[Robin Leadbeater]

That’s great David,  topping the brightness charts currently.  It is easily bright enough for the standard ALPY 600 now. Let’s hope the promised clear skies turn up on Thursday.

Robin

[Robin Leadbeater]

Hi Kevin,

I have just seen that the iPTF team have now classified it (type 1a) so no need to go for it, unless you want to of course.

https://wis-tns.weizmann.ac.il/object/2017haf

Interestingly the “SED machine” spectrograph they use is even lower resolution than mine. They are definitely a rival 😉

The location looks spot on to me in CdC if I overlay the DSS image so probably an epoch issue. (The TNS coordinates are J2000). It is quite close to the galaxy core though so separating it from the galaxy could be a problem.

Cheers

Robin 

[Robin Leadbeater]

I think VSnet takes the photometry data but you can submit an image with or without a magnitude directly to David Bishop,(at least that what I used to do !) 

 dbishopx at gmail.com

Robin

[Robin Leadbeater]

Nice image David. Photometry could be useful. Do you plan to submit it to David Bishop’s website? there are no measurements or images for this SNe there yet.

http://www.rochesterastronomy.org/snimages/

Only clouds and bands of rain on this side of the country tonight unfortunately.

I suspect it is close to maximum now and since it is a type 1a I had a go at estimating how bright it should get to at maximum.

According to NED http://ned.ipac.caltech.edu there are no redshift independent distance measurements for ngc4964 but based on the redshift the distance would be ~36Mpc. (Though for a relatively nearby target like this the errors could be high)

Using 36Mpc and an absolute V mag of -19.3 at maximum for type 1a SNe gives an apparent V mag at maximum of ~13.5 (not taking into account any extinction) so your mag 14 guestimate seems reasonable.

Robin

[Robin Leadbeater]

Thanks !

@Andrew

I have got quite adept at swapping between the LHIRES and ALPY now. They have separate cameras (Currently the ATK  314 and a stellacam on the LHIRES and ATK428 and ATK16ic-s on the ALPY) and are all wired up so I just have to physically swap them over. The one not in use sits in a box next to the scope. I have even got duplicate 200/600 modules for the ALPY now as well which can be changed over without needing readjustment other than aligning the camera angle. I tend to stick with one setup on any particular night though. 

@ Paul,

Sure, no problem. Let me know if you need any specific graphics, images etc 

Cheers

Robin

[Robin Leadbeater]

https://wis-tns.weizmann.ac.il/object/2017gxq

This  was discovered by Gaia on 17th  at mag  17 and announced on 28th Sept but was much brighter last night (~mag 15 or perhaps brighter) last night when I took the spectrum and  is still likely to be a few days from max so would be a good early evening standard ALPY candidate.

Robin

[Robin Leadbeater]

Just heard that a follow up by Swift was scheduled based on my classification 🙂

Robin

[Robin Leadbeater]

Hi  Jack

Chromatic Aberration.  The inability of a lens to bring all wavelengths to focus in the same plane. The LHIRES uses an achromatic doublet which shows the usual pronounced chromatism in the Violet/UV so the focus varies across the spectrum. 

Cheers

Robin

[Robin Leadbeater]

I saw the same changes in the similar system AZ Cas in 2012 as it entered eclipse and we lost the spectrum of the hot B star  (Though there is no H Balmer emission in AZ Cas)

http://www.threehillsobservatory.co.uk/astro/spectra_43.htm

Cheers

Robin

[Robin Leadbeater]

I know the feeling. I’ve been doing astronomical spectroscopy for over 10 years now and the curve has still not tailed off yet !

Note, I suspect the spectrum will not have been corrected for instrument response/extinction so the shape of the spectrum will not represent the actual spectral energy distribution. There may be some spectra of standards around taken on the same night though which could be used to produce a (relative) flux calibrated spectrum to give us an idea  of temperature.

Cheers

Robin

[Robin Leadbeater]

Hi George,

It might yet develop features in the spectrum so it will be worth keeping an eye on over the next couple of weeks. In classical novae the H alpha emission lines are relatively strongest after maximum. For example this animation of Nova Del 2013 by amateur Paolo Berardi covering the first week

http://quasar.teoth.it/html/spectra/novadel_15_21.gif

Cheers

Robin

[Robin Leadbeater]

Here are the target binning (blue) and sky subtraction (green) zones I used in ISIS to extract the spectrum of the PNV (The asymmetric sky background zones were deliberately chosen to avoid the cosmic ray hits)

Robin

[Robin Leadbeater]

The spectrum beyond ~7700A (~pixel 500) is unusable in its current state because of the severe optical etalon type interference fringes, common in IR spectrographs. A careful flat correction would be needed to remove them.

Robin

[Robin Leadbeater]

Attached are the spectra with and without sky background subtraction, (pink and blue respectively, to the same Y scale).

The strongest emission line is the O I airglow line at 5577A. There is also O I emission at 6300A and Na D emission (light pollution ?) at 5900A

Robin

[Robin Leadbeater]

Hi George,

Your plot includes the sky background (from air glow, light pollution and from M31) which dominates the spectrum. The strong emission lines are airglow and light pollution. To see the target spectrum you need to just select the target spectrum (the narrow band) subtracting the background first. If you look at my sky background subtracted and wavelength calibrated spectrum you can see there is no emission line, including at H alpha (6563A) currently.

Cheers

Robin

[Robin Leadbeater]

Here is the background subtracted spectrum. (IR end cropped where the fringes dominate).  Rather featureless with nothing obvious above the noise (SNR ~15)

Robin

[Robin Leadbeater]

Hi Nick,

I’ll have a try at extracting it from the background. I don’t understand where all the emission lines in the sky background come from though. They do not look like galactic lines to me. Do they have an unusual light pollution problem or something or perhaps they superimpose the calibration lamp spectrum?

Robin

EDIT:  ok the “emission lines” are actually severe fringing in the IR. I can see the O2 telluric band so should be able to cross check the wavelength calibration.

[Robin Leadbeater]

Hi Nick,

The author of the article,Francois Teyssier is the resident expert amateur on CV spectroscopy  in the ARAS group. He publishes a nominally monthly newsletter on the group’s activities in this area.

http://www.astrosurf.com/aras/novae/InformationLetter/InformationLetter.html

There have been a number of nova confirmations by amateurs recently and followup up spectra tracking the evolution of some targets. We have been getting a lot of support interpreting the data from professional Steve Shore.

I expect the FLOYDS spectrum should settle the matter. It is a rather strange low resolution 2 order echelle instrument though which needs a very specific data reduction pipeline. (looking at the spectrum image, subtracting the sky background should be an interesting challenge !)

Cheers

Robin

[Robin Leadbeater]

Good to hear. mag 16 makes it well within range, possibly with other observers too. I will put out an alert on the ARAS forum

Robin

[Robin Leadbeater]

Hi Nick

In good conditions, mag 17 is just within range at very low resolution (R~130) with my modified ALPY 200 and I don’t know anyone operating fainter currently but the contrast against the galactic background  does not look high based on your image so it could be very tough. I have noted it to have a look but no promises, particularly as there are no clear skies forecast here for the week ahead currently

Cheers

Robin

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