I am a beginner variable star observer from the Southern Hemisphere (but with experience in astronomy) and, when I was looking for VS to observe, I saw that Del Vel has almost no observations. Thus, there is no graph for when the eclipses occur.

VSX data: mag range of 1.95 - 2.43 V, period of 45.15 days and 1.3% (0.587 days) eclipse duration

It doesn't have data about how the magnitude varies in the visual spectrum, althought I know it is a bright star (already saw it at naked eye).

Does it vary in the visual spectum, or there simply is no data enough to determine this? Could I collect this information visually, or is this waste of time?

  • 2
    $\begingroup$ Obs: I use AAVSO and its data when looking for VS observations and informations. $\endgroup$ – Vitor Z. Feb 19 at 12:16

Yes it varies in the visible spectrum.

The paper The nearby eclipsing stellar system δ Velorum describes why this is difficult target. Surprisingly it is because it is so bright.

The absolute brightness of a star will vary significantly due to absorbtion in the atmosphere. If the sky is slightly hazy, then the stars will be dimmer. To measure the magnitude of a star, then, you don't directly measure how much light is coming from it, but compare it to nearby stars. But δ Velorum is one of the brighter stars in the sky, so there are fewer nearby comparison stars. This, combined with the long period of the orbit makes observations harder. This probably explains the shortage of observations.


I am the discoverer of delta Velorum's variability (along with the Galileo spacecraft) and I detected those variations visually, so yes, they can be observed, and they are really fun! If you go to the AAVSO VSX page of the star, you have a button called ephemeris that will produce a list of eclipses with their times of beginning - mideclipse - and end.

I copy them here: Dates in UT

26 Mar 2021 08:56
26 Mar 2021 15:58
26 Mar 2021 23:01

10 May 2021 12:32
10 May 2021 19:35
11 May 2021 02:37

24 Jun 2021 16:08
24 Jun 2021 23:11
25 Jun 2021 06:14

08 Aug 2021 19:45
09 Aug 2021 02:47
09 Aug 2021 09:50

22 Sep 2021 23:21
23 Sep 2021 06:24
23 Sep 2021 13:26

07 Nov 2021 02:57
07 Nov 2021 10:00
07 Nov 2021 17:03

Those are times for the primary eclipse. The secondary eclipse can also be observed but one has to create the ephemeris oneself using the period and epoch of Min II. The secondary eclipse is not so deep (0.32 mag. instead of 0.48) but lasts a whole day (durations are different because the orbit is eccentric).

Mideclipse will take place at

03/01/2021 04:49:43 Monday

04/15/2021 08:26:03 Thursday

05/30/2021 12:02:23 Sunday

07/14/2021 15:38:42 Wednesday

08/28/2021 19:15:02 Saturday

10/12/2021 22:51:22 Tuesday

Whenever you see a magnitude range in V, it means those variations are seen in the visual band (V= visual, most specifically Johnson's V band which is very similar to the eye response, especially for white stars like this one).

To detect the changes visually, you can use the following comparison stars:

gamma Velorum V= 1.70

beta Canis Majoris V= 1.98

gamma Centauri V= 2.16

iota Carinae V= 2.24

zeta Puppis V= 2.25

kappa Velorum V= 2.49

I attach a chart for your convenience.

There are few observations because not many people like to observer bright stars and because their changes are subtle and not everybody are confident to detect them. I hope you can take up the challenge and feel the same thrill of discovery I felt the night of July 1, 1997 when I found it dimmer than usual :)

Cheers, Sebastian Otero, Buenos Aires. AAVSO

delta velorum chart


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