Observation Report: 25th December 2007 (technically 26th)

[goober]

Time: midnight - 1am
Transparency: 7/10, but a large waning moon
Seeing: 6/10

Christmas Day, and despite driving 245km during the day (West Rosebud for lunch and Lilydale for dinner), I couldn't let a nice clear and steady sky go by. Five minutes setup time, and I was out and observing. The moon has washed out deep sky for me, so I bagged some doubles while waiting for the scope to cool.

Rigel: becoming my standard "evaluation" object. Nice easy split, seeing looked to be quite good. Nice, crisp star at 270x - no boiling or shimmer.

Eta Orionis: tight double for the 4", but a nice dumbbell shape at 192x and split cleanly at 270x.

Altinak: quite similar to Eta Orionis in terms of separation, nicely split. There is a bit more gold/yellow colour in this one though.

Sirius: started at 385x - basically a big, boiling mess of dazzling light. Stepped down to 270x and thought I spotted a companion star quite tight in against Sirius. Couldn't confirm it, and couldn't get it back again in the shimmer. Spent a bit of time looking for it again, but couldn't spot it. I'll look up the separation and PA, and be better armed next time.

Trapezium: six stars, quite easily tonight. E and F winked off a little from time to time, but they were there more than they weren't. I was surprised to see them, as I was very tired.

Eta Carinae: popping up over the neighbour's garage. Had a good look at the star itself rather than the region, and could just make out the homunculus shape around it. In my 12" GSO dob it was a bright and obvious "balloon" around the star, but here it's merely hinted at. Be good to compare this next year with the object higher and the moon not there.

Mars: best view of the season so far. Nice, steady disk at all powers from 154x to ridiculous 385x. Best view in terms of detail vs magnification was at 192x, with a barlowed 7mm Nagler. I could see a two dark patches, separated by the predominately pink colour of the planet. One of the patches was triangular in shape, while the other larger patch seemed to band right around the "bottom" of the disk (I say bottom, but I'm not sure if it was N/S/E/W - too tired to try and work it out at the eyepiece). It was very subtle, but once I knew what to look for I could begin to pick out the detail. I'm not going to be bold enough to try and identify what I was seeing. I couldn't make out a polar cap. Basically, my best view of Mars this opposition, but 2003 was much better in the 8" Skyhopper!

Happy and safe New Year to all.

[§AB]

Nice report Doug. Obviously you had WAY BETTER seeing than I had! Nice steady disk of Mars at 385x - damn thats awesome! I can only dream of that (so far...) This seeing shambles must be pretty local then.

[goober]

Steady featureless disk would be a better description. But at least it was steady :)

[§AB]

^^ oh ok lol!

[ngcles]

Hi Goober,

Nice report mate.

Sirius is a very, very tough split in any telescope no matter how large. If it was easy, it would have been detected a loooooonng time before Alvan Clark found it in 1862. The big problem is the brightness difference which is about 9-10 magnitudes. I've seen it split twice I think in 36 years of observing and have tried dozens, if not 100s of times so don't be surprised at all if you fail. The last time I succeeded was a couple of years ago with my excellent 31cm f/5.3 newtonian (Suchting mirror) on a Samson GEM at x410 (8mm TV Plossl + Ultima barlow) in seeing I would describe as excellent -- 8-9/10 on the US scale.

At the moment the "pup" is virtually due E of Sirius in about PA 90, so using an un-driven dob it should follow Sirius across the field. The seperation is about 8 arc-seconds at the moment (almost as good as it gets) and won't increase much in the next several years.

To get a feel for how 8 arc-seconds seperation should look at the magnification you intend to use on Sirius, take a look at the pair in the centre of nearby M47 -- Struve 1121 which is about 8 arc-seconds (almost identical) so you get a feel for it.

Star image asthetics are of little importance -- pump it up as far as you can reasonably go in the conditions. Dust-free squeaky-clean optics are also a considerable advantage because they cut down on the scattering of Sirius powerful glare.

I've seen a great many of what appear (to me) to be "doubtful" reports on the net of seeing Sirius split using 4 to 6" 'scopes at comparatively low magnifications ~ in the order of x100 to x200 where the observer noted that it was "easy to see" -- or words to that effect. Though the observers I feel in the vast majority were "honest" I also think many report a "false positive" as a result of an internal reflection within the eyepiece of Sirius itself.

This seems to me to be particularly prevalent with the multi-element exotic eyepiece designs of today which are more prone to internal reflections (on exceptionally bright stellar objects) than say a quality old-fashioned orthoscopic or plossl. The Kellner is another (old) design well-known for internal reflections. If the pup wanders in PA and/or seperation as you move Sirius around in the field it is an internal reflection. I can remember several times when I thought I had it (and let out an exclaimation) and then moved the 'scope only to see the pup wander. An eyepiece with an occulting bar fitted at the field-stop is also a good though old-fashioned idea (you hide Sirius behind the bar).

I'm not trying to discourage people from having a go, give it a shot by all means but don't expect success so easily! It may indeed take months or years and I'd expect the absolute minimum (high-quality) aperture for success to be in the order of 20cm.


Best,

Les D
Contributing Editor
AS&T

[Rob_K]

Good report Doug! :thumbsup: Nice work on the doubles! I imaged Mars last night at about 12:30pm (UT+11) with my little scope, so it's probably not much different to what you were looking at (fuzzy & all!) - I've attached it as a matter of interest.

Thanks for that information too Les, on splitting Sirius. I know that my smallest EP plus Barlow (necessary to get anywhere near sufficient magnification) would completely kill any star ranging towards mag 9, let alone any other limiting factors. So I take your point that large aperture is required as a starting point. Have you ever split Procyon?

Cheers -

[ngcles]

Hi Rob & All,

I have tried Procyon many times (at least a few dozen) with a variety of telescopes and have never suspected seeing the companion.

Best,

Les D
Contributing Editor
AS&T

[goober]

Thanks for the advice, Les. There are also some good tips on page 66 of the latest AS&T - the guy there seems to know what he's talking about ;)

[goober]

Rob, thank you. That is a nice image. It pretty much nails what I saw, with much better contrast. Is the triangular feature Syrtis Major?

[Rob_K]

No Doug, the triangular feature at top is made up of Mare Acidalium (darker & closer to top) and Niliacus Lacus. The fuzzy sweep at bottom is made up of a whole suite of features including Sinus Meridiani, Margaritifer Sinus, Aurorae Sinus, Mare Erythraeum and Solis Lacus. Would that I could differentiate them, lol!

Cheers -

[§AB]

I used my Vixen LVWs to split Sirius, and I believe these lenses have 8 elements. There ARE internal reflections of Sirius, which DO look deceivingly like a companion star! The "real" pup is infact a very tiny dot and is difficult to catch amongst all that glare and those diffraction spikes. I highly doubt it could be seen in 4-6" scopes at only 100x as a few observers on other forums claim.

[goober]

I had a crack at Sirius last night before the cloud rolled over. 4" Apo, 270x, and I did see a faint star trailing Sirius. However, I think the separation was much too great to be Sirius B. I assume I'm looking for a separation similar to Rigel (around 7")?