drawings of obscure summer objects
Posted 17 November 2009 - 11:50 AM
Last summer, I managed to get some good observing sessions under transparent and somewhat preserved skies in the french alps and directed my 17.5" dobsonian towards off-the-beaten-path targets. I made detailed draft drawings at the eyepiece at night and final copies at daylight.
First night was August 15th with great "dark-sky" conditions at 09:00pm UT and I spotted a faint object from Sagittarius (LEDA 932285+932333) : galaxy or planetary nebula, this is hard to tell ! This object was pointed by Matthias Kronberger from the DeepSkyHunters' group who described it as "The appearance of the nebula on the (blue) DSS-I image suggests a mild bipolar morphology; the red DSS-II image shows also a central star candidate immediately N of a superimposed star. Nothing in SIMBAD or NED at this position. VIZIER shows a double entry of the object in the LEDA catalogue of Paturel et al. (LEDA 932285 and LEDA 932333) but the object is clearly a line emitter and not a pair of (interacting) galaxies. There is no IRAS or radio source present at this position, which is probably one of the reasons why the object has remained unnoticed until now. The PN candidate is only 1.5 degrees distant from NGC 6818 (2Â° from NGC 6822) and easily found 6'N of the 7 mag star SAO 162831. I managed to observe the object last week with my new 15" under good transparency (ZLM ~ 6m,8 - 7m,0). Even without filter a very faint glow appeared at the position of the PN candidate. An OIII filter boosted the visibility of the object considerably and showed it as a roundish glow with approx. 20" size that could be held easily with averted vision. I also tried to see the two lobes individually but failed to do so, probably due the lack of contrast and the faintness of the object. The total brightness of the object I estimate to be ~15 mag, so it should be possible seeing it with apertures of 12" or even less."
The object is visible with averted vision (even on the screen...) just to the right from the faint star at center. I'am happy with the rendering because it is as difficult to see on the screen as it was behind the eyepiece !
My notebook says : "at 271x, small, extremely faint, seen 25% of the observing time at 271x, and still visible at 426x (also seen 10% of the observing time at 125x; it is round, about 12" in diameter, with soft edges and homogeneous; both UHC & OIII filters give a slight but definite contrast gain and there is a mag.15.5 star just outside of the E edge."
I will post another drawing tomorrow!
clear skies to all, Yann.
Posted 17 November 2009 - 01:15 PM
Posted 17 November 2009 - 06:08 PM
That is a tricky target to make out in your sketch. I had to spend a few minutes carefully viewing the area near the center of the drawing to make-out this elusive target. Congrats for glimpsing this difficult object.
Posted 18 November 2009 - 02:33 AM
This night, some slightly obscuring high-altitude clouds are wandering but fading out gently as time goes by. Another tough target in Cygnus is PK 69+3.1 (K3-46). There again, not much to be taken : the nebula is only glimpsed shortly from time to time with the help of an OIII filter.
Here is my technical description : "11:30pm UT : at 426x and 333x+OIII, small, extremely faint, seen more or less about 1% of the observing time; round with ill-defined edges, about 24â€ in diam., OIII filter gives a slight contrast gain but UHC and Hbeta are of no help; a small hook of stars is seen 1.2' to the W."
see you tomorrow for a new drawing, the last of this first summer night (but there will be other nights!),
Posted 18 November 2009 - 09:20 AM
Terrific sketches with a hint of the object. I like these very much.
Posted 19 November 2009 - 03:31 AM
Here is what I saw from NGC 7013 : "at 333x, medium sized galaxy, seen 50% of the observing time at 80x, and still visible at 426x; about 1.8â€™x0.9â€™, elongated NNW-SSE, with diffuse edges and a brighter center; mag.10 star 0.8â€™ from the NNW edge, located in a riche stellar field and surrounded by an irregular diamond-shaped star-pattern."
When the moon finally rised, I noted a subtle halo surrounding Jupiter, proof of a less than perfect transparency which nevertheless didn't bothered me (certainly because of the lack of bright stars during my starhops at the eyepiece!)
The first night was over but see you tomorrow for the second one, with the first spiral of my summer sessions !
Posted 19 November 2009 - 01:38 PM
Excellent observations of interesting and obscure Summer deep sky objects. Your combination of dark skies and a quality large aperture instrument allows the detection of these objects. Thank you for sharing them with us all.
Your web site is excellent as well.
Posted 20 November 2009 - 02:34 AM
Posted 20 November 2009 - 03:01 AM
My first target was the delicated spiral galaxy NGC 6701 in Draco, and -at last- some details are visible: the beginning of a spiral arm to the West and a subbtle knot on the opposite side !
My description was as follow: "10:00pm UT - at 271 & 333x, small galaxy, medium brightness, seen on the verge of direct vision at 80x, and still visible at 426x; elongated WNW-ESE with ill-defined edges and a brighter center, about 52â€x24â€ in size. a draft of a spiral arm is seen 10% of the observing time with averted vision on the W side turning NNW and a central bar is suspected thanks to a subtle knot (HII region or star?) 15â€ESE from the nucleus ; a mag.11 star stands in the direction of the ESE extension 18â€ from the edge and another of mag.9 is 5â€™ to the E."
Tomorrow another drawing : the first couple of my summer sessions !
clear skies to all, Yann.
Posted 20 November 2009 - 09:36 PM
Tremendous job on NGC 6701! I really enjoy your description and more importantly how that translates into your sketch. Nicely done.
Posted 22 November 2009 - 11:11 AM
Posted 22 November 2009 - 11:21 AM
NGC 6835 (up in the drawing) was "small, faint, seen 100% of the observing time at 80x and still visible at 426x; edge-on ENE-WSW, with diffuse edges and a brighter center; about 1.2â€™x0.3â€™. Clumps (or irregular surface brightness) are guessed mais not verified, and NGC 6836 stands 7.3â€™ to the S." NGC 6836 (down in the drawing) was "small, very faint, seen 50% of the observing time at 80x and still visible at 426x, round with ill-defined edges, homogeneous; very diffuse and not condensed, about 0.8â€™ in Ã¸."
Tomorrow will, the post will highlight a strange target !
clear skies to all, Yann
Posted 23 November 2009 - 05:46 PM
Excellent observations of these faint galaxies in Draco and Sagittarius. They make fine targets for large aperture Dobsonians such as yours. Thank you for sharing them wit us all.
Posted 24 November 2009 - 02:21 AM
Posted 24 November 2009 - 02:33 AM
My notes tell : "at 333 & 426x, very small nebula, extremely faint, seen about 10% of the observing time at 333x; round with well defined edges, homogeneous and about 10" in diam.; stars of mag.15 are 20" to the S 30" to the NNW."
See you tomorrow for another interacting couple !
Posted 26 November 2009 - 01:45 PM
My notes about NGC 770 : "at 271 & 333x, small to medium sized galaxy, faint, seen on the verge of direct vision at 80x and still at 426x; somewhat oval N-S with ill-defined edges, brighter to the center until a stellar nucleus; about 0.7â€™x0.5â€™ ; NGC 772 is 3.7â€™ to the N (center to center)."
An about NGC 772 : "at 271 & 333x, large galaxy, medium brightness, steadily seen with direct vision at 80x and still at 426x; oval WNW-ESE on the whole with ill-defined edges, brighter to the center; about 4.8â€™x2.0â€™; "spirality" more obvious at 125 & 154x; Northern arm going W and extending far from the central mass, seen 25% of the observing time at 125 & 154x; Southern spiral arm suspected less than 5% of the observing time (glimpsed a few times only during 30 minutes of visual inspection), going E on a shorter distance than the opposite one."
Very interesting pair indeed with this aperture, well beyond simple binarity !
Posted 26 November 2009 - 11:44 PM
I came back to see more of these excellent sketches. Very well done.
Posted 27 November 2009 - 01:49 PM
An excellent pair of observations of interesting targets. NGC 770/772 make a fine pair to study. Thank you for sharing them with us all.
Posted 28 November 2009 - 01:56 PM
My notebook gives the following description: "at 271 & 333x, small and faint, seen 50% of the time at 80x and still visible at 426x; splindle shape E-W with diffuse edges and homogeneous brightness; about 47â€x12â€ ; with difficulty (about 5% of the observing time with averted vision), the Eastern end is thinner than the W one; a mag.14 star is 20" from the SW galaxy border."
The second night was then over and we will start the third tomorrow !
clear skies to all, Yann.
Posted 29 November 2009 - 10:53 AM
The interactive couple NGC 6255 & HS 1653+3634 in Hercules was the starter from this night's menu. This barred spiral and its blue compact emission line companion offered a quite detailed view through the 445mm dobsonian, with its main caracteristics visually reachable (bar, halo and binarity).
Description of NGC 6255: "at 271 & 426x, medium sized galaxy, very faint, seen 100% of the observing time with averted vision, and still visible at 426x, oval E-W with ill-defined edges, of homogeneous surface brightness except for a brighter central bar; about 1.7â€™x1.1â€™ of overall shape, with HS 1653+3634 in the direction of the E extension, only 10" from the border."
Description de HS 1653+3634: "at 271 & 426x, very small, extremely faint, seen 50% of the observing time with averted vision and still visible at 426x; oval E-O with very diffuse limits and a brighter center; about 18â€x14â€."
see you tomorrow for the main plate of the night's menu !