Harvest Moon look-back and a cherry red Nova Delphini

The moon will be in waning gibbous phase for the next few nights. This is the view tonight with the two most prominent rayed crated Copernicus and Tycho marked. Both can be seen with the naked eye if you look closely. Binoculars make them easy catches. Credit: Patrick Chevalley, Christian Legrand / Virtual Moon Atlas

Hope you had a great look at the Harvest Moon this week. Tonight it will rise big and bright but not so round. You’ll notice a sliver missing along its western side marking the moon’s transition from full phase to waning gibbous.

The photo-map at left is a screen grab from Christian Legrand and Patrick Chevalley’s Virtual Moon Atlas, a fantastic free program for Mac and Windows.

Harvest Moon photographed on Sept. 19 from the San Luis Reservoir, Pacheco State Park in California. Credit: Kirk Bender

The atlas shows a very realistic moon with exact phase for your location, libration angle and lots of labeled features with in-depth descriptive information. The authors also offer a crazy variety of downloadable databases (Lunar Orbiter, Chinese Chang’e 2 moon data, etc.), picture libraries and different landscape textures available as add-ons. To get started, download the atlas HERE.

Prefer an atlas for your iPhone or Android? No problem. Check this list of lunar apps to find something you like.

I received several Harvest Moon photos in my e-mail the past few days. Thank you everyone who sent one! We were mostly cloudy here in Duluth, Minn. except for a short spell late last night when the sky cleared to reveal a brilliant white moon riding high in the southern sky.

Two views of the Harvest Moon from two very different locations. At left, Victor Pinheiro photographed the moon from the city of Espargos on the island of Sal, one of the Cape Verde Islands west of Senegal, Africa. The other was taken from Lynn, Mass. U.S. by Jimmy Peguero.

Twenty minutes later clouds returned, but rather than detracting from the scene, they diffracted moonlight into a set of pretty red and blue rings called a corona. Further west I was able to grab a look at the nova in Delphinus the Dolphin.

Remember the nova? It was caught in eruption on Aug. 14 and reached naked eye brightness before slowly fading to its current magnitude of 7.8-8.0. Like every nova, it’s now received a formal name – V339 Delphini, the 339th variable star discovered in the constellation Delphinus.

You can use this chart and a pair of 40-50mm binoculars to spot Nova Delphini (=V339 Del) now near 8th magnitude. That’s nearly the same brightness as the star it sits right next to. Click map for a larger version. Created with Stellarium

Bright moonlight made it difficult to get a good fix on the nova last night, so I toted out the 10-inch scope for a look. Wow! While many of you, myself included, have noticed its pink or reddish color, I’m here to report that this star is now a striking red.

Updated pic of the nova taken Fri. evening Sept. 20, 2013. Details: 100mm lens, f/2.8, ISO 400 on a tracking mount. Credit: Bob King

It reminded me of a shimmering ruby and was a close match for Hind’s Crimson Star, an amateur astronomer favorite and one of the reddest stars (if not THE reddest) in the sky.

An AAVSO chart you can use with a small telescope to follow the nova as it fades. Click for a larger version or click the link at right and download a chart. Credit and copyright: AAVSO

The color comes from the release of what’s called hydrogen alpha light. Energy from the nova explosion gets absorbed by hydrogen gas surrounding the star. Hydrogen atoms then release that energy as red light when they return to their original rest state.

Additional red light comes from dust in the star’s vicinity absorbing shorter wavelengths of light and allowing only warmer colors to pass, much like a sunset. Seeing red means seeing energy transferring hands.

While the nova was too faint to detect color in binoculars a small scope will show it well. I’ve included a brand new map you can use as well as a smaller version of a deeper map from the American Association of Variable Star Observers (AAVSO) so you can follow the star as it fades below 8th magnitude. I’d love to hear of your impressions of its color. Please take a look and let us know what you see.

The “waning” Harvest Moon and its reflection from Trieste, Italy this morning Sept. 20. Credit: Giorgio Rizzarelli

18 thoughts on “Harvest Moon look-back and a cherry red Nova Delphini

  1. Hi Bob, in reply to your post of a few days ago, I took some Harvest Moon pics this early morning at sea. I just finished choosing and sending them to you by email, that I see this post. Maybe you want to add one by myself to your gallery. You have large choice :)
    BTW did you get the pics I sent you a week ago? Particularly proud of separating Capella HL …
    Thanx for all the recent posts, very interesting as always

    • Giorgio,
      Congratulations on splitting Capella’s H and L dwarfs! The magnitude of the fainter one is only 13.7 and with a separation of 3.7″ that’s quite a feat! Nice work. I’m glad you wrote me here because I somehow missed it in my e-mail.

      • It’s a group of messages of Sep10, including 5 photos in total (Nova Del, Orion wide field including R Lep Carbon star, a pink cloud dawn, Orion Sword, Capella A/H/L), exif details and comments, including, yes, the tecnhiques I used to separate those 4 arcseconds of Mag14 Capella L.

        As you see I anticipated your question about Nova Del’s color: see next comment

  2. About Nova Del’s color which you ask… Basically, in August it appeared white (to me and friends) in telescope (I heard someone else saw it colored but we didn’t notice it), while since beginning of September it we agreed it has become decisively pink.

    In detail, I checked it about once per week, sometimes by a tele-lens photo to compare magnitude with near field stars, sometimes in the 8″ telescope both to measure in a different way the magnitude (since large aperture limits twinkling) and to check the color.

    About the Nova’s color:
    - At Aug21 (one week after peak) it was white in visual and mostly also in photo, showing a purple shade only at a low exposition which almost killed the near stars in field.
    - At Aug26 the shade became present in photo also at long exposition, as a pink color.
    - At Sep3 the star was decisively pink in visual and photo (see pic which I sent you on Sep10).
    - At Sep10 in visual and photo the star didn’t appear much more pink respect the previous week; on the other hand this could be due to the fact that this night had much humidity which could have reduced the color.

    My magnitude measures are of course in agreement with the AAVSO curve (I should find the time to subscribe and send my data).

    • Giorgio,
      Thanks for sharing your Nova Del observations. I hope to photograph it tonight – no time last night and too bright a moon. As long as you’re making the observations, it would be great to share them with the AAVSO and through them with professional astronomers worldwide. I’ve been a member since 1982; I’m now at 16,150 observations and hoping to reach 20,000.

      • BTW I now read better your article and see you quote Hind’s Crimson star (R lep). I checked it in scope about 2 weeks ago, it’s currently red-orange. In wide field also red-orange or with a pinkish shade, see again one of the pics I had sent, you know how to find the star (I personally think a line from Mintaka to Rigel, and go on for another such segment). If you lost the messages drop me a line and I resende all.

        I suspect the subjectivity of variable star color depends on the instrument: possibly a large aperture one, making the star more bright, also desaturates the color. What you think?

        • Giorgio,
          Take a look at it tonight and you’ll see a difference from two weeks ago. It was orangish-red to my eye then also but now the color is much redder. You’re right, it does depend on the instrument. Mine was a 10-inch, so it should have de-saturated the color somewhat. Despite that, the color was very pronounced.

          • Becoming Redder? Wow. Very interesting, considered that it’s at high brightness (at maximum or raising to it): from the usual star behaviour one would expect the opposite.

          • Giorgio,
            That’s how I’ve seen novae evolve in the past. Bright and pale at first – lots of light from the initial explosion – and then becoming redder not only from H-alpha but also from light radiating from a newly-formed shell of dusty debris condensing around the star. Eventually the shell should glow in OIII emission and appear brighter when viewed through an OIII filter.

          • >That’s how I’ve seen novae evolve in the past.
            We had a qui pro quo, when I said “(R lep). I checked it in scope about 2 weeks ago, it’s currently red-orange”, and later “Becoming redder?” I meant R Lep. When you wrote “much redder” did you mean R Lep or Nova Del?

            I saw the Nova Del pic @ 100mm you just added. The definitely pink color is very similar to my photo in C8.
            PS Thanx for the OIII filter tip – to put in the shopping cart :)

  3. Clouds finally cleared. Beautiful Harvest Moon this morning. I was going to look for Saturn with binoculars before sunset but I cannot tonight. I am working. Even a tougher challenge than Saturn would be Mercury now coming into a very poor evening showing. I probably will not see it till it comes back in the mornings in late November. Nov. 24 should be a very beautiful morn, showing Mercury, Saturn and ISON all 3 fairly close together. ISON will be a tough challenge from Nov. 26-29, very close to the Sun. But there is still the possibility that it may be bright enough to see on the 28th, especially if you can block out the sunlight and not the comet which will be extremely close by, like hiding the Sun by a building.

  4. Hi Bob, I checked Nova Del in the 8 inch scope yesterday night. At 10 days after my previous observation, the color is now impressive in visual, and very vivid in photo. The pink changed toward magenta, i.e. with more red component, in agreement with the AAVSO curve.

    I had an exceptional night, with seeing of 1 to 0.5 arcsec and pretty high transparency as well. You were right about Jupiter’s GRS, it’s very evident this year. We’ll have a great Jupiter opposition this winter.

    • Hi Giorgio,
      Thanks for the confirmation. I looked at it last night through my little spectroscope thinking I’d see the H-alpha line. I didn’t (the nova is too faint for it to show in deep red) but the H-beta emission line in blue was bright and obvious.

          • Thanx Bob. I’ve seen their website. Unfortunately they don’t sell outside USA but here in Europe there are brands selling such items, like Baader. I have to check prices.
            A question: when you mention you see in spectroscope Balmer (Halfa/beta) lines of a nova, do you mean emission lines (as the star is redder) or absorption lines due to outer layers (as usually detected for a star in spectroscope)?

          • Giorgio,
            You could check cloudynights.com for a used spectroscope, and if there are none, place a “wanted ad” for free. I’m glad you asked about the lines. Stars like Vega show Balmer lines in absorption across their spectra. At least with an inexpensive spectroscope like the Rainbow Optics, very few stars show emission. The nova showed a prominent H-Beta emission line and no absorption lines were visible. I might have been able to see more lines but not at 8th magnitude. Too dim. For fun I looked at the star through an H-Beta filter and it brightened up 2/3 of a magnitude compared to its 8th mag. neighbor. The effect was amazing!

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