Star catalogues useful for Photometry

Hi,

For a project I need to combine some filtered images (BVR) to a nice colour composite image.

The catch is that I need to weigh each of the images correctly. The B filter is slightly darker than the R so I need to measure the brightness of some stars on the image in R and B (and V!) and combine them accordingly to make a true colour final image.

Apparently the Landolt catalogue ( james.as.arizona.edu/~psmith/61inch/ATLAS/tableA.html ) is a good resource here. However it is concentrated around 0 Dec, and has nothing near M51 which is far far away from 0 Dec.

So does anyone know of a catalgue that contains the magnitude of stars with R,B and V filters? The best I can find, an then only for some stars is a B-V index, which still doesn't help me calibrate the Red image.

I'm hoping that there is just some interface to the HGSC or USNO catalogues that I'm missing. This data must be easily available somewhere!

Cheers,
~Al

Have you tried Aladin? It's an image server and so loads up images from a variety of sources - all wavelengths. I haven't used it in earnest but it looks well worth learning how to use it.

aladin.u-strasbg.fr/

Cheers

Dave McD

Cheers Dave,

I've downloaded it and got the RB and V fits images from IRAF into it and calibrated them so I can now click on (most) stars and get the magnitudes in B and R from the CSG2.2 catalogue, the first catalogue I bothered to look at. Guess I need to see what is in the other catalogues.

It also does the RGB combining, but I suspect that this is just a straight addition of the colours, and not weighing them.

Thanks for the pointer.
~Al

Don't forget to credit me in your project

If anyone else is following this, Aladin, from the use I've had so far, fills in some of the gaps in Starry Night Pro and gives lots more besides. I'm finding it a bit difficult getting to grips with it but it has some pretty cool functionality like layers.

If you are imaging and you come across some stars or other objects you can't find in your favourite star atlas, then give it a whirl. Or use it to get good data on magnitudes.

Cheers

Dave McD

If you are imaging and you come across some stars or other objects you can't find in your favourite star atlas, then give it a whirl. Or use it to get good data on magnitudes.

An example for those wondering about this tool



Thats a piece of Daves M51 image calibrated. The red crosses are from the GSC2.2 catalogue and the small blue crosses from the USNO-B1 catalogue, the amount of stars can be configured with filters, to only show above or below a certain magnitude etc. The info at the bottom has the data for the highlighted star.

It has a few more handy tools build into it, but I havent experimented with any more than this.

And its written in Java so it just works!

Cheers,
~Al