Original subtitles

imaging the nighttime sky can be one of

the most rewarding things to do

in amateur astronomy you're literally

collecting

photons of light from objects that are

hundreds

thousands or even millions of light

years away

this process can also be complicated and

in today's video

we're going to break down the basic

steps and techniques

and how to capture light flat

dark and biased frames to greatly

improve the details of your images

and astrophotography if you enjoy this

video

please like it and subscribe to this

channel but most importantly

let me know about your questions and

techniques for improving these frames

in the comment section below now let's

get started by taking a look at the most

important part of this process

collecting the

actual data of the target that we're

imaging this night

and what we call our light frames

light frames are the most important part

of this process

because they're the actual data of the

object that we're capturing in the

nighttime

sky nothing else beyond this initial

process

really matters unless we have sharp

properly exposed images to work with

down the line an important concept to

understand for our light frames

is referred to as the signal to noise

ratio

basically the more light frames we have

the more we can stack that data to pull

out

fine details of these deep sky objects

a resource that's helped me greatly with

understanding some of these concepts

is the deep sky imaging primer 2nd

edition

by charles bracken and i'll be sure to

leave a link to it in the description

below

tonight i'll be capturing my light

frames using a dslr

samyang 135 millimeter lens and the

ioptron sky guider pro tracking mount

which is already polar aligned and ready

to go

there are three main things that we're

going to do to make sure that we have

excellent light frames to work with and

those are making sure our camera's

quality is set to raw

adjusting our focus and setting our

exposure to the proper length

i've got a video that goes into more

detail of other specific settings

such as choosing things like your iso

and f number

and we'll be sure to tag it and include

a link in the description below

to capture our light frames let's start

by setting our camera to manual mode and

raw quality

next let's work on getting sharp focus

for our light frames

by focusing our equipment on the

brightest star we can find

one thing that can help you with this is

a botanav mask

after placing it over your camera lens

slowly adjust focus until the center

spike is perfectly between the other two

spikes

now that our camera is set to raw and

we've adjusted our focus

let's turn our attention to making sure

that we get the proper exposure

time for our target tonight which for me

is the orion nebula

let's test out different exposures for

our light frames by taking a 15 second

30 seconds 45 second

and one minute exposure

to determine which exposures worked best

i'm going to press the info button to

see the difference in the histogram for

each

image the trick is to get a histogram

that is about three-fourths of the way

over to the left

too far to the left and you don't have

enough difference between your object in

the background of space

too far to the right and you may lose

some of the brightest details of your

object

from the data getting clipped off

tonight it looks like the best exposure

for me

will be somewhere around 20 seconds

the exposure time that you choose is

going to vary greatly

it's going to depend on the target that

you're imaging

the capabilities of your tracking mount

and even the light pollution of your

area

to assist you in capturing your light

frames use something like a remote

shutter release

trigger to set how many exposures you

want and how long you want them to be

my goal tonight is to capture at least

200 separate 20 second light frames of

the orion nebula

before it gets too low to the horizon

and enters a good deal of light

pollution in my area

remember these light frames are the most

critical part of the process

and will take up the bulk of your time

with your night of imaging

the more light frames you have to stack

together

later on in the process the greater your

signal-to-noise ratio will be

which will bring out faint fine details

of these incredible deep sky objects

[Music]

alright i'm back outside after my camera

has captured some incredible images of

the orion nebula

for about the past hour and 15 minutes

my attention now turns to capturing the

additional frames that will be used to

take out any imperfections

in these light frames that were just

captured

and we're going to do that by beginning

the process with capturing

flat frames

flat frames will improve the quality of

our image

by removing unwanted differences in

brightness such as vignetting

and dust shadows on our sensor

to get rid of these imperfections your

flat frames need to be perfectly

illuminated across the entire field of

view when you capture them

to accomplish this i like to use the

incredibly

sophisticated and expensive scientific

instrument

known as the white t-shirt

begin by making sure your imaging setup

is in the exact same

orientation as it was for the light

frames and make sure you are still

shooting in raw quality

with the same iso and f number as before

the only thing you will want to change

on the camera is the mode

from manual to av

carefully stretch a white t-shirt over

the lens hood

making sure there are no wrinkles

once that's done you're going to need a

light source to evenly illuminate it

i like to use a white background on my

iphone with the brightness turned up to

100 percent

with both of those things in place press

the shutter button

to take your flat frames as for all

these frames

the more the merrier but there is

obviously a diminishing return when you

get to a certain point

on most nights of imaging i like to take

around 75 flat frames

our next type of frame is the quickest

to take and simply requires you to place

the cap

on your lens to make sure that no light

gets onto your sensor

these bias frames will improve our image

by removing the bias signal and read

noise from our sensor

switch your camera back to manual mode

and be sure to keep the same raw

quality and iso setting that you've used

all night

go into your settings and select the

fastest shutter speed available for your

camera

for this camera that's a shutter speed

of 4 000.

with all of these settings in place

click your shutter to take as many bias

frames as you'd like

on most nights i like to take around 75

of these as well

[Music]

finally we end our night with dark

frames

these are used to improve our image by

removing the thermal

signal and hot and cold pixels that may

have showed up

throughout the evening like bias frames

you want to make sure your lens cap is

on so that no light hits your sensor

but unlike bias frames you want your

exposure length to be the exact same as

the light frames that were captured

earlier in the evening

what i would suggest you do is keep your

equipment set up just as it was

outside and use your remote shutter

release trigger like before to capture

your dark frames at the exact same

length as your light frames were

earlier in the evening i normally try to

take between

75 and 150 dark frames

it just depends on how long the exposure

times are the temperature changes

outside

and honestly what time i want to get to

bed that evening

i hope you've enjoyed this video on how

to take all of these different types of

frames in astrophotography

i'm going to have a video coming up soon

that i'll be sure to tag and leave a

link to in the description below

that's going to walk you through exactly

how to stack each of these frames in

deep sky stacker

for the next step of our process be sure

to check it out if you're interested

please let me know in the comments

section below also about any questions

you have

or techniques that you know of to

improve this process even more

thank you all so much for your continued

support and clear skies from late night

astronomy