Celestron Advanced VX 6" RASA Handleiding

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Instruction Manual

Model: 91071

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ENGLISH| 1

6” OPTICAL TUBE ASSEMBLY

Overview

1Schmidt Corrector 8Dust Cover

2Lens Group9Battery Pack (Batteries not included)

3Lens Group Cell10Filter Drawer

4Dovetail Mounting Bar11Filter Holder with 2” Clear Filter (comes installed in Filter Drawer)

5Cooling Fan121.25” Filter Adapter

612V DC Jack for Cooling Fan13Camera Adapter (comes connected to Filter Drawer)

7Focus Knob 14Retaining Ring (comes connected to Filter Drawer)

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The Rowe-Ackermann Schmidt Astrograph 6 (RASA 6) is an incredibly fast (f/2.2) 6”

aperture optical system that delivers a flat field without optical aberrations. It is capable

of capturing stunning deep-sky astronomical images without the difficulties presented

by slower and longer focal length telescopes. The astrograph can only be used with

a camera.

Mounting the Astrograph

The RASA 6 has a CG-5 dovetail mounting bar. This is compatible with mounts that accept

a CG-5 or Vixen dovetail. The astrograph weighs 8.4 lb. Choose a mount with enough load

capacity to accommodate the astrograph, your camera, and any additional accessories

you want to use.

Choosing a Camera

When selecting a camera to use with the RASA 6, there are several things to keep in mind.

1. Sensor size – The optical design is optimized for use with sensors that have a

diagonal size up to 16mm. It will still perform well with up to 22mm–diagonal sensors,

but field illumination in the corners will be reduced.

2. Pixel size – The RASA 6 works effectively with a wide range of sensor pixel sizes.

Unlike many telescopes, it can work well with smaller pixels (e.g., less than 3 μm

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) due

to its fast focal ratio (f/2.2) and 6’’ aperture.

3. Obstruction – Since it mounts in front of the optics, select a camera that blocks as

little of the aperture as possible. Cylindrical cameras with an outer diameter measuring

less than 75mm work best. Many astronomical and “HyperStar-compatible” CMOS

cameras are especially well-suited to the RASA 6.

4. Backfocus – Backfocus, also known as flange focal distance, is the distance between

a camera’s sensor and the point where the camera body connects mechanically

to a lens or telescope. For flat-field astrographs like the RASA 6, it’s essential to

position the camera’s sensor precisely to match the required backfocus, ensuring the

telescope’s focal plane aligns with the sensor. Failure to do so may result in degraded

performance at the edges of the sensor, particularly with larger sensors. For the RASA

6, the correct backfocus distance is 17.5mm from the top flat surface of the camera

adapter (see drawing below). Cameras with sensors recessed more than 17.5mm into

their bodies are incompatible with the RASA 6, as their sensors cannot be positioned

at the proper focal plane.

Due to their large obstruction and long backfocus, DSLR cameras are not compatible

with the RASA 6.

CAMERA ADAPTER

IMAGE PLANE

17.50 MM

Product specificaties