Patrick Schmeer alerted us via several lists and facebook groups that K. Itagaki discovcered a bright possible nova in Delphinus:
PNV J20233073+2046041 2013 08 14.5843* 20 23 30.73 +20 46 04.1 6.8 U
Anytime I see a formal error of 0.001, I assume two things. First, this is purely Poisson error, which does not reflect real error. You need to at least compare (C-K) and take ~3 readings to get an uncertainty. Second, 0.001 Poisson error almost always means saturation. You indicate 90 seconds of exposure: was this all at one time? If so, you were dramatically overexposed. Note that your V=6.2 measure is very different than everyone else's at the same time. Give us details of your observation.
Yes, you're right. It was just a very quick target of opportunity last night and it was definitely oversaturated. I just thought I would post results, but I should have mentioned this...sorry.
Has anyone done PEPV photometry for this target? If so could you suggest some comparison stars. It would be useful if we are all using the same ones for consistency.
I've written a couple of blog posts about the nova.
What an exciting object!
Comparison with old DSS image of the same region - animation link is:
I would not worry too much about the Vmag observations that are much fainter than the visual light curve; just report what you see. There are a number of discrepant observations that will be checked in the next few days. It is cloudy tonight at HQ, but I hope to start observing again tomorrow.
If you go to VSX, and select a 10 degree radius circle with bright magnitude limits, you will find roughly 100 variables brighter than 8th magnitude within your image. I don't think you need to pick and choose which ones to submit to the International Database, except that I'd probably just use the ones that have an AUID and a sequence. That said, I do have a strong "like" for the cepheids: T Vul, SV Vul and S Sge. You could also pick some of the NSV objects, or the stars with uncertain classification, and try to classify them. This is a rich part of the galaxy, so lots of things that can be done with your images other than just measuring the nova!
As the nova gets fainter, the problem will be crowding with your wide-field DSLR image. Any photometry of fainter variables will likely be contaminated by their neighbors.
Many thanks for your suggestions. Some of the suspected variables look feasible with the accuracy I can get from the wide field DSLR shots, so trying to find out more about those would be interesting.
Yes, blending is a limiting factor, from my (catalog mag) vs (measured mag) curve, I see many affected stars starting at around ca 7.5 mag (all in all, SourceExtractor detects and analyses more than 4000 sources in the 20 x 15 deg^2 field)
E.g. out of the three Miras near maximum in Del suggested by Kevin Paxson in the LBV forum (S,T,X Del), two are too blended for my setup.
So when Nova Del 2013 gets near 7 mag, I'll probably switch from my 50mm lens to a 85 mm lens, and then finally to a 6" telescope.
Until then, I'd be happy to hear from others trying to work on suspected variables near the nova. It's not just more fun to do it in a team, it's also easier to produce convincing evidence.
Since this field has been extensively covered by ASAS-3 in the past decade I wouldn't expect too many new variables in the field, but khow nows...
Anyway I follow this field using 300mm (zoom) telephoto lens, but last week I also made images usin the 75mm focus.
Btw NGC 6905 is also visible on my images.
A cropped version: http://www.flickr.com/photos/26731206@N05/9551330515/sizes/l/in/photost…
Hello! I obtained a time sequence of the nova last night in I,B, and V. Exposures ran 1 to 3 seconds wiht my 8 inch LX200 and SBIG 402.
The comp and check stars were out of the field of view. Will any closer comps be available? Or are they too faint to serve that purpose? Best regards.
There are comp stars 79, 80, 90, 98, 100 on the D chart of the Nova (1 degrees FOV). Are they not good enough for you?
How big is your FOV? Since the nova is around 5.6 mag recently a small telescope or a DSLR camera with 1-8 degrees FOV must be good enough for photometry of Nova Del 2013.
For that sensor/optics combination I would guess the FOV is even < 0.5 deg, right?
There are so few bright stars in that FOV that you can get personally acquainted to them: using SIMBAD I found only 10 stars at all which are brighter than ca 10.0 mag in a 0.5 deg radius, and only five of them are brighter than ca 9 mag:
So the candidate pool for comp stars is quite limited.
DSLR photometry is one alternative. If you want to stay on the CCD track: for the epsilon Aurigae campaign it was demonstrated that you can get good results with a telephoto lens (with filter changer) mounted to a CCD, see Jeff Hopkins' page here: http://www.hposoft.com/EAur09/CCD/EAurCCD.html
I think an 8 inch SCT is too big for the nova recently.
Btw Arne made some CCD images with the BSM systems. Fainter AAVSO sequence will be available soon.
As Robert mentions, there is a preliminary calibration of this field at BVRI using BSM south that is available through Seqplot. I use a subset of about 4 8th magnitude stars near the nova for my differential photometry.
Thank you for the replies. My FOV is about 14x18 arcmin. I read the bright star photometry tutorial a while back. As I remember it, for bright star photometry, I would have to stack multiple images and/or defocus in order to use my system for bright stars such as this nova?
However, from the comments, it appears that the nova might simply be too bright for my setup at present, regardless of how how massage the technique.
I obtained about 300 images in each filter -B, V, and I - during the night's run. Once/if closer comps become availble, I thought that I would start by stacking them first in series of 10 to see if the SNR became acceptable, though I might have to increase that number depending on the SNR result.
Thank you all for your guidance. Best regards.
The amateur spectroscopic survey results are gathered in a data base
More than 250 spectra at resolution from 600 to 15000 and a daily coverage by eShel Spectra. Observers around the world : France, Italy, Spain, Germany, UK, US, Australy ...
The P.I. is Steve Shore (University of Pisa)
The nova is always in the permitted lines phase. Balmer and Fe II lines respect to continuum increase day after day since 18-08-2013
The survey is currently focused on near UV/blue region and check possible CN lines 3883 and 4216
A webpage shows the spectroscopic evolution of Nova Del 2013 with ARAS spectra and comments, explanations about nova pnenomenon, lines formation ... by Steve Shore (University of Pisa)