The Petzval objective or Petzval lens is the first photographic portrait objective lens (with a 160mm focal length) in the history of photography. It was developed by the German-Hungarian mathematics professor Joseph Petzval in 1840 in Vienna, with technical advice provided by Peter Wilhelm Friedrich von Voigtländer..
What is a petzval refractor?
Petzval Telescopes are the highest end of refracting telescopes in terms of clarity. Because they use a 4 lens optical system they are exceptionally well corrected, they have very fast focal ratios, and they are the easiest to use of all astrographs in the world of astronomy.
Who makes Askar telescopes?
Askar is the trademark of Sharpstar, a manufacturer specializing in high quality telescopes for astrophotography.
How much does the redcat 71 weigh?
Weight = 6.2lbs / 2.8kg (OTA only); 8.2lbs / 3.7kg (OTA with ring, dovetail and saddle).
What is chromatic difference?
[krō¦mad·ik ¦dif·rəns əv ‚mag·nə·fə′kā·shən] (optics) Variation in the size of the image produced by an optical system with the wavelength (or, equivalently, color) of light. Also known as lateral chromatic aberration.
What is the corrected lens for astigmatism aberration?
Astigmatism can be often corrected by glasses with a lens that has different radii of curvature in different planes (a cylindrical lens), contact lenses, or refractive surgery.
Which lens is used for astigmatism?
Eyeglasses for astigmatism include a special cylindrical lens to compensate for how light passes through the cornea. Generally, a single-vision lens is prescribed, but in some patients over 40 years old, an eye doctor might recommend a bifocal.
Is 30mm guide scope enough?
With more sensitive (and more expensive) CCD or CMOS-based guiding cameras, as mentioned below, flyweight guide scopes with apertures as small as 30mm can work well when guiding images with short focal length refractors as the main scope.
Is OAG better than guide scope? You can think of an OAG as more of an accurate, guaranteed good autoguiding measure when compared to a guide scope. This comes at the cost of setup difficulty, but it is worth it when possible. When at all possible I prefer to use an OAG, and in some cases I have to use one.
What is petzval surface?
The imaginary curved surface upon which images would be formed if curvature of field were the only aberration present. It is the curved surface in which the tangential and sagittal image shells of a point-focal lens coincide. See oblique astigmatism; curvature of field; anastigmatic lens.
What is coma in lenses?
Coma is an aberration which causes rays from an off-axis point of light in the object plane to create a trailing “comet-like” blur directed away from the optic axis (for positive coma). A lens with considerable coma may produce a sharp image in the center of the field, but become increasingly blurred toward the edges.
What is astigmatism aberration?
In technology of photography: Aberrations. Astigmatism occurs when the lens fails to focus image lines running in different directions in the same plane; in a picture of a rail fence, for instance, the vertical posts are sharp at a focus setting different from the horizontal rails.
What is a guide scope for astrophotography?
The guidescope is a small refractor or even a modified finderscope that is mounted along with the imaging telescope and camera and its job is to capture an image of a single star using its own small camera and then to analyse the movement of that star in the field of view using guiding software.
Do I need a guide camera astrophotography?
Autoguiding is an essential part of any serious deep sky astrophotography rig. Whether you’re guiding with a guide scope or off-axis guider, you’ll need a guide camera to go with it.
What are the four types of lenses? Within both prime and zoom types of lenses, there are a variety of lenses, all with different focal lengths.
- Macro Lenses. This type of camera lens is used to create very close-up, macro photographs.
- Telephoto Lenses.
- Wide Angle Lenses.
- Standard Lenses.
- Specialty Lenses.
Why are camera lenses purple? Chromatic aberration, also known as “color fringing” or “purple fringing”, is a common optical problem that occurs when a lens is either unable to bring all wavelengths of color to the same focal plane, and/or when wavelengths of color are focused at different positions in the focal plane.
What is fringing photography? Chromatic aberration, also known as color fringing, is a color distortion that creates an outline of unwanted color along the edges of objects in a photograph. Often, it appears along metallic surfaces or where there’s a high contrast between light and dark objects, such as a black wall in front of a bright blue sky.
Who is Joseph petzval?
Joseph Petzval (6 January 1807 – 17 September 1891) was a mathematician, inventor, and physicist best known for his work in optics. He was born in the town of Szepesbéla in the Kingdom of Hungary (in German: Zipser Bela, now Spišská Belá in Slovakia).
What is chromatic lens?
Chromatic aberration is a phenomenon in which light rays passing through a lens focus at different points, depending on their wavelength. There are two types of chromatic aberration: axial chromatic aberration and lateral chromatic aberration.
Do all lenses have chromatic aberration?
Chromatic aberration is an effect that occurs when a lens is not able to properly refract all the wavelengths of colour in the same point. It’s quite a common problem in photography that affects almost all lenses, though high-quality lenses will present with less chromatic aberration compared to lower-quality ones.
What is CA in photography?
In optics, chromatic aberration (CA), also called chromatic distortion and spherochromatism, is a failure of a lens to focus all colors to the same point. It is caused by dispersion: the refractive index of the lens elements varies with the wavelength of light.
What is the difference between coma and astigmatism?
Coma is caused by obliquely inciding parallel rays of light on a spherical lens, astigmatism is caused by obliquely inciding diverging rays of light on the spherical surface. Both errors can primarily be corrected by sophisticatedly combining several lenses and using aspheric lenses.
What causes coma lens?
Coma is caused by the curvature of the principal planes of the optical system. Coma can occur even at short distances from the principal axis. The comet like shape in comatic aberration is due to the refraction differences when light rays pass through the various zones of the lens.
What is the difference between coma and spherical aberration?
In spherical aberration, the images of an on-axis object point that fall on a plane at right angles to the optical axis are circular in shape, of varying size, and superimposed about a common centre; in coma, the images of an off-axis object point are circular in shape, of varying size, but displaced with respect to
What type of lens corrects astigmatism? Soft contact lens: Toric lenses are a specific type of soft contacts used to treat astigmatism. The lenses are weighted to ensure they remain aligned properly. They also have varying powers in different meridians (the imaginary perpendicular lines in your eye) to help correct your vision.