Sirius and a pup that is frightened of the dark

[alan potts]

Well never being one to give up on a something that is difficult I spent almost ywo hours with the little 70mm ED, which I have said I don't think is very good quality but this time I used the other one I have which is on the LX 200 as a finder. I have to say this one seems a bit better than the other using the same eyepieces, Delos 10mm ,6mm and 4.5mm.It only goes to prove that they are not all the same quality, one was bent when I got it so it mostly still is a little.

I think it would be nice me having drawn double blank if someone with nothing better to do and where the clouds permit have a go at it with an 80mm scope, I think Michael is going to try from Holland. After two hours I checked with the 115mm and it was still there, no one has taken it to the kennels to be put down.

Alan.

[John]

I could not split Sirius with my ED102 F/6.5 the other night Alan. The airy disk was pretty tight at 190x (Pentax XW 3.5) but I could not see the Pup. I may try my ED120 on it tonight, if it stays clear - that one is good for 250x when the seeing is good.

[chiltonstar]

I could not split Sirius with my ED102 F/6.5 the other night Alan. The airy disk was pretty tight at 190x (Pentax XW 3.5) but I could not see the Pup. I may try my ED120 on it tonight, if it stays clear - that one is good for 250x when the seeing is good.

I've had my ED80 and 5" Mak alongside each other - the Pup visible in the 5" but not the 80mm. I imagine that there may simply not be enough light hitting the eyeball to see the Pup with the smaller scope.....

Chris

[alan potts]

John,

I think the 120mm is the scope, my friend has one and I can't see a great deal of difference between his and mine, when you think you can buy 2 of them for the price and have enough left for a ethos, that is one good scope.

Chris,

I think this Mac of yours must be a very good scope for doubles, I am thinking of the 180mm version of these scopes for myself, then you can all have a drink on me because the wife will kill me, unless I can paint it white and kid her the GSO 150 RC has put on weight. I think the 80mm is big enough it is just the atmostphere need to keep still for a bit longer.

Keep trying with the 80mm Chris, I think from here it would be do-able.

I saw the pup last night with the 150 RC. I was using a magnification of X137 but it was easier to see at X105. What I find odd is when I go to the magnifications that John has to use I loose it altogether in the Rock Band light show the star tends to perform in. This can only be location.

I want to get something going with Antares now it is coming up earlier each night, John is knocking down the nearby houses as I write. No only joking , but he is going to give it a try a SGL 8, I hope they have the weather and the seeing.

Alan.

[alan potts]

Last night had 25mins on Sirius with the115mm, it seems to be easy with this scope, I can only think the optics are that much better than anything else I have, It always seems to be there in the 190mm M/N so I guess that can't be too bad either.

I wanted to stay out for Antares but got beaten in by the cold minus 7 and the wife telling me I should be in a mental hospital about every 10 minutes.

Alan..

[michael.h.f.wilkinson]

Had a good try last night in Tenerife with a C8 without success, conditions not really good enough for a tight star image. The Trapezium E & F were easy enough.

As I posted above, I used a red filter to cut down bad seeing and reduce atmospheric refraction. It really did the trick (still not easy though).

[alan potts]

Last week before the Moon was getting to high up in the night sky I was able to repeat the observations on Sirius A&B with three dfferent scopes. What I was doing was again observing this as it darkened, it was much easier to see the two stars before it got totally dark and the later it got the more difficult it was.

The 3 scopes were the 115mm refractor, GSO 150mm RC and the 190mm M/N. I was using magnification between 60-100.There is no doubt in my mind the more southern location I observe from helps no end, and the further south one goes the better, to a point.

I am going to try and pick up a cheap red filter on the back of advice from Michael, the annoying thing is I had one and gave it away, it was a camera filter and I never thought the two threads were the same, pays to check these things.

Sirius is past its best now and is setting earlier every night though it is still fairly high for me. Now my attention is turning to Antares which is rising earlier every night, this is a double I have never done but it should be doable with my scopes. It is sadly another star that never really gets high enough in the UK and don't get that high for me, well not as high as Sirius, it also seem to suffer scintillation as bad if not worse than the Dog star. This could just be down the hotter spring and summer air being more turbulent than the cold winter nights.

I would dearly like to hear from anyone that has cracked Antares as there is no such thing as knowing too much about these doubles and any advice would be most welcome.

Happy double hunting,

Alan.

[John]

I would dearly like to hear from anyone that has cracked Antares as there is no such thing as knowing too much about these doubles and any advice would be most welcome.

You are getting demanding Alan - I'll have to demolish a school to get a clear view of Antares. I'm not going to be popular around here

Can we find some circumpolar challenges please ?

[alan potts]

John,

The school will have to go. I think this is harder than the Pup split. It is meant to red and green secondry, I see the greeness but this could just be an effect of scintillation. I am not sure how high Antares gets from where you are in England but I think it is lower than Sirius and if thats the case it is going to be difficult, even after you have knocked the school down.

Circumpolar challenges, don't forget the star in the middle of M57, I will be trying that again.

Alan.

[michael.h.f.wilkinson]

I will give Antares a shot from Italy this summer. Should be a lot easier from there. The separation is smaller, but the difference in brightness is lower, and the colour difference may help.

[alan potts]

Michael,

Do you know the full infomation on gap and brightness? You should have about the same latitude as me from there but depends whether North or South Italy.

Alan.

[michael.h.f.wilkinson]

I will be in Tuscany.

The separation is just below 3", the main star is red and mag +0.96, and the companion is blue (or blue green) at mag 5.5 (B2V, I believe), so just 4.5 mags difference

[alan potts]

Michael,

Thank-you for the info, it is fairly tight then but nowhere near the limit of any of my scopes. I am sure the warm air turbulence will not help this and the scintillation. It is one of those doubles that if it were over head like Vega can be, we would not be writting these lines. Surely I should be able to see this with the LX, but so far never have, but I am bnot giving up.

Alan.

[chiltonstar]

Alan - if you get bored waiting for Antares to show itself in all its beauty, have a look at Porrima and Zeta Cnc if you haven't already.......

Chris

[John]

Delta Cygni is another close and unequal brightness one

[alan potts]

Chris, I will give these two a go when the clouds clear off which looks as if it will be today. I will also have a look at Delta Cygni again. I like the summer constalations but with being up every morning a 05.00hrs it is late for me before getting dark now, I like to sleep about 10.30, getting old. Its now 13.20 just been mixing concrete and I think I'll go and have a kip.

Alan.

[Moonshane]

Maybe I should give my 80mm F/6 a shot on the pup.

funnily enough I was looking at Sirius again last night as I have never managed a split. the big dob (16" f4) was used and there was no chance, the seeing was quite poor. I use an off axis aperture mask on this scope with a 170mm, 130mm and 100mm apertures these give f11, f14 and f18 respectively. the 100mm in particular reduces the exit pupil markedly and at 184x is around 0.5mm. to my surprise with the 100mm aperture I was pretty certain I managed a split but I'd like to verify this with further sightings and comparison with Rigel. I have to say that the double star images with 100mm aperture at f18 are really very nice. classic round stars with 'airy rings' as I call them;not sure if that's the right terminology.

[Moonshane]

Delta Cygni is another close and unequal brightness one

one of my faves is Izar, Epsilon Bootis. Beautiful yellow with blue green secondary. not a big challenge but better than Alberio in my opinion.

[alan potts]

Nice one Shane, it is not always aperture after all, I believe the secret is having it all under control, I have never split this with my 12 inch from a better location.

Alan.

[chiltonstar]

funnily enough I was looking at Sirius again last night as I have never managed a split. the big dob (16" f4) was used and there was no chance, the seeing was quite poor. I use an off axis aperture mask on this scope with a 170mm, 130mm and 100mm apertures these give f11, f14 and f18 respectively. the 100mm in particular reduces the exit pupil markedly and at 184x is around 0.5mm. to my surprise with the 100mm aperture I was pretty certain I managed a split but I'd like to verify this with further sightings and comparison with Rigel. I have to say that the double star images with 100mm aperture at f18 are really very nice. classic round stars with 'airy rings' as I call them;not sure if that's the right terminology.

Shane: I suppose this may be down to how much of the light in the star image is in the central Airy disk; with a 'frac or an apertured-down Dob it will be close to 84% (Norton's), but lower with a centrally-obstructed system like a Dob in normal mode. The light not in the central disk is spread out over the diffraction rings, making the wee Pup more of a challenge??

Alan: re aperture - agreed! My little ED80 humbled a 200mm Dob a few weeks back; in a side-by-side, Cassini was easily visible in the smaller scope, but not in the 200mm!

Chris

[John]

I managed the Sirus split again last night with my OO 12" F/5.3 dob. The 6mm BGO was the EP of choice again although the Pup was also visible with the 5mm BGO although not as consistently as with the 6mm.

I'm convinced that the curved secondary vanes are helping in this case as Sirius does show a pretty tight disk and minimal scatter. The high quality primary mirror will be helping a bit too I guess !

I must give it a go with my ED120.

[Moonshane]

that's definitely a future project John, making some curved vanes either like yours or my own design.

[alan potts]

I don't know John even no vanes with my 12 inch don't seem to make any difference. Maybe when I have a 12.5mm Hutech or BGO under my belt for next year or later this that will make the difference. Well again to both of you. How are you getting on knocking the school down for Antares.

Alan.

[John]

I don't know John even no vanes with my 12 inch don't seem to make any difference. Maybe when I have a 12.5mm Hutech or BGO under my belt for next year or later this that will make the difference. Well again to both of you. How are you getting on knocking the school down for Antares.

Alan.

The school is still standing !

Back on the scopes, would the size of the secondary in the SCT affect the tightness of the stars disk and amount of light scatter ?. My 12" has a secondary which is 21% the diameter of the primary. I believe an SCT's would be something like 33%.

[alan potts]

John,

I don't know the exact figure I have long since forgotten it. I am sure you are on to something though, in any case I firmly believe the optics in your scope will be better than in mine, I don't really think they are all they are cracked up to be, decent but nothing exceptional, I believe now for the money you can do better. I have checked and as far as I can tell the hub holding the mirror is 102mm across and the collector is 305mm.

Alan

In the last post I did mean to type Well Done to both of you!