Sirius is the brightest star in the night sky (Alpha Canis Majoris). Lore calls it the Dog Star, as it is the brightest star in Canis Major, the Big Dog. In Egyptian culture, the heliacal rising (helical: relating to or near the Sun - Helios) in the summer indicates that the river Nile is about to flood as meltwater from the Ethiopian highlands. The Nile was THE source of life for the high Egyptian culture. The Greeks called the hottest days in the summer "The Dog Days of Summer." They thought that the bright star Sirius rising in the morning adds to the heat of the summer Sun, and therefore called the hottest days "The Dog Days."
The Big Dog has a Little Pup as its companion, which leads me to this post's topic. Sirius B is the companion of Sirius A. It is a white dwarf star, not one of the seven dwarves. A White Dwarf star is a low-mass star at the end of its life and is very compact. Imagine the mass of the Sun but the size of Earth. A teaspoon of dense material weighs about a large SUV. More on the astrophysical properties another time.
Sirius B orbits A in roughly 50 years (they actually orbit their common center of gravity; more in another post). Their close and far distance varies between 8.2 and 31.5 Astronomical Units (AU). Currently, the Pup is at its greatest distance from Sirius A and offers a serious challenge to observe it with a telescope. The separations at the maximum distance is about 11 arcseconds, which generally is a good distance for binary observations. However, Sirius A outshines the Pup by roughly 10,000x in luminosity. That makes it HARD to observe.
The image below offers a sense of the orbital parameters and years suitable to observe, as well as a sense of how close the Pup is to the Hound.
Credit: Johannes Schedler / panther-observatory.com
To observe the Pup, you need:
Excellent seeing conditions. You need perfect conditions. No moisture, no win, no dancing heat columns above you. It will refract the light from Sirius so much that it is virtually impossible to have enough separation.
High magnification. 300x is good, and more is better.
X marks the spot. Use a stargazing app (SkySafari) or Stellarium to determine where to look for the Pup in the eyepiece. Sirius A will look like a scintillating starfish in the eyepiece ,and knowing where to look for the Pup will be necessary.
Clever tricks. I have read an occulting bar might help to block out Sirius A's glare. But knowing how to turn the occulting bar is necessary; otherwise, you will block the Pup.
My equipment
Visual:
Meade LX200 12-inch
Various 2-inch eyepieces and Barlow lens (2x)
Astromigaing:
Explore Scientific ED127
Celestron C8
ZWO 1600mm PRO
AM5 Mount
ASIAir
Attempts
February 10, Monday
Time: About 8 PM
Sirius Position: 31 degrees Alt
Seeing Conditions: Average.
Wind: None
Magnification: 200x to 300x
Result: My first attempt was to get out and test the gear. Find Sirius in the eyepiece and then realize the siriusness of the challenge. Have you ever seen a dancing star resembling the ornament star with spikes on top of the Xmas trees? That's how it looked. I didn't expect to succeed on the first attempt with no ideal conditions.
February 11th, Tuesday
Time: About 9 PM
Sirius Position: 35 degrees Alt
Seeing Conditions: Average
Wind: None
Magnificication: 300x to 450x
Results: Practice makes perfect. After discussing the Sirus challenge at the St George Astronomy Group's monthly meeting, I gave it another try. You gotta keep trying to figure out how changing conditions change your probability of catching the pup. There is a lot of refraction going on in less-than-ideal conditions.
February 12th, Wednesday
Seeing Conditions: Below Average
Wind: None, then 3-4 mph
Magnification: With the astroimaging equipment, magnification is not really meaningful. However, the important number is the separation of the Pup (11 seconds) and how many pixels this translates to in the image. I took a video and went through the frames.
Results: Here is the video I took. It's about 15 seconds. It will give you a sense of how difficult it is to observe. I thought the dancing star resembled what I observed visually in the eyepiece. And I had no idea that the ASIAir saves the video with music!
I went through all the frames in the video and still images I took, and I MIGHT have had a lucky frame. It's actually called lucky imaging, and in astroimaging, it refers to a technique where a large number of short exposure frames are captured rapidly, and then only the sharpest frames (considered "lucky") are selected and stacked together to create a final image with significantly improved detail, overcoming the blurring effects of atmospheric turbulence, especially when imaging planets or the Moon. I didn't stack my good frames from the regular observing session yet.
Below is a frame from the video. Sirius A is seriously blasting light.
Here is a frame at 1-millisecond exposure with a Luminance filter with 300% Zoom.
Here is one frame at 10 millisecond exposures:
February 15th, Saturday
Seeing Conditions: Poor.
Wind: 1-2 mph
Magnification: I refitted my Celestron C8 and swapped it for the ES127.
Results:
February 18th, Tuesday
Seeing Conditions: Below Average
Wind: 1-2 mph
Magnification: ~425x with the 8mm and 226x with the 15mm eyepiece.
Results: I went back to my 12-inch Meade and used my 8mm eyepiece with and without the Barlow lens. As it turned out, there was a lot of haze in the air. Sirius was sparkling brightly with rays emanating from the center like the petals of a flower. I thought a few times I saw it. visually, but I think it was more wishful thinking than actual observing.
February 27th, Thursday
Seeing Conditions: Average
Wind: No wind
Magnification: ~406x with the 15mm and 2x Barlow
Results: Visual observing seems to be the way to go, with good magnification and very good transparency. It was not windy, and I found that Sirius A was much less scintillating than any previous sessions. With the help of Stellarium, I was able to look for the Pup at the proper angle and distance from the Dog. I could observe a very faint point of light in the right spot. I thought I found it. I went to move Sirius to the edge of the eyepiece with the guiding speed, very slowly. The Pup appeared much better at the edge of the eyepiece, blocking the incredible brightness of Sirius A. I strive to be a good scientist and don't rely on one observation; I need a second independent event to confirm.
February 28th, Friday
Seeing Conditions: Below Average
Wind: No wind
Magnification: ~406x with the 15mm and 2x Barlow
Results: I went to confirm the observation from my previous night. The Pup was still in the right spot, and my method of using the guiding rate to move Sirius to beyond the edge of the field-of-view in the eyepiece proved to be successful again. Conditions were very good, despite Astrospheric showing below-average seeing conditions. If transparency is excellent, seeing is average, and there is no wind or little wind, the chances of success are very high. I swapped out the 15mm for the 8mm eyepiece, but seeing the Pup was much more difficult. I admit that I didn't find it. The field of view shrinks, and the low lluminance from the Pup is spread out even more, which might result in insufficient light hitting the retina.
March 4th, Tuesday
Seeing Conditions: Average to Below Average
Wind: No wind
Magnification: ~406x with the 15mm and 2x Barlow; ~305x with 20mm reticle and 2x Barlow.
Results: A good reference double star is Almach, or Gamma Andromeda. It is high enough in the sky for early evening viewing. It is one of the best of all double stars. It is roughly separated by roughly 10 arseconds, on the order of Sirius A and B separation. Gamma 1 is a K3 giant with a distinct orange color, whereas Gamma 2 is a fainter bluish B-type star. Each is double on its own as well, but I could not split them under my local conditions. The seeing conditions have never been above average for the last weeks, and I look forward to good or excellent conditions.
Additionally, I have used my 20mm 1.25-inch reticle eyepiece with a crosshair and a small red light to illuminate the image in the eyepiece. You can purchase it here: link. It helps get a sense of the arcsecond separation of double stars as you align them against the crosshair.
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