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Celestron RASA 8" f/2 Rowe-Ackermann Schmidt Astrograph optical Tube

Name: Celestron RASA 8" f/2 Rowe-Ackermann Schmidt Astrograph optical Tube
Brand: Celestron
SKU: RASA8
Price: 2399 EUR

The # 91073 Celestron RASA 8" is a portable and fast f/2 astrograph for really deep deep-sky images in a short time.

Aperture 203 mm

Focal length 400 mm

Focal ratio f/2

Large usable image field of 32 mm diameter

Working distance max. 29 mm from the flange or 25 mm from the T2-thread of the camera adapter (supplied)

Perfectly suitable for mirrorless system cameras and astro cameras

Ultra stable focus system with precise ball bearings - prevents from tilting of the primary mirror

Integrated 12V fan system for quicker cooling down

Integrated adaption possibility for filters (for example nebula filters)

Best contrast and reflection-free image due to XLT coating

Comes with Losmandy style dovetail bar

Manufacturer: Celestron

Product number: RASA8

EUR 2.399,00

incl. 19 % VAT (DE)

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excl. 11.95 € shipping costs (DE)

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Celestron RASA 8" f/2 Rowe-Ackermann Schmidt Astrograph optical Tube

The # 91073 Celestron RASA 8" is a portable and fast f/2 astrograph for really deep deep-sky images in a short time.

Aperture 203 mm

Focal length 400 mm

Focal ratio f/2

Large usable image field of 32 mm diameter

Working distance max. 29 mm from the flange or 25 mm from the T2-thread of the camera adapter (supplied)

Perfectly suitable for mirrorless system cameras and astro cameras

Ultra stable focus system with precise ball bearings - prevents from tilting of the primary mirror

Integrated 12V fan system for quicker cooling down

Integrated adaption possibility for filters (for example nebula filters)

Best contrast and reflection-free image due to XLT coating

Comes with Losmandy style dovetail bar

Details..
Technical data..
In the box..
Reviews..
FAQ..

Celestron 8" Rowe-Ackermann Schmidt-Astrograph - fast Deep-Sky Photo Telescope

The compact 8" Rowe-Ackermann Schmidt astrograph was developed by Celestron as complete telescope for astrophotography. Make spectacular wide field images with high resolution and ultra-short exposure time. The 8" RSA is optimized for mirrorless system cameras and, of course, for astro cameras like the ones from ZWO. The astrograph is not suitable for classic DSLR cameras, as their flange focal distance is too long.

Most important features of the 8" f/2 RASA:

The RASA provides a corrected image field with 32 mm diameter.

Due to extremely short exposure times, using an autoguider becomes unnecessary in most cases.

A built-in fan speeds up cooling down, thus the RASA becomes fully operational after relatively short time.

The primary mirror is held by stable roller bearings, so unintentional readjustment is excluded. Now focusing is more accurate and simple than ever before.

The RASA 8" is designed for the most up-to-date cameras like mirrorless system cameras and, of course, astrocameras up to 25 mm flange focal distance. The adaption to T2 is included in the scope of delivery. Fine tuning is made with T2 adapters from Teleskop-Service.

Astrophotographic results obtained with this telescope on Astrobin

Here you can find some astrophotographs made with this telescope model: Link to Astrobin

Aperture:	203 mm - 8"
Focal length:	400 mm
Focal ratio:	f/2
Central obstruction by the secondary mirror:	94 mm
100% illuminated field:	22 mm diameter
Usable and corrected image field:	32 mm diameter
On-Axis RMS spot size:	<3.7 µm diameter
Everywhere RMS spot size:	<4.55 µm diameter
Encircled Energy (390-800 nm):	>90% inside 8.4 µm circle
Design wavelength range:	390 to 800 nm
Working distance from the male T2 thread:	25 mm (T2 adapter is included in the scope of delivery)
Working distance from the connection at the front side (dovetail ring):	29 mm for self adaptions
Material optical tube:	Aluminum
Dimensions:	Length 628 mm - diameter 235 mm
Weight:	7.7 kg (17 lbs)
Max. camera weight:	9.1 kg (20 lbs)
Dovetail bar:	GGE/Losmandy style dovetail bar

RASA8 OTA

Losmandy style dovetail bar

Male T2 adapter and male C-Mount adapter

Mounting possibility for filters

Finder is not included in the scope of delivery.

Astrophotographic results obtained with this telescope on Astrobin

Here you can find some astrophotographs made with this telescope model: Link to Astrobin

Collimation of the RASA on the artificial star

A large and dark room (underground parking garage) is required for the collimation so that the artificial star can be set up at a sufficient distance. In addition, the camera is connected to the Rasa and linked to the computer. The live image is collimated.

The tension screws (3x) and the pressure screws (6x) are visible or must be exposed.

The star is slightly out of focus (focus counterclockwise), so that the star becomes a ring. If the Rasa is misaligned, the ring is not concentric, it is slightly narrower on one side and thicker on the other.

By carefully loosening the counter screws and adjusting the tension screws, the RASA can now be collimated. The position of the star in the live image on the computer will change.

The aim is to always move the star in the opposite direction to the thicker side of the ring. At some point, the ring will have the same thickness everywhere. The smaller the ring is, the closer you are to the focus and the more precisely you can adjust it.

When the ring is symmetrical on both sides of the focus and the star in the focus is round, we can end the collimation.

Question:
How can I adapt my astro camera with 17.5 mm working distance???

Answer from Teleskop-Service:
Many cameras from ZWO, Atik, QHY ... have a working distance of 17.5 mm (distance T2 internal thread to sensor). The RASA8 works optimally if the sensor is 25 mm from the T2 thread connection.

We recommend the following adaptation (from RASA to camera):

T2AbstimmA2 ... 1.5 mm length

TST2V5 ... 5 mm length

T2AbstimmA1 ... 1 mm length

You will then be exactly at the correct distance. The adaptation also works with the Celestron # 93614 nebula filter for the astrograph

Recommended accessories

Adaptors

TST2V5