[Alex Pratt]

Hi Denis,

I last saw Rob McNaught at an ASE meeting at Calton Hill Observatory in September 2007. Here’s a pic of him and Dave Gavine taken in the Observatory’s reading room.

You could ask Dave if he’s still in touch with Rob.

Clear skies,

     Alex.

[Alex Pratt]

Clear blue sky all day in Leeds, so one consideration was trying not to get sunburnt.

I monitored the transit (with my 102mm apo refractor and QHY mono camera) from before first contact up to shortly after 7pm when local rooftops intervened, then quickly transferred to an 80mm refractor set up near the front of the house to follow the last phases. Mercury looked like a tiny ball-bearing in silhouette against the Sun. Seeing wasn’t very good and it was tricky to achieve good focus.

The resident blackbirds weren’t happy that my presence was stopping them from accessing the birdbath, and some wasps took a long-term interest in my laptop computer.

The sunny weather brought back happy memories of observing the 2004 transit of Venus from Cyprus – and as I did on that occasion, had a beer at mid-event.

Cheers,

     Alex.

[Alex Pratt]

Thanks Jeremy.

I’ve observed a few Aldebaran occultations over the years, with varying success. On 1979 Jan 9 I observed and timed a DD and RB pair, using a stopwatch and time signals. Modern video systems and techniques allow us to obtain much smaller O-Cs than in the days of manual timings, personal equation, etc.

Clear skies for 2016.

    Alex.

[Alex Pratt]

In recent weeks the weather has been cloudy, cloudy with rain, or clearing and blowing a hooley, so it was a pleasant surprise to have a fairly clear sky and occasional light breeze for recording and timing the D and R events.

Clear skies,

     Alex.

[Alex Pratt]

Hi David,

There’s some discussions in past Journals of Scaliger’s work, as documented in the BAA Journal DVD Archive.

JBAA vol 57 no 3 (1947 March) has a paper by A. K. Bennett on ‘Scaliger J. J. 1540-1609’, but it may not answer your questions.

Best regards,

     Alex.

[Alex Pratt]

Hi Bill,

There will be some uncertainty in the result from Analyser if its profile was created from a small number of reference stars.

Analyser sometimes categorises a meteor as a sporadic (or other shower membership), giving an unexpected result. Two reasons for this can be the meteor’s angular velocity and its distance from the radiants stored in its internal catalogue. The meteor’s estimated velocity is an important factor and if this falls outside the expected ranges (for each known shower) it can fail the shower membership tests and be categorised as a sporadic.

Have a look in the UFO Analyser Uty tab and tick the ‘analyzelog’ box. This creates a txt file when analysing a meteor clip. The file contains details about the reference stars, the meteor’s angular velocity and how well it matches against currently active slowers.

Clear skies,

     Alex.

[Alex Pratt]

Hi Bill,

Yes, UFO_A is normally used to process meteor captures from a wall-mounted video camera, but it can also be used to analyse meteors from a one-off tripod-mounted session.

This would help to assess whether all your spectra are from Quadrantids or if there’s any DaDs in there.

The parent body of the Quadrantids is believed to be 2003 EH1, an Amor NEO. Multi-station observations of the Quadrantids in 2014 by the NEMETODE team showed that the meteors were extinguished at higher altitudes than the Geminids, even though they have similar Vg, suggesting that Quadrantids are more fragile material.

Cheers,

     Alex.

[Alex Pratt]

Hi Bill,

UFO Analyser can display the meteor trail against the star field, compute its probability of shower membership (from its internal catalogue) and it will measure its offset from the radiant.

This is more objective than an alignment by eye.

Clear skies,

     Alex. 

[Alex Pratt]

Hi Bill,

Here’s a plot of both radiants, from UFO Orbit.

If the December alpha Draconids are accepted as a genuine minor shower we can have cases where some of their meteors are mis-identified as Quadrantids, and vice versa.

Clear skies,

     Alex.

 

[Alex Pratt]

Hi Bill,

As discussed offline, the meteor shower data are suppiled in the ULE_J5.csv and ULE_J6.csv files bundled with the UFO software suite.

They are also listed in the IAU MDC

The Vg of the two showers are essentially the same, 41.36km/s (Quads) and 41.6 (DaDs).

UFO Analyser derives an estimate of the meteor’s velocity from a single-station recording, then UFO Orbit computes an estimate of its geocentric velocity using data from two or more stations.

Cheers,

     Alex.

[Alex Pratt]

Hi Bill,

Fascinating stuff.

You also have additional camera alignment options with David Anderson and Denis Buczynski.

I recorded 103 Quadrantids on Jan 3/4, but in addition there were 18 meteors that UFO Analyser categorised as J5_daD (December alpha Draconids). This shower has been confirmed by SonotaCo data, but its radiant lies close to that of the Quadrantids, being active at a similar time of year and with similar Vg.

 

I always regard shower membership from single-station work as provisional. A single-station meteor could be assigned J5_daD membership, then later identified as a Quadrantid from dual- or multi-station analysis.

 

Is it possible that you have a mixture of Quadrantid and December alpha Draconid spectra?

 

Cheers,

 

     Alex.

[Alex Pratt]

Hi Bill,

I really like your composite diagrams, showing the spread of colours along the range of wavelengths and the plot of their intensity levels. An excellent way to illustrate a meteor spectrum.

I had clear skies on Jan 3/4 and in spite of the almost Full Moon my Leeds_NW and Leeds_SE cameras recorded a total of 192 meteors, of which 103 were Quadrantids, with a mean mag of around 1.5.

I’m hopeful that we’ll obtain some multi-station data when you can operate a south-facing camera during Moonless nights.

Clear skies,

     Alex.

[Alex Pratt]

Thanks Jeremy, Bill.

Every 6 years the Galilean satellites of Jupiter undergo a long series of mutual eclipses and occultations (partial, annular and total), thanks to the alignment of their orbital plane as viewed from Earth. These are known as PHEMUs (mutual phenomena).

Satellites of other gas giants can also encounter PHEMUs, although the Jovian ones are the most well-known.

The worldwide observing campaign is administered by the Institut de Mecanique Celeste et de Calcul des Ephemerides (IMCCE, Paris). By combining data from numerous observations the ephemerides of the Galilean satellites can be refined.

I won’t post all my results on the Forum – this was just a nice example.

Clear skies,

     Alex.

[Alex Pratt]

Hi Nick,

 

Many thanks for your data.

 

Combining it with William’s data we have a nice Geminid, of absolute mag -2.8, duration 1.62s, detected at an altitude of 101km and extinguished at 58.9km. Its Vg of 32.8km/s and orbital elements are fully consistent with the Geminids stream.

 

Clear skies,

 

     Alex.

[Alex Pratt]

Hi William,

Congratulations on recording the fuel dump ‘comet’.

I also captured that meteor on my Leeds_SE camera. UFO Analyser categorised it as a -2.1m December alpha Aurigid, although it was well aligned with the Geminids radiant. I’m sure our dual-station analysis will rank it as a Geminid.

The faint object to the RHS of my meteor trail is not the glow of the fuel dump, it is a ghost image of the Moon, lying outside the FoV.

Clear skies,

     Alex.

[Alex Pratt]

Hi Robin,

I think my Leeds_SE meteor video camera recorded the early phase of the same event.

It timed its appearance at 20:00:05.3 UTC but of course the start of the trail was swamped by Moonlight.

The UFO Analyser software gave it a magnitude of -0.4 as it left my FOV. Yet again, the bright sky will have affected this estimate.

I’m sure that other video stations will have recorded the meteor, so that we can identify its shower membership, ground track and solar system orbit.

Clear skies,

     Alex.

[Alex Pratt]

Hi Sheridan,

I am very sorry to hear that Graham has left the Association. He contributed a great deal to the Computing Section, for the benefit of all.

As mentioned by Nick, the Letters column in the Journal gives recourse to reply to any comments about a paper, review or observation. Graham could take this route to support his book and his imaging techniques.

In the latest ‘Sky at Night’ Pete Lawrence demonstrated how beginners can take aesthetically pleasing images of the night sky with a ‘standard’ camera. Oh dear, but he didn’t explain how to take and apply dark frames and flat fields, etc. Should those scenes be re-shot with this vital information? Of course not!

We all started on that path, were pleased with our results, then found out that we could improve our images by stacking them, applying calibration, etc.

I hope Graham stays with us.

Clear skies,

     Alex.

[Alex Pratt]

Hi Nick,

Thanks for that advice. It’s probably the largest of the individual videos.

Will try again this evening.

Clear skies,

     Alex.

[Alex Pratt]

Hi Nick,

I downloaded the videos (MP4) to my Win 7 laptop and viewed them OK with Media Player, except for Lyn Smith’s talk. It gave a Player error and failed to run. Please check if you encounter the same problem. I downloaded it a couple more times, to no avail.

Thanks,

      Alex.

[Alex Pratt]

Hi Nick,

I’ve downloaded the videos and had a brief look at the talks. I look forward to viewing them in full. They are a great record of a most memorable meeting.

Many thanks to you and Gill for your hard work.

     Alex.

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