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Using UBVRI Filters for Photometry ... and Astrophotography?

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#1 levyjoelh

levyjoelh

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Posted 23 February 2021 - 10:17 AM

Hi All -

 

My main interest is Photometry but that does not mean I don't care about astrophotography.   

 

Best I can tell, the tolerances for UBVRI filters are tighter in the given spectra than LRGB filters.

 

For example, 

 

The traditional Chroma Blue filter from the LRGB set begins at a wavelength of about 415 and ends about 500.

The traditional Chroma B Filer from the UBVRI set begins at a wavelength of about 400 and ends about 500.

 

The traditional Chroma Red filter from the LRGB set begins at a wavelength of about 575 and ends about 725.

The traditional Chroma R Filer from the UBVRI set begins at a wavelength of about 525 and ends about 725.

 

The examples above are not exact, but close approximations base on the Chroma graphs.   

 

The actual graphs can be  seen here:   https://www.chroma.c...my-applications

 

Thoughts:

 

It would seem to me this means that I could use the UBVRI set for imaging (as desired) without the need to buy a whole new set (and filter wheel) for LRGB filters.   

 

I would not however,\want to use LRGB for photometry as you would "lose" the lower band of certain wavelengths.  

 

Is that reasonable? 

 

 



#2 happylimpet

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Posted 23 February 2021 - 11:10 AM

You can use anything for imaging.



#3 pbealo

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Posted 23 February 2021 - 02:47 PM

Very reasonable. 

A) I have seen ESO images from Chile where they do that

B) My club (ATMOB is putting together a new scope/camera combo where we will be using this technique to eliminate filter changes from our filter wheel

C) I'm going that route!

 

I do not believe it prudent to use RGB filters for photometric work unless you can correlate the magnitudes match those taken with standard BVR filters. 

Peter


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