M100 with Meade 14" ACF

[mrpizza]

I gathered the data back in March and finally got around to processing it.  For some reason I had some gradients in the  red and blue channels that I was not ale to totally remove.  I was able to eliminate the red halos around the bright stars by selecting red subs that  had a smaller FWHM than the other channels.  This meant  I had to take some extra red subs ( about 25% more in this case). https://www.astrobin.com/771f3a/

Meade 14" ACF

Mesu 200 MKII

QHY 268m

ONAG

 

Chris

 

 

[Xsubmariner]

Very nice image Chris, may I ask if it was taken with the f8 or f10 OTA? I have the f8 12” ACF OTA and still struggle to find the back focus sweet spot for my QHY268M. I was advised 150mm from the OTA 3.25. What back focus are you using and do you have a secondary focuser fitted in the setup?

[ollypenrice]

The galaxy's good but, as you suggest, the residual gradient in the background sky is a distraction. I'd be surprised if Pixinsight's Dynamic Background Extraction couldn't fix this as a first operation with the data still in linear form but, even just working quickly with a screen grab, Photoshop allowed a bit of manual cosmetic intervention on the background. Done with more care, I think it could work.

Olly

 

 

 

 

[mrpizza]

Xsubmariner -  I have the LX850 version that is F/8.  I use a Moonlite crayford focuser.  I also have the ONAG in the train that adds roughly 90 mm back focus.

Olly -  DBE and I are not on good terms.  I like your version much better!

 

Chris

[Sunshine]

A whole load of galactic detail here, love it!

[Xsubmariner]

6 hours ago, mrpizza said:

I use a Moonlite crayford focuser.  I also have the ONAG in the train that adds roughly 90 mm back focus.

Thanks for the information, assuming 55mm for FW and Camera backspace would suggest your backspace from the OTA thread to the sensor is in the region of 200mm. I recently fitted my night crawler to the OTA and can not achieve the recommended 150mm BF, your arrangement has given me hope to get my system dialled in. 

[tomato]

That's great work Chris, one of the most detailed M100 images I have seen on SGL. Achieving these sort of results on small galaxies is my Holy Grail in DSO imaging, I currently employ the large refractor of moderate focal length and small pixel camera approach to try and get there, but seeing your image makes me think again  about a large aperture RC coupled with today's high sensitivity CMOS cameras. However, would I be correct in saying that in your location you can experience the seeing conditions necessary to support this approach, I don't think I could get away with 0.5 arcsec per pixel with my turbulent atmosphere.

[mrpizza]

tomato - I'm 3 miles from the Atlantic at 17 feet above sea level.  Seeing is a hit or miss with all that atmosphere above me.  I use Voyager and can tell by the focus numbers how the seeing is.  I would guess that 40% of clear nights I shut down because focus numbers don't look good and I know from experience I would end up throwing subs out.

 

Chris

[juno16]

Gorgeous M100! Outstanding details.

I struggled with DBE too until Adam (Block) set me on the right course. I don't remember if it was on his free Youtube channel, or in the Fundamentals course, but after learning how all (well most) of the controls work and what they do, I could not even think about not using DBE. Truly one of PI's most powerful tools!

 

Jim

[tomato]

7 minutes ago, mrpizza said:

tomato - I'm 3 miles from the Atlantic at 17 feet above sea level.  Seeing is a hit or miss with all that atmosphere above me.  I use Voyager and can tell by the focus numbers how the seeing is.  I would guess that 40% of clear nights I shut down because focus numbers don't look good and I know from experience I would end up throwing subs out.

 

Chris

Thanks for the info, I believe Damian Peach does some of his planetary imaging from Barbados so I thought you might have similar good conditions but they must be specific to his location. 

I'm wish I could be more selective on my imaging nights, but then my imaging opportunities would be even more limited.

[mrpizza]

Jim- I subscribed to Adams fundamentals last Nov.  LOTS of material.  I have watched his DBE videos.  I need to check my patience and go over it again.  I know it would help.

 

Chris