I'm just learning about this and made my first observations the other day. I'm using a canon eos450d with my telescope. Software I'm using is Deep Sky Stacker and AstroImageJ (AIJ)
I'm a bit confused about how AIJ uses colour channels. I import FITS files into AIJ. The files have 3 colour channels. The first time I tried I just imported a single file and did the photometry on that. AIJ produced 3 magnitude for T1 which I thought represented the three colours red, green black. Next time I imported 5 images in FITS files each with 3 colour layers. I did the photometry but this time AIJ came up with 5 values for T1 Magnitude. I was expecting it to produce 15 meaning 5 images each with 3 colours.
I'd be grateful if someone could help me here.
If there is a way to read files in AIJ as you describe, I am not aware of it. I convert my CR2 files to FITS, debayer them and separate the red, green and blue channels before importing into AIJ.
I use IRIS (free, www.astrosurf.com) for all preprocessing prior to opening files in AIJ. After converting files to FITS, preprocessing (bias frames, darks, flats), and debayering, there is a menu item that allows channel extraction. Any or all of the RGB channels can be extracted.
IRIS is, in my opinion, somewhat cumbersome. AIP4Win is in my opinion better for DSLR RAW files, but I have Windows10, and there is an error which prevents AIP4Win running.
I also use IRIS and transfer FITS format files to AIJ for photometry. I can't comment on how cumbersome IRIS is because I haven't used anything else but I use the batch facility within IRIS. With this I can decode the raw files (science, flats and darks) then set the batch file running and the debayered sequences are produced ready to import into AIJ. It can take some time for a long sequence but I don't have to sit and watch it.
Hi Roy, I tried Iris but had problems using it - probably my fault. I am currently trying AIP4Win (V 2.4.1) which is running on my windows 10 machine. There is a stipulation in the installation instructions that you have to unzip the file into a folder, find the installation file, right click on that and select "Install as administrator". It doesn't work properly until you have restarted your machine. It does have a few odd chatacteristics. When clicking on some commands it comes with a diagnostic pop-up which looks like something someone might put in when debugging the program initially. At any rate you can clear the pop up and it carries on to do the command anyway.
At the moment I have IRIS, AIP4WIN and AIJ all installed and I'm trying to work out which one is best for me. They all work after a fashion and probably it's because I've not set something up properly.
I expect you are familiar with the link below, If you scroll down you come to a list of links headed "User Manual", Click on the link "Console Commands and Scripts". This takes you to a description of how to write the batch files. If you click on the link at the start ;"The full set of console commands......." you go to a description of each of the available commands.
I have based what I do on Mark Blackfords guide to using IRIS for DSLR photometry, with which I expect you are also familiar. I'm no programmer but the batch system looks vary basic to me (eg there is no logic - "if" statements etc ) which means a lot more coding is necessary. I have master files which I edit each time I use them for the number of images to be processed and the output file names so its necessary to know how it all works to use it but once its done, its done and it works well for me.
I have a set of files to process a sequence, another to process a single stacked image and files to stack the sequences into 2s or 3s to improve SNR.
Hope this helps
Maybe that tutorial helps you:
There are several other freeware tools, but most of them seem to run under Unix-like operating systems.
About Iris - I have used it long time ago and then IMHO it's FITS-files were created with signed pixel values, i.e. from -32### .... +32###. Is that still the case?
Tony and Tonisee,
Thanks you for your comments and links.
Tony, I'm familiar with the IRIS web site, but am not sure I've ever had a good look at the Console Commands and Scripts web page previously. I've often looked at the command list, but could never find the commands that would do the various things I need - preprocessing (bias, dark, flat) a batch of images, CFA convert a batch of images, channel separate a batch of images.
Would you be willing to message me offline and send me a file containing your script for processing a sequence of images from time series photometry?
Tonisee, I'll have a look at the tutorials in the link you sent me. Thanks. Concerning your question:
"About Iris - I have used it long time ago and then IMHO it's FITS-files were created with signed pixel values, i.e. from -32### .... +32###. Is that still the case?" I'm not sure that I can answer that.
Yes I would be happy to send you the files but I'm not sure how to get hold of your email address or private message you. If you can let me know I'll do it as soon as I can.
Tonisee - like Roy I don't think I can answer your question about signed pixel values but thanks for the link and especially the information about decoding Raw files for AIJ
For private messaging, make sure you are logged in to the AAVSO seb site. Click the observer initials above my image (arx) in this forum post. A dialogue will open with information about me, above which there should be a tab labelled 'Contact'. Click that, and a form will open which allows you to send me a message via my personal email. When I receive your messaage, I'll be able to see your email address and of course will be able to reply.
Re your question about signed pixel values. I've pasted below a few commands from the IRIS command list. Don't know if these help with your question.
Load into memory an unsigned 16-bits image. The level of the pixels is not modified, but the images is truncated for intensities higher than 32767.
Load into memory an unsigned 16-bits image. Value 32767 is subtracted from the intensity of all the pixels. The final level lies between -32768 and 32767.