Trying to find my nemesis

[RobertI]

My nemesis? I am talking about the Crescent nebula. I have tried to find this a number of times, although my efforts have been fairly ill prepared. In theory it is easy to find, being one third of the way from gamma Cygni to Eta Cygni and there is a prominent 'triangle of stars' to help find it. However I have never found said triangle or any sign of the nebula. So tonight, on a less than ideal luminous summer night,  I ventured forth,  with my 150PL and a 21mm Hyperion sporting a Astronomik UHCE filter - not the best filter for the job as it's designed for scopes of 5" or less but it does improve contrast signficiantly and it's all I have! Using my marvellous ES 8x50 straight though correct image finder, I located the area and tried to find the elusive Crescent. Again no sign of the triangle of stars, and after 20 minutes of looking and scanning, with observing hood in place, no luck. So I sought help from the internet and found a finder chart from Skyhound website. Comparing the chart with the eyepiece view I was gobsmacked to see the identical pattern of stars in the eyepiece - they were also in same orientation as the chart!! So I knew I was in the right place, now to see if I could see any trace. After a good half hour of staring, swapping eyes, moving the scope back and forth to increase visibility, I can confidently say that I could see.....part of it! I've indicated in yellow in the finder chart below the area I could see. I felt there were hints of the lower curve too.

 

I am hopeful that with my 8" SCT, darker skies and a UHC or OIII filter (both of which I'll have in the next week  or so) I'll be able to see more of the Crescent. A little project for the coming weeks and months.

I finished the session with a look at the Eastern Veil - frankly a piece of cake compared to the Crescent! The Veil was still pretty faint though and I have had much clearer views before - this just confirmed that conditions were really not ideal for seeking out the Cresent.

I'd be interested to hear other people's experiences with the Crescent.

[Stu]

Pretty tough at this time of year Robert. Once astro darkness returns I’m sure you will have more luck.

I first saw it in a 16” Sumerian Canopus at SGL10, nice views then, and subsequently in my 14” Sumerian Alkaid in which I think I saw more structure and detail; not sure if this was down to conditions or experience. In the Alkaid I could see the full curve and the central line, possibly some other faint detail too, can’t recall. Aperture certainly helps, as does a good OIII filter, I have a Lumicon which does the job well. As I recall, exit pupil plays a role too, a 31mm Nagler was better than 21mm Ethos on this target in the 16”, which equates to a 6mm vs 4mm exit pupil (f4.5 scope with SIPS which I think puts a x1.15 multiplier on the focal length). That was at a decently dark site though, about mag 21 SQM.

[RobertI]

32 minutes ago, Stu said:

Pretty tough at this time of year Robert. Once astro darkness returns I’m sure you will have more luck.

Thanks Stu, yes summer solstice is not the best time to observe faint nebs! I was pleased to finally locate it though - will motivate me to get out more in future. Good point about exit pupil, the 21mm is the widest practical eyepiece I have (I tried my 40mm Plossl - unusable - the eye relief was about 3 feet from the scope!) which gives exit pupil of 2.6mm and 60x. My C8 with reducer would give 3.3 and a similar mag. So I think I might need a longer FL eyepiece (in addition to darker skies and filters). Open to suggestions! 

Edited June 25, 2020 by RobertI

[domstar]

A great read. It's good to have a nemesis. I've had a few. It's so much more satisfying when it's vanquished. I also find that after the first time, it capitulates more and more easily each time. Cygnus is a lovely constellation but I find it very difficult to find a target there because there are just too many stars.

[RobertI]

10 hours ago, domstar said:

A great read. It's good to have a nemesis. I've had a few. It's so much more satisfying when it's vanquished. I also find that after the first time, it capitulates more and more easily each time. Cygnus is a lovely constellation but I find it very difficult to find a target there because there are just too many stars.

You’re so right about things capitulating more easily once you’ve found them - the Veil is a great example for me. 
 

I now have OIII and UHC filters which should really help with the Crescent, plus slowly darkening skies. Really looking forward to unearthing it’s glories! 🙂

[Phil Fargaze]

On my quest to visually view the northern Caldwell objects I came up against the challenge to view the Crescent Nebula (C27). From a dark site in Suffolk with my 10" dob I finally bagged it in Oct 2017 after a few attempts. Here is my log book entry:- "Very faint off circular transparent structure. Wasn`t sure if I was seeing all of it or part of it."

25mm eyepiece 48x OIII filter.  Conditions were good and the site is really dark and I still struggled to see it, so I would consider it a tough target. It`s definitely going on my list to revisit this autumn. 

Edited July 4, 2020 by Phil Fargaze

[RobertI]

2 hours ago, Phil Fargaze said:

On my quest to visually view the northern Caldwell objects I came up against the challenge to view the Crescent Nebula (C27). From a dark site in Suffolk with my 10" dob I finally bagged it in Oct 2017 after a few attempts. Here is my log book entry:- "Very faint off circular transparent structure. Wasn`t sure if I was seeing all of it or part of it."

25mm eyepiece 48x OIII filter.  Conditions were good and the site is really dark and I still struggled to see it, so I would consider it a tough target. It`s definitely going on my list to revisit this autumn. 

Well done on bagging it. Sounds like I will need to find a dark site too or a superb night if I am to stand a chance of seeing more than a glimpse. And my biggest scope is 8” so not the biggest.  Fortunately there is a very distinctive pattern of field stars which should make it much easier to find, but seeing it is another matter!

Edited July 4, 2020 by RobertI