Quick Test Last Night..

[JohnP]

Spent last night fitting & adjusting my new OAG. As a quick test when finished thought I would take a sequence of images of m57 using 5min, 10min, 20min & 30min sub to see if it is possible to get outer halo from Light Polluted Bromley. Anyway result shown below - just a simple stretch of raws in aip4win... Image acquired using ED80 + Atik16ic with Baader 7nm Ha filter.

As you can see it is just visible on 20 & 30min subs... Blimey don't think I'm going to bother with this...!

Cheers,  John.

[Mike]

It will become visible on shorter subs that are stacked. Just need lots. I'd go for it John. Looks promising.

[RobertM]

That's a good comparison John, though to me it looks like it is possible (just) - the question is whether anyone has the patience to get enough subs to make a good image.

btw, what was the calibrated background counts for each image?

Robert

[MarkS]

btw, what was the calibrated background counts for each image?

And what is the background count in electrons?

[JohnP]

Thks.

Statistics 5min Sub (Whole image) is - Min 269, Max 48844, Median 395
Statistic 30min Sub (Whole image) is - Min 699, Max 48605, Median 916

These numbers are straight from raws (uncalibrated)

(No idea why 5min sub has a higher Max than 30min sub....)

Avg background value for darks is approx 300..

Below is quick, cropped, uncalibrated stack of the 5 images I took (1x5min, 1x10min, 2x20min & 1x30min) - Halo def showing but you have to stretch image so far for it to show...   Not a lot for 85mins...!

The 7nm Baader is a very narrow band filter (maybe too narrow for me..) I may try again using my 12nm Ha filter..

[Rocket Pooch]

Well you got it!

Nice thought though trying to get that, what you need is a faster scope with more focal legth to get you in there! 

[JohnP]

ummm.... a 200mm f4 would do nicely Mr. Suddell....  Darker skies would be good as well.

[RobertM]

Sensitive camera, fast scope and dark skies ... sound's like you're ready for a DSC ?

Your background counts are interesting...

A median of 916 is very low for 30 mins around the Bromley area.  I did some 7nm Ha subs of this a few days ago but I don't think even the calibrated subs had background counts that low.  I'd better check the filters are the right way round !

I would say the 13nm will give a worse background count and mask more faint image detail, that's the advantage of the 7nm.  I would say 3nm would be of even more benefit (if they weren't so pricey that is).

Robert

[Fay]

I did 5x1800 on it last night, Atik & SW 120. Could not see that much of the outer halo. Used 12nm ha filter.

I think life may be too short!

[JohnP]

Just had a play with the 85mins of data that I took a week or so ago. Really tough to process - this is about best I could do. I have enlarged X200% (so same soft issues as Carole had with hers due to resampling). As you can see no hint of ring showing - it is so dim that any chance to show it just blows out m57...

John.

[RobertM]

Did you resample the stacked image? If so then I suggest you resample each sub separately then stack using star alignment (not unaligned even they may be no drift).

The result looks very good by the way ...

Robert

[Fay]

I think that is looking quite detailed John

[JohnP]

Hi Robert - yes I did a 200% upsample on stacked image in PS. Never thought of resampling individual subs before stacking.. I will give this a try - Cheers & thks Fay,  John