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V1369 (Nova Centauri 2013) magnitude estimate: comparison stars?

durval's picture
durval
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Joined: 2013-08-20

Hello folks, I've been doing some observations of Nova Centauri 2013 (V1369 Cen). I got its observation chart from VSP (chart ID "13189CZU"), but all 3 comparison stars shown are much dimmer (7.3, 7.6 and 7.8, while I estimate V1369 Cen to be around magnitude 5 right now). I understand that, for interpolation, I need both lower-magnitude and higher-magnitude comparison stars (at least one of each) in the same chart, and ideally of approximate brightness. Should I request more comparison stars? Or am I missing something? Sorry if this is a FAQ; I searched for but could not find an answer. Thanks in advance, -- Durval Menezes.

Chart scale
Sebastian Otero's picture
Sebastian Otero
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Joined: 2010-09-19

Hi Durval,

The problem is that you are using a wrong scale. You need a much wider field of view to include the brighter comparison stars.
Try with the code 13190ABG which corresponds to a chart with a 700 arcmin field of view, a limiting magnitude of 9 and the Binocular chart option marked.
You'll get all the needed comparison stars there.
I am currently using the 54,56,59, 60 and 62 closest to the variable.

Cheers,
Sebastian
 

V1369 (Nova Centauri 2013) magnitude estimate: comparison stars?
durval's picture
durval
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Joined: 2013-08-20

Hi Sebastian,

Thanks for your response. More below:

Sebastian Otero wrote:

The problem is that you are using a wrong scale. You need a much wider field of view to include the brighter comparison stars.
Try with the code 13190ABG which corresponds to a chart with a 700 arcmin field of view, a limiting magnitude of 9 and the Binocular chart option marked.

Great! In fact, this chart has many more stars. So, why is that other chart (13190ATA) being shown as "default" (ie, when one clicks on the "Create star chart" link on the Light Curve Generator page for this star)?

Sebastian Otero wrote:

You'll get all the needed comparison stars there.
I am currently using the 54,56,59, 60 and 62 closest to the variable.

Will try with those. A last question: is there an easy way to find out the designations (ie, catalogue numbers) for the comparison stars? I've been searching SIMBAD for their coordinates as shown in the photometry table, but I wonder whether there's an easier way...


Cheers,

--

   Durval.

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