PSN J09554214+6940260 in M82 - mag V 11.7

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Re: PSN J09554214+6940260 in M82 - mag V 11.7

Postby Paolo Berardi » Thu Jan 30, 2014 12:08 am

Yes, ATel gives B-V and compares the value to expected B0-V0= 0 value (without reddening)
*B-V=1.2 (instead of B-V~0 for a normal type Ia at the same epoch)"
So you get E(B-V) = (B-V) - (B0-V0) = 1.2


Thanks for the explanation François! That is a remarkable reddening value!

here is my first spectrum of SN2014J.


Well done Tony!
Now SN is mag V 10.7, about half a magnitude brighter than 24 jan. Light curve seems to be flattening...

Clear skies!
Paolo
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Re: PSN J09554214+6940260 in M82 - mag V 11.7

Postby Christian Buil » Fri Jan 31, 2014 2:44 pm

A spectrum of supernova SN 2014J in Messier 82 for the Jan. 31.

Image

Image

My telescope is a FS106ED refractor (10.6-cm diameter only) and the spectrograph
is an Alpy 600 operated with a narrow 19 microns slit, with no difficulties
(thanks to short focal length for guiding and low seeing
related to small refractor aperture).

Christian B.
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Re: PSN J09554214+6940260 in M82 - mag V 11.7

Postby Robin Leadbeater » Fri Jan 31, 2014 3:54 pm

Here is my result from last night using the new SA200. I have overlaid Christian's result from the same night with the ALPY 600. The resolution is lower of course but I am pleased that the shape is the same confirming the accuracy of the background galaxy subtraction, instrument response and atmospheric extinction correction.

Gianluca Massi has just used the SA100 with his robotic telescope to get the first confirming spectrum of SN2014K at mag 16.2 :o
(He already has 2 first confirming novae spectra with this setup)

Does the Star Analyser qualify as a "proper" spectrograph yet ? :lol:

Cheers
Robin
Attachments
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Re: PSN J09554214+6940260 in M82 - mag V 11.7

Postby Paolo Berardi » Fri Jan 31, 2014 10:02 pm

Christian, Robin, great observations! What more can you ask from a 10 cm aperture telescope and from a grating in converging optical path? A slit and slitless spectroscopy lesson...

Here you find a first paper about SN2014j (very interesting):
http://arxiv.org/pdf/1401.7968.pdf

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Re: PSN J09554214+6940260 in M82 - mag V 11.7

Postby Christian Buil » Sat Feb 01, 2014 12:08 am

Slit vs slitless spectrograph... a large question!

Slitless -> (positive) low cost, simplifed acquisition procedure, not very intrusive (similar to a filter) - (negative) more difficult to remove bakgroung (presence of the galaxy in the backgroud), low resolution, noise from the sky pollution (for me), less precise wavelenth calibration (but the need is lower), less stable specral shape (dependant of focus and seeing for example).

Slit -> (positive) high rejection of galaxy and sky pollution light (very critical for me because I observe in urban condition and also during full moon period), stable line shape and wavelhength calibration, high resolution, more easy to calibrate - (negative) some lost at the slit level (but not very critical if you use a moderated sized telescope - one of the explanation of the use a small telescope like FSQ refractor for me), cost (but relatively moderate for the Alpy), not alway intuitive during the first contacts.

Here the difference between a 1x1 bin acquisition and a 3x3 bin acquisition (the camera is the same, an Aik460 model) :

Image

Note the short exposure time for the 3x3 mode (5 time shorter and nearly same Signal to Noise Ratio). But in 3x3 bin secrum is very undesampled (horrific relative to Shannon theorem), and
consequently some artifact appear (critical for me). The1x1 spectrum mode is more robust to fixed noise. The 1x1 bin improve slighty spectral resolution, relative to 2x2 bin, and of course reltive to in 3x3.

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Re: PSN J09554214+6940260 in M82 - mag V 11.7

Postby Robin Leadbeater » Sat Feb 01, 2014 1:59 am

Hi Christian.

I agree with your plus and minus. Here some more pluses and minuses for slitless

plus - simpler absolute flux calibration. (100% of flux is always measured) Sometimes even possible to make differential measurements in the same field
no chromatic sampling effects in the slit
easier for robotic operation (do not need to accurately place the star on the slit)

minus - needs a separate guider (I can only take 20 sec exposures unguided so total read noise is high)
risk of interference from other stars and spectra (rotatate grating+camera or use 2 gratings at 90 deg in different filter wheel positions)
flat fielding is difficult


Cheers
Robin
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Re: PSN J09554214+6940260 in M82 - mag V 11.7

Postby Christian Buil » Sat Feb 01, 2014 10:48 am

I agree with your addition. The superiority of slitless mode relative to slit mode for absolute photometry is clear (but for compensate, I have introduced the photometric slit for Alpy/Lisa/Lhires... a slitless mode for these instruments in fact!).

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Re: PSN J09554214+6940260 in M82 - mag V 11.7

Postby Robin Leadbeater » Sat Feb 01, 2014 5:40 pm

Hello Christian,

I think if i was designing a spectrograph just for confirming supernovae I would replace the grism in Alpy 600 with a 200 line (or even 100 line) grism, fit a ~35um slit and attach it to a 20 inch f4 telescope. An Alpy 150 (75) should not be too difficult to build and because it would only need a small camera chip then maybe an exotic sensor as well :)
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Re: PSN J09554214+6940260 in M82 - mag V 11.7

Postby Tony Heidemann » Sun Feb 02, 2014 8:46 am

Hello,

I have taken 2 new spectra of SN2014J. Here they are:
Image
Image
clear skies

Tony Heidemann
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Re: PSN J09554214+6940260 in M82 - mag V 11.7

Postby admin » Mon Feb 03, 2014 8:36 am

C'est parfait Tony
L'idéal serait que nous soyons capables d'obtenir 1 spectre par jour
(Je devrais dire "vous soyez", car ma monture à fourche ne me permet pas d'accéder à M82 :-(

Deux liens sur les supernovae
Type Ia : http://www.astronomie-amateur.fr/feuilles/Spectroscopie/SuperNovae_Ia.html
http://ned.ipac.caltech.edu/level5/March03/Filippenko/Filippenko_contents.html - Thnaks to Robin

François
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