One double star, two refractors

[John Baars]

It was quite clear two nights on a row. Seeing on the second one a bit worse, but still good. I did some nice exercises with my two main refractors, the 150mm f5 on the first night and the 120mm f7.5 the second one. High magnifications gave no problems. On both nights I saw almost the same objects, most of them being Summer objects already.

Because of Daylight Savings it became dark around 23.30 hrs local time, but since my working days are over I don't have to be an early bird any more. To my great comfort. I began at 22.45 hrs, the sky still illuminated a bit by the sun. As always I took my time for some startesting. I always check the 150mm since I repaired it in the past. Everything was all right and I went on with double stars. Epsilon Bootes or Izar is a grateful object. So is Delta Cygni, which was a startest for 4 inch instruments a century ago. Great object when the sky is still not dark enough. Near NGC 6210, the planetary Turtle nebula, is a close double star. Near the right arm of Hercules. SAO 84572 or HD151070 or STF 2094. Magnitude 7 and 7.9. Separation 1.2 " That is close enough for separating a toy with plastic lenses from a real telescope.

I decided to have a close look through the 150 mm f/5 and another look on the next day through the 120 mm f/7.5
I did the same in the past, but always under less favorable seeing- and transparancy circumstances. I was a little bit surprised to see how good the 150 mm did the job. I was used to a somewhat "sloppy" separation, due to the seeing. This time was a very nice one, with the airy discs less smeared than I remembered. I magnified up to 300X, for a comfortable look, although I already saw them separated at less than 200X in both instruments.

Here is the image of SAO 84572 with the 150 mm.

SAO 84572 in 150 mm V300X.jpg (6.52 KiB) Viewed 1182 times

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Same star in the 120 mm.

SAO 84572 in 120 mm V300X.jpg (838 Bytes) Viewed 1182 times

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It is obvious that the 120 mm ED APO gives a cleaner view. The 150 mm has somewhat more light glowing around the two stars. On brighter stars that is more obvious. The airy discs in the 150mm Fraunhofer are a bit smaller. No optical news under the sun, but this was the first time I could compare it under almost equal circumstances.
If you want to read more about my adventures with the two scopes: click here

My list of some objects of the two nights:

Epsilon Bootes, double star, easy.
Nasr Alwaki, Sulafat, Sheliak, easy, beautiful surroundings, Lyra is always a nice little constellation.
Epsilon Lyrae, double double, easy and a magnificent sight in Lyra
Delta Cygni, double star, easy under good seeing, testcase for 4 inch under less optimal circumstances.
SAO 84572, ultimate test case for a 4 inch. You'll need perfect seeing.

M3, M13, M92, M56, NGC6229, M71. Some nice globulars. M13 being the showpiece. NGC6229 forms a nice triangle with two magnitude 8 stars.
NGC 6229:

NGC 6210, M27, M57, planetaries. As usual M27 is splendid with UHC filter. The 150 mm wins the game on M27 by far.
NGC6210 near SAO 84527 :

Last , but not least T Lyr, a red carbon star, from Brett's Carbon Starhunt viewtopic.php?f=109&t=17906

Some sketches are from the past. But the objects haven't changed much. I checked

[helicon]

Great report and sketches John. Congratulations on winning today's TSS Visual Report of the Day for 5/31/2021.

[Makuser]

Hello John. A great report and comparisons with the 150 f/5 achromatic and 120 f/7.5 ED apochromatic telescopes. And, I also enjoyed your excellent sketches too. Thanks for posting this interesting report John, and congratulations on winning the TSS VROD Award today.

[Lady Fraktor]

Very nice report John, good comparison between the two telescopes as well.

[Bigzmey]

VROD is well deserved for this fine sessions and report John.

I did similar comparisons on doubles in the past between Orion 120mm achro F5 and ES APO 102mm F7, and Celestron 150mm achro F5 (similar to your SW) and ES APO 127mm F7.5. I should say that F5 achros are quite capable doubles splitters, however with APOs the views were sharper and cleaner and I often managed to split doubles with APOs at lower powers compared to achros.

[John Donne]

A very fine outing with lovely illustrations John !
I am pleased that you had these two opportunities to exercise these telescopes.
And congratulations on ypur VROD award.
Thank you Sir .

[kt4hx]

Very nice indeed John and congrats on the VROD for the 31st. I see you touched on one of the northern objects for the June edition of the monthly DSO challenge - NGC 6210. Appreciate the fine sketch of this beautiful planetary.

[turboscrew]

Congrats on the VROD!
I wish I could see something too, but the Sun doesn't go further than 6° below horizon.
Even Vega is far too dim to be seen in the bright night sky.

When it comes to light pollution, Sun is hard to beat.