Home Location, The Netherlands

Telescope - Robtics RC10

The Robtics RC10 is a Ritchey-Chrétien Reflector telescope, with a diameter of 250 mm and a focal length of 2000 mm, this results in a focal ratio of f/8. I reduced it with a Astro-Physics CCDT67 reducer, so now it has a focal lenght of 1380 mm with a focal ratio of f/5.5. A Ritchey–Chrétien telescope (or RC) is a specialized Cassegrain telescope that has a hyperbolic primary mirror and a hyperbolic secondary mirror designed to eliminate optical errors (coma). They have large field of view free of optical errors compared to a more conventional reflecting telescope configuration. Since the mid 20th century most large professional research telescopes have been Ritchey–Chrétien configurations.

The Ritchey–Chrétien design is free of third-order coma and spherical aberration, although it does suffer from fifth-order coma, severe large-angle astigmatism, and comparatively severe field curvature. When focused midway between the sagittal and tangential focusing planes, stars are imaged as circles, making the RC well suited for wide field and photographic observations. As with the other Cassegrain-configuration reflectors, the RC has a very short optical tube assembly and compact design for a given focal length. The RC offers good off-axis optical performance, but examples are relatively rare due to the high cost of hyperbolic primary mirror fabrication.

In about 2009, Guan Sheng Optical (GSO) corporation, a wholesale optical manufacturer, introduced a line of significantly less expensive Ritchey–Chrétien telescopes. These telescopes were branded and sold as Robtics, Astro-Tech, Orion and under a few other brand names.

Solar Telescope - Lunt LS60THa/B1200FTPT

The LS60THa is a Solar Telescope with 60 mm aperture and 500 mm focal length. An internal etalon with air-pressure tuning adjustment allows for a <0.7 Ångstrom bandwidth. This Pressure Tuner system allows a better Etalon adjustment than other systems. The Pressure Tuner system adapted the Etalon to varying altitudes and atmospheric pressures for optimal performance. With the matched collimation lens set, the LS60THa is corrected for on axis coma, astigmatism and de-centering aberrations and provides a full spherically corrected flat-field Solar-Telescope. The Blocking filter is the B1200, that provides a smaller vignetting for imaging. The star diagonal in which the blocking filter is installed, is equipped as standard for 1.25" eyepieces and with a T2 camera connection. Fine adjustment is achieved with a Starlight Instruments 2" Feather Touch focuser with 1.5" travel and 10:1 reduction.

Mount - ASA DDM60 Pro

The ASA DDM60 Pro is on of the most accurate German Equatorial mounts. It's a direct drive mount with high resolution encoders, resulting in no backlash, no periodic error and perfect tracking. An equatorial mount is a mount for instruments that follows the rotation of the sky (celestial sphere) by having one rotational axis parallel to the Earth's axis of rotation. This type of mount is used for astronomical telescopes and cameras. The advantage of an equatorial mount lies in its ability to allow the instrument attached to it to stay fixed on any object in the sky that has a diurnal motion by driving one axis at a constant speed. Such an arrangement is called a sidereal drive. In astronomical telescope mounts, the equatorial axis (the right ascension) is paired with a second perpendicular axis of motion (known as the declination). The axis of the mount is equipped with a motorized clock drive, that rotates that axis one revolution every 23 hours and 56 minutes in exact sync with the apparent diurnal motion of the sky. Equatorial mounts differ from mechanically simpler altazimuth mounts, which require variable speed motion around both axes to track a fixed object in the sky. Also, for astrophotography, the image does not rotate in the focal plane, as occurs with altazimuth mounts when they are guided to track the target's motion, unless a rotating erector prism or other field-derotator is installed.

Focuser - Moonlite High Resolution Stepper Motor

The telescope is equipped with an electronic 2" Moonlite CS Crayford focuser. The Crayford focuser is a simplified focusing mechanism for amateur astronomical telescopes. The Crayford is similar in appearance to a Rack and pinion focuser, but has no teeth on either the rack or the pinion. Instead, a round axle is pressed (for example by a spring-loaded or thumbscrew-tightened piece of PTFE plastic) against a flat on the side of the focuser drawtube, relying only on friction to move the drawtube as the axle is turned. This also presses the drawtube against a set of four ball bearings against which it moves smoothly with minimal friction. The pressure exerted on the axle can often be adjusted for smoothest operation, and the drawtube may be locked in position to support heavy eyepieces or cameras.

Cooled CCD Camera - QSI 683wsg-8

QSI 683wsg-8 cooled CCD cameras are designed to produce high quality images with extremely wide dynamic range, linearity and low noise. Due to the high quantum efficiencies of CCDs, linearity of their outputs (one count for one photon of light), ease of use compared to photographic plates, and a variety of other reasons, CCDs were very rapidly adopted by astronomers for nearly all UV-to-infrared applications. Thermal noise and cosmic rays may alter the pixels in the CCD array. To counter such effects, astronomers take several exposures with the CCD shutter closed and opened. The average of images taken with the shutter closed is necessary to lower the random noise. Once developed, the dark frame average image is then subtracted from the open-shutter image to remove the dark current and other systematic defects (dead pixels, hot pixels, etc.) in the CCD. The Hubble Space Telescope, in particular, has a highly developed series of steps ("data reduction pipeline") to convert the raw CCD data to useful images. CCD cameras used in astrophotography often require sturdy mounts to cope with vibrations from wind and other sources, along with the tremendous weight of most imaging platforms.

Guiding Camera - Starlight Xpress Lodestar

The Starlight Xpress Lodestar is a Stand-Alone Autoguider powered through the USB port of a computer. With the ICX429AL SONY EXVIEW CCD used as the imaging chip, this very sensitive autoguiding camera is capable of finding very faint guide stars with little effort. To take long exposures of galaxies and nebulae, many astronomers use a technique known as auto-guiding. The autoguider can rapidly detect errors in tracking and command the mount motors to correct for them.

Planet Camera - Imaging Source DMK 21AU618.AS

The Imaging Source DMK 21AU618.AS is a Monochrome USB astronomy camera without IR cut filter. With 60 FPS (frames per second), the DMK 21AU618.AS is very fast. It is ideally suited to black and white astrophotography, in which very fast image sequences should be captured, freezing the seeing in planet photography.

LRGB Filterset - Astrodon Tru-Balance Generation 2

Astrodon Tru-Balance Generation 2 LRGB filters are designed to approximately equalize the flux of Kodak's full-frame CCD detectors (like the KAF8300 in the QSI CCD), including compensation for the solar photon flux. This means that RGB color combine weights will be approximately 1:1:1 within perhaps 10%. This allows to take equal time exposures for your RGB data and also just one corresponding dark exposure time. LRGB, short for Luminance, Red, Green and Blue, is a photographic technique used in amateur astronomy for producing good quality colour photographs by combining a high-quality black-and-white image with a lower-quality colour image. In amateur astronomy, it is easier and cheaper to obtain good quality, high signal-to-noise ratio, images in black and white. The LRGB method is used to work around this to get good colour images. The colour information from the colour image is combined with the overall brightness from the black-and-white image. As only the colour information is used, the noise in the colour image is not transferred to the final image, retaining the quality of the black-and-white image.

Narrowband Filterset - Astrodon 3 nm

Astrodon 3 nm Ha, SII and OIII filters. Narrowband filters enhance contrast of emission objects by accepting only a narrow range (3 nm) of wavelengths around the emission lines of hydrogen (Ha, 656 nm), oxygen (OIII, 501nm), sulfur (SII, 672nm) and others. They can be used to image when the moon is up, thereby extending imaging time. They can be used in light-polluted locations. The narrow range of wavelengths is defined as the FWHM (full-width at half- maximum intensity). Narrower filters decrease the background noise. However, narrower filters are more difficult to manufacture consistently, and are thus more expensive. Furthermore, it is difficult to maintain high transmission through the bandpass of the filter as it becomes narrower. If the peak transmission decreases as the filter is made narrower, the emission signal decreases and the gain in S/N (signal-to-noise) is not realized.

H-alpha (Hα) is a specific red visible spectral line created by hydrogen with a wavelength of 656.28 nm, which occurs when a hydrogen electron falls from its third to second lowest energy level. It is difficult for humans to see H-alpha at night, but due to the abundance of hydrogen in space, H-alpha is often the brightest wavelength of visible light in stellar astronomy. A hydrogen-alpha filter is an optical filter designed to transmit a narrow bandwidth of light generally centered on the H-alpha wavelength. They are characterized by a bandpass width that measures the width of the wavelength band that is transmitted. These filters are manufactured by multiple layers of vacuum-deposited layers. These layers are selected to produce interference effects that filter out any wavelengths except at the requisite band.

Doubly ionized oxygen (OIII) is a forbidden line of the ion O2+. It is significant in that it emits light in the green part of the spectrum primarily at the wavelength 500.7 nanometres and secondarily at 495.9 nm. Concentrated levels of OIII are found in diffuse and planetary nebulae and supernova remnants. Consequently, narrow band-pass filters that isolate the 501 nm and 496 nm wavelengths of light are useful in observing these objects, causing them to appear at higher contrast against the filtered and consequently blacker background of space (and possibly light polluted terrestrial atmosphere) where the frequencies of OIII are much less pronounced.

Ionized Sulfur emission (SII), at wavelenghts of 671.6nm and 673.1nm corresponding to the red part of the visible spectrum. SII is commonly observed in nebulae and, it has been found that the ratio SII/Ha tends to increase as absolute Ha intensities decrease.

Nitrogen (NII) filter for 658.4 nm emission line imaging. Wider Hα filters (4.5 - 10 nm) also includes NII emission at 658.4 nm. These emission lines are so close together that only a filter with 3 nm or less FWHM can readily separate their signals. Many objects are enriched in nitrogen and have [NII] emission, such as planetary nebula, Wolf-Rayet bubbles and supernova remnants.

Remote Location, Hautes-Alpes, France

Telescope - Orion Optics 10" ODK

The Orion Optics 10" ODK is a Optimised Dall-Kirkham Reflector telescope, with a diameter of 250 mm and a focal length of 1680 mm, this results in a focal ratio of f/6.7. An Optimised Dall-Kirkham telescope (or ODK) is a specialized Cassegrain telescope and is intended to simplify the design compared to an RC or classical Cassegrain by keeping one of the mirrors spherical. Spherical mirrors are far easier to manufacture than aspheric surfaces.

The Dall-Kirkham uses a spherical secondary in combination with an elliptical primary. The main drawback to a normal Dall-Kirkham design is that the coma is even stronger than in a classical Cassegrain, limiting the useful field of view. That's why most Dall-Kirkhams are optimised with a corrector; a lens group (usually two or three lens elements) ahead of the focal point to improve off-axis image quality. The primary mirror conic constant is slightly different than that for a conventional Dall-Kirkham and must be optimized along with the lenses during design. The usable field is much better than the Ritchey-Chrétien telescope without corrector. The Ritchey-Chrétien System with corrector has a better and bigger field.

The performances are equal or better than the Ritchey-Chrétien telescope. The spherical secondary can be fringe tested against the spherical convex surface or tested from behind. This is markedly an advantage over the hyperbolic secondary of the Ritchey-Chrétien design. Another advantage of either the basic Dall-Kirkham or the Optimised Dall-Kirkham design is that collimation of the convex spherical secondary mirror with respect to the optical axis of the primary mirror is almost trivial, because there is no single defined axis of a sphere. Any line that runs through the center of the sphere can be an axis.

Mount - Mesu Mount 200

The Mesu Mount 200 is an accurate German Equatorial mount. It's a friction drive mount, resulting in very little backlash, small periodic error and good tracking. An equatorial mount is a mount for instruments that follows the rotation of the sky (celestial sphere) by having one rotational axis parallel to the Earth's axis of rotation. This type of mount is used for astronomical telescopes and cameras. The advantage of an equatorial mount lies in its ability to allow the instrument attached to it to stay fixed on any object in the sky that has a diurnal motion by driving one axis at a constant speed. Such an arrangement is called a sidereal drive. In astronomical telescope mounts, the equatorial axis (the right ascension) is paired with a second perpendicular axis of motion (known as the declination). The axis of the mount is equipped with a motorized clock drive, that rotates that axis one revolution every 23 hours and 56 minutes in exact sync with the apparent diurnal motion of the sky. Equatorial mounts differ from mechanically simpler altazimuth mounts, which require variable speed motion around both axes to track a fixed object in the sky. Also, for astrophotography, the image does not rotate in the focal plane, as occurs with altazimuth mounts when they are guided to track the target's motion, unless a rotating erector prism or other field-derotator is installed.

Focuser - Baader SteelTrack with SteelDrive Stepper Motor

The telescope is equipped with an electronic 2" Baader Crayford focuser. The Crayford focuser is a simplified focusing mechanism for amateur astronomical telescopes. The Crayford is similar in appearance to a Rack and pinion focuser, but has no teeth on either the rack or the pinion. Instead, a round axle is pressed (for example by a spring-loaded or thumbscrew-tightened piece of PTFE plastic) against a flat on the side of the focuser drawtube, relying only on friction to move the drawtube as the axle is turned. This also presses the drawtube against a set of four ball bearings against which it moves smoothly with minimal friction. The pressure exerted on the axle can often be adjusted for smoothest operation, and the drawtube may be locked in position to support heavy eyepieces or cameras.

Cooled CCD Camera - QSI 683wsg-8

Guiding Camera - Starlight Xpress Lodestar

Narrowband Filterset - Astrodon 3 nm

Astrophotography Software

ACP / Planner / Scheduler, observatory automation software.
Adobe Photoshop CS6, general image editing software.
Ascom platform
AlignMaster, software to do a polar alignment.
AutoSlew & Sequence, software to control the ASA mount.
Autostakkert!2, image editing software specialized for planet photography.
Bahtinov Grabber, software to analyze the difraction pattern of a Bahtinov mask.
Cartes du Ciel, planetarium software to send goto commands to the mount.
CCD Commander, observatory automation software.
CCDAutoPilot 5.0, observatory automation software.
FocusMax, software to autofocus the focuser.
Maxim DL, capturing software for CCD camera.
Nebulosity, capturing software for CCD camera.
IC Capture, capturing software for the Imaging Source camera.
PHD Guiding, autoguiding software for Lodestar autoguider camera.
PinPoint Astrometric Engine, high-precision astrometry (measurement of position) software.
PixInsight, image editing software specialized for astrophotography.
Registax, image editing software specialized for planet photography.

Previous Equipment

Telescope - Sky-Watcher BKP 250

The Sky-Watcher BKP 250 is a Newtonian Reflector telescope, with a diameter of 250 mm and a focal length of 1200 mm, this results in a focal ratio of f/4.8. Also the tube length has been slightly shortened to optimize performance for prime-focus photography. The Newtonian telescope is a type of reflecting telescope invented by the British scientist Sir Isaac Newton (1642–1727), using a concave primary mirror and a flat diagonal secondary mirror. The Newtonian telescope's simple design makes them very popular with amateur telescope makers. Some advantages of the Newtonian design; they are free of chromatic aberration found in refracting telescopes, are usually less expensive for any given objective diameter (or aperture) than comparable quality telescopes of other types, since there is only one surface that needs to be ground and polished into a complex shape, overall fabrication is far simpler than other telescope designs. Some disadvantages are; Newtonians, like other reflecting telescope designs using parabolic mirrors, suffer from coma, an off-axis aberration which causes imagery to flare inward and towards the optical axis, they have a central obstruction due to the secondary mirror in the light path. This obstruction and also the diffraction spikes caused by the support structure (called the spider) of the secondary mirror reduce contrast. For portable Newtonians collimation can be a problem. The primary and secondary can get out of alignment from the shocks associated with transportation and handling.

Mount - Sky-Watcher NEQ6-Pro

The Sky-Watcher NEQ6-Pro is a German Equatorial Go-To mount.

Starterset - Bresser Messier N-203

The Bresser Messier N-203 is a Newtonian Reflector telescope, with a diameter of 200 mm and a focal length of 1000 mm, this results in a focal ratio of f/5. It was mounted on a manual German Equatorial Mount.