sky ......................................................... 2 2
2 .9 Solar System Objects ..................................................................... 2 2
2 .10 Deep Space Objects........................................................................ 2 4
2 .11 Messier Objects and the New General Catalog .............................. 2 9
2 .12 Magnitude of Objects in the Night Sky .......................................... 2 9
2 .13 Skyglow .......................................................................................... 3 0
3 A strophotography Basics ....................................................................... 3 3
3 .1 Introduction ...................................................................................... 3 3
3 .2 Some Accessories and Terms Related to Astrophotography ........... 3 5
3 .3 Digital Camera Basics ...................................................................... 3 9
v
vi Contents
3 .4 Digital Cameras Used for Astrophotography ................................. 4 0
3 .5 How Cameras Are Attached to Telescopes .................................... 4 4
3 .6 Mounts............................................................................................ 4 8
3 .7 Field Rotation ................................................................................. 5 0
3 .8 Telescopes and Exposure Time ...................................................... 5 4
3 .9 Noise Reduction ............................................................................. 5 6
3 .10 Signal to Noise Considerations ...................................................... 6 1
3 .11 Histograms ..................................................................................... 6 3
3 .12 Image Size and Field of View ........................................................ 6 4
3 .13 Focusing a Digital Single Lens Refl ex Camera on a Telescope ..... 6 7
3 .14 Planning to Insure a Successful Imaging Session .......................... 6 9
3 .15 Light Pollution ............................................................................... 7 0
4 V ery Short Exposure Astrophotography .............................................. 7 3
4 .1 Introduction ...................................................................................... 7 3
4 .2 Telescope Characteristics for Very Short Exposures ....................... 7 4
4 .3 Mount and Tripod Issues with Very Short Exposure
Astrophotography ............................................................................. 7 7
4 .4 DSLR Camera Considerations ......................................................... 7 8
4 .5 Total Integrated Exposure Time ....................................................... 8 1
4 .6 Very Short Exposure Astrophotography Techniques ....................... 8 3
5 A lt-Azimuth Mount Astrophotography ................................................ 8 9
5 .1 Introduction ...................................................................................... 8 9
5 .2 Equipment ........................................................................................ 9 0
5 .3 Equipment Issues ............................................................................. 9 2
5 .4 Field Rotation Mitigation ................................................................. 9 4
5 .5 Planning Your Photographic Session ............................................... 9 8
5 .6 Setting Up......................................................................................... 1 01
5 .7 Measuring the Maximum Exposure Time for a Mount .................... 1 02
5 .8 Imaging with an Alt-Azimuth Mount .............................................. 1 04
6 A strophotography with Lightweight, Portable,
Equatorial Mounts .................................................................................. 1 07
6 .1 Introduction ...................................................................................... 1 07
6 .2 Lightweight Equatorial Mount Characteristics ................................ 1 08
6 .3 Precise Polar Alignment ................................................................... 1 11
6 .4 Planning Your Photographic Session ............................................... 1 15
7 P iggyback Astrophotography and NightScapes ................................... 1 21
7 .1 Introduction ...................................................................................... 1 21
7 .2 Cameras and Lenses ......................................................................... 1 23
7 .3 Piggy Back Astrophotography; Telescopes and Mounts ................. 1 25
7 .4 Deep Space Photography with a Piggyback Camera ....................... 1 27
7 .5 Nightscape Photography .................................................................. 1 30
Contents vii
7 .6 Capturing a Nightscape .................................................................... 1 32
7 .7 Star Trail Photography ..................................................................... 1 33
8 A strophotography in Light Polluted Areas .......................................... 1 37
8 .1 Introduction ...................................................................................... 1 37
8 .2 Light Pollution Is Not a Friend ........................................................ 1 39
8 .3 How to Combat Stray Light? ........................................................... 1 39
8 .4 Artifi cial Skyglow ............................................................................ 1 41
8 .5 Why the Concern About Skyglow? .................................................. 1 42
8 .6 How Are Photographs Made of Objects That Have a Surface
Brightness That Is Less Than the Brightness of Skyglow? .............. 1 43
8 .7 Light Pollution Reduction Filters ..................................................... 1 47
8 .8 How Does This All Impact “Astrophotography on the Go?” ........... 1 49
9 C omputers and Computer Programs .................................................... 1 51
9 .1 Introduction ...................................................................................... 1 51
9 .2 Research, Identifying Objects to Photograph................................... 1 52
9 .3 Planning and Planetary Programs .................................................... 1 54
9 .4 DSLR Camera Control ..................................................................... 1 57
9 .5 Image Processing Programs ............................................................. 1 58
9 .6 Which Programs Should You Use? .................................................. 1 61
1 0 M astering DeepSky Stacker ................................................................... 1 63
1 0.1 DeepSky Stacker Overview .......................................................... 1 63
1 0.2 Getting Started ............................................................................. 1 63
1 0.3 Stacking Parameters Box ............................................................. 1 66
1 0.4 Results Tab ................................................................................... 1 67
1 0.5 Comet Tab .................................................................................... 1 69
1 0.6 Light Tab ...................................................................................... 1 70
1 0.7 Dark, Flat, and Bias/Offset Tabs .................................................. 1 73
1 0.8 Alignment Tab .............................................................................. 1 74
1 0.9 Intermediate Files Tab .................................................................. 1 75
1 0.10 Cosmetic Tab ................................................................................ 1 76
1 0.11 Output Tab .................................................................................... 1 76
1 0.12 Raw Digital Development Process ............................................... 1 77
1 0.13 Loading Files into DeepSky Stacker ............................................ 1 79
1 0.14 Running Deep Sky Stacker .......................................................... 1 80
1 1 P rocessing Very Short Exposures .......................................................... 1 91
1 1.1 Introduction .................................................................................... 1 91
1 1.2 Stretching Very Short Exposure Images
Using a Curve Stretch .................................................................... 1 93
1 1.3 Stretching Very Short Exposure Images
Using a Levels Stretch .................................................................... 1 98
1 1.4 Image Enhancement ....................................................................... 2 00
viii Contents
1 1.5 Processing Very Short Exposures Using 8 Bit Photo
Processing Programs ...................................................................... 2 02
1 1.6 Processing Very Short Exposures Using PhotoShop Elements...... 2 07
1 1.7 Alternatives to Photo Processing Programs ................................... 2 08
1 1.8 Which to Use; Photo Processing or Astronomical Processing? ..... 2 11
1 2 L ightweight Azimuth and Equatorial Mounts ..................................... 2 13
1 2.1 Introduction .................................................................................. 2 13
1 2.2 Signifi cant Attributes of Lightweight Mounts
and Tripods Related to Astrophotography ................................... 2 14
1 2.3 Celestron Mounts ......................................................................... 2 17
1 2.4 iOptron Mounts ............................................................................ 2 19
1 2.5 SkyWatcher Mounts ..................................................................... 2 21
1 2.6 Meade Mounts .............................................................................. 2 22
1 2.7 Traditional German Equatorial Mount ......................................... 2 24
1 2.8 Mount Selection ........................................................................... 2 25
1 2.9 Lightweight Alt-Azimuth and Equatorial Mounts
and Telescope OTA Characteristics .............................................. 2 29
1 2.10 Lightweight Mount and OTA Bundles ......................................... 2 31
1 2.11 Economics of Using Lightweight Mounts and Tripods ............... 2 34
1 3 P ortable Observatories ........................................................................... 2 39
1 3.1 Introduction .................................................................................... 2 39
1 3.2 Three Portable Observatories ......................................................... 2 41
1 3.3 Downtown City Apartment or Urban Condo Dweller ................... 2 46
1 3.4 Vacation in the Family Car ............................................................. 2 48
1 3.5 Commercial Air .............................................................................. 2 48
1 3.6 Air Transportable Power Supplies ................................................. 2 59
1 4 E ye Candy in the Night Sky to Photograph .......................................... 2 63
1 4.1 Introduction .................................................................................... 2 63
1 4.2 Summer; June, July, and August .................................................... 2 65
1 4.3 Autumn; September, October, and November ............................... 2 70
1 4.4 Winter; December, January, and February ..................................... 2 75
1 4.5 Spring; March, April, and May ...................................................... 2 80
A ppendix A: Planning an Astrophotography Imaging Session .................. 2 87
A ppendix B: Lightweight Mount Tripod Modifi cations .............................. 2 93
A ppendix C: U sing a 4 SE Mount with a Wedge
in the Equatorial Mode ............................................................ 3 03
I ndex ................................................................................................................. 3 15
A bout the Author
My first view in a telescope was breathtaking, the Orion Nebula in December 1965,
seen through the university’s brand new Schmidt Cassegrain Telescope then only a
few days old. Fast forward 20 years covering a career of engineering physics deal-
ing mostly with energy conservation and it was time for Halley’s Comet; time to
get that first telescope. Which telescope to buy? Thumbing through the adverts in
Sky and Telescope and there it was. Meade was advertising a “portable observa-
tory,” its 2045LX3, a 102 mm Schmidt Cassegrain Telescope complete with two
eyepieces, a tabletop tripod, and an aluminum carrying case.
Fast forward another 20 years and now I am retired but still using my 2045LX3
to view the night sky. While surfing the net in 2008 I found a new Meade DS2090AT
for $150 on eBay. Two weeks later it arrived and first light with no clouds in sight.
The 90 mm goto refractor clicked and whirred and WOW! I was thoroughly
hooked, an instant goto junkie and soon had a two more goto mounts: an iOptron
GOTO conversion kit for my Celestron C6S’s manually operated CG5 mount and
a SkyWatcher SynScan AZ goto mount for my Meade 2045 SCT.
T hen it happened. My granddaughter asked “Papou, can you make a picture of
that?” Soon I was hooked. While I had a traditional astrophotography setup with
my C6S, it was not convenient to use. On a whelm I put my DSLR at prime focus
on my Meade 2045 I had on my SkyWatcher SynScan AZ goto mount and started
photographing the night sky. The convenience of a grab and go astrophotography
kit was simply wonderful. I soon learned to use very short exposures of 15–30 s and
was thrilled at some of the images I made. I later added a 4 SE mount and entered
into the world of unguided short exposures of a minute or so.
M y efforts with very short exposure astrophotography with lightweight mounts
span a 4-year period with the typical interruptions due to extended periods of
cloudy weather, family considerations, and other personal commitments. This book
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