Notes and Links from the March 2019 Meeting

(Draft)

Member’s Observing Sessions

An appeal was made for volunteers to organise future Member’s Observing Sessions after this month.

Amateur Radio Astronomy

One of our members gave the first of a series of short talks on opportunities for amateurs using radio equipment.

After a brief history of Radio Astronomy, the possible motives were listed. The natural phenomena of meteors, Jupiter, the Sun and associated Aurora can be monitored together with satellite communications. Although radio astronomy can be carried out during the day at frequencies above 30MHz, frequencies below this are either absorbed or reflected back to earth or back into space by the Earth’s ionosphere. When sunspot activity is low after sunset there is an opportunity to listen to frequencies below 30MHz from space when the F layer of the ionosphere can fade a few hours after sunset. It is then possible to hear radio emissions from Jupiter between 15 and 38MHz.

An example of how to listen to meteors was given, and later some theory to explain why radio waves at different wavelengths are able to penetrate different media . An explanation on different antennas was given with an example of a simple YAGI antenna showing how this and Dishes are able to increase the Gain of a signal and improve the signal to noise ratio. The presentation finished with brief examples of equipment which will be discussed at later presentations.

Sky Notes for March 2019

  • Orion only a few more weeks. Betelgeuse at Right Ascension of 6 hrs sets six hours at the Equinox on the (1830 on the 21st).

  • from March 26th to 31st – early evening: Mars approaches the Pleiades and Hyades open clusters

  • on Friday, March 29th – before dawn around 05:45: Saturn just above the Moon above Uranus

  • See also Ian Morison’s Night Sky this Month on the Jodrell Bank site in Sky Notes and our EAS links page

News Roundup for March 2019

Our EAS member, Richard Rae, visited Complex 39A at Cape Canaveral ( the Appollo 11 launch pad) for the launch of the SpaceX Falcon 9 rocket which is now the workhorse for vehicles to and from the International Space Station.

Simon White of EAS speaking on Anatomy of an Astrophotograph

Simon White gave an explanatory talk with illustrations of the process – from the load in the boot of a car to the final photographic image of The Orion Nebula.

Requirements were categorised as:

Gear

The equipment used from telescope components to a laptop and a standard DSLR camera were described.

Tracking & Guiding

Given the maximum intended magnification, telescope alignment algorithms were explained in order to reach an acceptable tolerance of 5 minutes of guidance before the target crossed one pixel in the camera

Focus

A Bahtinov mask was suggested and explained to enable the adjusting of the focus until the camera imaged a characteristic six barred star diffraction from the centre of the field.

Exposure

Red Green Blue bucket images demonstrated that a compromise is needed in order not overfill the image and lose colours using a Bayer Filter.

Processing

Calibration

The formulae for combining Dark, Bias and Flat Frames taken by the camera were illustrated with clear explanations.

Computing power demanded when Demosaicing Bayer Filter the colour pixels in the raw image became clear.

Post Processing

Basic Stacking

Stacking of multiple images aims to maximise the Signal to Noice ratio up to a threshold after which improvement rapidly declines. The improvement to the Orion Nebula image enabled the Trapezium Cluster to be clearly resolved. Recommended Image stacking software:

See also: Simon White’s Orion’s easy target and Equipment used

our Links page: Software used by our members