- This topic has 48 replies, 16 voices, and was last updated 4 years ago by David Arditti.
6 January 2019 at 12:51 pm #574227owen brazellParticipant
I was interested in John Chuters article on Sirius B where he claims there are credible observations of Sirius B from the UK with instruments as small as 130mm. It would be interesting know to know what was the source of these credible observations and whether they were visual or imaging.. If the source of these observation is the SGL forum, probably the least credible source of any observational material known then I would question this piece and these observations given most very experienced double star observers fail to spot Srius B except with much larger instruments under exceptional conditions.
Owen6 January 2019 at 2:35 pm #580483
It was decided to set this as a challenge. I have not, or ever professed to being, an experienced visual or anything else, observer.
If it leads to a debate then that in itself is a good thing.
Let us see where this debate and the actual challenge goes before coming to any definitive conclusions.
I learn something new every day. It will be a sad day when that stops being the case.6 January 2019 at 7:35 pm #580485Michael O’ConnellParticipant
What is the current accepted position on the stories allegedly from the Dogon that they knew Sirius had companions?
Michael.6 January 2019 at 9:47 pm #580487Grant PrivettParticipant
Probably more convincing if it had also been unknown in the west at the same time.
Would love to see the artefact that proves them right.7 January 2019 at 7:21 am #580488
I was using a standard cheap 150mm X 1200FL Celestron Refractor in March last year. Being an achromat there was a huge amount of chromatic aberration.(CA) Here is what I found visually:
with 7mm eyepiece (X171) Sirius B was intermittently visible, with 5mm eyepice (X240) it was constantly seen, and with 2.3mm eyepiece (X522) it was very easy. I have a few not very well tracked, but quite distinct images. (I intend to take some better ones.) (Viewing from Brisbane, Australia. 27.5 deg South. 153 deg East.)
Regarding the Dogons’ knowledge, skeptical analysts indicate that the Dogon’s knowledge may have been contaminated by the researchers who were conducting their research shortly afterwards, as the information provided by the Dogon priests corresponds with European knowledge of the late 1920’s. Check it out with Mr Google.7 January 2019 at 8:55 am #580489
Here are the images: 15 seconds at 2000 ISO with 10mm eyepiece and eyepiece projection. Sirius B is the ragged streak hard up on the left hand side of Sirius. You will see that it is really there because the squiggle of the streak is different in each image and matches the other stars confirming that it is Sirius B. I have since ‘trained’ my drive and hope to do better next time. I have also included an image of the refractor, one of the common, garden variety, cheapie 150mm F8’s.7 January 2019 at 9:01 am #580490
Try again7 January 2019 at 9:05 am #580491
Many thanks, Peter, for a valuable and interesting contribution to the thread.7 January 2019 at 1:56 pm #580492Peter CarsonParticipant
About a year ago I observed Sirius B visually using a friend’s good quality 200mm APO refractor. It wasn’t easy but it was definitely observable. The refractor I was using had good contrast and colour correction which helped. Telescopes of poor contrast will struggle to show it because Sirius is magnificently bright in any aperture telescope.
Peter7 January 2019 at 3:53 pm #580493
I would concur Peter. I have been observing double stars for about 30 years now using a variety of high quality, high contrast telescopes including a 7″ F8 Mak-Newt with 1/10th wave quartz optics and 13% obstruction, an 8″ F6 Mak-Newt with 18% obstruction, 1/9th wave astro sitall optics and an OMC 200 Mak-Cas, F20, 4,000mm FL with 22% obstruction. I’ve failed to see it in all of those scopes despite numerous attempts. I have seen it twice in my Takahashi Mewlon 300, a 12″ high contrast Dall-Kirkham design and once in my 18″ F4.5 Newtonian which has a superb mirror. The first time in the Mewlon was back in October 2007 when it was just below 8″ separation. The seeing was excellent, the E & F stars in the trapezium stood out like there was always 6 on show but even so, the pup was just momentary glimpses in the glare of Sirius A but consistent in it’s position. A check the next day confirmed I had the correct PA. The next time was a couple of years later in the 18″ at Kelling Heath. Skies were claggy but seeing good so I changed my targets. Again the E & F stars stood out so I gave Sirius a go but first being a Dobsonian which always has some flexure I collimated the scope for that altitude. The observation was similar to that I’d had with the Mewlon previously. Then last month in the Mewlon, again E & F stars steady and tight (I think this is a pre-requisite in my book – if you can’t see them well, don’t even bother going for Sirius B). This time of course the seperation is 11″ and I had an almost continuous view of the pup for about half an hour, a faint spec just below the diffraction spike from the spider. Even so the pup was very faint and almost averted vision in the glare of Sirius B. It’s altitude in the UK does not help, even when the seeing is very good high up, it rarely is at the altitude of Sirius. I know an occulting bar would help but for me the beauty of observing this is seeing it against the glare of the primary and not in isolation.
Andrew7 January 2019 at 6:35 pm #580494Lars LindhardParticipant
It seems a small telecope will do it
https://www.cloudynights.com/topic/635377-sirius-b-observed/#entry90556298 January 2019 at 12:22 am #580496Grant PrivettParticipant
You can understand Owen’s concern though, as (above) an experienced observer manages it twice in 30 years while using a 300mm Mewlon and some other very useful sounding instruments and yet its now being seen in scopes much smaller than that used to discover it. Yes, optics are better now and baffling has improved, but the MKI eyeball hasnt changed much (and mine could certainly do with an upgrade).
And I’m with him on newsgroups, sometimes the content is low quality.
Raises an important question about observing dim companions of bright stars.8 January 2019 at 10:32 am #580497
I note the author did not answer Owen’s question on the source of the ‘credible observations’ but simply removed the word credible from the article. You never said John whether or not you had observed the pup yourself, I would like to think you had before writing such an article and suggesting or implying what aperture scope it might be visible in from UK skies.
Andrew8 January 2019 at 12:03 pm #580498
As mentioned it was decided to give this as a challenge by the group of people who manage the website, the ’webops’ group as we call ourselves. I volunteered to write the challenge. As you will see, challenges are put up regularly, as are tutorials etc etc. This is part of the the group‘s strategy to make the website a dymamic site that engages its members and seeks to encourage new members.
i have not personally observed the pup but then I have never tried. You are correct that I amended the article but I also said in my reply to Owen that a debate about this would be useful and that has indeed proved and is proving to be the case. I also stated that I did not regard myself as an experienced observer. Do I need to be to be a member of the BAA? There are many reasons why people choose to be a member of the BAA.
This does not detract from the issuing of the challenge as it is evident, to me at least, that this is not an impossible challenge with modest equipment and as is evidenced by the replies above.8 January 2019 at 12:35 pm #580499Gary PoynerParticipant
I remember seeing it in the late 1970’s visually with a 10inch F6.5 newtonian. It could have been 1978-79 but I’m having trouble locating that observation in my files (which is why I’m late to the discussion). I do recall that it was a very difficult observation to make, with the separation at or near maximum distance I think. If I find my notes, I’ll come back. Don’t think I dreamt it!
Gary8 January 2019 at 2:22 pm #580500owen brazellParticipant
Although not being an experienced observer is not necessary to be a member of the BAA or write articles a knowledge of astronomy should be. There are other issues with this article in that the orbit of the Pup is stationary and the Pup itself is at maximum elongation. If the BAA is to be regarded as a serious organization then its website and articles on it need to be right as well and a knowledge of the subject should be a pre-requisite to write about it.. I understand that you wish to make a dynamic website but there must be a threshold before you write.8 January 2019 at 3:40 pm #580501
Maintaining my membership of the BAA is one way that I have of continually learning about this fascinating hobby. If you were able to elucidate further on your previous reply regarding the orbit etc then I and others may further learn about Sirius and it’s Pup. In this way this debate is achieving its purpose. Your reply certainly indicates that you are able to do so. In fact I am confident that you can as, of course, I am aware of who you are and your expertise in many astronomical matters.
Please note that this is designated as an Observer’s Challenge. The challenge is to try and observe the Pup, should anyone decide to try and do so. There is no compulsion. In this respect it seems that it is possibe to do so, witness images and other replies earlier in this thread. The use of the word ‘challenge’, also indicates that it is not meant to be easy.8 January 2019 at 4:12 pm #580502Peter CarsonParticipant
I’m not sure I would have been quite as blunt as Owen, but I do agree that if the BAA is to remain the leading organisation in amateur astronomy it must be careful what it publishes. I’m not suggesting there is anything wrong in John’s observing challenge but in a wider context the BAA’s output does often get quoted in the general world of astronomy. If the BAA publishes something inaccurate, misleading or open to being misconstrued this downgrades the Association and the wider amateur astronomy world.
Perhaps the more expert and experienced amongst us need to come forward and volunteer to assist with what the BAA does?
To get back to the reason John issued the observing challenge, lets all encourage as many observers as possible to hunt out the pup before the chance of seeing it diminishes for the best part of a lifetime. (Seems Gary above is into his 2nd lifetime!)
Peter8 January 2019 at 4:23 pm #580503
I have to agree with all of this……9 January 2019 at 8:22 am #580505
Just checking my binary calculator Gary, at the start of 1978 it would have been at a separation of 10.8″ and PA 53 degrees. Ditto 1979, sep 10.5″ PA 51 degrees. Brilliant getting it back then, think I only had a 60mm refractor back in the 70’s and no I didn’t see it with that 🙂
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