Author Topic: Lake Sonoma 9/16/17  (Read 325 times)

dnsmiley

  • Observer
  • Posts: 23
    • View Profile
Lake Sonoma 9/16/17
« on: September 17, 2017, 09:43:55 AM »
I observed last night at Lone Rock parking lot at Lake Sonoma. There was a nice turnout, more than a dozen observers and some large scopes including two 20+" StarStructures. This was only my second time at Lake Sonoma, a few people said it was one of the largest gatherings they had seen in this location.

Compared to my first visit two months ago on July 24, transparency and darkness were noticeably worse, probably from residual smoke and haze from wildfires. The Milky Way lacked the clarity and richness I remember, but nevertheless I enjoyed hunting down a few new targets, mainly some globulars in Sagittarius I don't remember seeing before including NGCs 6638, 6528 and 6522 and revisiting favorites M28, M22, M2 and M15. NGC 7331, galaxy in Pegasus, was nicely shown in my C8 at 85x as elongated with a bright central area, but I didn't glimpse any of its companions. I had Barnard's Galaxy NGC 6822 on my list. I thought I glimpsed it with 7x50 binoculars, but couldn't confirm. I could not see it either with the C8 or a TeleVue 76 APO. It will have to await a better night I suppose.

Using my Lumicon O-III filter from back in the 90s, I saw the western portion of the Veil Nebula around 52 Cygni as beautiful "smoke" draping and rising from the star, but the view in my neighbor's 8" achromat of the eastern Veil also with filter was much better, and many more stars were visible. Do O-III filters degrade over time? Mine seemed too aggressive in blocking light.

My friend and I packed up as the Pleiades were rising. Even if transparency seemed a bit lacking, it was a wonderful night meeting some old friends and making new ones, both of the human and astronomical kind!

satterwill

  • Observer
  • Posts: 6
    • View Profile
Re: Lake Sonoma 9/16/17
« Reply #1 on: September 17, 2017, 11:25:48 AM »
Filter transmission characteristics can change over time, but are you sure that the 8" achromat was also using an O-III (even then, not all O-III filters have equally narrow passbands) as opposed to something like a UHC or NPB filter that will pass a few other spectral lines as well, resulting in brighter (less dimmed) stars?

dnsmiley

  • Observer
  • Posts: 23
    • View Profile
Re: Lake Sonoma 9/16/17
« Reply #2 on: September 17, 2017, 11:57:27 AM »
You are probably right, I'm thinking it must not have been an O-III filter, but I thought O-III showed the Veil best? I was impressed with the view.

John Pierce

  • WebHack
  • Administrator
  • Observer
  • *****
  • Posts: 308
    • View Profile
Re: Lake Sonoma 9/16/17
« Reply #3 on: September 17, 2017, 01:55:42 PM »
I've gotten my best view ever of the veil using a DGM NPB filter, on a 18mm in a 20" f/5 Obsession...  this filter passes deep red in addition to o-III and hbeta, so the parts of the veil that photograph as red/pink show up too, while a pure narrowband O-III filter only shows you the parts that photograph as blue-green.


dnsmiley

  • Observer
  • Posts: 23
    • View Profile
Re: Lake Sonoma 9/16/17
« Reply #4 on: September 18, 2017, 05:12:25 AM »
I may have to get one of those, sounds good. I will say I have enjoyed the Veil with unfiltered 7x50 binoculars at a dark site, wonderful wide field view.