Sirius B

[David Swan]

After quite a bit of frustration, I am now delighted with the performance of the Hyperstar. Good grief though. Centering the corrector plate, ensuring the sec. mirror holder is not tilted with respect to the corrector, rotating the corrector to minimise zonal errors, minutely altering the sensor – Hyperstar distance, altering the tilt of the sensor slightly…… Need I go on.

[owen brazell]

I understand from double star experts that no living person has seen Procyon B. The last observation of it was with the 36″ refractor at Lick at the turn of the 19th century

[Dr Paul Leyland]

Title deliberately ambiguous.  Excellent astronomical seeing is essential for a visual observation, as are precisely aligned and scrupulously clean optics.  However, I wasn’t expecting to see Procyon B through an eyepiece.  Like the travails reported by David Swan, swapping a camera for an eyepiece is too much of a faff.  Actually, it isn’t, it’s the reverse that’s painful — having to spend hours taking all the flats in all filters again because the CCD will undoubtedly have rotated from its previous position.

No, I was planning on Lucky imaging to let me see the companion.

Hmm, perhaps it’s time to retake the flats anyway …

[David Arditti]

I looked for the first time tonight for the pup from my observatory in Edgware, Outer London, Lat. 51N. I did not read the Observers’ Challenge and deliberately did no research in advance to tell me where it should be, in terms of PA, so as to get an unbiased result.

I looked for the Pup at culmination with a C-14 at 300x and 480x. I tried normal monocular observing, I tried using two eyepieces with a Denkmeier binoviewer, and I tried the addition of a dispersion corrector, set to correctly remove the spectral dispersion for the altitude. In all cases I could clearly see what I thought was the Pup, and I estimated its PA as 75 deg. by eye. It was easiest to see at the higher magnification, but once seen with that, could be seen at the lower magnification as well. It could be seen as well with one eyepiece as with two, but less well with the dispersion corrector: I imagine the the loss of light from the prisms in the corrector negated any benefit of concentrating the light better, but with the binoviewers, loss of light was countered by the benefits of binocular viewing.

My C-11 is always used for CCD imaging and has a Hyperstar system in place, so for visual purposes my next telescopes down in size are a 10″ Newtonian and a C-5, but they are on a mounting in a location from which Sirius is obstructed by a fence, so I could not try to see it with them.

I did try with my Celestron 100mm f9 ED doublet refractor that is mounted with my C-14. Using a magnification of 346x, having identified the Pup through the C-14, I intermittently thought perhaps I could see something at the correct PA, as an enhancement of the diffraction rings, but at other times I thought not, and I could not convince myself ultimately.

So my conclusion is that from London the Pup is very clearly visible with 356mm aperture, and would certainly be visible in a smaller telescope – maybe, at a guess, down to 200mm.

It’s now occurred to me that as I have my C-5 (127mm SCT) mounted on a dovetail, I can move it to the mounting I have the C-14 and 100ED on, so I could test the C-5 on the Pup in future. Past experience has been that the C-5 is less effective on doubles than the 100ED, because of more light in the diffraction rings due to the large central obstruction, so, despite giving a brighter image, it seems unlikely it would show the Pup.

[Jeremy Shears]

That’s a really interesting and encouraging observation, David. 

i see there is a report on observing the Pup in S&T this month and the author was successful with a 130 mm refractor, although I presume from a more southerly latitude.

[Dr Paul Leyland]

Much better seeing last night so had another go, taking images in several filters to see if that would enhance the contrast.

Nothing obviously visible but I’ve some software in development which may help.  All that’s needed now is a copious supply of round tuits.

[David Basey]

Hi,

I had a dim memory in the dusty recesses of my mind that many years ago S&T ran an article on detecting Sirius B and the benefits of using a hexagonal mask.

I have now dug it out and it may be of some interest and indeed utility. The issue in question is June 1975 p407.

Basically Dennis di Cicco created a carboard mask that fitted over the aperture of a C14. Cut out from the cardboard was a hexagonal hole scribed on a 13.25 inch circle.

The idea is that this creates six strong diffraction spikes around the primary which suck a lot of the glare out of Sirius A. Rotate the mask so that the secondary is positioned between the spikes and Sirius B is more readily seen.

The reported results look good, it was indeed more easily detected with the mask. Also included in the article are photographs with and without the mask and the difference is clear.

While this approach is fine for refractors and SCTs, something like a Newtonian with a spider mounted secondary which already creates diffraction spikes might be more problematic.

Anyway, it could be worth a try.

David.

[David Swan]

Very interesting, David. Thanks for this.

[David Arditti]

The night after my previously reported observation, on February 22, I managed to get my C-5 (127mm SCT) mounted where I could get Sirius with it. I first had to cut down much of a giant weed in my elderly neighbour’s garden, that was in the way. I seem to do most of my gardening at night. Anyway, despite careful collimation, I certainly could not see Sirius B. There is no possibility with a telescope that gives such a messy diffraction pattern as this. But using a refractor of the same aperture, particularly a relatively long focal length one, would be a very different proposition, and I’d like to someone give this a go on a number of occasions from the UK.

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