Observing Report 18th/19th/20th September

[lunator]

18^th September (Seeing III/V, Transparency III/V)

After 3 weeks of cloud the sky was finally clear and I managed to get some observing time in. I was not going to do anything too complicated as I just wanted to get some observing under my belt.

I thought I would start in Hercules as it is high in the West and has a nice selection of doubles. I started at Alpha Herc. A well known pair easily split despite the difference in magnitude. In the 24mm Hyperion the pair were easily split with a lovely surrounding set of field stars.

The next target was Delta Herc. Just to the North West of Alpha. This pair is also easily split in the 24mm (x94). The pair are again in a relatively rich field of stars and with a bright white primary and a faint orange secondary.

The third target was Mu Herc. this is a multiple star with the primary being a quite bright yellow pair and the secondary being a much fainter orange pair. The secondary is a double consisting of 2 red dwarf stars close together. The seeing was limiting magnification to around x250 and I could get this pair elongated but not split. One for a better night.

Hercules was dropping into the murk that is the ‘Richmond light pollution dome’ I moved onto one of my favourite doubles Pi Aquila. This is a pair 1.4” apart. They were easily split at x250 and were still split at x125 (18mm Orthoscopic). The pair consist of 2 yellow star with a small difference in magnitudes.

Whilst in the area I had notice on the Cartes Du Ciel that near Pi Aqr was the neglected pair HJ1435 which hadn’t been measured since they were 1^st discovered in 1828. I thought as I was ‘in the area’ I would have a crack at finding this pair. The WDS data gave the following info

HJ1435 1828 8.0”/293 11.00/11.00

I used the 24mm eyepiece which gives about 0.75 of a degree and slowly scanned North West of Pi Aqr. The pair HJ1435 is just under a degree North West of Pi Aqr and using the star field from CduC I was able to find the right field. Sure enough there was a double there and they were both around 11^th magnitude.

Using the microguide and no Barlow I measured the PA as 295^o and the separation of just under 2 divisions. This gave a preliminary separation of about 13”. The stars also known as TYC 1065-00930-1 & TYC 1065-00936-1

they are a good fit to the WDS parameters except for the separation.

I finished the evening off with a look at Albireo which is always a great view.

19^th September (Seeing III/V, Transparency II-III/V)

This night was slightly clearer than the 18^th and my main aim was to re-investigate the HJ 1435 pair.

I started in reverse order from the 18^th with a view of Albireo. It looked fantastic in the 24mm (x94) and I also used the microguide to measure the separation. This was around 4.5 divisions. This seemed to be consistent with the measure of HJ 1435.

I moved down to my candidate pair for HJ 1435 and took some further measures. This came in with an average PA of 295^o and a separation of just under 2 divisions. Whilst I was in the area I noted AG389 a fairly wide pair of 8^th & 11^th magnitude.

Once I had made these measures I moved onto the double H N 84 a wide double about a degree SSW of Beta Sagitta. This is a very good analogue for Albireo with a yellow primary and a blue secondary.

I then moved onto ‘The other double/double’ in Delphinius. The pair STF 2725 & 2727 (Gamma Del) in the 24mm both pairs were easily split and the rich background field complemented the bright pairs. A great view in a low powered field.

I finish the night in Equuleus with a look at STF2735 & STF 2737. The first pair is a tight (1.9”) pair of about 1 magnitude difference. They were nicely split in the 9mm Ortho x250. The second pair was Epsilon Equ and is a nice easy split in the 24mm for the AB-C components. The AB pair could not be split but at 0.7” the seeing was upto it.

20^th September

This night was a night to start getting ‘scientific’ I needed to get the microguide more closely calibrated and to see if the star diagonal affected this in any way.

Before I started my Mother in Law who is living with us at present wanted to see a couple of objects so I showed Her M57 and Albireo. See was impressed by both objects.

When I was back on my own I started the calibration programme. The chosen stars were Albireo, Beta Lyrae, Epsilon^1/2 Pi Aqr, Gamma Del.

The process involved aligning the stars in the microguide with or with the star diagonal. Measuring the position angle using the drift method and when the PA agreed with the WDS measuring the separation in terms of the divisions of the microguide.

The separation was not affected by the star diagonal as it appears the additional piece I used when observing without the star diagonal was about the same length.

I also added a 2x Barlow to give me a focal length of 4500mm

From previous analysis the scale constant without a Barlow was 7.8” per division and this was further confirmed with these results.

This is a table showing the results

Star Divisions Separation “ per Division Note

Albireo 4.4 34.7 7.9

Albireo 10.5 34.7 3.3 2x Barlow

Beta Lyra 5.9 46 7.79

Pi Aqr 0.4 1.4 3.5 2x Barlow

Gamma Del 2.8 9.1 3.25 2x Barlow

Eps Equ 3.1 10.5 3.38 2x Barlow

Average 16.8 55.7 3.3

The average gives a scale constant of 3.3” per division.

When I compare the scale constant of the OMC with and without a Barlow and my old Newt with the 3x Barlow they do fall close to a single trend-line.

2250 fl = 7.8” per division

3600 fl = 5.7” per division

4500 fl = 3.3” per division

[mik]

A very informative and interesting report thanks for sharing

Mick..

[lunator]

Cheers Mik

I hope to get a some more observing in tonight but the clouds are hanging around abit...

[starf]

hello ian, sounds like you had a fair few sessions with some nice observations.

your eyepiece seems a useful bit of hardware if your into measurements of any kind, but i just saw how much they sell for and decided to go and have a cup of tea instead :-)

regards

mike

[lunator]

Hi Mike

I got mine secondhand and it cost £70.

Funnily enough I was wondering how the baader compared to the microguide whilst I was taking the measurements.

Cheers

Ian