Problems with the Dog

[Moonshane]

I'll be having another go at this later if it stays clear. also thinking about getting a red filter.

[John]

Got it again tonight. Not easy (as usual !) but that little Pup was definitely glimmering through the Sirius light scatter on and off as the pair drifted across the FoV. The Baader GO and CO 6mm orthos plus the 5mm XW did the job best with occasional glimpses also had with the 6mm Ethos and even the 4mm Radian. 

It's difficult to describe this split as it's nothing like other doubles due to the effect the the immensely bright Sirius has on the optics of the scope, eyepiece and I suspect the eye. The diffraction glow around the bright star varies constantly in extent, stability and transparency but there are occasional steadier moments and thats when the Pup glimmers though. On a typical drift across the FoV you might just get one or two momentary glimmers or on others you might see a little string of them at one spot when everything comes together.

Strange business, both compelling and frustrating at the same time. Come to think of it, that sort of sums up astronomy really 

[Moonshane]

based on your description John, I think I have had it tonight but never convinced myself. I think I need to get my 16" dob on the case and get to a site with no / few houses to give myself a better chance. I do wonder if the few degrees lat. difference in our observing positions makes it a bridge too far from here. will be interesting to see if I can get it from SGL9. on the other hand, maybe you have sharper eyes than me!

[John]

based on your description John, I think I have had it tonight but never convinced myself. I think I need to get my 16" dob on the case and get to a site with no / few houses to give myself a better chance. I do wonder if the few degrees lat. difference in our observing positions makes it a bridge too far from here. will be interesting to see if I can get it from SGL9. on the other hand, maybe you have sharper eyes than me!

I guess you can tell from my description Shane, it's a really tough and elusive target that seems to play with you, in a sense. Over the past 30 mins, despite moving the scope so Sirius is in the max open sky between houses and trees, I've not been able to pick the Pup up again despite using the same eyepieces and the same techniques. It's possible that the seeing has changed slightly as Jupiter is not quite as crisp as it was earlier and the moon is now higher in the sky and starting to cast it's glow around too.

I've been trying tricks like looking at the bright Jupiter for a while then switching quickly to Sirius to see if dark adaptation / pupil size can be played with. That seemed to help once or twice. I tried the H-Beta filter and that did produce a really tight Sirius A but I lost too much light to see the Pup with that. It might work with your 16" though ?.

I'm probably going to pack in now but it's been a good session - nice to see virtually all of a GRS transit for a change !

[chiltonstar]

Got it again tonight. Not easy (as usual !) but that little Pup was definitely glimmering through the Sirius light scatter on and off as the pair drifted across the FoV. The Baader GO and CO 6mm orthos plus the 5mm XW did the job best with occasional glimpses also had with the 6mm Ethos and even the 4mm Radian. 

It's difficult to describe this split as it's nothing like other doubles due to the effect the the immensely bright Sirius has on the optics of the scope, eyepiece and I suspect the eye. The diffraction glow around the bright star varies constantly in extent, stability and transparency but there are occasional steadier moments and thats when the Pup glimmers though. On a typical drift across the FoV you might just get one or two momentary glimmers or on others you might see a little string of them at one spot when everything comes together.

Strange business, both compelling and frustrating at the same time. Come to think of it, that sort of sums up astronomy really 

A nice description! I had another look last night as well, but Sirius is now for me too near a house late in the evening, and the seeing was barely average, with the image streaming to the right because of the rising air.

Chris

[AndyWB]

Well, I tried last night in the 250px. Sirius does look a bit rainbow coloured - I assume due to low altitude and atmospheric diffraction? I got nothing, though, just this unstable point of light. Checked Rigel and the Trapezium just to test things - Rigel was an easy split, and I got the F component of the Trapezium that had been eluding me. Then went back to Sirius - but still nothing. I do think that the extent of the diffraction was probably greater than the 4.5" separation. It might have to wait until I'm out of town to try this.

[chiltonstar]

Well, I tried last night in the 250px. Sirius does look a bit rainbow coloured - I assume due to low altitude and atmospheric diffraction? I got nothing, though, just this unstable point of light. Checked Rigel and the Trapezium just to test things - Rigel was an easy split, and I got the F component of the Trapezium that had been eluding me. Then went back to Sirius - but still nothing. I do think that the extent of the diffraction was probably greater than the 4.5" separation. It might have to wait until I'm out of town to try this.

I still haven't seen the F component with my 5".....I need a night with good seeing earlier in the evening when it's better positioned for me.

I believe the split with Sirius is now more like 10 arcsec, isn't it?

Chris

[Stu]

Yep, 10.1"

Stu

[chiltonstar]

Yep, 10.1"

Stu

......hence why it is now "relatively" do-able in a smaller scope, unlike a few years ago!

Chris

[michael.h.f.wilkinson]

The coloured "disco-ball" effect described by many is indeed atmospheric refraction, and using filters to narrow the bandpass can help a lot in reducing it. I have not used H-beta filters for this, but This would reduce a lot of glare from Sirius A as it has an A1V spectral type, which means very strong absorption lines of hydrogen. However, the DA2 spectral type of Sirius B also has these strong absorption line so it is also reduced in brightness quite a lot by an H-beta filter. H-alpha would suffer the same drawbacks, but at least it should reduce seeing effects as well. OIII did not work well in my case: the atmospheric refraction is gone, but seeing was quite horrible in the this blueish-green wavelength. A simple red filter worked best for me (an maybe an IR pass filter could work as well in a big enough scope, because those tend to transmit some of the deepest visible red as well)

[chiltonstar]

The coloured "disco-ball" effect described by many is indeed atmospheric refraction, and using filters to narrow the bandpass can help a lot in reducing it. I have not used H-beta filters for this, but This would reduce a lot of glare from Sirius A as it has an A1V spectral type, which means very strong absorption lines of hydrogen. However, the DA2 spectral type of Sirius B also has these strong absorption line so it is also reduced in brightness quite a lot by an H-beta filter. H-alpha would suffer the same drawbacks, but at least it should reduce seeing effects as well. OIII did not work well in my case: the atmospheric refraction is gone, but seeing was quite horrible in the this blueish-green wavelength. A simple red filter worked best for me (an maybe an IR pass filter could work as well in a big enough scope, because those tend to transmit some of the deepest visible red as well)

I first used an old "ruby line" filter (from the days when lab lasers were ruby) which worked well, but I now have a "deep red" eyepiece-threaded filter  (less than £10) which seems to work as well. For me, the beneficial effect is more noticeable with my 5" Mak than either of my 'fracs - I suppose this is because of the greater amount of scattered light thrown around by a scope with a secondary obstruction like a Mak.

Chris

[Mark at Beaufort]

I have just ordered a standard Red (25) filter to use with my 10" Dob to see if I can pick up this Pup. I have the feeling that Orion will be getting some attention at SGL9 with the HH, Flame Neb and Sirius B

[michael.h.f.wilkinson]

I first used an old "ruby line" filter (from the days when lab lasers were ruby) which worked well, but I now have a "deep red" eyepiece-threaded filter  (less than £10) which seems to work as well. For me, the beneficial effect is more noticeable with my 5" Mak than either of my 'fracs - I suppose this is because of the greater amount of scattered light thrown around by a scope with a secondary obstruction like a Mak.

Chris

A ruby line filter would certainly be a good choice. I must say I haven't had a chance to have a go at Sirius this year (got the pup last year), the weather has been horrible. Might have a go from the Alps, weather permitting at the end of Februari.

[AndyWB]

I believe the split with Sirius is now more like 10 arcsec, isn't it?

D'oh! Yup, I forgot that diagram, and it does explain why I found two different sources saying different distance - and of course, that's comparible with Beta ORI, which is why it was mentioned. It's funny how easy it seems for a similar separation - I mean, it's not like Rigel is dim...

And I should've said refraction, not diffraction.

[Moonshane]

I have 'bitten the bullet' albeit more like nibbled the .22 with a cheapie red filter (#25A) which will be in my hands shortly so will be interesting to see if this helps at all.

[alan potts]

Last night my wife opened the window and told me that swearing at the scope will not help things. From that opening need I say any more about the last two nights attempts and nothing that looked even slightly like a PUP.

The only Pup I saw  was a local dog that popped by to see if any grub was on offer, it got a lump of brick thrown at it for it troubles, I missed that as well.

Alan

[chiltonstar]

Although clear here from 22:00 onwards, the seeing was not fantastic, but still very good. Couldn't catch the Pup tonight though as it was too close to a house S of me, but I did manage to see Trapezium F at last - visible every now and then at x125, but I couldn't see it at higher mags.

Chris

[alan potts]

Well done on Trapezium F star Chris, it can be tricky. I am really down in the dumps with weather conditions, very poor seeing for me, really bad last night, none of my scopes see through clouds.

I have struggled this year seeing E&F trapezium together, I done it once but that's it. last year I could do these things at will. The weather is very strange, two days ago it was 25 degrees at two in the afternoon, it is normally no more than zero at this time of year. Since New Year we have only had one cold night and that was only minus 2, odd.

I will keep trying Sirius as it looks as if there is a bit of a following on this subject, I feel it is one of the very best double targets in the sky, it is addictive but it gets me angry sometimes.

Alan.

[Moonshane]

weird how things work. I see E&F routinely in my 12" dob but no hint that I am happy with yet of the pup.

[chiltonstar]

weird how things work. I see E&F routinely in my 12" dob but no hint that I am happy with yet of the pup.

...may be a magnitude issue; I'm only looking with 5" aperture, so Trapezium E & F require a night of good transparency (last night was, after the rain) as well as good seeing. I believe that Sirius B is a lot brighter than E or F and therefore (against a dark background) easier to see in a 5", but of course conditions giving good optical contrast are necessary to pick it out from the halo around Sirius A.

Chris

[Joves]

Well done on Trapezium F star Chris, it can be tricky. I am really down in the dumps with weather conditions, very poor seeing for me, really bad last night, none of my scopes see through clouds.

I have struggled this year seeing E&F trapezium together, I done it once but that's it. last year I could do these things at will. The weather is very strange, two days ago it was 25 degrees at two in the afternoon, it is normally no more than zero at this time of year. Since New Year we have only had one cold night and that was only minus 2, odd.

I will keep trying Sirius as it looks as if there is a bit of a following on this subject, I feel it is one of the very best double targets in the sky, it is addictive but it gets me angry sometimes.

Alan.

Have you managed to see the pup in the past, Alan?

[John]

I can see E & F often with my ED120 refractor, very occasionally with my ED102 (the E often though) and both usually stand out really strongly with my 12" dob and I'm peering around for the 14th mag G (no luck so far though !)

To date only the 12" dob has shown me the Pup star although I feel that the ED120 has been very close at times.

[Joves]

That's interesting, John. Seems I've been pushing the proverbial uphill trying to see it with the TV-76. I was hoping I might have better luck with the Genesis, which I'm sure will have a better chance than the 76, but even that seems like wishful thinking.

I should probably use this as motivation to reacquaint myself with the LX90.

[chiltonstar]

I rather like the paper referenced above which looks at the maths of seeing a faint double star in the presence of a bright companion. It uses a probability approach which to me sums up the situation very well; in other words, if my understanding of the approach is correct, it's not that you won't see the Sirius split with a small scope, just that your chances of seeing it are much lower than with a larger scope, all else being equal. Certainly matches my experience; I've looked a fair number of times at Sirius with my ED80 and seen the split clearly only once, whereas I've seen it in my 5" Mak a few times now, and each time is a little easier because the Mk 1 has been trained to know what to look for. Still needs a night with excellent seeing though, and no dewing on the optics.

Chris

[alan potts]

Joves,

Yes I have seen it a good many times, last year it was a nightly split, this year though is a different matter, but I am playing a little game to try and crack it as the UK would see it, or at least at the same declination.

I have just split the pair but it was at 23 degrees above the horizon and that is higher than it gets in England, so not within my rules. Oddly the star was jumping around like a electric arc up until it was 18 degrees high then all seemed to carm down and after half an hour the split was reasonable to do on X120 with the 115mm APO. I was also really taken aback at just how clean the airy disc was with the 3mm Radian at X268. At the high power the star was there to see all the time without issue, but after it had passed the limit, so to speak so it don't count.

Juptiter was fantsaic as well, I have had very clear and steady sky tonight, well above about 18 degrees Dec.

Alan.