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Just to confirm what most have said.
I fix and repair 114 mm and 150mm short tube ‘no name ‘reflectors for a local distributor here in Auckland New Zealand.
These telescopes are not recommended.
This design is called a ‘Bird -Jones’ reflector. Occasionally there are also incorrectly referred to as ‘Catadipotrics’ reflectors however this is more to do with advertising and is really misleading.
It uses an inbuilt ‘corrector' lens to increase the focal length. The mirrors used are spherical. The corrector lens attempts to reduce the inherent aberrations and distortions found in spherical mirrors- like marked coma.
They are notoriously difficult to collimate. Images become distorted even at relatively low magnifications.
These designs are not recommend for astro use as they give inferior images.
Money is much better spent on a long tube design with a parabolic mirror. If it is longer then F/7 or F/8 spherical mirrors can work reasonably well.
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