Sharnbrook Observatory

v.200 uploaded: 1st January 2019

Sharnbrook Observatory

Welcome to my web site!

This version includes new images of Comet 46/P Wirtanen and the region around Orion's belt. Some galleries have

also been updated.

All of the images on this site are my own, taken using amateur telescopes and equipment.

As ever, I hope this encourages you to get out there and enjoy the treasures of our universe at first hand.

Best Wishes,

Peter Garbett

Galleries...

African Skies

Mars

Venus

Equipment

Comets

Sun

The Aurora

Deep Sky

Moon

Jupiter

Saturn

NLC

Comet 46P/Wirtanen

Comet 46P/Wirtanen is a short-period comet with an orbital period of 5.4 years. The comet is relatively small with an estimated diameter of just 1.2 kilometres.

The object was the original target for ESA’s Rosetta spacecraft but the launch window was missed so 67P/Churymov-Gerasimenko was Rosetta’s target in the end.

Comet 46P/Wirtanen was discovered by Carl A. Wirtanen in 1948 at the Lick Observatory, California via photographic plate. The plate was exposed on 17 January 1948 during a stellar proper motion survey at the observatory. It took over a year before the object was recognised as a short-period comet due to a lack of observations.

46P belongs to a small family of comets that have a higher level of activity than expected for their nucleus size. They emit more water vapour than they should.

Perihelion passage of comet Wirtanen was on 16 December 2018 when it passed a mere 0.078 AU (7,220,000 mi) from Earth.

15th - 16th December, 2018

13 x 2 minute exposures with astro-modded Canon EOS 450D DSLR

800 ASA, 135mm lens @ F3.5

Orion's Belt and Sword

Whilst the camera was set up for Comet 46P/Wirtanen, I couldn't resist imaging the region around

Orion's belt and sword.

15th - 16th December, 2018

8 x 2 minute exposures with astro-modded Canon EOS 450D DSLR

800 ASA, 135mm lens @ F3.5

A Chance Capture!

When I examined the individual frames for the Orion's belt and sword stack, I saw what at first appeared to be a short meteor trail. The odd thing was

that tracks of identical length were found on subsequent frames, just displaced a little towards the east. I immediately realised that this was likely to be a

geostationary satellite as this region of Orion is close to the celestial equator and geostationary satellites orbit high above the Earth's equator. Since the

camera was piggy-backed on my C14 telescope, and tracked the westward apparent motion of the stars, a geostationary satellite would appear to get 'left

behind' and hence show a track headed towards the east. To prove the point all I needed to do was measure the angular length of the track. Using the stars

Alnitak and Alnilam in Orion's belt which are separated by an angle on the sky of 1 deg. 21' 22" and 159mm on my monitor screen, the satellite trail (59mm

in length) corresponded to 30'.2. An exposure of 2 minutes should produce a trail of angular length 30'.1 calculated from the Earth's 23h 56m sidereal rate.

This close agreement is well within measurement uncertainties and so I can be confident that indeed the track is that of a geostationary satellite. Very

close examination of these frames revealed other fainter tracks of other satellites.

Below is a pair of successive 2 minute exposures showing the track produced by the geostationary satellite.

The Sun going into 'hibernation'!

As can be plainly seen from the graph below, the Sun is at solar minimum with lots of days when the surface is spotless. All of the data for the graph is

from my own regular observations.