Abstract:
We have recently developed a narrow band imager (NBI) using a
n air gap based Fabry-P ́erot
(FP) interferometer at the Indian Institute of Astrophysic
s, Bangalore. Narrow band imaging is achieved
by using an FP interferometer working in combination with an
order sorting pre-filter. The NBI can be
tuned to a different wavelength position on the line profile b
y changing the plate separation of the FP. The
interferometer has a 50 mm clear aperture with a bandpass of
∼
247.8 m
̊
A and a free spectral range of
∼
5.3
̊
A at
λ
= 656.3 nm. The developed NBI is used to observe the solar filam
ent in the H
α
wavelength.
The instrument is being used to image the Sun at chromospheri
c height and it is also able to scan the
H
α
spectral line profile at different wavelength positions. We
have also made Doppler velocity maps at
chromospheric height by taking the blue and red wing images a
t
±
176 m
̊
A wavelength positions separately
away from the line center of the spectral line. In this paper,
we present a description of the NBI including
lab test results of individual components and some initial o
bservations carried out with this instrument.
