Open the Science Archive query form, and start digging!
1. First challenge: selection of the images
You can restrict the search for a given object (for instance: Target Name = NGC 1313), or for an area around given coordinates. Select some (or all) instruments (for instance, FORS1). Select “On-the-sky exposures” to get actual data. You can further restrict the search for a given time range (the date format is DD MM YYYY, for instance from 15 12 2003 to 17 12 2003), and then click Search. You will get a long list of frames that you can retrieve.
If you followed this example, which is encoded as the default values for the entries in the form, you will have found the files that were used for this image of NGC 1313
You may also retrieve this example dataset just by hitting return on the form.
The first challenge is to find a suitable dataset, i.e. one that has enough frames to lead to a nice final image. As a very broad guideline, at least 60s exposure should reveal many stars, 500s will give a nice deep image, but over several thousand seconds may be required to show some faint nebulae. If you think you have found a hidden treasure, check the images we have online to make sure we have not published it yet.
At a later stage, you will need to retrieve the biases and flat-fields. You can restrict the dates around the selected observations using the start and end night fields, and select the filter by typing its identifier in the “Filter” field. Use % as the wild-card character, eg %V% will retrieve all the filters containing “V”.
2. Data retrieval
Once you have identified a series of frame that can constitute a hidden treasure, mark them (little box on the left), and click the “Request” button.
You will then be asked to log onto the ESO User Portal. If you don't have an account already, you will need to create one: follow the link “I would like to create a new account”. This process is very quick, and of course all data provided are treated confidentially).
For the “Profile Category” entry, select “Amateur Astronomer” (unless another category fits you better).
For the “Media Type” entry, select FTP. You will receive an email with a link that activates your account.
Note that if you select another data retrieval method, you will not get the data. Also note that there is a 30GB limit for each request. If you really need more data, you will need to split the requests into several consecutive requests.
Once the data are requested, they will be extracted from the Archive, which can take a few minutes up to a few hours. You will then receive an email with the instructions on how to transfer the data.
3. Second challenge: data processing
All the data are stored in FITS format. It is therefore critical that you know how to do the astronomical processing for these files, and that you have software than can do it. If you don't know about this file format or are not interested in finding out more, this competition is probably not for you.
Packages like Scisoft contain free software for image processing on Linux. These are the professional tools, so they are extremely powerful, but not necessarily simple to use. John Kolena has a list of image processing software.
The images all need to be de-biased and flat-fielded. It is then likely you will want to stack several images obtained through the same filter.
4. Third challenge: image combination
The subsequent processing to go from a FITS file to a standard graphics format can, for instance, be done with the ESA/ESO/NASA FITS Liberator or with Stiff and Photoshop or GIMP.
You can process the data in any way you want, and combine them as you wish. The end or intermediate results can be enhanced using any technique. The only thing that is strictly forbidden is to paint on the image. Only tiny cosmetic defects can be painted over, such as cosmic rays, bad pixels, satellite trails, etc.
5. Upload the result
Once you have produced an image you are pleased with, save the original file in your working format (for instance .psd for Photoshop, or .xcf for GIMP), and generate a moderately sized JPEG for submission. Keep the original – we shall request it if you are shortlisted for a prize.
First join the “ESO's Hidden Treasures” group in Flickr. If you don’t have a Flickr account, create a free one on www.flickr.com
In the Group Pools, click "Join" link, then "Join this group".
You need to upload your image to the ESO Hidden Treasures group.
First, upload them on Flickr: click on "You" menu -> Upload photo and videos, then "Chose photos and videos". On next page, make sure you select "Public" in the privacy settings, and hit "upload" –this can take sometime. Write the relevant information in the caption of the image, and save.
Once this is done, you need to add your images to the ESO Hidden Treasures pool; via this link, select the image(s) you want to submit to the competition, and click "Add to group". Done! Your entry is submitted. Note we will contact the winners via their Flickr account, so keep an eye on your mailbox on Flickr.