Resolution Choices with DayStar Filters
  • A: USE FULL APERTURE requires a barlow.
    Insert the barlow, then insert the DayStar Filter behind it. Now you're ready to observe in high resolution for amazing detail. The barlow power required for full aperture observing is 30 divided by the f ratio of your telescope.
    For example, an F/8 needs a 4X barlow. ( 30 divided by 8 = about 4) .
  • B: OR USE AN APERTURE MASK uses no barlow. Stop down your front aperture. Use no barlow.
    Just insert the DayStar Filter in the focuser of your telescope and you're ready to observe full-disk. The aperture you need to reduce down to is your Focal Length (EFL) divided by 30
    For example, a 2500mm EFL telescope would use an 83mm aperture mask.

  • C: OR TRY A COMBINATION OF THE TWO IDEAS use a smaller barlow and a slight aperture reduction mask.
    Use half your aperture and a lower power Barlow for a nice compromise between resolution and field of view.
  • ANY DayStar Hydrogen Alpha filter can be used on any telescope configured this way. 0.7Å or 0.4Å, it's your choice.

For further explanation on focal ratios, visit our Application Page

Sample Refractor Telescope Configurations with Resolution Choices:
Telescope on which DayStar will mount
wpeA4.jpg (20435 bytes)
Reduced aperture
Focal Length
wpeA2.jpg (38961 bytes)
Half Aperture - barlow needed
Focal Length
wpeA2.jpg (38961 bytes)
Full aperture - barlow needed
Focal Length
AP 155mm F/7 Starfire
FL = 1085mm
35mm aperture
FL = 1085mm
70mm aperture mask - 2X barlow
FL= 2170mm
155mm aperture - 4X Barlow
FL = 4340mm
TeleVue TV76 F/6.3
FL = 479mm
40mm aperture - 2.5X barlow
FL = 1197mm
65mm aperture - 4X barlow
FL = 1915mm
Celestron 150mm F/8
FL = 1200mm
40mm aperture
FL = 1200mm
100mm aperture - 2.5X barlow
FL = 3000mm
150mm aperture - 4X barlow
FL = 4800mm
With DayStar Filter rear-mounted filters, an observer has a choice of high or low resolution configurations on a choice of dozens of telescopes.

* HALF-BANDWIDTH: The term half-bandwidth refers to an optics industry standard of measure.  On a chart depicting the peak where light is transmitted, that peak's width is measured at the point 50% between zero and full transmission. This term is called half-bandwidth.

The Sun Today
Hydrogen Alpha Filters
Current Delivery Times:

4-6 weeks for:
Blocker and Trimmers
ION Filters
CaII H line filters
Quantum upgrade:  
Quantum SE Filters
SolaREDi 60 Scopes
SolaREDi 80 Scopes

3-6 months for:
Quantum PE Filters
Ca II K Line PE Filters
Sodium Line FIlters
Solar System Filter Wheel

All DayStar Hydrogen a filter assemblies need to be used in conjunction with a lens cover and Energy Rejection Filter.

Offering absolute precision control over wavelength transmission. . .

DayStar Filters LLC • 149 Northwest OO Highway • Warrensburg, MO 64093 - USA
Telephone: 866-680--6563 • service@daystarfilters.com • FAX: 1-866-791-0448