“Do Dz” asterisms in Hercules
Posted 14 September 2021 - 08:46 PM
I’m just starting the Asterisms observing program with the astronomical league, and I’ve been collecting information online for some of the more obscure asterisms. The required list mentions several “Do Dz” asterisms (numbered 5-8) in Hercules, but I can’t find any information online about these when doing a Google search. Does anyone know about these or where I can find an original reference?
Posted 14 September 2021 - 08:59 PM
Thanks! I just found that article too. Looks like the DoDz "clusters" were discovered by Dolidze and Jimsheleishvili, and the S&T Oct 2015 article may provide more info.
Posted 14 September 2021 - 09:25 PM
Well, as luck would have it, my copy of the book "Deep-Sky Wonders" by S&T (2020) describes every one of these Dolidze-Dzimselejsvili clusters, along with all of the other asterisms mentioned in S&T articles over the years. I just answered my own question....love it when that happens.
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Posted 14 September 2021 - 10:10 PM
Here are my notes of the DoDz's in Hercules using an 18" f/4.3 Starmaster. These kind of asterisms don't usually interest me, so I'm sure they were fairly quick observations.
DoDz 5: ~20 brighter stars in the field of the 13mm Ethos including a nice double [11.6/12.9 at 8"] and a wide bright pair [11.3/11.8 at 32"]. Includes a number of mag 9-10.5 stars but there are no rich regions and this group appears to be an asterism.
DoDz 6: this is a group of 6 brighter stars in a distinctive, elongated group (SW-NE). Includes a wide pair of mag 9 stars [54" separation] with three mag 10-11 stars to the NE. At the SW end is the faintest mag 13 stars.
DoDz 8: bright, scattered asterism constisting of 7 mag 8-10 stars forming a distinctive 14' group. Most of the other stars within the boundaries are 13th magnitude. The brighter stars form a nice group in the 80mm finder at 25x.
DoDz 9: at 105x this is a very nice scattered low power field but does not look like a cluster. Most distinctive is a wide pair [mag 8.2/9.2 at 52" separation]. The pair is oriented WNW-ESE and perpendicular to a 10' string of four mag 9-10 stars to the west oriented N-S. Off the south end of this string is a 4'-5' group of fainter stars that are fairly uniformly distributed. The star at the N end has 3 or 4 nearby companions. The field also includes a number of mag 9-10 stars to the N and NE of the bright pair. I would place the center of the field at roughly 18 08.7 +31 36, which is 6' further N than the catalogued position for DoDz 9.
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Posted 14 September 2021 - 10:15 PM
Posted 15 September 2021 - 02:37 PM
Many star clusters that look like random arrangements of field stars in large scopes look like star clusters at 16-17x in an 80mm scope.
This is one (out of many) reasons to keep a small refractor handy as a second scope when your primary scope is 10" or larger.
Some classic examples:
--Cr399, The Coathanger
--M45 The Pleiades
--M44 the Praesepe cluster
none of those is particularly engaging at 100x in a dob, but is fantastic in a small refractor at 16-30x.
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Posted 16 September 2021 - 03:25 PM
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