Sh2-155 Cave Nebula

[ApophisAstros]

24 x Luminance @ 186s
19 x Red @ 186s
17 x Green @ 186s
18 x Blue @ 186s

Imaging telescope or lens:SkyWatcher 120ED Imaging System for Canon DSLR Cameras
Imaging camera:ZWO ASI183MM Monochrome 4/3" CMOS USB3.0 Deep Sky Imager Camera
Mount:Skywatcher EQ6-R PRO Synscan
Guiding cameras:Skywatcher 9x50 Finderscope,  QHYCCD 5L-II MONO
Focal reducer:Skywatcher 0.85x Focal Reducer/Corrector for Evostar-120ED
Software:ADOBE PHOTOSHOP CC,  DeepSkyStacker x64 by Luc Coiffier, Tony Cook, David C. Partridge Deepsky Stacker 4.1 64bit,  Astro Photography Tool
Filters:ZWO CCD LRGB Filter-Set 36mm,  zwo EFW 7-position Filter Wheel for 36mm Unmounted Filters
Accessory:QHYCCD PoleMaster
Resolution: 5223x3328
Dates: Aug. 2, 2018
Frames: 43x186"
Integration: 2.2 hours
Avg. Moon age: 19.93 days
Avg. Moon phase: 72.71%
Astrometry.net job: 2179182
RA center: 344.236 degrees
DEC center: 62.618 degrees
Pixel scale: 0.629 arcsec/pixel
Orientation: 259.273 degrees
Field radius: 0.541 degrees
Data source: Backyard

Roger

[MarkS]

Hi Roger,

I'll be straight out and honest here.  Your processing just hasn't done justice to this object.  It's not an easy object to image but your version is far too red.  With the camera you have, I've no doubt that you've captured reasonable data and that you simply need to make some tweaks to your processing.  But you've gone beyond my level of experience and I really don't know how to help.

Anyways, good luck!

For comparison (in case it is helpful) here is a wider field version of my own:  http://www.markshelley.co.uk/Astronomy/2015/cave.html

Mark

[Carole]

I am also a bit out of my depth with this mono camera as I really can't get my head around the "many short subs" system. 

To my mind there is just not enough data here, and if it was a Mono camera I am used to I would say the subs are not long enough, but maybe it's just that there aren't enough subs. 

I think you are really going to have to take advice from those experienced with this sort of camera.

On the plus side, you seem to have got the RGB alignment much better in this image.

As an experiment, I wonder what would happen if you did do longer subs?

Carole

[MarkS]

I am also a bit out of my depth with this mono camera as I really can't get my head around the "many short subs" system. 

To my mind there is just not enough data here, and if it was a Mono camera I am used to I would say the subs are not long enough, but maybe it's just that there aren't enough subs. 

There may not be much data in each sub but because the read noise is so low, it is still swamped by that data, which is exactly what you want because you don't want read noise being a large source of noise in an image.  Shiraz's tables are one of many ways of telling you how to reach that goal.  But if you do choose to do short subs you will obviously need more of them to reach the same total imaging time.

Gone are the "old days" where folk were forced to do narrowband subs of 30minutes or more.  Unless an old CCD with high read noise is being used!

Mark

[Carole]

Thanks Mark, I know it works with these chips but as it works differently to the type I am used to I can't really advise.

Carole

[MarkS]

Thanks Mark, I know it works with these chips but as it works differently to the type I am used to I can't really advise.

And I'm unable to advise on LRGB processing!

Mark

[Carole]

I am helping Roger as much as I can with the LRGB processing, but as we all know it takes time to learn and improve our skills, but getting the right number of, and length of subs in the first place is something Roger will have to find out either by asking those who have used these type of mono cameras, or by self experimentation.

If what he has achieved so far is anything to go by, he will get there, just takes a bit of time. 

I remember when I got my first Mono camera, it took me months to find a satisfactory way of aligning the different filters and I had no help with that, just reading posts on forums and getting gradual advice from occasional people I encountered at astro camps etc.  Then improving processing skills with the odd top off here and there over an extended period.

Carole

[ApophisAstros]

I totally agree with all said and thank all for comments and suggestions and especially Carole for all her help and "Imaging Lessons", your a real trouper !! I thought of an idea for the OAS forum. How about a "Imaging Workshop" thread IE i would post those tables i found about various sub lengths as an example so they are always there for all in OAS, Maybe easier to find than trolling the GoOracle!!
I didn't expect to achieve anything near what i have this week already , i thought perhaps it would take ages to align and find targets at first but its so much easier doing this with a CCD than it is with my DSLR .  Astro Photography Tool is mustard for imaging , it covers all the bases. On capturing,  the great thing is you can always add to previous captures and reprocess so i'm not too worried about the lack of processing acumen at the mo , i'm just blown away with how enjoyable it is imaging now.
Roger

[Carole]

i'm just blown away with how enjoyable it is imaging now.

It's great that you feel like that Roger, that was exactly my reaction when I first changed from DSLR to Mono imaging = "blown away". 

Of course the processing is more of a pig, but I think worth the effort.