A quasar outburst - PKS 1222+21

[Christian Buil]

Quasar PK 1222+21 is in a impressive outburs phase
From vsnet alert:

Outburst of quasar PKS 1222+21 continues
(PKS 1222+21 = 4C 21.35 = ON 238)

object date (UTC) mag comment
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PKS 1222+21 20140302.942 13.99C outburst
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Stefan Karge (SKA)
Taunus Observatory (MPC B01)
60cm-CGT + CCD + Clear


Now at V = 14.0 (normal magnitude is V = 17.5).
It is a far quasar at z = 0.435

Here three quasars at différent redshift all taken the
March 6, 2014. Of course PKS 1222+21, but also
3C232 (more faintest at z=0.530) and a very far quasar
CSO 1061 at z=2.669 (the Lyman alpha UV line enter
in the visible part of the spectrum - note also V=16.2 with Alpy and
a Celestron 11 telescope...).

I encourage observarion of challenging PKS 1222+21 object
(RA = 12 h 24 m 54 s, Dec. +21° 22' 46")



Christian B.

[Hubert Boussier]

Bonjour Christian,

Voyant ton message hier soir, par curiosité, je suis allé voir (enfin, disons plutôt que j'ai pointé mon télescope) aux coordonnées que tu donnes :
"I encourage observarion of challenging PKS 1222+21 object
(RA = 12 h 24 m 54 s, Dec. +21° 22' 46")"
Je n'ai rien vu qui ne soit indiqué sur les cartes(magnitudes maxi de 16.5), s'il y avait quelque chose mag 14, je devrais le voir. Donc soit je ne suis pas au bon endroit soit les coordonnées ne sont pas les bonnes, soit ... plein d'autres raisons qui peuvent m'avoir fait faire une erreur de pointage. Aurais tu une image du champ pour comparer ?

Je te joins l'image que j'ai faite hier soir.



et la carte de la zone 'CDC).




A+

[Olivier GARDE]

Bonsoir Hubert,

Le quasar n'est pas à la place que tu indiques, mais sur la gauche de ton image (la flèche verte que j'ai rajouté)

[Hubert Boussier]

Bonjour Olivier,

Je comprends maintenant mon erreur, en effet sur le logiciel Carte du ciel, le paramétrage des coordonnées EQ par défaut est "coordonnées équatoriales apparentes", il faut le régler en "astrométrique J2000" pour retrouver la position que tu indiques, cela fait un petit décalage qui explique que je ne regardais pas au bon endroit.
Je retenterai ma chance ce soir.

Merci beaucoup

[Christian Buil]

Bien vu Hubbert le positionnement. Ah les coordonnées apparentes...
Pour vous aider, voici les images de champs réalisées lors de l'observation
avec le C11 (camera guidage Alpy, 60 sec de pose pour cette prise).

Evite le eShel pour ce genre de truc Olivier
Alpy, LISA, Lhires III 150 t/mm sont de rigueurs !

Christian

[Martin Dubs]

Hello Hubert,

you are not the only one who fell into this trap. The same has happened to me with CdC. The reason may be that you correctly set astrometric (J2000) coordinates, but then you switch from an equatorial view to azimutal view (e.g. to check where the object is at the moment). When you switch back to equatorial view you find yourself in the apparent position with equinox of the date! without probably noticing it. One way to avoid this is to use the expert modus, but this is really only for experts. A simpler way is to create a user defined object with J2000 coordinates and plot it in the chart. This avoids the confusion and if you double click on this object you can read the different coordinates or move the telescope to it.
Maybe that is helpful for others as well.

Regards, Martin

[Hubert Boussier]

Hello Martin
I checked my CDC (version 3.8), it works as you said. I was not aware of this CDC peculiarity. As the horizon view is only available in AZ view, I change very often from EQ to AZ view in order to check if an object is visible from my observatory.
Now I will pay attention to this point. Thank you Dub.

All the best

[Paolo Berardi]

Congratulation Christian, very nice spectra of fascinating objects that "open" the far ultraviolet window to our instruments. It seems to me incredible that an amateur equipment today allows to capture the spectrum of a mag 16.2 object! I remember when, years ago, I read in the Lhires III user guide a limiting magnitude of V 5 for 2400 l/mm and V 9.2 for 150 l/mm grating. Ok, we talk about KAF400 camera and SNR of 100... but I now understand that a lower SNR spectrum could be anyway valid, also for research. To observe so faint subjects should be put into account some difficult to properly center and mantain the target on the slit.

Paolo

[Martin Dubs]

Hello Hubert,

we had this problem with astrometric coordinates in CdC, when switching between Azimutal and Equatorial view. The problem still persists, but in the newest beta version (3.11 svn 2989) you can open two charts, one with astrometric coordinates and the other with horizon view and apparent coordinates. In earlier versions you could also do that but the astrometric coordinates were not correct . It has been changed upon my request. Because of this bug I pointed at the wrong target at OHP once.
This is quite useful, you make one chart for overview and pointing the telescope, the other chart with the guide window, properly oriented and maybe a third chart with the finder view.

Regards, Martin