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Home > Articles > Observing > Other > The TOA-130 Reveals "the Pup"

The TOA-130 Reveals "the Pup"
By Ralph Aguirre - 12/3/2006

This weekend while viewing under sub freezing temperatures, myself and other members of our “Sacramento Valleys Active Astronomers” tired our luck at finding Sirius B otherwise known as "the Pup." Our group generally gets out and views every clear weekend, as long as the skies are clear and not completely overcast, and this night was no exception.
Despite temperatures being in the high 20's, we were out again in force, with our propane heaters keeping us warm, and Kendrick’s heaters keeping our scopes dry, and dressed for the cold temperatures, so we can enjoy these crisp winter skies as much as possible.

I was using my new Takahashi TOA-130 refractor, which has proven to produce some of the most spectacular stellar images I’ve ever seen in any refractor. Other scopes present that night were a TMB CNC 152 APO Triplet, a Takahashi FSQ-106 Quadruplet Fluorite, and another Takahashi FS-102 Fluorite Doublet.

Nasa's HST view of Sirius and "the Pup"


The night was very clear, and the stars were producing very sharp pinpoints throughout the sky. The larger stars usually show perfect round balls of light instead of pinpoints.
Sirius was an exception to this however. Its brilliance is such, that it would pulse in and out of brightness where I could never get such a sharp focus on it, so it never appears as a perfect round ball with a sharp defined perimeter. Nearby red giant Betelgeuse however, does look this way, showing a perfect round red ball of light.

Sirius is the brightest star visible from Earth, shining at an apparent magnitude of -1.5. The reason it's so bright to us, is because it's only about 8.7 light years from earth, our fifth closest star, not so much because of its size, because it's only 1.8 times larger than our own sun. It also burns hotter than our own sun and is roughly 26 times more brilliant in the amount of light it gives off. It is known as the "Dog Star" because it is in the center of the constellation Canis Major, or Great Dog.
Sirius is also part of the large asterism, the Winter Triangle, the other two stars of which are Betelgeuse in Orion and Procyon in the smaller dog, Canis Minor.
Sirius it is part of a binary star system with its companion star, Sirius B, referred to many as being "the Pup."

Sirius B, is a white dwarf star, and about 7,300 miles in diameter, or roughly 92% of the earths diameter. It shines at an apparent magnitude 8.7, which if by itself, should be an easy star to see in the sky with just about any size telescope. One incredible fact about Sirius B is that it spins on it's axis at an amazing 23 times a minute ( 23 rpms!) The separation of Sirius A and B varies from 3 arc seconds to 11.5 arc seconds over its 50 year period. This should be an easy star system to split in most telescopes, but because of the tremendous brilliance of Sirius A, seeing Sirius B becomes much more difficult. For comparison, in the famous "Double Double" of Lyra, Epsilon 1 is separated by 2.6 arc seconds, Epsilon 2 is separated by 2.3 arc seconds and the separation between Epsilon 1 and 2 is 3.5 arc minutes.

Last night was my first attempt to view “the Pup" in my new refractor. I've tired to view this several times in the past with my C14, but despite that being such a phenomenal deep space instrument, it has never been able to hold Sirius sharp enough to reveal “the Pup.”
I waited Sirius to come up high enough, so the low effects of the horizon wouldn't work against me at in locating the little pup. Finally, it reached a point where I was going to give it a try. I turned off the nearby propane heater, slipped in the 17mm Nagler, and pointed the refractor at Sirius. Sirius was a brilliant star, shining a very bright white blue. The 58x was not enough to see any signs of “the Pup,” so I slipped my 7mm Nagler into the diagonal. This brought the magnification up to about 140x. Sirius was violently dancing in the eyepiece. It would expand and collapse under its own brilliance. It was a beautiful bright powerful looking star, and just in itself, a spectacular object to view.
I stood motionless with my eye glued to the eyepiece, and begin to notice a dim tiny dot of light appearing every so often at about the 2 o’clock position from Sirius A. I reached for my feathertouch focuser, and got Sirius as sharp as I could, making it as perfectly round as I could, while also centering it in the field of view of the eyepiece. There was definitely something there. Every so often, the brilliant glow of Sirius would diminish enough, to see this tiny star. It was definitely “the Pup,” peeking its head out from under the light of Sirius’s brilliant glow.

TOA and TMB, both on "the Pup"


I called others nearby to see it. You had to watch it for a minute or so, to see the dance of the glow rise and fall, but as it diminished, everyone acknowledged that “the Pup” was there, definitely in that 2 o’clock position.

The Massive 6" TMB beside me, swung over to it also, and Mike put Sirius in the eyepiece. I looked into the TMB, and there it was again, just slightly brighter with the extra inch of aperture, but definitely there, in the same 2 o’clock position.

I went back to my TOA, and put my 2" Barlow into my diagonal, and put in my 9mm Nagler, increasing the magnification to 220x. The pup became even more obvious, and easier to see. It was still very dim relative to Sirius, teasing and playing peek-a-boo with us trying its best to hide behind Sirius. It was no match however, for either the TOA, or TMB that night.

I've read that people have had difficult times attempting to view “the Pup." I was prepared to move Sirius just out of the field of view of the eyepiece, incase I couldn’t see the Pup, or also play around with different levels of neutral density filters I’ve read people use, in helping them view the Pup. Neither of these techniques were necessary with either of these two amazing refractors we had. Maybe the 86% phase of the moon we were viewing under helped tone down the brilliance of Sirius, but more likely, it was the incredible optics in both the Tahakashi TOA-130, and the TMB CNC 152 that made viewing the pup so effortless.

It was a pretty fun night of viewing despite the cold temperatures. The propane heaters made all the difference in being out in the cold, especially on such a clear night.

Of all the objects we viewed that night, as we do every night that we are out, it will be finally seeing “the Pup” peek its tiny head outside of Sirius brilliant glow, so effortlessly, which I will remember most of all.

...Ralph
Founder of Sacramento Valleys Active Astronomers


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