Free planetarium

 
User avatar
pzampella
Observer
Posts: 15
Joined: 12 Dec 2016
Location: Madrid
Contact:

Astrophotography

18 Apr 2017 02:35

Bambusman, After some background substraction this is what I got:
► Show Spoiler


I still need a lot of works (and more images to stack).
Attachments
M51.jpg
 
User avatar
Bambusman
Astronaut
Posts: 57
Joined: 22 Aug 2016
Location: Germany, Baden-Württemberg

Astrophotography

18 Apr 2017 09:24

pzampella wrote:
Bambusman, After some background substraction this is what I got:
► Show Spoiler


I still need a lot of works (and more images to stack).

this looks pretty good already!

did you edit a tiff or jpg file, also whats the original resolution of this image?
 
A-L-E-X
Explorer
Posts: 292
Joined: 06 Mar 2017

Astrophotography

19 Apr 2017 13:08

Watsisname wrote:
Midtskogen's trick is pretty simple and powerful with a good choice of blur size.  Another technique you could try is to characterize the light pollution and remove it by subtraction or difference modes in an image editor.  Here's a quick summary of how I do it using GIMP: 

1) Open the image

2) Choose the "color picker tool", with the settings "sample average" over a large area (a good portion of the image area), and "set to foreground color".  Then click on the image over an area that is relatively empty of galaxies/nebulae/stars (mostly background noise).  The idea is that you're detecting the average color of just the light pollution in the image, which in a deep sky image should be pretty uniform.

3) Create a new layer filled with this foreground color.  Set the layer mode to "difference", and then slide the opacity until it best cancels out the light pollution.  I find this is usually around 50%.

This is what I get using this method + a bit of curves adjustment on your ISO800 image.  Scaled up 200% to see effects a bit better:

► Show Spoiler


This is a really nice capture by the way.  After the little bit of processing you can even see the star formation regions!


As for the question of ISO vs. exposure time, always go with the lowest ISO / longest exposure time combination that you can manage while obtaining a neutrally exposed image.  Higher ISO can achieve a neutrally exposed image more quickly, but it will be more noisy.

The theory is that you want to maximize the signal to noise ratio (S/N), which represents how much of the light being recorded is actually from the object you want to image, vs. noise from random fluctuations. S/N increases as the square root of the exposure time.  Raising the ISO itself does not do anything for S/N -- it's just acting as an amplifier of both signal and noise by binning pixels together.  But with higher ISO and shorter exposure time, you'll get a noisier image.

Other ways to improve S/N are to stack several images together, which acts to average out the noise.

Indeed.  My experience is that at higher ISO the colors wash out (limited dynamic range at higher ISO?)  Light pollution also seems much more pronounced at higher ISO, regardless of the exposure time.  ISO 1600 is about the limit if you want to be able to see subtle star and nebula colors, but realistically, I've found it's better to push exposure times longer (as long as star streaks aren't apparent) and keep the ISO to 400-800.
 
User avatar
pzampella
Observer
Posts: 15
Joined: 12 Dec 2016
Location: Madrid
Contact:

Astrophotography

19 Apr 2017 16:28

Bambusman wrote:
Source of the post did you edit a tiff or jpg file, also whats the original resolution of this image?

I stacked RAW files into a TIFF file, and that TIFF file was the one that I processed.

A-L-E-X wrote:
Source of the post I've found it's better to push exposure times longer (as long as star streaks aren't apparent) and keep the ISO to 400-800.


Then I'll keep it on ISO 800. Thanks!
 
A-L-E-X
Explorer
Posts: 292
Joined: 06 Mar 2017

Astrophotography

19 Apr 2017 16:54

What camera are you using?
 
User avatar
pzampella
Observer
Posts: 15
Joined: 12 Dec 2016
Location: Madrid
Contact:

Astrophotography

20 Apr 2017 15:43

A-L-E-X wrote:
Source of the post What camera are you using?

Canon EOS Rebel T5 (1200D).
 
A-L-E-X
Explorer
Posts: 292
Joined: 06 Mar 2017

Astrophotography

22 Apr 2017 06:04

Look up the best settings on sensorgen.org, they have the "sweet spots" for various combo, look for DR > 10 stops to maintain star colors.
 
User avatar
pzampella
Observer
Posts: 15
Joined: 12 Dec 2016
Location: Madrid
Contact:

Astrophotography

02 May 2017 07:20

Well, after 4 hours of multiple sessions with different expositions (51x30s, 39x90s, 62x90s and 20x240s, each one at ISO800), this is the final result:
► Show Spoiler


I don't think it's possible to make any more improvement without a better and darker sky. Any thoughts?
Last edited by pzampella on 03 May 2017 00:43, edited 1 time in total.
 
User avatar
Mosfet
Pioneer
Posts: 490
Joined: 24 Oct 2016
Location: Italy

Astrophotography

02 May 2017 08:36

You sacrificed a bit of background data with weaker structures for a darker sky, and by doing so you exalted spiral structures.

I'd wish I could make something like that!
"Time is illusion. Lunchtime doubly so". Douglas N. Adams
My mods - My specs: Asus x555ub - cpu i5-6200u, ram 4gb, gpu nvidia geforce 940m 2gb vram
 
User avatar
pzampella
Observer
Posts: 15
Joined: 12 Dec 2016
Location: Madrid
Contact:

Astrophotography

03 May 2017 00:34

Mosfet wrote:
Source of the post I'd wish I could make something like that!

Mosfet, is not that hard! I was just following midtskogen idea of background removal. To achieve that using PixInsight I just had to create a mask to protect brightest stars and galaxies, and then I streched the image with the Histogram Transformation Tool. This could also be done using Photoshop, for example.
 
User avatar
HarbingerDawn
Explorer
Topic Author
Posts: 160
Joined: 22 Aug 2016
Location: CT, USA
Contact:

Astrophotography

03 May 2017 09:21

Some recent shots of mine

Jupiter on 9 April 2017 - Enlarged by 3x for ease of viewing
Image

Venus 7 hours ago ;) - Enlarged by 2x for ease of viewing
Image
Ryzen 7 1700 OC to 3.8 GHz, 32 GB DDR4 RAM, GTX 970 4096 MB VRAM
Posts on old forum: 8717
 
User avatar
ZackG
Space Tourist
Posts: 24
Joined: 11 Dec 2016

Astrophotography

03 May 2017 10:22

Here's my pic. Unfortunately this was taken with a very old DSLR camera. Only 6 MP
Attachments
Milky Way In New York.png
 
User avatar
DoctorOfSpace
Pioneer
Posts: 586
Joined: 22 Aug 2016
Location: SpaceX Mars Colony
Contact:

Astrophotography

03 May 2017 11:25

Awesome pictures HarbingerDawn and ZackG

It's not the megapixels in your camera that count, but how you use them.
CPU: Intel Core i7-5820K 4.2GHz 6-Core Processor - RAM: G.Skill Ripjaws V Series 32GB (4 x 8GB) DDR4-2400 Memory - GPU: EVGA GTX 1080 Ti FE 11GB
Quando omni flunkus, moritati
 
User avatar
ZackG
Space Tourist
Posts: 24
Joined: 11 Dec 2016

Astrophotography

03 May 2017 15:42

No, I take good care of the camera. the problem is that the CCD I think is old and maybe damaged and also the pictures are saved in a SD drive. but that picture is used with a bulb setting thanks to my intervalometer with 10 second exposure.
 
User avatar
Watsisname
Pioneer
Posts: 586
Joined: 06 Sep 2016
Location: Bellingham, WA

Astrophotography

03 May 2017 19:01

That's a nice image of the galactic center -- can clearly see the dust lanes and star clusters. :)

HarbingerDawn wrote:
Source of the post Venus 7 hours ago 

Getting bigger and bigger!

Who is online

Users browsing this forum: No registered users and 1 guest