M27 and NGC 6888 (Crescent Nebula)

[7170]

Well the imaging season started for me this week. Although the mount is still very poorly polar aligned and the moon was out I none-the-less I had two enjoyable evenings this week, and as a bonus it wasn't too cold! I was hoping tonight would be good too but there is lots of high altitude cloud so have given it a miss.

I'm in south west London (Surbiton) so suffer from light pollution, though we are far enough away from the center to have reasonable viewing (especially after 10pm) and on the odd occasion excellent viewing if rain has cleared the muck out of the atmosphere. I usually focus on double and variable stars so don't get wound up about light pollution.

I decided to have a go at M27 and the Crescent Nebula as easy targets as I wanted to check all was well with my new guiding setup. I thought I would share the images, not because they are good but because they give an indicator of what someone living on the outskirts of a major city with modest equipment may expect to achieve given light pollution, so hopefully they maybe of interest to some.

Dithering was not activated so there are lots of white specs but I was generally pleased with this shot of M27. Quality would have been improved if I had taken it up to 60 minutes. Gain was modest at 28.

I'm quite pleased with this one of the crescent nebula given our location. If you look at it through the eyepiece you see nothing. Only when you start to take long exposures and stack do you start to see the shell come out of the sky glow (though only very slightly here). If you didn't have as much light pollution you would have no issues in taken an image of this.  One day I want to try it with a UHC or OIII filter.

I also took some photos of V2117 Cyg (HD 193837) with 20 second exposures, and slightly above it there is a magnitude 14.9 star, so that is a good guide on the magnitude a camera lets you get down to here without issue. I use APT, PHD2 and EQMOD.

[Special K]

That Crescent is one faint object!  Thanks for posting

[carastro]

I live in the SE of London, so am in the same boat.  I find bright targets are OK, but better without the Moon, but faint targets are impossible even sometimes with narrowband.

I presume these are luminance subs.  If you have an Ha filter give that a try, it comes out well even from our locations.

Carole 

[mapstar]

I remember my Views of the crescent at the Isle of Skye last year in the 22" dob.

It was photographic in quality and filled the 17mm Ethos looking like a giant jelly fish. Truly stunning and proof that unpolluted skies provide breath taking views .

 

[estwing]

I second what Mapstar says as I was at the eyepiece with him!

It was incredible...do dark skies, make the effort, it's worth it.

[GavStar]

This is the crescent nebula through the eyepiece of my night vision monoculars attached to my C11 in my South West London back garden. (Phone photo taken about a month ago)

At dark skies it would be even better, but you can get breathtaking views at light polluted sites as well. ?

[mapstar]

3 hours ago, GavStar said:

This is the crescent nebula through the eyepiece of my night vision monoculars attached to my C11 in my South West London back garden. (Phone photo taken about a month ago)

At dark skies it would be even better, but you can get breathtaking views at light polluted sites as well. ?

Thats a good photo with the equipment you were using making all the difference but like you say no where near the detail you'd pick up away from the urban light pollution.

I'm hoping to get another view next week of the crescent from Skye and was stunned by the scale and detail, the 17 Ethos just framed it brilliantly. I will try to get a photo using my smartphone and post it here. 

[estwing]

Astro Photography Damian??!!!!...you might find yourself evicted from the big Dobmob house!!!!

[GavStar]

9 hours ago, mapstar said:

Thats a good photo with the equipment you were using making all the difference but like you say no where near the detail you'd pick up away from the urban light pollution.

Please could you comment further on the extra detail you got with the Ethos 17 and 22 inch dob in Skye? I thought I got pretty good visual views of the crescent so am interested that you mention it’s ‘nowhere near’?

[estwing]

Find an image of it in black and white..and that's what it looked like

[GavStar]

17 minutes ago, estwing said:

Find an image of it in black and white..and that's what it looked like

There’s obviously a huge range of black and white images of this object (including two in this thread). If you could post an example that is a close representation that would be very helpful.

[estwing]

[GavStar]

Here’s an interesting report on CN of a comparison of the crescent nebula using a 30 inch dob in dark skies with Ethos eyepieces and night vision monoculars.

My mind does boggle at a 30 inch dob with NV.

https://www.cloudynights.com/topic/636169-30-f276-nv-report/

[Stu]

@7170 those are some excellent images, and a fantastic example of what is achievable under bad light pollution. I’m not a million miles from you (well actually only a few miles  ), so know what you have to contend with. The Crescent in particular is a really good result given the conditions.

Many of us have family or other commitments which make heading off somewhere dark for the weekend every month impossible, so it is great to see examples of continuing with the hobby without letting the LP win.

You are welcome to come along to our sessions either on the outskirts of Esher (a little darker than Walton and Surbition) or when we head to darker skies at Ranmore or Bignor.

I look forward to seeing some more of your images.

[7170]

On 10/10/2018 at 08:24, Stu said:

@7170 those are some excellent images, and a fantastic example of what is achievable under bad light pollution. I’m not a million miles from you (well actually only a few miles  ), so know what you have to contend with. The Crescent in particular is a really good result given the conditions.

Many of us have family or other commitments which make heading off somewhere dark for the weekend every month impossible, so it is great to see examples of continuing with the hobby without letting the LP win.

You are welcome to come along to our sessions either on the outskirts of Esher (a little darker than Walton and Surbition) or when we head to darker skies at Ranmore or Bignor.

I look forward to seeing some more of your images.

Many thanks Stu. I tried again yesterday evening, this time with 65x60s exposures, it also served as a nice test of Ekos. The moon was out but seeing was not too bad.  This is probably as good as I can get here given the light pollution and equipment, with no filters, without resorting to a disportunatually large number of stacked frames which for me takes the impulsive fun out of it. Gain was only 50% so that could have been increased too.

You are absolutely right about not letting LP win. Its surprising what you can see here especially on a day where rain has cleared the atmosphere of muck or after 10pm when LP seems to drop, presumarly in line with people switching things off and going to sleep.  

I've made a note to get in contact with yourself in the not so distant future with regards to coming along to one of your sessions - baby number 2 is due shortly so I suspect I won't get a pass to go any time soon from the boss alas!

@carastro, yes there were luminance subs only.

[7170]

As a follow up i've been doing some Photometry recently and ran the image of M27 though it and it picked up the following number of stars above magnitude 11 to put things in perspective in a suburban environment (based on the TYCHO-2 catalog).

• magnitude 11: 13
• magnitude 12: 129
• magnitude 13: 93
• magnitude 14: 40
• magnitude 15: 20
• magnitude 16: 5

The dimmest star being magnitude 16.683.