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6th Feb 2013 - On with the doubles

Guest Ely Ellis

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Guest Ely Ellis

Wednesday 6th Feb 2013

I have given up on watching the weather forecast and just take to looking outside occasionally.
Just before 20:00, I poked my head through the curtains and noticed the wonderful clear sky, so time to grab the scope and setup.

So, mount outside, scope fitted, quick polar align, then switch on and do a mount align. Decided to add some more images to my doubles so rather than align and then fit the camera, I carried out the mount align with the camera on the scope, which was a doddle this time as all alignment / calibration stars were within the camera frame.

As mentioned in previous reports, I have a total blank to the West from North to South, so could only view East. Leo was nicely position so I loaded Nexstar Observer List and filtered out the impossible. I then began to work my way through the list of doubles.

A start with 54 Leo, a nice bright double of 4.5 and 6.5, but with a separation of just 6" made this not so easy to split, however I did return to it later in the evening for a visual and even on a 25mm EP it was clear and easily split.

Next, 3 Leo, a wide separation of 25" made the split easy, but due to the difference in magnitude, 5.9 and 10.6, made imaging difficult. A very bright primary and very faint secondary, with the secondary just visible with an 8 second exposure.

Similar magnitude doubles are obviously easier to image, so I picked a few close ones, so next up was STF 1447, mag. 7.3 and 9.1, not a good choice as I could not split this at 4", the image gives an elongated star, so the double is there, but just not split.

STF 1442, at 8 and 8.6 with 13" split was an easy one, very easy to split both imaging and visually.

HJ 476, a little unsure about this one. Magnitudes of 8 and 10.3 with a separation of 24" should have been an easy target, but I imaged a fairly bright primary, but such a faint secondary, it is difficult to see even with an 8 second exposure. Maybe my data is wrong about the magnitudes or whether this is even a double or not!

STF 1582, a good double, fairly close mag. at 8.2 and 9.7, 12" separation was easy to image and split, but couldn't quite be sure when observed visually later.

STF 1360, another easy pair, 8.3 and 8.6 with 14" separation made this pair very easy both to image and visually.

That was it for Leo, but a quick swing round to my favourite winter double, 145 CMA, low on the Southern horizon, an excellent pair to view, with excellent colour and contrast difference. Unfortunately it's never very clear as it’s so low it suffers from atmospherics.

Ok, what now, still fairly clear so off to Ursa Major.

Start with Zeta UMA (Mizar), this is not the Mizar / Alcor split, although Alcor was in the same frame, but Mizar Aa and Mizar Ab. Both very bright, but easily split.

Next was XI UMA (ALULA AUSTRALIS), a bit ambitious with only 3" separation at mag. 4.3 and 4.8, no, didn't split it, I did get slightly elongated star though, which shows something there. Exposure times were down to 1/10th second but just couldn't split them.

57 UMA, another pair I just couldn't resolve. I could see slight elongation at 1 second exposure, any slower and too bright, any faster and it was barely visible. Magnitudes of 5.4 and 8.4 at 5.5" separation, I was asking too much.

STF 1520, back to the easy pairs, 6.6 and 7.9 with almost 13" separation made this an easy target and a nice easy split.

STF 1415, and another easy pair, 6.7 and 7.3 with a nice wide 17" separation.

STF 1544, 7.2 and 8.2 with almost 13" separation, similar to STF 1520, but slightly dimmer, but just as easy.

Finally, STF 1427, 7.5 and 8.0 with a 9" separation, nice and easy but strangely dim, of course when I looked outside, I found I was looking through the clouds, but I did get them.

So, at around 23:20 with the cloud rolling in, I thought a good time to call it a night. I did do some visual too, as I like to see if I can split these with my own eyes. Some of the difficult ones with the camera were possibly visual but using averted vision, so could not be 100% sure.

One mistake I made was to fit my UHC-S filter in line, which seemed to create larger halos around the stars. So, I won't be using that again.

I will post some images when I have done some cropping, although not wonderful objects like the DSO's, with most having very little colour differences, they may be of some interest.



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