Mag +7.4 Nova In Cygnus

[martinastro]

Had two observing sessions with this Nova. The first at 03.00 BST and the next at 04.30 BST. During the first Cygnus was low in haze and the Moon was fairly bright. During the next session Cygnus was half way to the zenith in a darker sky however the haze was awful. Despite these conditions I could see the Nova easily in 10x50mm binos and took several images at ISO800 and 30 seconds. The Nova is there.





Here's John McConnell's image which he sent over.

[martinastro]

This is my second observation of Nova Cygni made on April 13/14th 2008 at 03.45 BST. In contrast to the previous night this was an excellent session. The sky was completely clear with good transparency with cool, calm, and crisp air. The waxing Moon was low in the west and hidden behind a lazy horizontal bank of cloud which resulted in the sky looking surprisingly dark. Cygnus was high in the NE and looked an impressive sight. With my 10x50mm binoculars I could see Nova Cygni very easily as a white star in what was once a dark blank patch of sky. There was a companion field star to its west and the two gave the impression of a wide double although the Nova was distinctly brighter. I could actually see the brighter star above the Nova with the naked eye!. I was rather impressed by the scene and can say with much delight that this is my best view of this 'guest star' to date. This is a single image taken with my 200mm zoom lens at ISO800 with a 30 second exposure with aperture wide open.

[martinastro]

Made a typo on the image. That should read Deneb not Sadr.

[brianb]

I managed to get a shot in a short window in the cloud round about the same time (0300 UTC Apr 14th) but haven't got round to postprocessing yet. Had a busy day ... and (surprise surprise) the sky is properly clear for the first time in ages tonight! Moon is a bit of a nuisance and just at the moment I need a coffee and a warm up!

[brianb]

Curfef - clouded over approx. 0100 UTC.

This nova is close to the long period (Mira type) variable Chi Cygni, you could download charts from the BAA Variable Star Section web site and make magnitude estimates using suitable comparison stars.

[brianb]

OK, I've processed the images I got on Monday morning - 0303 - 0304 UTC 14 Apr 2008.

Cropped from stack of 6 x 5 sec, 200mm f/4, unfiltered, undriven. Nova = V2491 Cyg is between the lines. The circled stars are comparison stars K, L, M & N from the BAA chart for Chi Cyg - mags. 8.11, 8.39, 8.68 & 9.01. The presence of the circles confuses my eyes but on the original I see the nova definitely fainter than K, definitely brighter than N, about equal to L and a shade brighter than M so say 8.5. The nova shows distinctly red in this image, further complicating estimates of brightness.



The faint star very close to the nova is identified in Starry Night Pro v6.2 as TYC2660-1754-1 unknown spectral type mag 10.25

BTW Chi Cyg appears to be missing from this image, comparison star X (11.33) is clearly recorded but Y (11.92) is dubious. Anyway Chi must be around minimum; the extreme range from the catalogue is 3.3 - 14.5 so the faintness is not necessarily unusual.

[martinastro]

Thanks for the BAA link Brian. Visual mag estimates will need to be made visually though at the time. Using images is not a good idea. Your est sounds bang on though because when I saw it in the binos I thought it was fainter than the last published est of +7.6. I seen the nova as pure white visually. Maybe if it's fading the red colour will become more distinct. I made a visual last night and could see the nova very easily at 00.30 despite Cygnus being low in haze. It sure looks to be turning red on your great image. Recall the last bright nova in Cygnus which was blood red - that was some sight.

It amazes me how under observed this nova really is. There is very little talk about it on the net.

Clear skies

[brianb]

Visual mag estimates will need to be made visually though at the time. Using images is not a good idea.

Certainly estimates made the way I did that rough one are not directly comparable with visual or photoelectric V measures, but if repeated using the same equipment they should give a good enough light curve.

The real problem with my estimate was that the image was exposed too long - small differences are easier to detect when the stars are close to the magnitude limit because overexposed stars "all look the same" being burned out in the centre.

However give that the nova has turned red, the comparison stars aren't, they're not especially close and Moon is interfering, I'm not sure that I would trust a visual estimate to within 0.2 mag. I'll have a go next time I get a clear sky (tonight with any luck) having identified the position & got the charts.

Must check the AAVSO site, they may have a interim chart set published.

[martinastro]

Yes, any additions to the light curve, whether visual or photographic is a good thing. I had a quick look at it last night at 00.30 BST using the 10x50s and found it quite easily, it still looks steady. White in the binos but I intend to turn the scope on it tonight in the hope of catching the red hue. Didn't take any images though as the Moon was fairly bright.

[brianb]

Early hours of last night (Sat 26th/Sun 27th April) I imaged the field again. Cropped from stack of 10 x 5 sec plus 5 x 15 sec, 300mm f/4.



The nova has faded and lost its red hue but is still well with reach of binoculars.