DP 100

The NortheK DP 100 is a classic achromatic refractor, made with Carton doublets. Cells and tubes are original and especially designed by Northek.

Maurizio Forghieri, a renowned manufacturer of achromatic and apochromatic optics that took part of the NortheK project whit  the Maxproject Team, verified piece by piece all the performances of this telescope. Thanks to his valuable advice the NortheK DP 100  has reached the highest quality standard.

Each doublet has been verified and submitted to both  the optical bench that the star test.  As the colour is very limited because of the focal ratio, the astronomical vision is extremely nice.

The tube is made of carbon fiber on exclusive NortheK project, the joints and fittings are in anodized Halo 25 alloy, everything has been made with numerical control and for the internal configuration of diaphragms it has been used a professional program for optical design.

The focus is the prestigious 2″ Feather Touch 2000. We also put an extra-care in giving an attractive look to this instrument, so that it can appeal not only to the experts.

Maxproject Team believes that a well produced 100 mm. achromatic can still be considered a universal instrument for the modern amateur: the observation of the sun, the moon and the solar system are just some of the applications that you can enjoy from the balcony of your house. As it has a reasonable size and it’s not too heavy, it is possible to use it with small, light and transportable stands.

This is a high-class telescope and, upon request, it can come with a connection bar to mount to the frame.

The DP 100 from NortheK is the classical refraction instrument doing two specific tasks.

The first one is to allow all users, even those with difficult observation setting, small mounts or a sky polluted with artificial light, to get a high quality product and enjoy the distinctive characteristics of NortheK products.

The second aim of this instrument is to complement to primary telescope. It could then be useful to observe the Solar System or to replace the main instrument for convenience. For those who have a fixed location it is certainly practical to mount the DP 100 in parallel to the main telescope in order to keep this good refractor handy.

In any case, thanks to its great potential, this is an instrument that you won’t be wanting to re-sell again as it will become part of your astronomical set. Just to mention some of its strengths, this telescope is very easy to carry and to use with small mounts (Sphinx, Eq6, etc.) therefore it can be used without problems at the weekend or on holiday.

The price is very competitive considering the high standard of the optical tube. The quality is far better performing than most of the imported products which don’t give any optical and mechanical consistency and for those reasons the DP 100 can be easily purchased even by astronomers with a limited budget.

For this optical tube it is also possible to add motorized focuser to the orginal Feather Touch but  some technical limitations should be considered. It is not possible to install Robofocus.

The increasingly greater need to have transportable instruments available, with good aperture and quality optics has pushed the manufacturers to design telescopes that are more “compact” and easy to handle. For example, think about latest generation apochromatic refractors designed with very high F/D ratios, which are  then publicised as able to produce marvellous wide range photos and offer excellent high resolution performance at the same time, maybe passing over the fact that to obtain 200 magnifications a 5X Powermate is necessary.

NortheK, a company from Biella, which has distinguished itself with the production of very sophisticated professional standard telescopes in optics up to 600 mm in diameter, proposes, against the run of the market, a Fraunhofer open air-spaced achromatic refractor with a free aperture of 100 mm in diameter, 1300 mm focal length and f/13 ratio. This is perfect for an instrument designed for high resolution observation. A well-made 100 mm can be considered a universal instrument for the modern amateur astronomer: for example, just think that in the last century these instruments were defined “ordinary” for observation of the solar system.

The telescope was purchased complete with case, a solid aluminium trunk with well-shaped interior (the tube enters precisely), which is also very light and can be transported by a person. We were first struck by the beauty and elegance of the rectified and enamelled carbon tube, with 1 mm thickness per part and external diameter of 102 mm. The objective, with anti-reflective substrate coating, is positioned in an adjustable cell made from Halo 25 alloy monoblock piece, purple in colour and with tapered shape, while the ray shade, built Anticorodal 6060 aluminium, can be screwed into the same. The front lens is protected by a pressure plug while the inside of the tube is well partitioned and blackened to reduce reflections to a minimum. The daylight examination using the Chesire eyepiece highlighted perfect collimation with the objective lens perfectly aligned with the focuser.

The focuser is 2″ crayford FTF 2000 Feather Touch model, with 10:1 reduction. It allows smooth focusing without play, travel of 66.04 mm and has a brass collar looking mechanism. On delivery of the telescope, the manufacturer recommends purchase of the 31,8 eyepiece reducer and 1,40″ FT estensions from the 2000 range (indispensable when using an angle finder) and 3,75″ extensions (indispensable for observation with  direct focus). The handle, measuring as long as the dovetail, is very useful and facilitates transport of the tube, while the sercher in an execellent 9X60 mm with direct viewing and quick-coupling support. In all, the telescope reaches 1400 mm length and weighs only 6 kg. These measurement put the Vixen GP equatorial mount, on which it is positioned, to the test, but when observing the moon and planets, the images are still with damping times of about 2-3 seconds.

Observing from outside, the entire surface of the objective lens is uniform, there are no scratches and Newton’s colours cannot be noted. The diffraction image of a star high on the horizon highlighted excellent collimation with perfectly round and regular rings, separated by a dark space and without scattered light. The intra/extra-focal diffraction figures highlighted excellent correction of spherical aberration; zonal errors or astigmatism are not visible. Only on very white and bright objects and on stars, can a weak violet halo be seen surrounding them and in most cases, can only just be perceived or not seen at all; an excellent optical yield with secondary spectrum residue, which come very close to that of an apochromatic refractor. Observing a star in focus magnified 250 times (Pentax XL 5.2 mm eyepiece) a perfect Airy disk can be seen, surrounded by a power ring which seems drawn by a compass: it is certainly the best star test that we have performed for optics of this type. In comparaison, the Vixen 102M, puchased many years ago and which we consider an excellent achromatic refractor, showed a decidedly inferior star test.

The following evening with a particularly good seeing, we observed the 12th day of the Moon at 55X using the Mark 5 binocular visor, including Zeiss prismatic diagonal, a 1.7X corrector and a pair of OMNI 40 mm eyepieces. The image of the moon seemed to be cut out from the background sky: splendid, rich in minute details, very bright and still. In succession, we first inserted a pair of Ortho Genuine 9 mm eyepieces and then a 7 mm pair, experiencing the over flight effect of the Moon’s surface and a net sensation of tridimensionality due to the high quality of the images. In the eyepiece, or better, within the range of the eyepieces, the Aristarchus, Herodotus and Vallis Schroter craters are spectacular with many details and without false colours: details apart, it almost seems as if we are looking through a 150 mm apochromatic refractor at f/10. With the 2.6X corrector and a pair of Ortho Genuine 9 mm eyepieces at 375 magnifications, we observed the lunar terminator with very high image contrast to our grat satisfaction, allowing to push magnification to unthinkable levels for a telescope of this diameter.

But, we didn’t stop here and we tried to exaggerate: on removal of the binocular visor, we inserted a 50.8 mm angle finder, a 2.5X Powermate and a Pentax XL 5.2 mm eyepiece in order to obtain 630 magnifications. Just one crater in the eyepiece this time: Schiller. Definition obviously was reduced but the  image, even if very “dark”, is incredible, new details do not emerge but the view of the crater is estraordinarily good! It seems impossible to observe at these magnifications using a 100 mm, but…

Observing Saturn with 245 magnifications was particularly interesting (Mark 5 + 1.7X corrector + Ortho  Genuine 9 mm eyepiece): the still sharp and contrasted planetary disk showed several details with some shade: Excellent Cassini division.

The optics and mechanical quality of the DP 100 are at the top of the market. It is an instrument recommended for all amateurs astronomers that want to undertake observation of the solar system and, if used with top quality accessories and eyepieces, there are no regrets regarding larger diameters.

Waiting for Jupiter………

Roberto Milan ™

Mauro Favaron ™

Instruments in use by two Beta Testers: Sky W. Mak 180 mm – Apo Zen 150 mm – Dall Kirkham 300 f 20 (readapted NortheK).