Contact information

Ursa Astronomical Association
Kopernikuksentie 1
00130 Helsinki

Ursa Astronomical Association

Starry sky image - 4.8.2020 at 01.00 Hyvinkää Observation number 92538

Visibility III / V

Timo Inkinen, Ursa (Etelä-Suomi)

Delta Cygni is a cramped twin star in Swan in the middle of the Milky Way. Its components have magnitudes of 2.87 and 6.37 and their angular distance in the sky is close to Finland's winter seeing limit, ie two angular seconds (2 "). A larger image of this item will appear on my website and those percentages in the corners of the image are the scaling of the image from the original 100% image.

I have acquired a second lens telescope for my incoming season, especially for visual observations (TS 102 / F11 ED). The current TMB 152/1200 (LZOS) APO lens tube now remains largely in shooting mode without disassembling its camera for visual viewing. Each tube sees at approximately the same location in the sky and typically in the same size field of view.

In the optimal situation, I can now effortlessly visually observe the object of observation with that 4 "F / 11 lens tube and then take a photo of it with the adjacent 6" F / 8 TMB 152/1200 lens tube and my ASI 183MM Pro camera.

Basic information (and a little more) about this narrow double star can be found on this page:

The second image shows a night view of my backyard captured at the end of the observations. I personally find it sensible to move my selection of subjects somewhere other than deep sky subjects. Such brief, two-star observations allowed by a rapidly coming observational situation are one example of this transition.

More similar observations
Additional information
  • Observation target
    • Starry sky image
    • Keskitaso
  • Constellation
    • Cygnus
  • Weather
    • Seeing sattui olemaan havaintohetkellä erinomainen, kuten usein on sumun vallitessa taivaalla. Katsoin ja testailin näet uuden ED -linssiputken kuvalaatua hyvin suurilla 300...450x suurennuksilla ja olin tyytyväinen näkemääni selkeään Airy-disk näkymään, mikä kertoi selvästi tuon ED-putken rajat.
  • Darkness
    • Mediocre
  • Seeing
    • Excellent
  • Stars
    • Binary star info

      Binary stars are star systems, where there are two stars close each other. Binary stars are classified to optical or physical binaries.

      In optical binary star systems two stars are apparently close each other, but in reality they are located far each other in different distacies.

      In physical binary systems the stars are bound up with gravity and they are orbiting each other. Stellar systems with more than two stars are called multiple star systems.

      Binary star Albireo in Cygnus in composed of blue and yellow star. It is unknown if this of a physical binary. Image Mauri Korpi.


      M40 eli Winnecke 4 on Messierin luetteloon virheellisesti päätynyt tähtipari. Kyseessä on optinen kaksoistähti. Tähdet eivät siis ole fyysisesti lähekkäin. Kuva Tero Hiekkalinna.

      M40 aka Winnecke 4 is stellar pair incorrectly taken into The Messier catalog. It is an optical binary. Image Tero Hiekkalinna.

Technical information

TMB 152/1200 LZOS APO + ZWO ASI183MM Pro, TS 102/1122 ED (visual observations of that binary star that stood out very clearly on that tube).

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