M57 The Ring Nebula

M57 Ring Nebula
M57 Ring Nebula. Date: 5 Sept 2016, Loc: Rennesøy, Norway, Telescope: Esprit 120 ED 840 mm f/7, Camera: Apogee Alta U16M, Mount: ASA DDM160, Exposure: LRGB 4/4/4/4 min, CCD-temperature -20 C

Don't do this

Three hours before twenty guests arrive at a dinner party at a Corsican winery, one should not agree to clean and collimate the host's dusty, dilapidated 8 inch Newtonian, in order to show twenty curious guests some exciting celestial objects. The poor instrument showed signs of incorrect use. The owner had stored it in the attic for many years.


When bright, easy objects are not accessible on the sky, it is unwise to attempt to show a faint planetary nebula to guests in a festival mood, - people who have no experience with astronomical telescopes. I made this mistake when the only region of sky visible was the Zenith, and it was hugged by towering trees. Lyra was visible between the tree crowns.


Of the twenty guests, only one was able to see the Ring Nebula. He was a painter and sculptor from Paris. He became so ecstatic upon seeing the ring that he teared up. So perhaps the event was a success after all :-)


Enriches the Galaxy

Solar type stars end their multi-billion year lives in the form of an expanding bubble of helium, carbon, oxygen, 

sulphur, nitrogen and other elements less massive 

than iron. Old solar-type stars throw off all the gas that surrounds their dense helium core. When the core is finally exposed, the enormous shells of discarded gas are irradiated. The are called planetary nebulas, and they enrich the galaxy's portfolio of elements which have proton numbers between hydrogen and iron. Supernovas enrich the galaxy with iron and heavier elements.


20 km/s

The star in the middle of the Ring Nebula blew off its outer gaseous layers 4000 years ago, and the nebula is expanding at 20 kilometers per second. Expanding shells of gas remain invisible as long as they are not ionized by intense ultraviolet light. The star's naked core illuminates the enormous expanding cloud of gas with ultraviolet radiation. The UV-wavelengths excite atoms in the nebula which then re-emit the energy in longer wavelengths of visible light. The colors depend on which elements are present. In the photo, blue gas in the center of the nebula is helium. Surrounding helium is hydrogen and oxygen. The outermost red color is nitrogen and sulphur.


The Ring Nebula is approximately one light-year in diameter and 2000 light-years distant.

IC 1396 in Cepheus

IC 1396 is an emission nebula, ionized by a blue, type O star, the brightest star at one o'clock to the center of the photo.


Twice as far as the Orion Nebula

The distance to the nebula is less than 3000 light years, about twice as far as the Orion Nebula. IC 1396 is several hundred light-years in diameter, and extends over three degrees on our sky. This is the same angular diameter as six full moons. IC 1396 is so large on the sky that if one could see it with the naked eye (the nebulosity 

is extremely faint), one could not entirely cover it with the thumb at arms length.


12000 solar masses

An extensive study published in 1996 in Astronomy and Astrophysics concluded that the entire mass of IC 1396 is around 12,000 solar masses. Approximately 4000 solar masses are cold, molecular gasses, - visible on the photo as dark clumps. The fluorescing areas are ionized gas consisting of about 300 solar masses.

IC 1396. 5 Sept 2016, Loc: Rennesøy, Norway, Telescope: Esprit 120 ED, Camera: Apogee Alta U16M, Mount: ASA DDM160, Exposure: LRGB 6/6/6/6 min, Field:  2,3 x 2,4 degrees.

NGC 7000, North America Nebula

NGC 7000 is an emission nebula, meaning that its gaseous hydrogen, oxygen and sulphur are strongly irradiated by ultraviolet light from a nearby star. This ionizes the nebula, causing its gasses to fluoresce in various wavelengths of red light. The star in this case is probably Deneb, the bright star marking the tail of the swan Cygnus. If Deneb is the UV-source, then the distance to NGC 700 is 1600 light years, only 300 light years farther than the much brighter Orion Nebula. The breadth of the North America Nebula is about 100 light years.



Because of time constraints, the astrophotograph is processed without making flat and bias-frames to remove pixel and signal noise. Each of the 24 subframes (red, green, blue and luminance) were exposed only one minute, and there are six of each. That is why the image

suffers from vignetting and noise.


The Dark Side

At 59 degrees north latitude, the night sky reaches maximum darkness 27th August. This is the first night after 21st April when the sun sinks to more than 18 degrees below the horizon. Eighteen degrees is the minimum limit for astronomical night, because the upper reaches of atmosphere are not illuminated by the sun.


Always cloudy

The nights have been cloudy and rainy on the Isle of Rennes this summer and fall. The night of 4 September, however, was one of the rare clear and stabile nights we have had since last winter. Since the following day was a workday, exposures were fewer and shorter, and I had to sacrifice flat- and bias frames :-(


NGC 7000. Date: 5 Sept 2016, Loc: Rennesøy, Norway, Telescope: Esprit 120 ED, Camera: Apogee Alta U16M, Mount: ASA DDM160, Exposure: LRGB 6/6/6/6 min, Photographic field is 2.5 x 2.5 degrees.

Effelsberg 100-m Radio Telescope

Effelsberg radio telescope
At its completion in 1972, the 100-meter diameter Effelsberg radio telescope was the world's largest fully steerable telescope. It remained so for 30 years.

Largest in Europe

Operated by the Max Planck Institute for Radio Astronomy in Bonn, the Effelsberg 100-m Radio Telescope is the second largest steerable single-dish radio telescope in the world. It is located near Bad Münstereifel in North Rhine-Westphalia. Inaugurated in 1972, it was the largest steerable dish in the world until the collapsed Green Bank Telescope in West Virginia was rebuilt in 2002 with a 100 x 110 meter dish. Effelsberg and Green Bank, however, still have the same resolution at a given wavelength because both telescopes have a 100 meter diameter circular aperture.


Effelberg's main reflector

  • diameter: 100 m
  • mean surface error: 0.5 mm
  • focal length: 30 m
  • sagitta: 20.83 m
  • total area: 9090 sq m, aperture area: 7850 sq m


Effelsberg has a symmetrical* Gregorian** configuration. The primary reflector is a paraboloid with a focal length of 30 m. The secondary reflector is concave ellipsoidal, with a diameter of 6.5 meters. It is located 32 meters from the primary reflector, two meters behind (towards the sky) primary focus.



Through nine different receivers at both the primary and secondary focus, the telescope detects radio emissions ranging from 90 cm (300 MHz) to 3.5 mm (90 GHz).

* The slightly larger Green Bank radio telescope has a non-symmetrical (off-axis) configuration. This increases its reflecting area by elliminating the shadow of the secondary supports and housing.

**The concavity of the secondary mirror (or radio reflector) defines if a telescope is Gregorian or a Cassegrain. In both types, the two foci of the secondary's conic are located at the primary mirror's prime focus and behind the primary at the secondary focus. The classical Cassegrain has a convex hyperboloid secondary inside prime focus, whereas the Gregorian has a convex ellipsoidal secondary outside prime focus.

Equipped for wide-field astrophotography

Trial installation of the piggyback refractor, camera and filterwheel. When completed, the facility will have three focal lengths: 6448 mm f10.4; 2108 mm f/3.4; 840 mm f/7

Trial installation of the piggyback refractor, camera and filterwheel. When completed, the facility will have three focal lengths: 6448 mm f10.4; 2108 mm f/3.4; 840 mm f/7

Esprit 120 ED, Apogee U16M and filterwheel are connected to power supplies and pc by cabling that pass through the mount and pier, and a conduit under the floor.



A direct drive mount (DDM) requires excellent ballance on both axes. There is no clutch or break on the declination and polar axis. A ring of permanent magnets produces torque against a ring of electromagnets in order to rotate and lock the axes. To counteract imbalance, the processor increases amperage to the electromagnets to exert opposite torque. When the torque becomes too large, the control program shuts down the axis to avoid overload.


Off balance

The Apogee filterwheel (bottom right) must be turned inward to avoid collision with the dome rotation ring. Consequently, the refractor must be pushed back several centimeters from the balance point so the filter wheel will not hit the backplate behind the main mirror of the Cassegrain. The center of gravity is now shifted away from the declination axis. The mass of Esprit 120 + U16M + filter wheel = 16 kg. To compensate, it is necessary to increase the mass of the secondary mirror support ring on the Cassegrain.


Field size
blue: Esprit 120 (840 mm f/7); orange: Cassegrain primary focus (2108 mm f/3.4); red: secondary focus (6448 mm f/10.4)

Three focal lengths

The map of the Pleiades shows the photographic field of view of a Kodak KAF-16803 CCD sensor. The sensor's surface area is 36.8 x 36.8mm. The blue square shows the field of the Esprit 120 (840mm f/7). The orange rectangle indicates the field when the camera is placed at primary focus (2108 mm f/3.4). The small red square represents the image field when the U16M is mounted on Cassegrain focus (6448 mm f/10.4).


Maps and field markers are from the planetarium software C2A, version 2.1.2.

Solar image, 15.mai 2016

Sun 15 May 2016
Click to enlarge, then click again for full resolution.

I am always impressed to see what a 120 millimetre apochromat can manage, even when its aperture is reduced to 90 millimetres.


A sunspot group that resembled a flattened smiley face was located in the southern hemisphere one week ago, during the Mercury transit. Amazingly, a new group in the northern hemisphere looks similar, at least superficially, with pattern recognition in high gear :-)


left: 9 May 2016

right:  15 May 2016

The sun

Date: 15 May 2016, 14:30 (12:30 GMT)

Telescope: Skywatcher Esprit ED 120

Mount: Astrosysteme Austria ASA DDM160

Solar filter: Thousand Oaks Type 2+, 90 mm diameter

Camera: Lumenera SKYnyx2-2M


Seeing: moderate

Exposure: 11 ms

Number of images in stack = 20 x 3 (three image mosaic)

Photo stacking: AviStack2

Transit of Mercury

Mercury transit
The transit of Mercury 9 May 2016 at 16:24 (13:24 GMT) Click to enlarge, then click again for full resolution.

Several trial runs the last few days indicated that a roll of filter material (black polymer) I have had since the 1999 solar eclipse,  was not suitable for high-resolution solar photography.


The Thousand Oaks Optical Type 2+ filter, on the other hand, is very well suited for high-resolution solar photography. Unfortunately, my filter was only 90 millimetre diameter, made for the Meade ETX-90. I had to reduce the telescope's aperture from 120 mm to 90 mm. Nevertheless, the resolution decrease caused by the full aperture black polymer filter was greater than the resolution decrease caused by aperture reduction with the type 2+ filter.


I cut an annulus of thick plywood and made a cylinder of foam plastic sheeting to adapt the 90 mm type 2+ filter to a Skywatcher ED 120 refractor. Duct tape secured all the parts.



Mercury traverses south of two sunspot groups at 16:24 (14:24 GMT) 9 May 2016.


Filter: Thousand Oaks Optical Type 2+

Optics: Skywatcher Esprit ED 120 mm (stopped down to 90 mm) + TeleVue Powermate 4x

Camera: SkyNyx 2.2

Stacking and processing: AviStack2

The ASA DDM160 in a 4m ScopeDome

Video of the Dinium Observatory
A two-minute video of the observatory.

Patrick Moore's house

A visit to Selsey, West Sussex this week gave me the opportunity to see Farthings, the house of Patrick Moore. Added bonus: a collection of memorabilia at The Sir Patrick Moore Pavilion of the Selsey Cricket Club.

Saddle for auxiliary telescopes

ADM saddle
Dovetail saddle manufactured by ADM Accessories mounted near the centre of mass of the large optical tube.


A standard D series saddle from ADM Accessories enables mounting auxiliary telescopes piggyback on the 62 cm telescope.  In order to fasten the ADM saddle to the ASA truss tube, my neighbour, a professional machinist, cut a 510 mm long, 20 mm thick aluminium plate to fit the M6 threaded mounting holes on the mirror cage of the ASA truss tube. The ADM saddle is fastened to the aluminium plate near the centre of mass of the optical tube assembly, just above the middle of the image.


Thirty-four kilograms of additional counterweights on the declination axis balance the mass of the saddle assembly, 120 mm refractor (not shown) for wide-field imaging, filter wheel and camera.