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Solar Spectrum Solar Observer Series 1.5 25mm 0.5A H-Alpha Filter


Solar Spectrum Solar Observer Series 1.5 25mm 0.5A H-Alpha Filter

In stock
can be shipped within 3-4 days

£4,499.00
Price includes VAT, plus delivery


Solar Spectrum 0.5 Angstrom H-Alpha Filter with 25mm clear aperture and active temperature control

Solar Spectrum stand-alone H-Alpha filters may be used on a variety of telescopes. Typically these are Refractors but it is also possible to adapt Schmidt Cassegrain and Maksutov reflectors. Regardless a suitable energy rejection filter must be used. For air spaced refractors this can take the form of a simple UV/IR cut or H-Alpha filter mounted internally. For oilled and Petzval refractors and any reflector, a front mounted energy rejection filter is required. The best of these are the Baader D-ERF types which will offer the best optical performance.

A rear mounted H-Alpha etalon requires that your telescope will operate at about F28-32. F30 is often chosen as an optimum. As no F/30 telescopes exist, owners use a tele-centric (not the same as a barlow) to bring their telescope to ~F/30. Examples are as follows

An F/6 telescope requires a 5X tele-centric
A F/7 or F/8 telescope requires a 4X tele-centric
A F/11-f/12.5 telescope requires a 2.5X tele-centric
A F/15 telescope requires a 2X tele-centric

We offer dedicated solar tele-centrics barlows from Baader in 2x, 3x and 4x multipliers.

Any Solar Spectrum Filter may be used on any aperture telescope with proper energy rejection. Please note that a full solar disc is only possible up to around 2500mm of focal length with the 25mm clear aperture of the Solar Observer Series 1.5. Increased focal length will offer partial solar views due to the size of the Sun in comparison to the Etalon aperture.

The Solar Observer range of filters from Solar Spectrum have active temperature control to maintain the centre wavelength (CWL) of 656.28nm. The filter allows adjustment of the filters CWL to the red or blue using active temperature control. This maintains the bandpass of the filter unlike a tilt based system and also allows the unit to provide optimum results in a wider range of ambient temperatures. Adjustment of the CWL allows different features of the sun to be optimised for visual or photographic purposes.

Solar Spectrum Filters are precision made and have a reputation for excellent consistancy. The Solar Observer series 1.5 is available in either 0.65A, 0.5A or 0.3A versions with a 0.05A tolerance operated at F30.

Additional accessories in the form of dedicated Solar Tele-Compressors in 0.7x and 0.4x are also available. These reduce the effective focal length of the system, providing both a wider field of view and also minimising seeing effects. These tele-compressors screw directly into the Solar Observer Series filters.

Please contact us for full details about how to use a Solar Spectrum Filter with your telescope and what other accessories you will need.

Solar Spectrum filters are normally supplied to order, although we attempt to keep stock of some models. Lead times for filters will vary with type. Please contact us for more information.

Browse this category: Rear Hydrogen Alpha Filters