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06/08/22 Cal Estrada 1 Introduction to DSLR Astrophotography Relatively simple and inexpensive. No guiding required. Using consumer Canon DSLR’s. Home use camera: Canon t3i, 18 MP No field laptop required. ISO up to 6400, 30 sec or bulb exposures, swivel screen, zoom live focussing Sensitivity diminishes in the red “Ha” emission wavelength. Fast Reflector vs APO Larger aperature, faster f/#, no chromatic aberration, dewing takes longer, affordable. Stack of multiple shorter exposures vs single long exposure No guiding required (no AG mount, separate guide scope & camera, or laptop) Freeware “Deep Sky Stacker”, process images on a cloudy or rainy night Polar Aligned Equatorial Mount Decent unguided 60-90 second exposures at 800 mm using Celestron CGEM “Local” Dark Sky sites Blackbird SP, Tuckahoe SP, Cherry Springs SP, Cape Hatteras NC

Introduction to DSLR Astrophotography

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Introduction to DSLR Astrophotography. Relatively simple and inexpensive. No guiding required. Using consumer Canon DSLR’s. Home use camera: Canon t3i, 18 MP No field laptop required. ISO up to 6400, 30 sec or bulb exposures, swivel screen, zoom live focussing - PowerPoint PPT Presentation

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Page 1: Introduction to DSLR Astrophotography

04/22/23 Cal Estrada 1

Introduction to DSLR Astrophotography

• Relatively simple and inexpensive. – No guiding required. Using consumer Canon DSLR’s.

– Home use camera: Canon t3i, 18 MP• No field laptop required. • ISO up to 6400, 30 sec or bulb exposures, swivel screen, zoom live focussing• Sensitivity diminishes in the red “Ha” emission wavelength.

– Fast Reflector vs APO• Larger aperature, faster f/#, no chromatic aberration, dewing takes longer, affordable.

– Stack of multiple shorter exposures vs single long exposure• No guiding required (no AG mount, separate guide scope & camera, or laptop)• Freeware “Deep Sky Stacker”, process images on a cloudy or rainy night

– Polar Aligned Equatorial Mount• Decent unguided 60-90 second exposures at 800 mm using Celestron CGEM

– “Local” Dark Sky sites• Blackbird SP, Tuckahoe SP, Cherry Springs SP, Cape Hatteras NC

Page 2: Introduction to DSLR Astrophotography

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Celestron CGEM mount with Go-To and Autoguider $1500 new

Astro-Tech $ 450

8” f/4, 800mm fl

To Polaris

Polar alignment scope with offset

Imaging Setup, 8” f/4 on Celestron CGEM

Hand Controller with 40,000 object Go To Data Base.

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Camera Setup and LPR Filter Transmission

T Adapter

2” Baader MPCC

2” Hutech LPR Filter

Programmable shutter timer. Bulb Mode. N x 90 secs

UV and IR Blocking with notch filtering of Orange Street lights and transmission of Ha light

Swiveling Live Focus Screen

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Step by Step Procedures: Setting Up Scope• Laser collimate Telescope at Temperature

• Level Telescope Tripod.

• Balance DEC and RA Axis with camera attached (counterweights and dovetail)• Polar Align and center 2 or 3 alignment stars. No drift alignment needed

On Primary Center Mark

“Centered” on secondary

Returns to laser aperature

Page 5: Introduction to DSLR Astrophotography

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Imaging Procedures• Camera Setup

– Manual Mode, 90 sec exp, 1600 - 6400 ISO, RAW Mode for stacking.

– Focus on bright star or Jupiter using “Live Zoom” feature

– If not “go to” equipped, find what object you’re looking for• Star Maps and TelRad or finder scope. Start with easier, brighter objects.

– Take lots and lots of “light” frames, many will be unacceptable for stacking

1 x 75 seconds @ ISO 6400.

Note lots of noise in raw images

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Screenshots from Deep Sky Stacker. M3 Cluster

8 x 75 secs @ 6400 ISO Light Frames Only. No flats or darks. Best images without trails or periodic error.

Stacked Image, no post processing

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Single 75 sec light frame9 x 75 sec light frame stack @ ISO 1600 using modified DSLR

PS adjust levels, contrast, sharpen, vibrance

Using Deep Sky Stacker http://deepskystacker.free.fr/english/index.html

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Objects imaged with light frames only (no flats, darks, or bias frames) Unguided stacks @ 1600 ISO. Levels adjusted and sharpened using Photoshop.

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Miscellaneous and other details• Maximize “SNR” or Signal to Noise Ratio

– Signal: Photons you want to keep• Good focused images long exposure images

– Noise: Artifacts you don’t want– Light pollution (orange street lights).

• Use LPR filter– High ISO noise (most common)

• Take lots of light frames and stack– Dark Signal (removed by dark frames)– Vignetting, dust or smudges (removed by flat frames)– Dew. Newtonians better than SCT’s

• Optional Accessories: Many available at AstroMart (http://www.astromart.com)

– Coma corrector for fast Newtonians• http://www.optcorp.com/product.aspx?pid=10026

– LPR Filters (especially in light polluted “orange” skies)• http://www.optcorp.com/product.aspx?pid=105-156-840-1155-850-4172

Next Talk: More Advanced Astrophotography Techniques: Autoguiding, Flats Fields, Dark Frames and Dithering