This document is an instruction manual for Bintel Dobsonian Telescopes, covering models BT 152, BT 202, BT 252, and BT 302. It provides comprehensive guidance on assembly, usage, maintenance, and specifications for these astronomical instruments.
Function Description:
Bintel Dobsonian telescopes are designed for high-resolution viewing of astronomical objects, including planets, the Moon, deep-sky galaxies, nebulas, and star clusters. They feature precision optics and a Dobsonian mount, which allows for easy aiming and tracking of celestial objects along two axes: altitude (up/down) and azimuth (left/right). The telescopes are intended for amateur astronomers, offering a user-friendly experience for exploring the night sky.
Important Technical Specifications (Summarized from BT 152, BT 202, BT 252, and BT 302 models):
- Focal Length: Ranges from 1200mm (BT 152, BT 202) to 1520mm (BT 302).
- Aperture: Varies from 152mm (BT 152) to 304mm (BT 302).
- Focal Ratio: Ranges from f/7.9 (BT 152) to f/5 (BT 252, BT 302).
- Mirror Coatings: All models feature aluminum with SiO2 overcoat.
- Minor Axis of Secondary Mirror: Ranges from 47.0mm (BT 152, BT 202) to 70mm (BT 302).
- Weight: Optical tube assembly weights range from 19.5kg (BT 152) to 37kg (BT 302, including base).
- Tube Length: Ranges from 1181mm (BT 152, BT 202) to 1450mm (BT 302).
- Tube Outer Diameter: Ranges from 176mm (BT 152) to 360mm (BT 302).
- Focuser: All models utilize a Crayford design. BT 152 has a 1.25" focuser, while BT 202, BT 252, and BT 302 have 2" Crayford focusers with 1.25" adapters. Some models include a 10:1 microfocus.
- Eyepieces (Supplied):
- BT 152: 25mm & 9mm Bintel Plössl (1.25" barrel diameter).
- BT 202: 30mm Superview (2"), 15mm & 9mm Bintel Plössl (1.25" barrel diameter).
- BT 252: 30mm Superview (2"), 15mm & 9mm Bintel Plössl (1.25" barrel diameter).
- BT 302: 30mm Superview (2"), 15mm & 9mm Bintel Plössl (1.25" barrel diameter).
- All models include an ND #96 Filter.
- Magnification (with supplied eyepieces):
- BT 152: 48x & 133x.
- BT 202: 46x, 80x & 133x.
- BT 252: 48x, 83x & 139x.
- BT 302: 47x, 100x & 167x.
- Finder Scope:
- BT 152: 6x power, 30mm aperture.
- BT 202, BT 252, BT 302: 8x power, 50mm aperture, Achromat.
- Finder Bracket: Dovetail base, spring-loaded X-Y alignment for all models.
- Cooling Fan: Included with Battery Pack for all models.
Usage Features:
- Assembly: The Dobsonian base requires initial assembly, which takes about 15 minutes using provided Allen wrenches and an adjustable crescent wrench. The optical tube assembly is then mounted onto the base.
- Finder Scope Installation and Alignment: The 8x50 achromatic finder scope aids in locating objects. It must be accurately aligned with the main telescope by centering a distant object in both the finder scope's crosshairs and the telescope's eyepiece. The finder scope's focus can also be adjusted.
- Eyepiece Insertion: Eyepieces are inserted into the focuser drawtube and secured with a thumb screw. The manual advises starting with a low-power eyepiece for locating and centering objects, then switching to higher magnification if desired.
- Focusing: The telescope is focused by slowly rotating the focusing knobs until the object comes into sharp focus. The focuser tension can be adjusted, and the focuser position can be locked.
- Collimation (Mirror Alignment): This critical process ensures optimal performance. It involves centering the secondary mirror in the focuser drawtube and then adjusting the primary mirror's tilt using spring-loaded thumb screws on the back of the mirror cell. A collimating tool (like an Orion Collimating Eyepiece or Bintel Deluxe Laser Collimator) is recommended. Star-testing helps verify collimation by observing the symmetry of a defocused star image.
- Astronomical Observing Tips:
- Site Selection: Choose a location away from light pollution, avoiding rooftops and chimneys that cause air turbulence.
- Seeing and Transparency: Atmospheric conditions affect viewing quality. Good "seeing" (minimal star twinkling) allows for sharper views at higher magnifications. "Transparency" refers to clear, moisture-free air.
- Cooling the Telescope: Allow the telescope to reach "thermal equilibrium" with the ambient temperature for best performance. A cooling fan is provided for this purpose but should be turned off during use.
- Dark Adaptation: Eyes need about 30 minutes to dark-adapt for optimal night vision. Red-filtered flashlights are recommended to preserve dark adaptation.
- Tracking Celestial Objects: Due to Earth's rotation, objects appear to move across the field of view. The Dobsonian mount allows for smooth, continuous manual tracking by gently nudging the telescope.
- Eyepiece Selection: The manual explains how to calculate magnification (Telescope Focal Length / Eyepiece Focal Length) and real field of view. It advises using low-power, wide-field eyepieces for locating objects and deep-sky viewing, and higher-power eyepieces for planets and the Moon. The 2" focuser allows for wider field of view eyepieces.
- Objects to Observe: Guidance is provided for observing the Moon (best during partial phases, with a Moon filter), the Sun (only with a full-aperture solar filter), planets (Jupiter, Saturn, Venus, Mars), stars (for color and double stars), and deep-sky objects (requiring dark skies and low magnification).
- Starhopping: This technique involves using a star chart or atlas to navigate the sky by moving the telescope from one bright star to another, gradually approaching the desired object.
Maintenance Features:
- Storage: Store the telescope in a clean, dry, dust-free place, safe from rapid temperature and humidity changes. Keep the dust cap on the front of the telescope when not in use.
- Cleaning Lenses: Use quality optical lens cleaning tissue and fluid designed for multi-coated optics. Blow off loose particles first, then gently wipe the lens in a circular motion. Avoid rubbing too hard.
- Cleaning Mirrors: Mirrors generally only need cleaning once a year. Improper cleaning can scratch coatings. To clean, carefully remove the mirror cell from the telescope, then remove the mirror from the cell. Submerge the mirror in a solution of room-temperature water with dishwashing detergent and isopropyl alcohol. Gently wipe with clean cotton balls, rinse with lukewarm and distilled water, then air dry or use a Q-Tip for stray drops. Reassemble once completely dry.
- Warranty: Bintel Dobsonian Reflecting Telescopes come with a two-year limited warranty against defects in materials and workmanship from the date of purchase. This warranty covers repair or replacement at Bintel's option, provided the instrument is returned freight paid and proof of purchase is supplied. It does not cover abuse, mishandling, modification, or normal wear and tear.
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