Hi everyone,

 

I’m parting with my 10 inch Dobsonian after 6 years of fantastic observing.  I’m giving members of our society the chance to  make me an offer for it before I take it to eBay.

 

The telescope specs are as follows.

 

Make: Callisto

Telescope Design:  Newtonian

Mount:  Dobsonian (alt-az)

Aperture:  250mm (10 inches)

Focal length: 1250mm

Ratio:  F5

Finder telescope: 9x50

Red Dot Finder

Eyepiece:  25mm Plossl

Limiting magnitude:  about +14.

Dawes limiting resolution:  0.5”

 

This telescope is just about small enough to be described as easily portable; the tube fits comfortably on the back seat of my Citroen Saxo (as it also did in my Ford Fiesta and Ford Escort in previous years).  The base is accommodated easily in the car-boot.

 

The mirror is looking slightly tarnished in places; I can’t say that this has dramatically affected the performance.  Objects like M13 (Hercules Globular), M57 (Ring Nebula) and other deep sky objects look as good as ever.  When the telescope is well-collimated (as it is at present) it will provide you with stunning views of the Moon, the phases of Venus, surface markings on Mars, cloud belts on Jupiter and the rings of Saturn.  It is primarily a telescope for deepsky observing though (star clusters, nebulae and galaxies).

 

This telescope isn’t suitable for imaging which requires any kind of tracking.  It can be used in conjunction with a digital camera to take pictures of bright objects such as the Moon, the filtered Sun and brighter planets (see my website for examples).

 

I haven’t attached pictures of the telescope to this email but I can send some if you would like more details.  If you want to come and see the telescope for yourself (if you haven’t already seen it on various observing evenings) then that can be arranged.

 

Finally, I’m enclosing a selection of some of my observing records to highlight what the telescope is capable of.

 

I’m looking for offers in the region of £250.  If you have any more questions – feel free to email or give me a ring.  If I don’t hear from anyone in the next week then it’s going on eBay.

 

Cheers,

 

Adrian

--------------------------

Dr Adrian Jannetta

NASTRO Group Moderator

Email: adrian@...

 

 

---------------------------------------------------------

 

Astronomy Log records (2003 – present)

 

 

Gemini Nebula (NGC2371) on Dec 28^th 2003

Star hopped to this one with Plossl 32mm, 39x.  Wasn't sure I could see it even though I was certain it was centred in the eyepiece.  Changed to Plossl 25mm, 50x and it was there!  A small pale disk at the limit of averted vision.  This 13^th magnitude planetary nebula was victory from my light-polluted back garden!

 

Comet Schwassman-Wachmann on Apr 23^rd 2006

Observed fragment C of the comet.  Much brighter and easier to detect compared to fragment B (seen several nights earlier).  Over a period of 45 minutes the motion against the background stars was obvious.

 

Rasalgethi (double star, Hercules) on Aug 26^th 2006

At highest magnification (Plossl 9mm X2.0, 278x) this 3rd magnitude star blazed a fierce orange light and close by - a fairly narrow separation of 5 arcseconds  - was a faint white/greenish companion.

 

E.T. Cluster (NGC457) on Aug 27^th 2006

View the E.T. cluster at low magnification (TeleVue Plössl 40mm, 31x) and the "alien with outstretched arms" pattern of stars really stood out against the dark background.  Orange Phi Cassiopeia embedded in this open cluster looks stunning at low power.  Phi Cas marks the left eye of the alien and is much brighter and orange than the other eye!

 

Andromeda Galaxy (M31) on Aug 27^th 2006

Probably the best view that I've had with the 10" Dob.  The nucleus looked star-like and was surrounded by a haze that showed indefinable structure in places.  There was a hint of a dust lane below the core (to the north) - a slight dimming of the nebulosity.  M110 and M32 were both visible in the same FOV.

 

Hercules Globular Cluster (M13) on Aug 28^th 2006

A spectacular view of the cluster with Plossl 32mm (39x) and with Meade QX Wide Angle 15mm (83x).  Roundish diffuse ball of light with a slightly non-symmetric shape.  Stars within M13 were resolved throughout and tendrils of stars seemed lead out of the cluster (especially on the right-hand side).  During moments of clarity it seemed that the number stars was countless.

 

The Flame Nebula (NGC2024) on Nov 19^th 2006

A faint reflection nebula next to Alnitak in Orion’s Belt.  The nebula was obvious when (a) the brilliance of Alnitak was outside the field of view and (b) the tube was nudged to create a bit of movement.  In fact, some structure (a dark lane) was apparant in the faint haze of the nebula while the tube was vibrated.

 

The Moon on Jan 27^th 2007

A stunning view of the craters and mountains along the lunar terminator.  Of particular note were the craters: Clavius (with a curve of craters on it's floor thrown into relief), Tycho (whose prominent central peak cast a long shadow across the floor of the crater) and Plato (whose mountainous rim cast a jagged shadow onto the crater floor).

 

Saturn on Feb 7^th 2007

Another fine view of Saturn this evening.  While the seeing probably prevented the Cassini Division from being resolved, I was able to see a number of satellites close to the planet.  At 50x Titan (to the NE) and Iapetus (to the W) were easily visible.  At 83x a string of very faint points of light were visible near the NE edge of the rings; these were Rhea, Tethys and Dione.  A total of five moons despite bright moonlight!

 

Jupiter on Aug 9^th 2007

Despite the low altitude, the view of Jupiter this evening was superb.  The most obvious change since I last saw Jupiter this clearly was that the northern equatorial belt was not visible at all – it’s gone!  The southern equatorial belt (SEB) was clear - indentations and other structure were visible during moments of steady seeing.  Just off-centre of the SEB was the Great Red Spot, again, easily visible as a brightening on the north side of the SEB.  At 9.30pm a moon was visible very close to the western limb of the planet and it became progressively closer over the next 20-25 minutes until it disappeared behind Jupiter.  I identified the moon as Europa next day.  Io and Ganymede were located some distance to the east, with Callisto to the west.  The 4th magnitude star Omega Oph was also in the FOV looking like a 5^th moon of Jupiter. 

 

Neptune on August 13^th 2007

Star hopped using the red-dot finder from Delta Capricorni.  Neptune's bluish colour distinguised it in a field with only fainter stars.  At higher magnifications (>100x) the disk became more obvious but it was difficult to focus without comparably bright stars in the same FOV.