Dim and Dusty NGC 4945

Peter Ward · #1 13-03-2008, 09:52 PM

From my light polluted Sydney backyard......

http://www.atscope.com.au/BRO/gallery4.html

Criticisms and comments welcome. Oddly enough, used a CCD

skwinty (Steve) · #2 13-03-2008, 10:25 PM

Hello Peter
Welcome back
Stunning picture of ngc4945.
Please post details.
Regards
Steve

2020BC (Bill Christie) · #3 13-03-2008, 10:28 PM

Very, very, nice.

A corker.

Ric · #4 13-03-2008, 10:47 PM

A great image Peter, lots of lovely detail in this one and a couple of extra faint fuzzys.

A top image.

Peter Ward · #5 13-03-2008, 10:49 PM

Thank you Bill, Steve.

RC14, STL11k, AO8 guided, 2.5 hours all up.

The uploaded file is about 1/2 scale and a 1/2 frame crop.

Just a few observations.
I like to present Galaxies with some scale.
These island universes have so much hidden detail !!

..which is lost when presented looking like a fly spec on a sheet of A4.

Ngc 4945 is quite a low contrast Galaxy...yes I was surprised to see a few h-alpha star forming regions which are so often "burnt out" by too much contrast being applied to the data.

I was hoping to get a tad more data in tonight...by beaten again by coastal cloud and a waxing moon...sigh...

skwinty (Steve) · #6 13-03-2008, 11:05 PM

Hi Peter
Thanks for detail.Could you give some idea of calibration procedures applied for this shot.ie dark, flats etc.
Am trying to come to terms with all the ins and outs of calibration of ccd's and cmos sensors and judging from your pix you have this waxed.
regards
Steve

Peter Ward · #7 13-03-2008, 11:39 PM

Quote:

Originally Posted by skwinty

Hi Peter
Thanks for detail.Could you give some idea of calibration procedures applied for this shot.ie dark, flats etc.

I continually update both my dark and flat library, as the closer in time they are to the data frames , the better the calibration seems to be.

For flats, median (i.e at least 3) combined sky flats are essential. Aim for about 1/3 full well capacity. Move the scope around a few degrees from flat to flat.

Darks with a temperature regulated astro CCD are pretty easy. Just match the temperature and time of the light exposure. Again use about 3 or more median combined to avoid cosmic rays producing black "holes".

Also make sure you use the same focus, filter and camera orientation for any of the above (yes...*a lot* of work) and even then when shooting from urban areas smog, haze etc. will conspire to still give gradients.

skwinty (Steve) · #8 13-03-2008, 11:46 PM

Thanks Peter
That helps to put things into perspective
Regards
Steve

dugnsuz (Doug) · #9 14-03-2008, 12:12 AM

Quote:

Originally Posted by Peter Ward

..which is lost when presented looking like a fly spec on a sheet of A4.

Beautiful Image Peter.
I'm currently imaging a fly spec!!
Doug

skwinty (Steve) · #10 14-03-2008, 12:15 AM

Hi Peter
Sorry to pester you again.
One last question.
How many integrations did you make and at what exposure time?
Regards
Steve

Peter Ward · #11 14-03-2008, 12:45 AM

Quote:

Originally Posted by skwinty

Hi Peter
Sorry to pester you again.
One last question.
How many integrations did you make and at what exposure time?
Regards
Steve

No problemo....the clouds have cleared & I'm getting some nice late night data!

10 minute subs. There were 9L and 2x 2x 2x RGB

skwinty (Steve) · #12 14-03-2008, 12:53 AM

Thanks Peter
Hope the clouds stay away
Regards
Steve

gbeal · #13 14-03-2008, 06:18 AM

Mount choice wasn't stated, but I presume it was that rock that you mentioned in a posting ages ago, sorry, couldn't help myself.

Garyh · #14 14-03-2008, 08:46 AM

Excellent result Peter,
That scale and your RC combo have brought out a ton of detail..
What else can a say!
Top work!

Peter Ward · #15 14-03-2008, 10:01 AM

Well, my PME does sit on a pier mounted on a very large rock. Does that count?

Quote:

Originally Posted by gbeal

Mount choice wasn't stated, but I presume it was that rock that you mentioned in a posting ages ago, sorry, couldn't help myself.

Alchemy (Clive) · #16 14-03-2008, 11:33 AM

sorry no criticisms of this image. its a stunning image worthy of a comment.

Can you put up a really cruddy one so we can all have a go at you

jase (Jason) · #17 14-03-2008, 03:09 PM

Lovely Peter, certainly considering the quantity of data you're working with. I do however wonder how much more you could extract from this target given more data. The extremely faint galactic "smudge" upper left (pixel location x:450 y:195) may become more pronounced. Thanks for sharing and well done.

skeltz (Rob) · #18 14-03-2008, 10:07 PM

looking good there peter ,looking good