This is the first real processing step. After you upload the files click on ‘Process Files’ and you will see all your uploaded files with 4 processing buttons/steps next to it. The one highlighted in darker blue is the next one to be done for each file and initially all of them should be set to ‘Observation target’. The four steps have to be done in order for each file, but it does not matter in which order you do them for your files. You can process each file from the beginning to the end, or do the first step for all of them – your choice. Note that the current manual has a ‘Photometry’ button which we have now taken out – it is part of the last button called ‘Photometric Calibration’.
When you click on ‘Observation Target’ you will be asked to select from a drop-down menu which target region the file is for and which Device the picture was taken with. We could, in principle, identify the target region using the coordinates, but as some targets are very close to each other and there is overlap (depending on the field of view), this will cause errors – hence the decision to ask the user. The question for the Device is only to: i) speed up the astrometric solution (since you had to provide the pixel scale) and to ii) store this information for later. For example one might find that data from certain devices have systematic errors and we then can account for this in the analysis if we know the Device the image was taken with.
After you click ‘Enter details into database’ you will get back to the Processing Files screen and can do the next step – “Meta-data”. If you click on this the software will try to extract the following information from the FITS header of your file: Time and date of the observation; Filter that has been used; Exposure time (in seconds) of the image. The date/time is vital to plot lightcurves, the filter needs to be correct to calibrate the data, and the exposure time (together with the Device information about main mirror/lens diameter) will be used for statistics.
This meta-data extraction is usually automatic, but the first time you process a file for a particular device you need to teach the software which information is stored in which header card. Hence, this slightly more tricky process needs to be done only once (and is also described in the manual).
Basically you will be asked in which format the date/time is stored. This can either be as date in one card, time in another card, or both in the same card as e.g. 2017-09-11T18:06:23, or as Julian date. If you have selected the format you then need to select the FITS header card in your file which contains the information for that field, e.g. the Julian date. Similarly you need to identify the card that contains the filter used and the total exposure time. Note if you have stacked images we’d like to total exposure time and not the single exposure time for the individual images.
If some of this information, e.g. the total exposure time, is not in your header you can leave this field blank, but you will then have to put this information in manually for every image you process. Note: We currently are not able to cope with Devices that have two filter wheels where the filter used is e.g. either in FILT1 or FILT2 in the way that one has: FILT1=Blank, FILT2=Visual or FILT1=Blue, FILT2=Blank In this cases we’d ask you to leave the filter card blank and manually add it every time you process an image.
Once the time/date format and header cards are correctly identified, click on “Add header cards to device” and you are done. If you now use “Meta-data” for another image from the same device the website will display what it has extracted from the header and you can check it – the full header is also displayed at the bottom of the page. Behind the extracted filter information the page also displays what it thinks the filter name means i.e. a letter such as B, V, R, I, etc. So if your card entry is ‘Visual’ or ‘visual’ or ‘vis’ or ‘TG’ or tg’ it will interpret it as ‘V’ and calibrate it into the V-Band.
If any of the information is wrong you can manually edit it using the blue: “This is incorrect, modify values” button. You will have to do this every time if you have left one of the header cards blank. But once you set up everything the first time, this step is very quick. Note that after this is set up, you cannot change the header cards. If you change the card names in your FITS files you will need to set up a new Device for these images!!!