9 January 2019 at 11:53 am #580507
On 2018-11-30 I was imaging HL CMa, which many of you know is uncomfortably close to Sirius. It’s essential to place the latter outside the field or it dazzles both CCDs and eyeballs. However, at least there is a bright (far too bright) guide star nearby. A SBIG-8 camera has a small CCD for guiding purposes and it was used with the minimum possible exposure time of 0.11 seconds. Sirius was still over exposed but, to my surprise, the Pup showed up occasionally in the autoguider window.
After taking the science data another 100 images at 0.11s were taken of Sirius. The one from the moment of best seeing appears here. The blooming from Sirius runs from top to bottom on the full frame, of which this is only a small crop. It’s fortunate that the camera was orientated at a good angle to the line joining the stars.11 January 2019 at 7:56 pm #580518
I seem to remember seeing the Pup on (a very few) occasion(s) with the 0.275m Mak-Cas owned by the Oxford University AS. This would have been around 1980 or so, My memory is suspect and I no longer have access to any contemporary records so treat this report with the suspicion it deserves.12 January 2019 at 1:03 pm #580521Peter AndersonParticipant
This evening there was a lull in my usual lunar occultation work and I turned my C14 onto Sirius. Now my C14 has always suffered from a slight haze on the inside of the corrector plate, and I have never plucked up the courage to remove and clean it like I did my old C8. Further the alignment of the secondary is tweaked to approximately correct to give good star images but is not perfect and in/out of focus images at high power will testify. So what I am saying is the optics are not perfectly clean nor perfectly aligned. Conditions were relatively steady. So I first of all inserted a standard (40 to 60 degree field) 8mm – 24mm zoom eyepiece. At 24mm (X163) the pup was very difficult to see close to the brilliant image of Sirius. It was easier to zoom in to the 8mm focal length (X489) when it stood out so plainly with black sky all around that I was wondering whether I was looking at the correct star. Zoomed out back to X163, (now knowing precisely where to look), I was able to spot it, by moving my eye around the eye lens a little, to cause the rays emanating from nearby Sirius to avoid this area and so reveal the ‘pup’ very close to Sirius. Re-inserting my standard 25mm eyepiece (X156), I managed to repeat this operation.
Now my views on this are, short of using an occulting bar: Firstly, if using a Newtonian, check that the spikes from the diagonal support will not be in the way.
Secondly, ensure that the conditions are sufficiently good to obtain a sharp and relatively stable star image.
Thirdly, don’t muck around with a low magnification. Go straight to 400 or 500 so that the pup will be a reasonable angular distance from Sirius. Only when thus located, scale back and check out the lowest magnification that you can reasonably see it. I would suspect this to be around X150 or a tad less. There is no point trying to initially pick it up at a low magnification!
As I reported earlier in this thread, these results tonight were very similar to those with my 150mm refractor last March, except that the refractor produced a much fainter image and a whole lot of colour from chromatic aberration.
I will try 150mm refractor with the 112 mm aperture stop to see if I can still pick up the pup.
Now I must confess, that tonight I did not play fair at all. Not only was I using the C14, but you probably don’t want to know the altitude of Sirius at around 11hrs 30min when I observed it. I will tell you anyway… around 65 degrees!
So whatever I have recommended should be taken with a grain of salt when you factor in its altitude from your site.12 January 2019 at 4:36 pm #580522
Owen as a BAA and SGL contributor, I was interested in how you justify your comment on SGL being “the least credible source of any observational material known” ? Have you done a study or can you provide a credible reference?
On a different tack, I suspect visual acuity is as important as telescope aperture, seeing and other sky conditions to observations of the Pup.
Regards Andrew12 January 2019 at 6:30 pm #580523
I don’t know about Owen, but I certainly find you have to take whats there with a large pinch of salt.
I just looked at a discussion in the deep sky section about whether M31 was a naked eye object and another in the imaging section on what affordable CCD camera to buy. Didnt exactly inspire confidence.
Looking more generally, there were postings from participants that were at best naive/lazy (even some with 20,000 posts), others who slavishly followed someones opinions because they had taken some nice pics and a few were clearly just plain biased in favour of stuff they had owned. I have no doubt it also has a percentage of observers who manage to “see” rather more than their instrument actually delivered and enjoy the immediacy of the applause available.
Personally, I couldnt say its worse than CloudyNights or any other fora but, while appreciating a proportion of participants will undoubtedly know their stuff, theres very much a need to be able to filter out the noise – and that can be difficult while you are yourself inexperienced.12 January 2019 at 7:25 pm #580524
“I have no doubt it also has a percentage of observers who manage to “see” rather more than their instrument actually delivered and enjoy the immediacy of the applause available.” a trait shared with Percival Lowell!
Also “clearly just plain biased in favour of stuff they had owned” a passion shared on SGL by a recent President of The BAA and Takahashi!
Of course it’s a forum that does not seek peer reviewed posts and us such needs care in deciding what to take as accurate. However, to condemn it as the worst without justification is committing the offence it is accused of.
There are many fine images posted there and discussions which myself, Robin Leadbeater and other BAA members have contributed to. It does not seek to replicate the BAA but engages a wide audience interested in astronomy. In my view it is better to participate and improve such a form than sit on the sidelines sniping.
Regards Andrew12 January 2019 at 9:11 pm #580525
I think that, if you look back at my posting, you will find that I don’t say that it is the worst. If Owen wants to defend that position, thats entirely up to him.
If asked an opinion, I would say it is much the same as all the others, only with a more UK slant in equipment choices. But thats hardly pouring praise on it! Some discussions will be sound and informed, some average, others will be hijacked by fools.
The net gave us access to more knowledge and with that came a greatly increased supply of gibberish. I think you will find that what I said can be summed up as “The advice may only be worth what you paid for it”.
I wish good luck to those of you who do help add quality to the fora and admire your tenacity, but find that what I have to do already fills my waking hours.
Also, I don’t think its sniping to point out that a source of information may be significantly suspect.13 January 2019 at 10:33 am #580526
Grant , I don’t want to make a big issue of this but I apply Richard Feynman saying:
Have no respect whatsoever for authority; forget who said it and instead look what he starts with, where he ends up, and ask yourself, “Is it reasonable?”
rather than what it cost me.
Regards Andrew13 January 2019 at 11:47 am #580527
Yep. Its no big deal. We disagree. It happens.
But, should I respect that saying from Feynman more because he was an authority on quantum electrodynamics?
Ho hum. Back to the gardening.13 January 2019 at 12:02 pm #580528
No you should not, anymore than I should disregard your advice as it was free!13 January 2019 at 12:20 pm #580529
Touche. 🙂14 January 2019 at 12:40 am #580530Peter AndersonParticipant
Last night I had another ‘lull’ in my occultation observing and moved over my 150mm refractor to check out whether I could see ‘the pup’ with the aperture stopped down to 112mm. (The altitude was around 55 degrees.) Okay, I was a bit cocksure and this attitude (pride comes before a fall), clearly deserves what it gets. The weather has changed here and the moist south-easters are blowing. As a result, though okay for occultations, conditions are not appropriate for splitting difficult double stars. Once again I was enchanted by the exquisite diffraction disc and rings of a refractor, somewhat larger when stopped down to 112mm, but while the disc appeared to remain fairly stationary, the rings, whilst still for the most part sharp and discrete were in constant random motion. Most of the problem was the twinkling type random flashing from the central disk. I increased the magnification to X522, and knowing where to look, with the full 150mm aperture could only maybe say that I glimpsed the pup once or twice. I could not say that I really saw it. At 112mm aperture absolutely nothing. And yet on the other occasion just a few days ago with the same instrument, same eyepieces, it was really easy at high magnification! (report above.)
Now what lesson have I learned? Firstly to reiterate, but this time very strongly, that steady seeing (and a clear sky) are essential. Now obviously altitude will play a significant part in the opportunity to achieve this. Because good altitude is a ‘given’ for me, it is quite unfair to directly apply my observations to those possible from northern Europe.
From the appearance last time in the 150mm I would feel that the original claim of visibility with a 130mm instrument is ‘do-able’ under the right conditions. The difficulty is to get those conditions from England where Sirius at 52N latitude rises to a maximum altitude under 22 degrees even allowing for refraction.14 January 2019 at 9:57 am #580533John ChuterParticipant
It has been pleasing to see that this challenge has generated interest, both in debate and in observations. This was always the intention and I have also learned things I was not aware of astronomically which, as mentioned, is why I’m a member etc.
The challenge was not meant as a UK based challenge and that is not inferred anywhere in my piece. So it is doubly pleasing that observations are coming in from well outside the UK.
There are always differences of opinion, both here and on other fora. The level of expertise also varies enormously but that is to be expected and not, in my opinion, something to use as a criticism of other internet fora. The more useful tack would be to correct errors and impart knowledge when it is apparent that someone doesn‘t understand something. Of course, the manner in which this is done is important.11 February 2019 at 10:33 am #580663
Now that we’ve had several images of Sirius B posted, including today’s picture of the week, does anyone fancy trying for Procyon B? The separation is only about half that of Sirius, so it will be much more of a challenge. Although the primary is 2 magnitudes fainter, so is the secondary.
I intend to give it a try after returning to La Palma this week.11 February 2019 at 6:58 pm #580664David SwanParticipant
You know this of course, but it is also worth saying that the greater altitude that Procyon achieves from our vantage point should help with seeing. I just need to get the Hyperstar off my C8 and put the secondary mirror back for native FL imaging. After all the faff with getting things aligned just right…16 February 2019 at 2:12 pm #580693Robin LeadbeaterParticipant
Just spotted this on the S&T website
“Monday night, February 18th. That evening around 10:30 p.m. MST (5:30 UT February 19th), there’s a good probability that the 17th-magnitude 4388 Jürgenstock will occult the sky’s brightest star for up to 1.8 seconds.”
The event is not visible from the UK but anyone on the narrow path though North America could get (very a brief) view of Sirius B free from the glare of its bright companion. (Sirius is predicted to be totally eclipsed for just 0.2sec !)
Robin16 February 2019 at 2:20 pm #580694Robin LeadbeaterParticipant
I’ve just seen there is now a revision to the path noted at the bottom of the page. (The original track was calculated based on the position of the centre of mass of the A-B system rather than Sirius A !
I hope you have not already made your travel plans !
Robin18 February 2019 at 1:36 pm #580704
No joy last night. Seeing was quite poor.19 February 2019 at 8:05 pm #580712David ArdittiParticipant
I long ago decided as policy always to keep my C-11 in Hyperstar mode permanently, and the secondary resides unwanted in a drawer. It’s such a faff getting the Hyperstar alignments just right, as you say, it’s not worth going back to long FL imaging after prefecting it. Better to get another telescope – good 2nd hand C-8s go pretty cheap – and swap them on the one mount.19 February 2019 at 8:29 pm #580714David SwanParticipant
Sorry, this has nothing to do with Sirius B. It was a big deal though. Please don’t eject me from the thread 😉
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