Archive for the ‘Variable Stars’ Category

ASASSN-16ma declining?

November 11, 2016

Poor weather prevented any observations last night but tonight the sky cleared after a late afternoon storm and I estimated the nova at magnitude 6.3.

asassn-16manov11

So, it’s been gradually declining for 3 days, but whether that continues remains to be seen.

ASASSN-16ma update

November 9, 2016

As mentioned in yesterday’s updated post (with finder chart), conditions last night were less than ideal, but when the clouds cleared enough, I estimated the nova’s magnitude at 6.1.

asassn-16manov10

 

ASASSN-16ma: easy binocular object

November 8, 2016

Last night’s observation of ASASSN-16ma was with 7×50 binoculars rather than my Meade LX-90 8″ SCT. The nova is now on the verge of naked eye visibility!

asassn-16ma

I estimated the nova at magnitude 5.5 last night with one before mine at 5.4 and two subsequent observations of 5.8 and another at 5.9. Mine are highlighted in purple as usual.

Here’s the section of Sagittarius of interest as it currently appears from Adelaide, low in the south-western sky at around 9pm:

sgr

The nova is just west of the circled star HIP 90012, the 6.2 (labeled 62) magnitude star near the middle of this AAVSO finder chart:

x16923acn

If you rotate this chart 90 degrees to the right, it will have roughly the same orientation as the Stellarium sky scene.

Alnasl is the star labeled 30 (magnitude 3.0) at bottom right of the finder chart. Kaus Media corresponds to the label 27 and Kaus Borealis with the star labeled 28. Kaus Australis and Φ Sagittarii do not appear on the finder chart, but would be off to the left of the unrotated chart.

As I write this, the sky here in Adelaide is quite overcast, so there may be no observation from me tonight.

 

Update on two novae in Sagittarius

November 7, 2016

Poor weather then being away for work for three days last week has kept me away from variable star observing since October 29. Last night (November 6) I observed TCP J18102829-2729590 and ASASSN-16ma again.

While the first is on the decline currently (around magnitude 9):

tcp-j18102829-2729590-lc-nov-7

On the other hand, I caught ASASSN-16ma on the rise. My October 29 observation gave a visual magnitude of 10.3 whereas last night it was 7.3. Several hours later others were recording it at around 6.5:

asassn-16manov-7

So, ASASSN-16ma has exceeded TCP J18102829-2729590’s maximum (so far) by around one magnitude. If this rate of increase continues, who knows, maybe it will reach naked eye visibility. Here’s hoping!

 

TCP J18102829-2729590’s undulations

October 29, 2016

My visual estimate of nova TCP J18102829-2729590 last night was magnitude 8.0 using my trusty Meade LX-90 at 82x magnification. In my light-polluted corner of suburban Adelaide, 7×50 binoculars just aren’t good enough for this.

The third observation from right, three days ago, showed an apparent rapid increase in brightness. For me, one of the attractions of novae is their less than predictable nature.

Looking at the light curve today, my observations look a bit like (purple) buoys bobbing up and down on the surface of an undulating ocean.

tcp-j18102829-2729590-lc-oct-29

Maybe I’m spending too much time looking at novae at the moment. My wife would probably agree with you, even though she’s very understanding. 🙂

ASASSN-16ma = PNV J18205200-282210

October 29, 2016

ASASSN-16ma, the nova candidate in Sagittarius, has been designated PNV J18205200-282210 by IAU CBAT as per today’s AAVSO alert notice.

I made another visual estimate of the nova again last night at magnitude 10.3.

asassn-16ktlcsep29

Two novae in Sagittarius!

October 28, 2016

Since my last post I’ve made two more observations of TCP J18102829-2729590, on Oct 26 and 27. Mine are the larger purple data points. Fraser Farrell pointed out a nice recent Sky & Telescope News article about this nova.

tcp-j18102829-2729590-lc-oct-28

Another nova was discovered in Sagittarius on Oct 26: ASASSN-16ma. There are only a few observations of this one so far. Mine is at top right under the cross hairs.

asassn-16ktlcsep28

ASASSN-16ma is currently three magnitudes fainter than TCP J18102829-2729590, but the latter arrived on the scene first, after all.

The weather looks good for tonight and tomorrow so I hope to get some more observations in over the weekend.

Nova TCP J18102829-2729590 still on the rise

October 24, 2016

tcp-j18102829-2729590-lc-oct-25

Nova TCP J18102829-2729590 in Sagittarius is still on the rise although not at the same rate as a day or so ago. Early days though: these things are unpredictable.

The official AAVSO alert notice was posted overnight: https://www.aavso.org/aavso-alert-notice-560

I have ongoing alignment problems with my LX-90 8″ scope (16 years old) and they caused me enough grief last night that I couldn’t make a visual estimate before the nova was below my fence line. I’ll try again in the next day or two.

Nova in Sagittarius

October 23, 2016

Not far from one of my favourite Cepheid variables (W Sagittarii), a nova in Sagittarius was discovered 3 days ago (TCP J18102829-2729590) by Koichi Itagaki of Japan. It has risen from magnitude 11 to 8 in that time.

The plot below shows the 10 visual and Johnson V observations submitted so far to the AAVSO International Database:

tcp-j18102829-2729590-oct-23-lc

Two thirds of the visual observations are from Andrew Pearce in Western Australia. My single observation so far, made tonight, is under the cross hairs at upper right, with Andrew close on my heels. It’s always reassuring when two observations made close in time (less than an hour in this case) by different observers agree, within the limits of precision of the chosen method (visual estimation: approximately one tenth of a magnitude).

Many of my visual estimates of variable stars are made with 7×50 binoculars. Tonight I used my Meade LX-90 8″ telescope (magnification of 82x) because the nova is still too faint for my binoculars. There’s a beautiful asterism near the nova that makes the field hard to miss and makes for an enjoyable observation.

x16826ks

Last night I took images of the nova with the intention of carrying out wide field DSLR photometry, however there’s a star quite close to the nova. When combined with the amount of defocus normally used for DSLR photometry, separating the light from the two stars becomes impractical. So, I haven’t submitted an observation (untransformed) from that imaging run.

I’ll follow this object visually with interest for as long as the weather and my equipment allow.

Nova Lupi 2016 update

October 5, 2016

The nova in Lupus (ASASSN-16kt) continues to decline, having peaked at a visual magnitude of 5.6, declining to 6.5 in less than a day.

The plot shows my two binocular observations before the weather in Adelaide went loopy (as opposed to Lupi), the last under cross-hairs at magnitude of 7.2. It’s now down to around magnitude 9.0.

asassn-16ktlcoct05

The sky is clear tonight, and may be okay for a couple more days, so I might attempt some tri-colour DSLR observations. Tonight’s out due to an ASSA meeting. Typical! 🙂