Telescope Reviews: A telescope time machine: Sirius B 40 years later

There is a rule in mirror grinding; a person, new to mirror making, will complete a higher quality 8 inch mirror and complete it faster if he/she first does a 6 inch mirror. I even recall it being said that one could accomplish the larger mirror by doing two mirrors, a step smaller for each.

Well, I didn't listen. The first, and last, mirror I ever ground, polished, and mounted was an 8 inch. I started it at age 15 and finished the telescope at age 16 or 17. It had lots of sleeks (sleek: a word in telescope making which means one did not clean the grit off the mirror stand properly before going to the next finer grit), probably a lot of pits, and definitely no better than 1/2 wavefront error. Perhaps even 1 whole wave of error. I remember it would be about 25 years later when I was looking through it at Saturn and the thought crossed my mind to "stop" this 8 inch F8 scope down to a 6 inch (and therefore F 10.7). I cut out a piece of cardboard, installed it on the front of the ota and saw the Cassini division on Saturn through this scope for the first time. In fact, it was the first time I had ever seen the Cassini division.

With this mediocre product I saw Sirius B. It was 42 years ago, now. It was perfectly placed, about 10 arc seconds from Sirius A. It was pretty. But I paid no real attention to this observation until years later, I learned from reading about other observer's comments, that seeing Sirius B was something kind of special.

Starting about five years ago, seeing on the dibonsmith page that Sirius B was approaching a decent separation from Sirius A, I began to try to see it; with an 8 inch SCT, then a 92mm apo, a 90mm achro; all with no luck.

This morning, not an hour ago. I saw Sirius B.

Here is how the observation came about. I had recently obtained a 12 inch dob, a very capable scope, but a bit reduced in aperture due to a severe tube deformity (i.e. hit the ground, hard). I was using a 4mm Plossl, which surplusshed labels as "professionally made"...for less than $17.

Sirius had just risen above the tree line; about 20 degrees elevation. The sky was very steady. Sunrise was only a half hour away so the sky had already brightened significantly.

I had first looked at Rigel in Orion to get a sense of the apparent visual separation of Sirius B from Sirius. I had read that the separation between Rigel B and Rigel was about the same.

Gaining a good idea of how far from Sirius, Sirius B would be I then began to gaze at Sirius. I saw a faint dot of light. It followed Sirius out of the field of view; it tailed Sirius. I nudged the scope-ota toward the north and saw stars entering the field of view on the same side of Sirius as Sirius B was seen. Though very nearly directly behind (i.e. following) Sirius, the faint dot was just a touch north of directly behind. And, again, it was almost dead on the same distance from Sirius that Rigel B was from Rigel.

The 4mm plossl gave a magnification of 380X (c. 30X per inch of aperture). I tried a short-barlowed 12mm plossl giving a magnification of 20X per inch of aperture. I could not see the dot. I tried a 5mm TMB/Burgess Planetary giving a magnification of 305 (c. 25X per inch). I could not see the dot. I tried a 2.5mm TMB/Brugess Planetary giving 610X (c. 50X per inch of aperture). I could not see the faint dot. I returned to the 4mm Plossl, and, yes, I could see the faint dot.

I went inside. Checking my copy of Webb's Celestial Objects for Common Telescopes, Volume Two: The Stars, on page 11 I found a diagram which gave the angle position of a secondary (a comes) from the primary, based on first noticing whether the secondary was preceding or following, north or south. Plugging in the following and slightly north, I obtained an angle measure of 80 degrees.

I then went online to dibonsmith. I don't know who dibonsmith is, but I sure have come to appreciate him/her and Webb over the years. Looking at the 80 degree place on the dibonsmith diagram of Sirius/Sirius B, I saw that the year for this position was 2012. Dead on!

A well figured but significantly dinged ota. A $17 Plossl. In full twilight. 20 degrees above the horizon.

Not only did I see Sirius B this morning. I also remembered experiences and feelings some forty years earlier. As well all have heard, and know, a telescope is a time machine...