Seeing the "Pup" - how can you be sure?

There's a lot of excitement this observing season about seeing Sirius "B" - known affectionately as "The Pup" since it is a white dwarf that orbits Sirius, the "Dog Star."

It's especially hard to see because:

• The Pup is close to and about 10,000 times dimmer than Sirius - sort of like trying to catch the glow of a firefly circling close to a bonfire a few hundred yards from you.

• Sirius is the brightest star in our sky and it's glare makes it difficult to see anything near it. What's more it dances like crazy in anything but the steadiest - very rare - seeing conditions.

• At nearly 42 degrees north latitude, Sirius never gets any higher than 32 degrees in my sky, which means I'm always looking through a lot of atmosphere and that adds to the difficulty, even if the atmosphere happens to be steady.

On the plus side , the Pup orbits Sirius every 50 years and since it's orbit is an ellipse, the distance between it and Sirius varies considerably. We're entering a period where for the next several years the distance between the two will get constantly larger making a sighting of the Pup more likely. But how can you be sure you've seen it? Many amateurs report they have, but frequently these reports are not believed by other amateurs. I don't expect to see it - not this year, and maybe never, but the debate over whether others have seen it got me to thinking about the whole problem of "splitting" difficult double stars, such as this, and so in a discussion forum on Cloudy Nights I asked a simple question - how can you be sure you have split a double.

Oh, of course many times it's obvious. Doubles can be easy, charming, and verybeautiful. But a split is not obvious with the challenging ones and there's plenty of opportunity to fool yourself. I'm not interested in proving my observing prowess to others - I'm interested in simply knowing for sure that I have seen what I think I have seen.

I asked, in part:

A lot of time I do my double-star observing while purposefully keeping myself ignorant of things, such as position angle. Then if I sketch what I see and my sketch is reasonably accurate in terms of position angle and separation, I have confidence that I did indeed see what I thought I saw. I still can't prove it to you (that sounds next to impossible to me) but I can prove it to me, and that's goal enough.

But I know the PA, separation, etc. of Sirius B and I can't forget it, so when conditions are borderline and the Pup - as one report stated - keeps peeping in and out - how do I know I'm seeing it?

I found this answer not only to the point, but very helpful.

. . . Without at least some of these tests, I HAVE been fooled, came in and checked the PA, and kicked myself.

Don't get distracted by your first glimpse. Be cool. Keep looking all around the primary, because little things will appear all around. Is your little thing any different from the rest?

Change eyepieces, and see that the separation scales with magnification.

Rotate your eye wrt the eyepiece, see that the star stays put proving it's not your eye.

Rotate the eyepiece in the holder, proving it's not the eyepiece.

If you are using a refractor, rotate the diagonal in its holder, proving its not that.

If you are using an equatorial mount, swing the scope to the other side of the polar axis, proving it's not the objective.

It helps to not know the PA, but too late for that in your case. Conversely, realize that guessing the correct PA is not enough, alone, to assure you've seen it. Assuming you can guess within + or - 10 degrees, a monkey has a chance in 18.

I really appreciate your question. So many people just toss it out there that they've seen it. It's getting easier as the separation increases, so maybe even I will see it again some day.

By the way - when I asked permission to use this, the writer replied:

Help yourself, so glad you enjoyed them. But don't credit me. You think I made them up? Where I got them is water under the bridge. Learn them and they're yours.

I pass on the advice to any double star observer - learn them and thy're yours ;-)