In case you missed it . . .
In case you missed it . . .
Sort-of puts us in context in terms of the bigger picture!
Ted, Donald, It's not conventional photography as we know it.... to misquote a certain Mr Spock , but it has proved challenging generating the attached images which are from Hubble Space Telescope source data.
I've always been fascinated by astronomy, and astrophotography since a child. 50 years ago, I could only dream of generating images of galaxies, nebulae,deep space, planets, etc.
Living in cites most of my adult life, night sky has mainly been neon lit with the moon the only 'accessible' astronomical photographic target. (I have photographed sunspots and a single solar eclipse.)
However, with the advent of digital imaging , the Hubble Space Telescope, NASA and the European Space Agency things changed .
It is not widely advertised, but the images/data captured by publicly funded space research projects are 'free' to tax paying citizens once the scientific research is completed. You just need to get a user id and download what you are interested in. (NASA and ESA also will send out disks with the information you request at no charge!!!!)
Source images are monochrome, captured using filters appropriate to specific wavelengths ( ie colours?) and are made available as FITS files (*.fits).
There is a free utility (FITS Liberator),available from NASA / ESA websites which allows the fits file to be viewed , 'optimised' and then converted to tiff which can be imported into any post processing package you favour. At that point the fun begins , constructing 'false' colour composites for yourself.
Not sure that C&C is totally relevant to these images, but all comments are welcome
NGC 602 (N90)
Blue Planetary Nebula, Centaurus (ngc3918)
Crab Nebula (detail, internal structure)
Last edited by James G; 25th July 2013 at 05:45 PM.
What's those pairs of ellipses in the first pic?Not sure that C&C is totally relevant to these images, but all comments are welcome
Ted, bred in Liverpool, but spent 'Swallows & Amazons' holidays with my grandparents in boondocks Ireland......night skies to bring tears to the eyes! Ahh well.....
I'm afraid the ellipses are artefacts associated with the source images. As I understand it there are 4 images captured for each exposure. 3 are mosaic plates and are combined. The fourth is a kind of zoom in to what would be part of the combined mosaic image. More simply put it seems that the Hubble camera uses a composite lens to capture the image and artefacts sometimes appear.
I noticed that they have been eliminated from the exceptional images published by NASA as part of their publicity and educational material. I guess I could have photoshopped them out myself, but I was satisfied with the colour composite I'd achieved.
I also admit to taking a somewhat perverse delight that friends and family have never noticed what seems to be an obvious anomaly when they have viewed the image. Just shows, CiCs members know what they are looking at
I took a serious look recently at buying a telescope and getting into astro photography but apart from the large investment needed and the lack of available darkness or clear skies, one other thing that discouraged me was the unlikelihood of producing anything that could hold it's head up in comparison to the amazing images coming from Hubble and the like.
That is data that I am very interested at having a look at.
Wow Captain Scarlett.... should have known
Wonderful images, very inspiring. I have been indulging in astrophotography past year or so and the view of Earth from Saturn as Donald states, "sort of puts us in context of the bigger picture". I must try the FITS liberator and see how it works. Meantime, thought I could share a view of Saturn as taken from Earth, i.e., from my telescope and DSLR. :grin:
James, do I need to download all three RGB images to stack and then convert to Tiff? Thanks.
Haseeb, its a bit more complicated .... There are a number of 'help' articles on the Nasa site, and I've listed a few below.
You can find the guide to 'making' images from Hubble data at this site http://hubblesource.stsci.edu/servic...es/2005-02-10/
But in summary the steps are as follows:-
1) get access to the NASA MAST or ESA archive of data (You register with a user id and Password)
2) do a search for items either using co-ordinates (RA & Dec) or use an NGC or Messier reference. ( Make sure you select for UV,Visible, or IR sources)
3) you should be presented with a list of available observations. These will be 'grouped based on co-ordinates and date/time of capture. There will be a nuber of observations in each group, usually one for each filter used, and an additional for a 'composite' of all the observations in the group. You need to tag and download all those you are interested in.
4) they are downloaded as Fits files, so you need to have downloaded the FITS LIBERATOR application, which will allow you to open them in your browser.
5) Once opened, you can play around with the settings within the LIBERATOR panel to adjust the image to get the best contrast, brightness etc.
6) When satisfied, you can then save them to (Tiff format).
7) At this point you can have anything from 2-6 monochrome images, depending on how many filters where used during the observation. You need to transfer them to a layered file ( I use Photoshop, but I presume Gimp and other apps like Elements support this.)
8) Now it is really up to you how you proceed. I normally try to assign each filter to it's nearest visible light equivalent and then 'colourise' it accordingly, but to be honest, since astronomical images are mostly false colour, you can choose whatever colour you wish for each layer.
9) having colourised the layers I then decide to what extent I want to blend each, and adjust vibrance , contrast, brightness etc until I get something that satisfies me.
The following links may help:-
Hubble Legacy Archive http://hla.stsci.edu/
Hubble Archive Request Page http://hla.stsci.edu/hlaview.html#
MAST Portal (Alternative to above) http://mast.stsci.edu/portal/Mashup/...tal.html?useAV
ESA Archive Request Page http://www.sciops.esa.int/index.php?...HST&page=index
User Guide for FITS Liberator http://www.spacetelescope.org/static.../userguide.pdf
Thank you greatly James for taking the time out to explain. Sounds fascinating.