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Nova Del 2013

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SET's picture
SET
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Joined: 2010-07-23

Folks,

Get out and observe Nova Del 2013. Even in bright moon light I just observed it. It is very easy to find using the AAVSO "a" chart made for the nova. Lots of great visual observations are coming in from all over the world.

Chris Stephan   SET

Burton, Ohio  USA

N Del / out of focus tech / flux interferance from nearby star?
CNY's picture
CNY
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Joined: 2010-07-23

I finally got out to observe this nova. It's been a very cloudy and rainy here in Georgia much of the year. It's an easy star hop from the head of Delphinus, even with full moon and high thin clouds. I try to stay unbiased and avoid looking at recent estimates at least 12 hours before observing. I used binoculars 15X70mm and the chart 12522Q. Using the "out of focus" technique tends to help make mag differences more obvious to me. My comp star was 5.7. While in focus the Nova and the 57 star looked identical in brightness. After unfocusing the Nova, it appeared slightly brighter than the 5.7 comp. I believe my visual precision is not better than 0.2 mag, so that is where I came up with my 5.5 estimate. I also checked the 48 star and the Nova was obviously much fainter. After posting the observation online, I pulled up other observations. It appears that the trend is fainter than my estimate for that time. Most estimates for that time are fainter than the 57 comp. My first thought is that everyone else is wrong (Just kidding). My thought is that perhaps a star in the field near the nova went out of focus and flux added to the Nova's light. There is an 8th mag star pretty close to the Nova and while out of focus it could have blended in a bit with the nova's light. Things may look very different when the sky is clearer and the moon is not a factor.  Star color could also come into play. The 5.7 comp looks pretty red in the Wikisky image. I was just wondering if any other visual observers have had similar circumstances or any tips. Anyhow , I look forward to revisiting the field soon with my binocs.

Avoid wide gaps and red comps
lmk's picture
lmk
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Joined: 2010-07-23

First of all, visual estimates using the 48 and 57 comps is not ideal, the wide gap in brightness makes accurate estimation more difficult. There are several comps closer to the 57 which should be used instead, such as the 55 south of the 35, which is nice white color too.

Second, the 57 is somewhat red with a B-V=+0.93, though not exceptionally red. But if you notice it gets fainter as you defocus, thats due to Purkinje coming into play. As it gets apparently fainter this way, your cones become less involved and your more blue-sensitive rods start to dominate, shifting its appearance to look more fainter to you. Its always best to use white or solar color comps to avoid problems with Purkinje.

Mike LMK

AAVSO 49 Bay State Rd. Cambridge, MA 02138 aavso@aavso.org 617-354-0484