Special Application Filters:

H-alpha and Red Continuum Subtraction Filters
[O III] and Green Continuum Subtraction Filters
H-beta and Blue Continuum Subtraction Filters
[S II] may be used with Red Continuum Subtraction Filter
Photometric UBVRI Filter Sets

All of the special filters below except the UBVRI filters are available in both standard grade and research grade.   UBVRI filters are available only in research grade.  For nearly all amateur applications the standard grade filters are fine.  Research grade filters should be considered if one is making scientific measurements or doing other sensitive work.

Type:
H-alpha Filter

Uses:
Imaging emission nebula - Isolates the strong Hydrogen-alpha emission line
while suppressing other wavelengths, including most light pollution from city lights.
Often used with the Red Continuum subtraction filter for sensitive work.
For examples of images taken with an H-alpha filter and SBIG cameras visit our
Image Gallery

Type:
Red Continuum Subtraction Filter

Uses:
Optional filter used in conjunction with H-alpha filter
for subtraction of red background continuum.

Type:
[O III] Filter

Uses:
Imaging emission nebula - Isolates the strong [O III] emission line
while suppressing other wavelengths, including most light pollution from city lights.
Often used with the Green Continuum subtraction filter for sensitive work.

Features:
3 nm passband centered on 500.7 nm
Transmission > 65% at center wavelength
Blanked to 1.2 microns (Infrared blocked)
Mounted in 1.25" metal cell designed to fit CFW8 carousel or any threaded 1.25" nosepiece.
Filters may be removed from cells for easy cleaning.
Available in two grades:
Standard grade - commercial polish with no AR coating
Research grade - optical polish to 1/4 wave and AR coated

Price for Standard Grade:
$225.00

Price for Research Grade:
$799.00

Order Form
(Direct Only)

Type:
Green Continuum Filter

Uses:
Optional filter used with [O III] filter for subtraction of the green background.

Features:
10 nm passband centered on 510 nm
Transmission approximately 70% at center wavelength
Blanked to 1.2 microns (Infrared blocked)
1.087" diameter, 5mm thick.
Mounted in 1.25" metal cell designed to fit CFW8 carousel or any threaded 1.25" nosepiece.
Filters may be removed from cells for easy cleaning.
Available in two grades:
Standard grade - commercial polish with no AR coating
Research grade - optical polish to 1/4 wave and AR coated

Price for Standard Grade:
$185.00

Price for Research Grade:
$599.00

Order Form
(Direct Only)

Type:
H-beta Filter

Uses:
Imaging emission nebula - Isolates the blue H-beta emission line
while suppressing other wavelengths, including most light pollution from city lights.
Often used with the Blue Continuum subtraction filter for sensitive work.

Features:
3 nm passband centered on 486.1 nm
Transmission > 70% at center wavelength
Blanked to 1.2 microns (Infrared blocked)
Mounted in 1.25" metal cell designed to fit CFW8 carousel or any threaded 1.25" nosepiece.
Filters may be removed from cells for easy cleaning.
Available in two grades:
Standard grade - commercial polish with no AR coating
Research grade - optical polish to 1/4 wave and AR coated

Price for Standard Grade:
$225.00

Price for Research Grade:
$799.00

Order Form
(Direct Only)

Type:
Blue Continuum Filter

Uses:
Optional filter used with H-beta filter for subtraction of the blue background.

Features:
10 nm passband centered on 476 nm
Transmission approximately 70% at center wavelength
Blanked to 1.2 microns (Infrared blocked)
1.087" diameter, 5mm thick.
Mounted in 1.25" metal cell designed to fit CFW8 carousel or any threaded 1.25" nosepiece.
Filters may be removed from cells for easy cleaning.
Available in two grades:
Standard grade - commercial polish with no AR coating
Research grade - optical polish to 1/4 wave and AR coated

Price for Standard Grade:
$225.00

Price for Research Grade:
$599.00

Order Form
(Direct Only)

Type:
[S II] Filter

Uses:
Special narrow band filter for imaging the deep red doubly ionized S II emission line.
May also be used in conjunction with the red continuum filter.

Features:
3 nm passband centered on 672.4 nm
Approximately 70% transmission at center wavelength
Blanked to 1.2 microns (Infrared blocked)
1.087" diameter, 5mm thick.
Mounted in 1.25" metal cell designed to fit CFW8 carousel or any threaded 1.25" nosepiece.
Filters may be removed from cells for easy cleaning.
Available in two grades:
Standard grade - commercial polish with no AR coating
Research grade - optical polish to 1/4 wave and AR coated

Price for Standard Grade:
$225.00

Price for Research Grade:
$799.00

Order Form
(Direct Only)

Type:
UBVRI Filters

Uses:
Photometry.  This is the Bessell filter prescription of the Johnson-Cousins
filter set specifically designed for photometry with CCD cameras.

Features:
Research grade UBVRI filters.
All surfaces optically polished.
Anti-reflection coating.
Matching clear filter available.
1.087" diameter, 5mm thick.
Mounted in 1.25" metal cell designed to fit CFW8 carousel or any threaded 1.25" nosepiece.
Filters may be removed from cells for easy cleaning.
(See filter passbands below)

Price:
$175.00 each.
$90.00 for extra CFW8 carousel.
$90.00 for matching clear filter.
$950.00 for UBVRI set + extra CFW8 carousel.

Order Form
(Direct Only)

Filter Summary

Filter

Center
Wavelength

3 nm

672.4 nm

$225

$799

3 nm

656.3 nm

$225

$799

10 nm

645 nm

$185

$599

3 nm

500.7 nm

$225

$799

10 nm

510 nm

$185

$599

3 nm

486.1 nm

$225

$799

10 nm

476 nm

$185

$599

N/A

$175 ea

---

---

N/A

$950

AR Coating on any Standard Grade Filter may be special ordered for an additional $100
Allow additional 3 - 4 weeks for delivery. 

Click here to see detailed curves for each UBVRI filter