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Some more doubles


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Couldnt be doing with hours of imaging last night so set about double star bagging in Gemini and Orion and had a really good couple of hours despite the counterweight slipping to its stop part slew, woke me up that one did :rolleyes:

A clear few hours this evening, very damp, seeing about 2.5 -3 not the best mainly due to high thin cloud, damp and high level turbulence.

Using the Meade 127 ED Triplet in the observatory linked to Skymap Pro11 I went on the hunt for some obscure doubles in Gemini and Orion.

STF 830 Gemini

2 very similar mag components (8 and 8.5) at a nice easy 12 arcsecs separation. The primary component looked yellow but I couldn’t really discern any colour contrasts in the secondary.

STF 889 Gemini

An obvious orange 7 mag primary with a yellow 9.5 mag secondary. An easy separation of 21 arcsecs. Again the colour difference was not easy to discern, atmospheric conditions maybe preventing this tonight.


8 and 8.5 with 19 sepeartion – unremarkable

20 Gemini (STF924)

A lovely yellow and blue almost equal mag pair at a comfortable 20 arcsecs separation. Mags according to the book at 6.3 and 6.9.

Nu Gemini

Binopair. The scope view at 50 mag was massive, a bright yellow 4.2 mag primary with a fainter orange 11.7 secondary at a really long 112†separation. A lovely sight.

15 Gemini

Just slightly off the FOV of Nu Gemini An obvious colour contrast of white / blue with mags of 6.6 and 8. The big 21.7 arcsec separation makes this a nice comfortable pair to split.

Epsilon Gemini

White and Blue at mags 3 and 9 with a big 110 arcsecond separation. A good looking pair in a nice background

STF 761 & STF 762 Sigma Orionis

These are an interesting grouping forming what appears to be a triangle. An unassociated mag 6ish star forms the head of a triangle with the 2 stars as the base about 2 – 300 arcsecs away. One of the base stars is 761 at 8 and 8.5 mag with an estimated 60 arcsecs split.

Halfway between the head star and 761 lies a multiple system 762 lying somewhat parallel to the base is the Sigma Orionis system A, B, C, D and E.

The brightest A-B are a striking 4 and 6 mag at a separation of 0.2, now this took some mag to split and had me squinting but stretching it with 200x I made out some dark sky between them at times of steady seeing.

Now the C component is 11.4 arcsecs away and at a mag of 10.3 shows a nice brightness contrast to the other members.

The 7.5 mag D component lies 12.9 arcescs away from AB and the E component at 6.5 mag lies 42.6 arcsecs away from AB.

All main components form a staggered line and together with 761 makes for an interesting field of view.

Alnitak STF 744

A very nice Blue White 1.9 mag primary component with a close mag 4 secondary at 9.9 arcsecs separation. These spilt quite easily with 100x. A third component at 2.4 mag lies quite a way off at 57.6. Could not discern colours in second and third components

STF 757

Now for a test of conditions, scope and eye. This is a triple but the primary is split by a 1.6 arcsecond gap but the 8 and 8.5 mag difference make splitting these a little simpler than if the secondary were faint. The 3rd component is a similar mag of 8.5 but is at 51 arcsecs an=d was easy by comparison.


Edited by philjay
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The Sigma Orionis system is one hell of great sight isn't it. I've looked at it with a variety of scopes over the years and I'm always impressed. AB is indeed very tight and have only managed it with the big dob. I bet it looked great through an APO, I will have to try it with my little 81mm triplet to see if that can split it, it's got a good chance as I Ibbo and I split one in Cancer which was 1.8".

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Fantastic write up Phil, as a newbie I think I am far off from giving these a go with the scope I have, but these write up's will serve as a future guide as and when I can get a whopper of a scope!!

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You know I never really thought much about doubles and multiples in the past, then when I got the F15 I just got hooked. A couple of hours going through the Cambridge Double Atlas or SAC database is very satisfying.

Tell the truth Mick this is the 1st time I have looked at Sigma Or and wow I never knew there was so much in it :)

Darren you dont need a whopper of a scope to hunt out doubles, my little 1964 vintage 60mm Swift scope (sadly sold now) was a little cracker at splitting em, the double double in Lyra was a synch with it.

Have a go with your Dob at Sigma Orion or Alnitak, quite easy to find using an atlas or planetarium software. Then of course there is Castor in Gemini a lovely multiple with great colour, youll like that one.

John, remind me to take you through Bootes doubles at SGL7, its loaded with em and is fascinating, I reckon that constellation has mnore doubles than singles.


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