CN FORUMS ARCHIVE Telescope Reviews: Sirius B

>However, in this context I am afraid to mention that I have recently noticed a report of a comparo of the Lick refractor and an Astro Physics 180 EDT on the gas giants (it was in the web, I actually do not find the link). The "small" Apo clearly outperformed the old giant on the planets...similar results may occur when observing Sirius B...?

Well, having actually used several Clark refractors, and made and used a 175mm f/12 apochromat (as well as many other apos, achromats, reflectors and CATs), I will have to doubt this claim as a blanket statement.

Obviously, the apo will have vastly superior color correction. But it surpasses belief that the 36" lens by which Amalthea was discovered can be called inferior to a 7" apo. Can one see Amalthea with a small AP lens? And split 0.2 arcsec doubles as Robert Aitken did with the 36"? Or reveal Procyon's companion (much harder than Sirius B) as the 36" first did to Schaeberle?

It is known for certain that the 36" was diffraction limited when it left Alvan Graham Clark's hands in about 1887. Since then, of course, the lens suffered devitrification, becoming quite cloudy on the first surface of the crown element. It was, however, restored in the late 1980's by David Hilyard, a master optician. Whether he left it quite as good as AG Clark originally had it is unknown to me. I don't know if Hilyard finished the figuring with the use of an interferometer or not. But the objective was tested in the late 1970s by interferometer before it was retouched. I have the static fringe picture. And this was recently analyzed by Bill Zmek, a noted expert, who determined that as left by Clark the objective was diffraction limited.

So to some extent this is an unfair comparison, since it could not have been made when the 36" was in pristine condition. I would like to read the actual comparison in order to understand what was done. Within the next few months, I may be able to observe Sirius from Kitt Peak, where the seeing is often exquisite. I certainly hope that my 145mm refractor will show Sirius B from there. If not, then I shall have to more seriously doubt all these claims, the best of which to my knowledge comes from Sue French who saw B through a small scope during the Winter Star Party in the Florida Keys. I am inclined to believe her claim, but doubt the others.

As to central Texas, why there the seeing can also be exquisite, as I know from experience. My best Mars view occurred 10 years ago through John Gregory's 8" apo from Lakey, TX. It was stunning. And since then I have seen the "canal" illusion through my own 8" achromat, though only once. But nothing to match the view in John's apo.

So, please excuse me for sounding so negative. I trully hope that I'm wrong, but so far all my years of experience in telescope building, testing, and observing double stars incline me to doubt virtually all the claims for seeing this star through small telescopes. The strong desire to see the star can play tricks on the observer's psychology.

So enough said. I have no proof that it can't be seen with a small scope. But I have not done so, despite looking for it with a lens I made having a Strehl ratio of at least 96.5% and possibly as high as 99%, based on my interferometry. The seeing conditions have been very good or excellent, when I've attempted to see it. I knew where to look and patiently searched, etc. So, why have others at higher latitudes had so much success, when I have failed over and over, but yet seen other faint difficult objects next to bright ones?

It makes me wonder....and doubt.

Cheers,
Roger Ceragioli

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