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Red Dots Observing Campaign 2017

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weo
weo's picture
Red Dots Observing Campaign 2017

AAVSO Alert Notice 583 announces an observing campaign on three red variables (GJ729 = V1216 Sgr, Proxima Centauri = V645 Cen, and Barnard’s star = V2500 Oph) - the Red Dots campaign. Please see the notice for details and observing instructions.

Many thanks and Good observing,

Elizabeth Waagen, AAVSO HQ

hambsch
hambsch's picture
V1216 Sgr

Hi,

I observed this star and see a bright object (about V mag 10) close to the position of the variable, which is not on the Chart (https://www.aavso.org/apps/vsp/chart/X19283W.png)

In GUIDE9 I see a red star close to V1216 Sgr of mag 10.4 about which has identifier TYC 6859 1332 or HIP92403.

Is this the varaible or is the separation as given from the coordinates in VSX very small Guide says about 12 arcsec.

More information would be appreciated.

Josch

 

hambsch
hambsch's picture
Position in VSX not correct

Ok, If I look at the instructions page and finder chart then the coordinates given are not correct due to the large proper motion of the star.

Josch

clkotnik
clkotnik's picture
Data Upload Requirements

As I read the PDF linked from the announcement, I saw something a bit unusual in my admittedly limited experience.  I just want to check that this is intentional.  

In the section Data Upload Requirements, the MAG field should be the instrumental magnitude of the target and MTYPE field should be set to DIF.  The AAVSO doc on the file format notes this is very rare.  While not specified in the PDF, I assume the CMAG should also be the instrumental magnitude as is normal practice.  I know I was tempted to just create this file out of VPhot which would not have given the results described.

Just checking - this is intentional, right?

 

best regards,

Cliff

Faguisau
Position V2500 is not correct

 

Hello,

I was observing the star V2500 Oph and in my photo appears a star of approximate order of 9.0 that does not appear in the chart. In addition the coordinates indicated for V2500 does not appear any star in my photo.

https://www.aavso.org/apps/vsp/chart/?chartid=X19303YC

More information would be appreciated.

 

File upload: 
HQA
HQA's picture
Barnard's Star

Hi Figuisau,

Barnard's star is an extreme example of proper motion - it moves about 10arcsec per year!  The problem is that VSX reports the J2000 coordinates, but not the current epoch coordinates, and so the position in your CCD image tonight will be very different than the VSX position of 17 57 48.49 +04 41 36.2.  Josch already reported a similar problem with V1216 Sgr.

This is an issue with VSX, and I've mentioned it several times.  Most of the bright stars are nearby and have high proper motion.  The equinox of J2000 is already 17 years distant, and so these high proper motion stars are not at the VSX position, and equally bad, they won't be at the VSP position (either DSS, which is ~1985 epoch or dot-plot, ~1994 epoch, options).  You just have to compare your CCD image with the chart, and look for the "new" bright object - that is most likely the variable.

So first, and most important: these stars are NOT at their VSX positions.  Perhaps someone can plate solve and give the current positions on this forum, or find a catalog that does the proper precession to report the position.

Arne

Faguisau
Thank you !

Thank you !

Jupe
Jupe's picture
Barnard's Star current Coordinates

Hi Arne,

From June 17th, the coordinates I get for Barnard's Star are:

RA:  17 57 47.54    DEC:  +04 44 37.6

John Briol

HQA
HQA's picture
Barnard's Star

Thanks, John!  As you can see, most of Barnard's motion is to the north.  It moves so rapidly, in fact, that it is an ideal target for schools in teaching them about proper motion, as with just a handful of images scattered throughout a semester, you can easily track the motion using modern astrometric software like Pinpoint.  While obtaining a modern position is important, you also need to realize that these stars move with respect to a background of stars, and over the years, neighboring stars that were well isolated from the target using aperture photometry now reside within the aperture, affecting long-term measurement accuracy.  Some of the Landolt standards are this way, as Arlo chose many nearby white dwarfs for his blue stars, and they tend to have large proper motion.

There were several astrometric catalogs in the 1960's dealing with proper motion, such as the New Luyten Two-Tenths Catalog that contained about 58K stars with more than 0.2arcsec/year motion.  These will be several arcsec from any J2000 catalog at the current epoch.  The sky is not constant, either in position or brightness!

Arne

Raymond
Raymond's picture
Barnard 2016/17

Hi

I observed Barnard's star last and this year with the following positions

2016-08-08  RA: 17:57:47.59   Dec: +04:44:28.2

2017-06-15  RA: 17:57:47.57   Dec: +04:44:37.5

Almost no change in RA; a proper motion of about +10.9"/year in declination deduced from this (only) 2 observations (see image; south is up).

Raymond

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