Constellation Portraits Auriga

Auriga

click image

Auriga the charioteer, the brightest star on the right is Capella, I was not able to fit the top most star Delta Aurigae into the 50mm's field of view. I have not observed Auriga much in the past, in fact the first time I've seen open clusters M36, M37, and M38 was when I looked at the RAW files for this image in the monitor.

I'm very new to Astro-imaging and I'm starting to see it's a bit different to visual observing. You don't get the instant emotion when you see a celestial object for the fist time, in real time with your eyes against the eyepiece. When I'm observing visually my brain process what my eyes see just as when I look at an image on the monitor, but we have other senses. When I see something for the first time I'm taking in the image, but also the feel and smell of the air at the time, the cool breeze, the mosquitoes queuing to feed on me.The satisfaction when I locate an object or not. And the sense of depth looking thru the eyepiece.

Imaging on the other hand enables us to see things that we would other wise not be able to see visually. And perhaps just as important, give us tremendous efficiency and flexibility to view and analyze the data any time after the fact. We can go back to see and compare it as many times as we'd like. I guess this is also the reasons why professional astronomer embraced astrophotography in lieu of visual observations during the turn of the previous  century. And there's also an addicting feeling you get when you see a successful image coming to life on the monitor,

Image Data

Optics: Tamron 17-50mm f/2.8  set at 50mm f/2.8

Camera: Canon EOS X5 DSLR (unmodified)
Mount: Fixed Tripod

Exposure: 33 X 4sec at ISO 1600 RAW

Calibration: Darks, Flats,and Bias in DeepSkyStacker by Luc Coiffier

Processing: Gradient removal in Iris by Christian Buil, levels, curves, color in PS

Location: Quezon City, Philippines

Date Time: February 21, 2012. 7:51-7:57pm PHT

Conditions: Cloudless clear sky

Constellation Portraits Canis Major

Canis Major

The brightest star Sirius from our point of view on earth. Captured during a rare cloudless and transparent sky in Quezon City on February 21, 2012. M41 or NGC2287 open cluster the heart of the dog, can be seen near the center.

Image Data

Optics: Tamron 17-50mm set at 50mm f/2.8

Camera: Canon EOS X5 DSLR (unmodified)
Mount: Fixed Tripod

Exposure: 37 X 4sec at ISO 1600 RAW

Calibration: Darks, Flats,and Bias in DeepSkyStacker by Luc Coiffier

Processing: Gradient removal in Iris by Christian Buil, levels, curves, color in PS

Location: Quezon City, Philippines

Date Time: February 21, 2012. 7:23-8:05pm PHT

Conditions: 28C, 80RH, cloudless clear sky

Constellation Portraits Taurus

Taurus

Taken the same night as the Orion Portrait, but with a different lens a canon 50mm 1.8 set at f/2.8. This lens produced smaller star spot sizes than the tamron 17-50, but with a bit more chromatic aberration at least at f/2.8. The tamron exhibits both coma and severe astigmatism especially near the corners,  hence the bird like shape of the stars near the edge of the Orion image, the canon at f/2.8 has coma too but much less astigmatism.The canon  50mm is harder to focus accurately, but is a great bargain of a lens cheap and very light.Few lenses will beat it at f/4, but at much higher prices. Only 32 light frames were captured before the clouds rolled in.


Image Data

Optics: Canon EF 50mm f/1.8  set at f/2.8

Camera: Canon EOS X5 DSLR (unmodified)
Mount: Fixed Tripod

Exposure: 32 X 4sec at ISO 1600 RAW

Calibration: Darks, Flats,and Bias in DeepSkyStacker by Luc Coiffier

Processing: Gradient removal in Iris by Christian Buil, levels, curves, color in PS

Location: Quezon City, Philippines

Date Time: February 10, 2012. 8:33pm PHT

Conditions: 27C, 70RH, mostly cloudy

Constellation Portraits 50mm Astrophotography

Orion

click image

Taken under mag 3.5, light-polluted skies, in the middle of Quezon City. I was amazed that the image captured star almost to magnitude 11 with just 4 seconds exposure. Knowing that 4 second sub-exposures will have low signal to noise ratio, to partially compensate I took lots of frames (41) for stacking to improve the s/n ratio.

Why 4 seconds and not 60 or 300 seconds? Well I'd love to shoot that long, but I don't have a tracking mount yet, I was shooting with a fixed tripod. And 4 seconds with a 50mm lens near the celestial equator where the stars have the fastest apparent motion, is the longest exposure with no star trailing when viewed at 100%. There are formulas for computing the maximum exposure time for a given focal length and declination, before star trailing becomes apparent. But its simpler and more fun for me to just experiment with different exposure times from 1 to 15 seconds. Nearer the the celestial poles where stars have the least apparent motion I can get away with 5-6 second with not to much trailing.

Motivated by the reasonable result of this, I plan to do a series of constellation portraits as I wade my way to the deep waters of astrophotography. I am also planing a series of short essays of the subject images posted here.

Image Data

Optics: Tamron 17-50mm f/2.8  set at 50mm f/2.8

Camera: Canon EOS X5 DSLR (unmodified)

Mount: Fixed Tripod
Exposure: 41 X 4sec at ISO 1600 RAW

Calibration: Darks, Flats,and Bias in DeepSkyStacker by Luc Coiffier

Processing: Gradient removal in Iris by Christian Buil, levels, curves, color in PS

Location: Quezon City, Philippines

Date Time: February 10, 2012. 7:30-8:00pm PHT

Conditions: 27C, 70RH, partly cloudy