Flux to magnitudes

Technology VStar
1

Dear all,

I loaded flux data to VSTAR but I do not succeed to transform these data
to magnitudes. I installed the plugin but do not find where to get transformed values

Do you know where to find ?

Thanks
Best
Jeff

2

Hi Jeff

Welcome to the forum. :slight_smile:

Can you tell me what observation source you are loading from, e.g. Kepler or some other FITS file and what plugin you are using?

If you can also attach the file, that would help me reproduce what you are seeing.

Thanks.

David

3

Dear David

Thanks for your reply.

It is a simple 2 columns JD/flux

here is the file, I suppose that we enter somewhere the magnitude for flux = 1 in VSTAR ?

Best

Jeff
test_2COL.txt (509 Bytes)

1 Like
4

Hi Jeff

Apologies for the delay.

There is not currently a specific feature for converting flux to magnitude.

It would be possible to do this via an observation transformer plugin, and we could experiment with this using the VeLa Observation Transformer plugin which can be installed via Tool → Plug-in Manager (VeLa observation transformation tool) with a formula like:

mag = -2.5*log10(flux/flux0)

where flux is a value in your file and flux0 is the zero-point flux for the source photometric system. flux0 may relate to your comment about entering the magnitude for flux = 1.

Is this heading in the direction you are after?

It would also be possible to create a custom observation transformer plugin.

David

5

Dear David

Many thanks for your reply.

ok I wondered what was VELA. It is used to create formulae.

I thought (but I was wrong) that a specific feature was included in VSTAR
to convert flux to magnitudes but we must do it ourself..

I will look at this when I will have some time

Thanks
Best regards
Jeff

6

Thanks Jeff.

Yes, VeLa can be used for even more than that. It’s essentially VStar’s scripting language, but expressions and functions are the focus:

VeLa · AAVSO/VStar Wiki · GitHub

We can prototype this with VeLa before writing a custom plugin.

Tracking this issue at Create flux to magnitude observation transformer plugin · Issue #568 · AAVSO/VStar · GitHub

David

7

Hi again Jeff

I also meant to ask: when you say flux here, do you mean instrumental magnitudes from photometry (of CCD/DSLR/… images) or is the flux here something else?

David

8

Dear David, I mean real flux 1 = max, not instrumental magnitudes

9

many thanks for your links for VELA I will read at them :+1: