What photometric filter

Affiliation
American Association of Variable Star Observers (AAVSO)
Sat, 02/24/2024 - 20:24

I'm an AAVSO newcomer and newbie in photometry. I want to buy  36 mm V and B filters for my  optic system (Celestron 11"/STT-8300 camera). I have read CCDPhotmetric guide and I have doubts about the selection: Sloan or Johnson, Chroma or Baader? Could you recommend? Thanks,

Luis

Oviedo, Spain

Affiliation
American Association of Variable Star Observers (AAVSO)
Luis,

 

I have a set of…

Luis,

 

I have a set of Chroma filters. That said: I won them in a raffle, so the price was right! They are more pricey than Baader, for sure. I also have one or two "spare" Baaders. This will probably not affect your camera, but the Baader filters seem taller than Chromas and may have an issue in space confined EFWs, like ZWOs. My Baader filtes fit into my SBIG EFW.

Sloan filters have the issue that AAVSO does not have measures of comp stars in Sloan. I would stick with JC or Bessel filters, and make sure they are the ones that follow the "standard" transmission functions, not the "square wave" transmission functions.

I hope that helps. But you will find a plethora of opinions out there for sure!

For analysis I use VPhot exclusively. Its a great AAVSO tool and is pretty easy to use.

Peter

BPEC

 

Affiliation
American Association of Variable Star Observers (AAVSO)
Optolongs

I agree with Keith.  You should consider the Optolongs.  I have had good results with mine.

Arne Henden gave these a favorable review in one of the AAVSO forums.   The last time I looked at the prices for the Baaders and Optolongs you could get the full set of Optolongs (U,B,V,R,I) for about the same price as three Baaders.  I'm told  astrophotographers are interested in buying the U filter for making pictures of Venus, so that could be an additional discount.  (You will probably never need the U.)

The only problem I see is that US retailers now only seem to offer the Optolongs in 1.25" and 2", but I haven't done a serious search for other sizes recently.  I contacted the Chinese manufacturer ~3 years ago and multiple sizes were available from them.

Phil