Invisible Nebula (stupid question #1)

[Marky1973]

Had some clear sky last night so thought I would have a go at the Elephant's Trunk and the Crescent. The moon was up and the conditions were not great, but I'm also working on my guiding and getting that right, so it was just experimentation time. I did have some trouble getting the alignment stars on screen in APT which had me worried, but I am pretty sure, once I had aligned, that my pointing was fairly accurate.

So I had ago with both nebulae, about 90 minutes of 5 minute subs on each at ISO800, darks, flats, bias.

I was slightly worried when the test images seemed blank on APT, but they were on a small screen so I just went with it.

Anyway, stacked and stretched in PS and both images failed to show up any discernable nebulosity - stars were fine -  but I thought there woudl be something more obvious with 5 minute exposures?

Example of the Crescent stacked images below.

I am sure there is probably something in there, but I don't think any subtle tweaking will bring it out in a decent way. So, am I right in thinking that it is likely that, in combination with the moon and less than great visibility, it is possible to wash an image out in such a way that the stars are still visible, but the nebula disappears? If it isn't then there was something more serious going on.

Said it was a stupid question - equipment as in list below.

[Leveye]

Moonlight and Nebulas never mix for me. I've done the crescent before and it showed up in each 5 minute exposure even with an un-modded DSLR. I'd try again when the moon takes a break.

[steppenwolf]

I am surprised that there is no nebulosity visible from The Crescent as you were on target (see below) and 5 minutes would normally be expected to yield some result. However, the effect of the Moon on DSOs should not be underestimated!

On a brighter note, the guiding is working well.

[D4N]

The moon kills faint fuzzies unless you are doing narrowband.

I made a comparison last year that was quite striking showing the difference with and without the moon.

http://stargazerslounge.com/index.php?/topic/231826-What-a-difference-a-week-makes---Ced-214

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[Marky1973]

Moonlight and Nebulas never mix for me. I've done the crescent before and it showed up in each 5 minute exposure even with an un-modded DSLR. I'd try again when the moon takes a break.

Cheers Leveye....I really didn't realise the moon would have that much effect, but then I haven't really been trying with DSOs "properly" while the moon is about....my original plan was to try a bit of moon imaging, but then realised I didn't have the right adapters to get my ZWO hooked up to the ED80...so at least I will have something to do, rummaging around in my "astronomy" draw while I wait for the next opportunity!

[Marky1973]

I am surprised that there is no nebulosity visible from The Crescent as you were on target (see below) and 5 minutes would normally be expected to yield some result. However, the effect of the Moon on DSOs should not be underestimated!

On a brighter note, the guiding is working well.

crescent copy.png

Thanks Steve...I'm slowly getting the hang of guiding! Had all sorts of trouble with PHD2 when I started out and almost thought the ST80/ZWO combo wasn't working.... but seems to be getting better - amazing what you can achieve when you read the manual! ;-)

[Marky1973]

The moon kills faint fuzzies unless you are doing narrowband.

I made a comparison last year that was quite striking showing the difference with and without the moon.

http://stargazerslounge.com/index.php?/topic/231826-What-a-difference-a-week-makes---Ced-214

Sent from my iPad using Tapatalk

That's a really telling comparison, thanks for the link...obviously need to think about my targets more carefully....just always so excited when I can see a star...couple the moon with the poor seeing and I was probably on a hiding to nothing! :-)