Accessories for H-alpha solar observation / imaging


A competely equipped M68 H-alpha Telescope - with all recommended accessories

Our sun is a fascinating target even when the solar activity is low - given that the telescope aperture can be increased sufficiently. When equipped with a heated SolarSpectrum H-alpha filter, telescopes from 80mm aperture to 280 mm aperture will show incredibly faint, rapidly changing structures. A SolarSpectrum filter with matching D-ERF-filter and telecentric beam accessories will turn almost every telescope into a highest resolution H-α-telescope. These heated H-alpha filters are manufactured for observatories and ambitious amateurs who want to utilize the aperture and resolution of their existing large telescopes for detailed imaging and monitoring faintest solar features, instead of just taking a quick look at our closest star with a comparably small objective aperture.

SolarSpectrum filters have no central obstruction and the whole H-alpha stack of optical elements inside is precision heated with a autocorrecting thermo-controller. There is no need for frequent manual or visual calibration or readjustment of the H-alpha line during the course of a day. Hence SolarSpectrum filters are the brand of choice for long term solar observation, time-lapse photography or public observation - were a large crowd of people must be served quickly without constant realigning of the H-alpha image.


H-alpha Telescope with T-2 accessories and Solar Spectrum Sundancer Filter

The thermal calibration range is wide enough to shift the observed center wavelength – to observe in the red or blue wing of the H-alpha-line. SolarSpectrum filters are for those who prefer quality over price. They are available in different HBWs (band-widths). This influences solar surface contrast as shown in the photographs to the right.


Image Data: Solar Spectrum Solar Observer Serie 1 - 0,5 Å, Celestron 150/1200 Fraunhofer with 160mm D-ERF, TZ-4 Telezentrik and TIS DMK41 Camera. © Andreas Murner

en-hwbSolar Spectrum Research-Grade filters are selected to deliver a very homogenous image across the complete field of view. The new series of SunDancer filters in addition allow for manual fine tuning to widen H-alpha wing observation.

Be warned: this intriguing combo of fast-changing protuberances, filaments, flares and surges rising up from the sun´s surface can cause you to become addicted to solar-observing!

>> See all Solar Spectrum H-alpha Filters <<

Accessories from Baader Planetarium

2459260_telecompressor-0-4x2" Research Grade 0.4x Telecompressor (46mm clear aperture)

  • The RG 0.4x Telecompressor is with 46mm clear aperture perfectly suitable amongst others for RG46 Research Grade Solar Spectrum H-alpha Filters
  • 74mm focal length, optimized for videography and for showing the whole sun. Ø 16 mm corrected image field
  • gets mounted eyepiece-sided directly onto the SolarSpectrum filter and reduces the previously by the telecentric system extended focal length again by a factor of 0.4
  • 2" male threads on both sides, fitting Universal Flange Adapter #2958240 (included with SolarSpectrum H-alpha filters
  • Telecompressor is used to adjust the focal length to possibly poor seeing conditions and / or enlarging the field for photographic- or webcam applications

2459257_telecompressor_side_backResearch Grade TZ-3 Telecentric System (46mm clear aperture, 3x focal length)

  • Telecentric with 54mm outer diameter and 2" (50.8mm) threads on both sides – T-2 Adapter and 2" m/f inverter ring included
  • 46mm clear aperture - suitable for research grade filter.
  • extra long backfocus of 250mm for optimized focal length reduction or binoviewing
  • Aplanatic, with 3x focal length extension to achieve a parallel f/30 beam with f/10 refractors – without field curvutare
  • Specially calculated and produced for H-alpha, with 99% Strehl (99% definition brightness at 656,3 nm)

sundancer2Solar Spectrum Sundancer Series 1 and 1,5 (19mm and 25mm clear aperture)

  • Solar Spectrum Sundancer Filter Series 1 & 1,5: Standard-Filter with a clear aperture of 19mm and 25mm respectively. Shows the full sun disc up to effective focal lengths of approx. 2200mm
  • Different Halfbandwidths available – please choose "Version"
  • incl. Pre-mounted Adapterset: 2x 2" SolarSpectrum Universal Flange #2958240, 1x 2"a to T-2i Reducer #2958242, 1x 2"a to T-2a Adapter #1508035, 2 pc. T-2 Dust caps (#2904000, #2904010)
  • Noiseless heated H-alpha – Filter (lambda = 656,3 nm) with additional tilt-finetuning.


TZ-optical systems are essential for undeteriorated performance of heated SolarSpectrum filters:

Please note that for H-alpha observations below 1 Ang halfbandwidth (FWHM) a telecentric lens system is absolutely mandatory, in order to achieve the recommended focal ratio of f/30 to (preferably) f/40! Because only with a telecentric approach you can create a perfectly parallel optical path which is essential for the unrestricted function of such a complicated etalon.

A TZ-lens-system is an ESSENTIAL prerequisite. One could also optically - or by means of a Barlow lens - bring a telescope to a focal ratio of f/30, but this does not mean at all that a parallel optical path is created. And mind you, a still slightly conical optical path with f/30 sent into an etalon with 0.5 Ang FWHM would only provide the contrast as if the filter had a FWHM of 0.7 Ang or much worse.

It doesn't have to be a TZ-4. The new is much better in terms of optical calculation than the 20 year older TZ-4.  So it makes sense for the user to start with a TZ-3 RG and rather stop down the telescope aperture to get to f/30. This will bring out the real contrast of the chosen SolarSpectrum-filter much better than with a poorly matched system where, for example, the older TZ-4 has a smaller clear aperture than the Solar Spectrum-Etalon would require. In the long run, a newly calculated, large RG TZ-4 is in preparation - it is worth to wait for it and to get familiar with H-alpha observation with the TZ-3 first. In the end one will certainly need both systems (RG-TZ-3 and RG-TZ-4) and adjust the telescope aperture  individually - as the system would require to enable an f/ratio of f/30 at minimum or f/40 as optimum.

Only AFTER the H-alpha etalon you can extend the field size by reducing the f-ratio with adding the new ResearchGrade telecompressor 0.4 into the optical train.

Basically - a Barlow lens has no place in an H-alpha system!

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