Archive for the ‘VStar’ Category

Another peak for V1369 Cen

January 8, 2014

I just came inside after making another visual estimate of V1369 Centauri. The roller-coaster of the nova continues as shown by the updated light curve.

V1369CenJan92013

 Click on the image to enlarge it. My several observations are in purple as usual.

The nova in Centaurus from Stockport

January 5, 2014

I spent last night at a really well-attended ASSA member’s night at Stockport Observatory last night, an awesome start for 2014.

A number of members enjoyed views of the nova in Centaurus (V1369 Cen). The cross hairs in the light curve below are over my visual estimate just after 1am; as in previous posts, the observations in purple show others I’ve made (only 5 up to this point).

V1369CenJan52013

The details of the observation are as follows:

V1369 Cen Obs Details Jan 5

When I first submitted the observation to AAVSO at around 3am, it was around 0.3 magnitudes brighter than the previous one. Others have since submitted more observations around the same time with similar magnitude values.

The nova was clearly visible to the unaided eye from Stockport at that time, as were the 4.7 and 4.3 comparison stars I used for the estimate (shown, by the conventional labels, as 43 and 47 above).

An observation a couple hours earlier at around 10:30pm when the nova was closer to the horizon was around 4.8 but I was a little uncertain of the estimate due to the low altitude so I didn’t submit that one to AAVSO.

Will the current rise continue past the last peak? The only way to find out is to keep watching!

I also made visual estimates of the Classical Cepheid l Carinae and LBV (Luminous Blue Variable) η Carinae. I had aimed to make estimates of others (R Carinae and V Puppis) but didn’t quite get there. I was too busy having a good time looking at other objects through my Meade LX-90 ‘scope and sharing views with ASSA members.

V1369 fading again

December 30, 2013

I made a visual estimate of magnitude 4.4 of the nova overnight. Subsequent observations show that it has dropped further since.

Here is the updated light curve:

V1369CenDec302013

The observation under the cross-hairs is my last (magnitude 4.4) observation and the others in purple (click image to enlarge) are the estimates I’ve submitted to AAVSO so far. 

Sebastian Otero’s latest forum reply asks whether the current fading will be the nova’s last one and suggests possibly not, given its erratic behaviour so far.

V1369 light curve update

December 28, 2013

I just made an estimate of V1369 Cen (at about 2am on Dec 29) at magnitude 4.3. It may actually be closer to 4.2 but I could not convince myself of that with respect to nearby magnitude 4.0 and 4.3 comparison stars. Visual and Johnson V observations are shown below (via VStar), with my estimate in the cross-hairs and a polynomial fit (in red) to make the outline of the light curve more obvious.

V1369CenDec292013

Regarding the polynomial fit, bear in mind of course George E.P. Box’s maxim that:

Essentially, all models are wrong, but some are useful.

So far, 628 observations have been submitted to AAVSO. Of these, 214 are visual observations.

What a fascinating, meandering, unpredictable progression. I’ll try to monitor this nova as much as possible over the next week, while still on holidays.

Estimates of V1369 Cen and light curve update

December 21, 2013

Once the weather had improved, I was able to make two estimates of V1369 Cen, in the early hours of December 12th and 14th, and submit them to AAVSO.

In the week following these observations, work was all-consuming (in a positive way) and I needed to get plenty of sleep. The weather is uncooperative in Adelaide again at the moment. Being on leave for a couple of weeks makes it less of a problem getting up at an early hour when the weather does improve again.

The nova continues to be interesting as shown by the current light curve.

NovaCenDec21

This AAVSO article provides a great summary of the evolution of the nova so far.

I continue to watch this object with interest.

V1369 Cen light curve and cloud, cloud, cloud (did I mention cloud?)

December 7, 2013

Not even a glimpse this morning at 4:15 am and for the next hour.

“Partly cloudy” was a slight exaggeration and the forecast currently doesn’t look good for most of the coming week.

adelaide_forecast_dec7

Of course, that part of the sky was clear by the time I emerged after an unusually long saturday morning sleep in.

Reports from others suggest that the nova may have peaked. Here’s the light curve so far, consisting of 55 (non fainter-than) observations.

V1369CenDec72013

It shouldn’t be too surprising that there are fewer observations for this nova in the same period of time as there were for V0339 Del which was:

  • Visible in the evening sky rather than the early morning.
  • Not as bright (around a magnitude less at peak).
  • Visible in northerly latitudes.

Despite the forecast, I’ll try again tomorrow morning. A fellow ASSA member told me that the southern sky was clear around 30 minutes before I was observing yesterday morning. The weather pays no heed to the likes of us.

Bill Bradfield Astronomy Award (2012)

November 17, 2013

In December 2012 I was humbled to receive the Bill Bradfield Astronomy Award.

From the ASSA awards page:

The award is named after Bill Bradfield, a Past President and Honorary Life Member of the Society and discoverer of 17 comets – the most comet discoveries by an amateur astronomer in the 20th century.

The description of my award on that page is as follows:

David received the Award for the creation and development of VStar. VStar is a variable star data visualisation and analysis software tool, which David has provided free to the astronomical community. Visit the VStar web site to download the software and for more information.

The physical award has been sitting next to my 2011 AAVSO Director’s award but it took awhile for the web page to be updated.

VStar cited in “Amplitude Variation in Pulsating Red Giants” papers

November 14, 2013

VStar was cited and made use of in two recent papers by John R. Percy and co-authors:

Date Compensated Discrete Fourier Transform (DCDFT) and Weighted Wavelet Z-Transform (WWZ) were used, DCDFT for period search, WWZ to look for amplitude variation over time within a period range. I was particularly happy to read the following in the acknowledgements sections:

We also thank the team which developed the VSTAR package, and made it user-friendly and publicly available.

The creation of a freely available, multi-platform, user-friendly tool was a central design goal. Thank you John, Viraja, and Romina for your use of VStar and kind words. Any feedback you might have on how to enhance VStar further will, of course, be gladly accepted.

Note that as an alternative (or in addition) to pointing to the AAVSO VStar page when citing VStar in a paper, I’d like to suggest that this paper be used:

Benn, D. 2012, “Algorithms + Observations = VStar”, JAAVSO, v40, n2, pp.852-866.

The paper can be found in eJAAVSO.

In any case, I’m pleased to see the adoption of VStar on the rise. It encourages me further to continue active development.

NOW: Nova Observation Withdrawl

September 11, 2013

It’s been 5 nights since I’ve been able to observe V0339 Delphini (was Nova Delphini 2013) due to cloudy conditions. Sigh.

Tonight looked promising before dinner and before I put the kids to bed. Cloud cover had rolled in by the time I got back outside though.

I haven’t looked at the light curve for a couple of days. I’d say it’s down to 7.5 or pushing towards 8.0.

He goes away and looks…

NovaDel2013Sep11

Yes, around 7.5. The weather forecast for Adelaide doesn’t look much better for the next few days so I may have to be a spectator for awhile.

Edit: I just managed to glimpse the field through binoculars but there was too much cloud to see the nova.

Nova Del 2013 designation change and update

September 9, 2013

Nova Delphini 2013 now has a more “normal” variable star catalog designation: V0339 Delphini.

Since my last post, the nova has dropped from 6.8 to 7.2 and the light curve continues to show a decline, although less steep the last few days.

NovaDel2013Sep9.tsv

I’ve been clouded out the last 2 nights but my observation from 3 nights ago is in the cross hairs and my humble 10 observations so far are shown in purple.

We really do have a great opportunity in the southern hemisphere to make observations of events that would otherwise be missed. Obviously I’m not the only person down here who is observing this object but for a few hours in some cases, the record shows that the observations are a bit thin.

NovaDel2013Sep9Zoomed

That stray magnitude 6.4 observation to the right of the cross hairs appears to be discrepant. There’s a fair amount of spread in the visual estimates but there’s also some disagreement from the photometric (Johnson V) observers.