Starship Asterisk*

by **Anthony Barreiro** » Mon Jul 02, 2012 8:50 pm

Gorgeous picture. It's interesting to see the different orientation of Aldebaran, Hyades, Venus, Jupiter, and Pleiades when seen from south of the equator, compared to how I'm used to seeing them. And very cool to see faint Vesta and Ceres. I've found that during twilight faint solar system objects are sometimes relatively more visible than stars of similar magnitude. Maybe that's because they're reflecting sunlight instead of shining with their own light? But I'm not sure.

by **Guest** » Mon Jul 02, 2012 1:47 pm

I feel sorry for the few negative responders. This is a beautiful photograph. Wake up & smell the coffee before your last sunrise is gone!

by **starstruck** » Sun Jul 01, 2012 5:25 pm

Many thanks, Luigi, for your explanation (and Chris for clarifying also). Seems I was having a little coma of my own trying to figure, but now it's all clear

by **luigi** » Sun Jul 01, 2012 3:36 pm

Chris Peterson wrote:
starstruck wrote:May I ask, what is "comma", to which you also refer in your post above? I have not come across this term before in relation to photography; tried to find out about it online, but have so far drawn a blank. Thanks.
The optical aberration is called coma, which is probably why you didn't find what you were looking for by searching online.

Sorry for the typo and thanks for the correction.
"It's coma in spanish so my mind decided it was comma in english likte the punctuation sign"
Thanks Chris.

by **Chris Peterson** » Sun Jul 01, 2012 2:53 pm

starstruck wrote:May I ask, what is "comma", to which you also refer in your post above? I have not come across this term before in relation to photography; tried to find out about it online, but have so far drawn a blank. Thanks.

The optical aberration is called coma, which is probably why you didn't find what you were looking for by searching online.

by **luigi** » Sun Jul 01, 2012 2:42 pm

starstruck wrote:Thanks for providing your exposure information for your great picture Luigi, and congratulations for having it selected as an APOD.

In my ignorance, I had to look up the "Polarie tracker" you mentioned, as I had never heard of this before and did not know what it was. I subsequently found the device online; it seems very compact and, if it works well, I imagine it would be quite a useful tool for astrophotography, for longer exposure times. I was actually a little surprised that you would find it necessary to compensate for the Earth's movement for just a 30 second exposure with a 50mm lens, but I guess using the Polarie was your insurance for getting a nice clean image without evident trails in this instance. May I ask, what is "comma", to which you also refer in your post above? I have not come across this term before in relation to photography; tried to find out about it online, but have so far drawn a blank. Thanks.

In 30 seconds you are right that tracking is probably not needed, I used the half-sidereal mode of the polarie and it was enough it may have been enough without tracking at all but as you said it's an insurance.
Comma is an optical problem that most lenses have and makes the stars look like triangles instead of circles. Since I needed to use dim stars to find the asteroids I couldn't allow comma in the photo.
You can see comma using a lens wide open and taking a look at the stars near the borders, instead of perfect circles or points you will see little triangles.
The defect is corrected closing the aperture of the lens, some lenses need to be closed 1 stop, others 2, etc.

by **starstruck** » Sun Jul 01, 2012 11:24 am

Thanks for providing your exposure information for your great picture Luigi, and congratulations for having it selected as an APOD.

In my ignorance, I had to look up the "Polarie tracker" you mentioned, as I had never heard of this before and did not know what it was. I subsequently found the device online; it seems very compact and, if it works well, I imagine it would be quite a useful tool for astrophotography, for longer exposure times. I was actually a little surprised that you would find it necessary to compensate for the Earth's movement for just a 30 second exposure with a 50mm lens, but I guess using the Polarie was your insurance for getting a nice clean image without evident trails in this instance. May I ask, what is "comma", to which you also refer in your post above? I have not come across this term before in relation to photography; tried to find out about it online, but have so far drawn a blank. Thanks.

by **luigi** » Sun Jul 01, 2012 12:08 am

Ann wrote:It's a fine picture, Luigi. Well done!

Ann

Thank you Ann!

by **Ann** » Sat Jun 30, 2012 9:15 pm

It's a fine picture, Luigi. Well done!

Ann

by **luigi** » Sat Jun 30, 2012 2:00 pm

Psnarf wrote:I've never seen sunlight bounced off of Venus make such a prominent reflection before. Is that reflection on the Rio del La Plata or the Samborombon Bay? I suspect the latter, to avoid the light pollution from Montevideo. Reminds me of the moon reflected off of a calm mountain lake.

Great job, Ensign Luigi!

I'm also amazed by how bright Venus looks in the morning and the bright reflection on the water. If you have access to a body of water to the East go and look and it will be a great sight!

It's Rio de La Plata. Montevideo is not really a very big city in terms of light pollution so it doesn't affect the photos. The horizon is quite clear from artificial lights except for boats and buoys. I think the lights of Buenos Aires itself contribute more to light pollution than Montevideo.

Thank you!

by **Psnarf** » Sat Jun 30, 2012 1:54 pm

I've never seen sunlight bounced off of Venus make such a prominent reflection before. Is that reflection on the Rio del La Plata or the Samborombon Bay? I suspect the latter, to avoid the light pollution from Montevideo. Reminds me of the moon reflected off of a calm mountain lake.

Great job, Ensign Luigi!

by **luigi** » Sat Jun 30, 2012 1:20 pm

spambot wrote:Very clever but how were Vesta & Ceres spotted? Were they expected? How were they identified. How many other enabled objects appeared because of the digital time-lapse?

Hi, I'm the photographer.

Thanks to NASA for choosing my photo, it made me very happy after so many days of conjunction hunting!

I've been following this conjunction and trying to catch both asteroids for a few days. I used stellarium to plan the field of view needed to catch both asteroids. Once at home I used stellarium again to match the stars against the sky-chart and find both Ceres and Vesta. I checked and double checked. At my website I also labelled a couple of reference stars that were useful to spot the asteroids on that day.
Curiously the asteroids were visible in the photo until dawn, I never ever photographed an asteroid without a dark sky so I was surprised.
What I really liked was to be able to get the Pleiades, the Hyades, Jupiter, Venus, Ceres and Vesta in the same photo. I like conjunctions and that's quite a gathering to me!

To make the photo I took a 30'' exposure at F5.6 ISO1600 using a Canon 5DII, 50mm lens and a Polarie tracker. Taken at 06:40am, it's still dark at that time in the South Hemisphere.
I had to use F5.6 because I had comma at F4 and that could make spotting the asteroids problematic.

Thank you for the comments!

Edit: If anyone wants the full-res version of the photo to hunt for Ceres & Vesta using sky-charts just ask me by email (from my website) I'll be happy to send you the file.
You need the date,time & location: June 27th 2012 at 6:40am from Buenos Aires, Argentina.

I hope somebody else goes asteroid hunting!

by **nuube** » Sat Jun 30, 2012 11:24 am

Calling todays APOD impressive is almost insulting.
Astronomy and Photography are far more than symbiotic.
The collection of skills required to create the pic are a living process in the minds of
astrophysicists. It is that process that transcends the beauty of the image.
I can't wait to see Ceres through "the eyes of Dawn"

by **spambot** » Sat Jun 30, 2012 9:06 am

Very clever but how were Vesta & Ceres spotted? Were they expected? How were they identified. How many other enabled objects appeared because of the digital time-lapse?

by **ritwik** » Sat Jun 30, 2012 8:38 am

too much photo-primping .. draws my attention away from astronomy to photography

by **APOD Robot** » Sat Jun 30, 2012 4:06 am

Conjunctions near Dawn

Explanation: Now shining in eastern skies at dawn, bright planets Venus and Jupiter join the Pleiades star cluster in this sea and sky scape, recorded earlier this week near Buenos Aires, Argentina. Venus dominates the scene that includes bright star Aldebaran just below and to the right. The planets are easy to spot for early morning risers, but this sky also holds two of our solar system's small worlds, Vesta and Ceres, not quite bright enough to be seen with the unaided eye. The digital camera's time exposure just captures them, though. Their positions are indicated when you put your cursor over the image. In orbit around Vesta, NASA's Dawn spacecraft arrived there last July, but is nearing the end of its visit to the main belt asteroid. In August, it will set off on its planned journey to Ceres, arriving at the dwarf planet in 2015.

<< Previous APOD

This Day in APOD

Next APOD >>

[/b]

Starship Asterisk*

APOD: Conjunctions near Dawn (2012 Jun 30)

Post a reply

Expand view Topic review: APOD: Conjunctions near Dawn (2012 Jun 30)

Re: APOD: Conjunctions near Dawn (2012 Jun 30)

Re: APOD: Conjunctions near Dawn (2012 Jun 30)

Re: APOD: Conjunctions near Dawn (2012 Jun 30)

Re: APOD: Conjunctions near Dawn (2012 Jun 30)

Re: APOD: Conjunctions near Dawn (2012 Jun 30)

Re: APOD: Conjunctions near Dawn (2012 Jun 30)

Re: APOD: Conjunctions near Dawn (2012 Jun 30)

Re: APOD: Conjunctions near Dawn (2012 Jun 30)

Re: APOD: Conjunctions near Dawn (2012 Jun 30)

Re: APOD: Conjunctions near Dawn (2012 Jun 30)

Re: APOD: Conjunctions near Dawn (2012 Jun 30)

Re: APOD: Conjunctions near Dawn (2012 Jun 30)

Re: APOD: Conjunctions near Dawn (2012 Jun 30)

Re: APOD: Conjunctions near Dawn (2012 Jun 30)

Re: APOD: Conjunctions near Dawn (2012 Jun 30)

APOD: Conjunctions near Dawn (2012 Jun 30)