[Aavso-photometry] Source for photometry filters

Sat Apr 19 17:19:48 EDT 2008

> Can anyone recommend a good source and brand for photometry filters?
> I'm trying to keep my costs down and my local supplier has
> discontinued all but the Custom Scientific brand.  I'm using an SBIG
> filter wheel that accomodates 1.25" filters.

The Schuler filter (originally Schüler, now sold by AstroDon):
<http://www.astrodon.com/products/filters/photometric/>
<http://www.astrodon.com/custom/_2e2a/content/files/SchulerUVBRIYel.jpg>
are the least expensive ones and not specially polished nor AR
coated (4 mm thick Bessell prescription).

The other vendors usually sell especially polished and AR coated
photometric filters that are much more expensive:

SBIG = Custom Scientific (Bessell prescription):
<http://www.sbig.com/products/filters.htm#UBVRI>
<http://www.sbig.com/products/ubvri_filters.gif>
<http://www.sbig.com/products/ubvri_filter_curves.htm>
<http://www.sbig.com/products/u_filter.gif>
<http://www.sbig.com/products/b_filter.gif>
<http://www.sbig.com/products/v_filter.gif>
<http://www.sbig.com/products/r_filter.gif>
<http://www.sbig.com/products/i_filter.gif>
<http://www.sbig.com/sbwhtmls/filters.htm>
<http://www.sbig.com/sbwgifs/UBVRIfilters.gif>
<http://www.sbig.com/sbwhtmls/ubvri.htm>
<http://www.sbig.com/sbwgifs/ubvri_u_chart.gif>
<http://www.sbig.com/sbwgifs/ubvri_b_chart.gif>
<http://www.sbig.com/sbwgifs/ubvri_v_chart.gif>
<http://www.sbig.com/sbwgifs/uvbri_r_chart.gif>
<http://www.sbig.com/sbwgifs/ubvri_i_chart.gif>
(the Ic one is like in most Bessell prescription filter sets without
the recommendable short-cut)

SBIG just for ST-402ME (BVIc+Clear):
<http://www.sbig.com/products/402_new.htm>
<http://www.sbig.com/sbwhtmls/402bvi.htm>
<http://www.sbig.com/sbwgifs/cfw_402_bvi_graph2.gif> (ST-402) vs.
<http://www.sbig.com/sbwgifs/cfw_402_bvi_graph.gif> (Bessell)
<http://www.sbig.com/sbwgifs/cfw_402_I_filter_and_qe.gif>
(the Ic one is with the recommendable short-cut)

Custom Scientific (Bessell prescription)::
<http://www.customscientific.com/astrostand.html>
<http://www.customscientific.com/astroresearch.html>
<http://www.customscientific.com/ubvri.jpg>
<http://www.fli-cam.com/FLIproducts/cs-filters.htm>
<http://www.fli-cam.com/images/bessell.gif>
(the Ic one is like in most filter sets without short-cut; they offer
also Fukugita 1996 SDSS filters)

Andover (5 mm thick Bessell prescription):
<http://www.andcorp.com/Web_store/UBVRI/Johnson.php>
<http://www.andcorp.com/Web_store/UBVRI/ubvri.php>
<http://www.andcorp.com/Web_store/Images/Graphs/UBVRI_Johnson.gif>
(the Ic one is like in most filter sets without short-cut)
<http://www.andcorp.com/Web_store/UBVRI/Kron.php>
<http://www.andcorp.com/Web_store/UBVRI/ubvri.php>
<http://www.andcorp.com/Web_store/Images/Graphs/UBVRI_Kron.gif>
(here the R filter looks weird: the Ic one is what we actually want
as it has a short-cut)

Omega Optical (5 mm thick Bessell prescription):
<https://www.omegafilters.com/index.php?page=prod_astro_index>
<https://www.omegafilters.com/images/ubvri.gif>
<https://www.omegafilters.com/pdfs/Filters_for_Astronomy_Flyer.pdf>
<https://www.omegafilters.com/index.php?page=shop/browse&product_line_id=9>
(Bessell 1990 5 mm filter prescription for NIR sensitive UV-
coated Thomson and GEC CCDs; Ic one is like in most filter
sets without short-cut; they offer also Fukugita 1996 SDSS
filters)
<http://www.konkoly.hu/staff/racz/Schmidt_UBVRI.html>
<http://www.konkoly.hu/staff/racz/Schmidt_UBVRI.gif>
<http://www.konkoly.hu/staff/racz/OmegaOptical/XBSSL_U.gif>
<http://www.konkoly.hu/staff/racz/OmegaOptical/XBSSL_B.gif>
<http://www.konkoly.hu/staff/racz/OmegaOptical/XBSSL_V.gif>
<http://www.konkoly.hu/staff/racz/OmegaOptical/XBSSL_R.gif>
<http://www.konkoly.hu/staff/racz/OmegaOptical/XBSSL_I.gif>

Optec:
Johnson 7.0±0.2 mm UBVRIJH Filters (12.7mm unmounted for SSP)
<http://www.optecinc.com/optec_014.htm>
<http://www.optecinc.com/17031_johnsonu.jpg>
<http://www.optecinc.com/17132_johnsonb.gif>
<http://www.optecinc.com/17133_johnsonv.gif>
<http://www.optecinc.com/17134_johnsonr.gif>
<http://www.optecinc.com/17135_johnsoni.gif>
<http://www.optecinc.com/17137_johnson_j.gif> (just for NIR PDs)
<http://www.optecinc.com/17138_johnson_h.gif> (just for NIR PDs)
<http://www.optecinc.com/17043_johnsonv.gif> (just for UBV PMTs) 
(they offer also Strömgren ubvyHbnw filters for SSP)
Bessell 5±0.2mm UBVRI Filters (25.4mm diameter mounted for SBIG CFW)
<http://www.optecinc.com/optec_065.htm>
<http://www.optecinc.com/optec065001.jpg>
<http://www.optecinc.com/bessell_25,4mm_transmission.pdf>
Bessell 5 mm UBVRI Filters (50mm diameter unmounted for IFW)
<http://www.optecinc.com/optec_021.htm>
<http://www.optecinc.com/17250_bessel_u.gif>
<http://www.optecinc.com/17446_bessel_b.gif>
<http://www.optecinc.com/17447_bessel_v.gif>
<http://www.optecinc.com/17448_bessel_r.gif>
<http://www.optecinc.com/17449_bessel_i.gif>
(Bessell 1990 5 mm filter prescription for NIR sensitive UV-
coated Thomson and GEC CCDs; Ic one is like in most filter
sets without short-cut)

Chroma Technology :
UBVRI Filters for Photometric Astronomy
5 mm UBVRcIc Filter Recipes (Bessel type)
<http://www.chroma.com/index.php?option=com_content&task=view&id=34&Itemid=47>
<http://www.chroma.com/images/stories/filters/astronomy_graph2.jpg>
<http://www.chroma.com/images/stories/filters/astronomy_graph3.jpg>
(the Ic one is like in most filter sets without short-cut)

Glen Spectra:
Astronomy Bessell Photometric Filters
<http://www.glenspectra.co.uk/glen/filters/astronomy.htm>
<http://www.glenspectra.co.uk/glen/filters/images/ubvri.gif>
(the Ic one is like in most filter sets without short-cut)

Fingerlakes Instrumentation FLI UBVRI Sets:
<http://www.fli-cam.com/FLIproducts/fli_filters.htm>
(no further details beside the price)

Astronomik (LRGB Typ IIc interference G filter):
<http://www.gerd.neumann.net/v2/deutsch/astronomik_lrgb.html>
<http://www.gerd.neumann.net/v2/english/eng_astronomik_lrgb_type2.html>
<http://www.gerd.neumann.net/v2/bilder/Astronomik-LRGB.gif>
(the BAV recommended the LRGB Typ IIc G Filter as V filter a few
years ago; interference-only filter that doesn't have the typical red
tail of colored glas filters but still matches the V band standard
more than reasonably well)

Idas UBVRIL filter set (photometric interference filters):
<http://www.sciencecenter.net/hutech/idas/ubvril.htm>
<http://www.sciencecenter.net/hutech/idas/pics/ubvril.jpg>
<http://www.fli-cam.com/FLIproducts/cfw.htm>
<http://www.fli-cam.com/FLIproducts/hutech.htm>
<http://www.fli-cam.com/images/Product%20Images/Hutech_ubvril.jpg>
<http://www.ne.jp/asahi/starfactory/home/products/Accessories/IDAS/index.html>
<http://www.ne.jp/asahi/starfactory/home/products/Accessories/IDAS/ubvril_sp.jpg>
<http://www.icas.to/e/lineup/ubvril.htm>
<http://www.icas.to/e/lineup/ubvril.pdf>
(looks like a inteference-only filter set; V and Ic looks about OK;
the UBR ones look a bit far off from the standard; the BVR ones
don't have the typical red tail of standard colored glas filters, the
Ic one has a short-cut as it should)

There is not something like a one and only "Bessell prescription"
for 4 and 5 mm thick UBVRcIc filters (even if the manufacturers
try to let it look like this) !
Most Bessell prescription filter sets I saw look like as the old
prescription for UV-coated, NIR-sensitive CCDs as published in:
  1990PASP..102.1181B - Bessell, M. S.
  UBVRI passbands
  <http://adsabs.harvard.edu/abs/1990PASP..102.1181B>
These of course don't use the advantage of adapting the filters
to the nowadays usually much more blue sensitive CCD chips
that are common with amateur and pro CCD cameras.
Bessell explicitly states that the prescription for the 4 and 5 mm 
thick sets should be optimized to get the entire system response
of the setup (transmission scope * FRs * ... * camera window *
chip cover glas * CCD QE) to match the standard as good as
possible:
  1995CCDA....2...20B - Bessell, M. S.
  UBVRI Filters for CCD Photometry
  <http://adsabs.harvard.edu/abs/1995CCDA....2...20B>

Clear skies
 Wolfgang

-- 
Wolfgang Renz, Karlsruhe, Germany
Rz.BAV = WRe.vsnet = RWG.AAVSO