Coronado ST 70/400 SolarMax III BF15 <0.5Å Double Stack OTA

 

Observing the sun in H-Alpha is a lot of fun using these compact SolarMax III telescopes! The integrated ‘True’ Etalon filter provides higher contrast and a sharper image than other solar telescopes with smaller filters.

SolarMax III telescopes have an improved focuser with sensitive focusing and other high-quality features. The filters can be removed from the Solarmax III, allowing the solar telescope to also be used as an achromat for observing the night sky.

The sun is observed at a wavelength of 656 nanometers - known as H-alpha - showing an ever active solar surface and prominences at the sun's edge. There is always something to see on the sun in the H-alpha!!

RichView™ tuning: The Doppler effect causes the wavelengths of interesting structures to vary around the H-alpha line of 656.3 nanometers. This effect is particularly noticeable in the change between the central solar disk and the edge (prominences). The RichView™ tuning system allows you to adjust the filter, to find the best possible contrast.

 

Double Stack: Each SolarMax telescope is also available with a Double Stack. This means that two Etalon filters are installed, one behind the other. This reduces FWHM of the transmitted H-alpha line light to less than 0.5 Angstroms. Without a double stack, the FWHM is below 0.7 angstroms.

The smaller FWHM means noticeably higher contrast. The structures on the sun appear three-dimensional. The narrower FWHM of the filter also means the image is darker and requires fine readjustment using with the systems tuning system.

BF blocking filter: The deflection optics with the eyepiece receiver also accommodate the blocking filter. This filter reduces the brightness of the solar image and is therefore a very important part of the solar telescope, and which must under no circumstances be removed! For purely visual observing, a small blocking filter is sufficient, but for photography a larger one should be selected.

Sol Ranger: Pointing a telescope at the sun is more difficult than you may think and can often involve involuntary glimpses of the sun with unprotected eyes! The Sol Ranger finder scope is a special solar finder that uses a ground glass screen. This allows you to point your telescope at the sun easily, safely and quickly.

Delivery includes a Cemax eyepiece. The eyepieces of this series are specially optimized for observation in H-alpha. The optimization applies to the remuneration. The eyepieces have no 'filtering effect' and can therefore also be used at night.

 

SPECIFICATIONS

Optics

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Type of build
Solar H-Alpha
Type
Refractor
Aperture (mm)
70
Focal length (mm)
400
Aperture ratio (f/)
5,7
Resolving capacity
1,97
Limit value (mag)
11
Light gathering capacity
100
Max. useful magnification
140
Tube weight (kg)
3,5
Bandwidth
< 0,5
etalon filters (mm)
60
Blocking Filter (mm)
15
Double Stack
yes
Filter systems
H-alpha
Tube construction
Full tube

Focuser

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Connection ( to eyepiece)
2
Type of build
Gear rack
Free aperture (mm)
51
Gear reduction
1:10 Fine movement
Connecting threaded socket (camera-side)
T2
Rotating
yes
Adjustment range (mm)
65

Mount

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Type of build
OTA
Mounting type
no mount

Included accessories

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Prism rail
Vixen-Style
Tube clamps
yes
Finder scope
Solar finder
1.25'' eyepieces
18mm
Transport cases
yes
Deviating optics
Blockfilter

General

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Series
SolarMax III

Area of application

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Sun
yes (H-alpha)

Recommended for

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Beginners
no
Advanced
yes
Observatories
no