Astro: Milky Way

Hi all, my first actual image posting to this group!

This was taken using a Canon 450d, unmodified, with the 18-55mm stock
lens on a barn door mount, mid 2011. From memory it was several
exposures ranging from 1 minute to 5 minutes, total of about 15 minutes.
I've re-processed this set many times trying to extract detail - the
point at which I actually felt good about the results was after I had
learnt to use flats. It brought out more detail in the image, detail
that I had no idea was there.

The old processed image is mw.jpg
The new processed image (with flat calibration) is milkyway.jpg

Unfortunately I can't find any pictures of my barn door mount, but it's
a pretty basic one hinged design, using a stepper motor which rotates
360° every minute. I've got both the motor in the base and the nut in
the top arm hinged too, which reduces the tracking error. The timing of
the stepper is controlled using an Arduino.

Oh poo, my client said it didn't post these

Sorry!

On 6/04/2012 9:32 AM, Chris wrote:
Hi all, my first actual image posting to this group!

This was taken using a Canon 450d, unmodified, with the 18-55mm stock
lens on a barn door mount, mid 2011. From memory it was several
exposures ranging from 1 minute to 5 minutes, total of about 15 minutes.
I've re-processed this set many times trying to extract detail - the
point at which I actually felt good about the results was after I had
learnt to use flats. It brought out more detail in the image, detail
that I had no idea was there.

The old processed image is mw.jpg
The new processed image (with flat calibration) is milkyway.jpg

Unfortunately I can't find any pictures of my barn door mount, but it's
a pretty basic one hinged design, using a stepper motor which rotates
360° every minute. I've got both the motor in the base and the nut in
the top arm hinged too, which reduces the tracking error. The timing of
the stepper is controlled using an Arduino.

Welcome!

You are off to a good start. I started with a barn door mount turned
manually at first then by the works of a wind up alarm clock (stepper
motors hadn't been invented yet). Later built a 2 hinge model but it
didn't work any better than the one hinge.

This was nearly 60 years ago so I was greatly handicapped by the poor
films of the day and commercial processing that was awful for our images
often cutting negatives in half and printing half of one shot with half
of another. I had to learn dark room work to get anywhere.

A DSLR like yours was beyond comprehension back then. No reciprocity
failure to deal with that screwed up color balance as each layer had a
different response after a couple minutes. Lenses had far more issues
than those of today as well.

Looking at your image the lens is adding distortion. Common with stock
zoom lenses. Though they are better than most fixed lenses when I
started at any price. Try stopping it down a stop or two. It should
clear up those stars and have surprisingly little effect on the fainter
parts of the image. Film had rather low resolution compared to a DSLR
so tracking errors weren't all that noticeable. Today's digital cameras
show such errors more quickly. You might get best results by stacking
and aligning many 1 minute images rather than fewer 5 minute images.
Depends on sky conditions and noise level of your camera what the
optimum exposure would be. Long enough to limit noise yet short enough
tracking errors are hidden. Might take some experimentation to find the
sweet spot.

Flats are a definite necessity many beginners fail to use as they get
results without them. Not realizing how much better it would be with
flats.

Your image also suffers from a gradient. I removed it in the attached
image. That improved the colors and brought out additional detail. I
also applied some color noise suppression as once the gradient was
removed color noise became evident in the fainter parts of the picture.
I also removed some of the tracking error to bring out more fine
detail in the Milky Way's brighter regions. Unfortunately the lens
issues remain as does some tracking error I couldn't remove without
hurting the image in other ways.

Brighter stars are so saturated they are white driving out any color to
the edges only. This could be due to too long of subs or sharpening
that appears to have been applied. Sharpening is fine for extended
objects but can drive color from stars and give them an unnatural harsh
look. I usually mask stars so the sharpening is applied only to the
nebulous part of the image. If applied to stars it must done with care
and lightly.

The IR cut filter wiped out most of the HII regions showing them blue
due to H beta and OIII emission being picked up. A few minor HII
regions without much OIII or H beta do show some hints of pink however.
This came out once I removed the gradient and pushed saturation a bit.

Considering the image is south up I assume you are from south of the
equator. Rather hard to mount a DSLR upside down on a barn door platform.

Keep imaging and posting. Best way to improve.

Rick

On 4/5/2012 7:02 PM, Chris wrote:
Hi all, my first actual image posting to this group!

This was taken using a Canon 450d, unmodified, with the 18-55mm stock
lens on a barn door mount, mid 2011. From memory it was several
exposures ranging from 1 minute to 5 minutes, total of about 15 minutes.
I've re-processed this set many times trying to extract detail - the
point at which I actually felt good about the results was after I had
learnt to use flats. It brought out more detail in the image, detail
that I had no idea was there.

The old processed image is mw.jpg
The new processed image (with flat calibration) is milkyway.jpg

Unfortunately I can't find any pictures of my barn door mount, but it's
a pretty basic one hinged design, using a stepper motor which rotates
360° every minute. I've got both the motor in the base and the nut in
the top arm hinged too, which reduces the tracking error. The timing of
the stepper is controlled using an Arduino.


--
Prefix is correct. Domain is arvig dot net

Nice image Chris.
Actually I have to admit that I prefer the old image. Even if it lacks a
flatfield it looks more natural to me than the new version.

Stefan

"Chris" schrieb im Newsbeitrag
...
Hi all, my first actual image posting to this group!

This was taken using a Canon 450d, unmodified, with the 18-55mm stock
lens on a barn door mount, mid 2011. From memory it was several
exposures ranging from 1 minute to 5 minutes, total of about 15 minutes.
I've re-processed this set many times trying to extract detail - the
point at which I actually felt good about the results was after I had
learnt to use flats. It brought out more detail in the image, detail
that I had no idea was there.

The old processed image is mw.jpg
The new processed image (with flat calibration) is milkyway.jpg

Unfortunately I can't find any pictures of my barn door mount, but it's
a pretty basic one hinged design, using a stepper motor which rotates
360° every minute. I've got both the motor in the base and the nut in
the top arm hinged too, which reduces the tracking error. The timing of
the stepper is controlled using an Arduino.