NGC6888 in HST palette

[Paramount]

Hi
Here is another narrow band image that I took with the new Microline x814 camera, it uses a Sony interline chip with 3.69 micron pixels and has over 9 mega pixels in the sensor. This was attached to my Televue NP127/FLI astrograph in place of the Proline 16803 as I wanted to try some narrower FOV higher resolution shots. Exposure times are as follows
Ha 23x10 minutes, OIII 18x10 minutes and SII 22x10 minutes. There is very little SII in this subject.
All the raw frames were calibrated with darks, flats and bias frames. Processing was mainly stretching the weaker channels, colour combine to HST palette, levels with some minor curves adjustments, colour balancing, contrast adjustments, a little high pass filtering and shadows and highlights.
The large size image can be seen at the following link
http://m8.i.pbase.com/o9/29/869929/1/160651878.GFEsNwru.NGC6888HSTmax200 0.jpg
Best wishes
Gordon

[gregbradley]

Great shot Gordon.

Tremendous detail in the neb itself. With this chip in particular and the 694 as well you have to change your exposure strategy as the camera has quite small wells plus its 66% QE in Ha and about 60%+ in O111.

So perhaps even 5 minute subs may have been appropriate to stop the star bloat on overexposed bright stars. The low read noise means there is no liability.

Greg.

[Paramount]

Hi Greg
Thanks for the comments, that is a good point about the well size and sensitivity, the chip is the 814 by the way and not the 694 so the pixels at 3.69 are even smaller than the 4.54 of the 694. The Elephant trunk I shot with 10 minute subs at 2x2 binning and the stars did suffer a bit, I may try some 5 minute subs as you said to see the difference. Interestingly I shot a 10 minute 2x2 binned sub with luminance of the Iris nebula and it was so over saturated due to the bright core that it didn't even register!
Best wishes
Gordon

[Slawomir]

Hi Gordon,

Echoing Greg's comment - LOTS of detail in your image- in particular in the nebula, nicely done :thumbsup:

I am using a camera with the same chip and currently shooting 15-minute subs on a f/5.6 scope. Here is an example of one of my recent images: http://www.astrobin.com/full/189183/C/?real=&mod=

I have seen great photos taken with this chip that were composed from 30-minute subs. From closely inspecting your photograph, I believe you might have a CCD tilt that results in elongated and somehow blurred stars. But that is just my hardly educated guess... :)

[Paramount]

Hi
Thanks for the comments, I'm aware of a potential tilt issue with the camera and I think this due to the adapter that FLI provided to convert the standard nosepiece of the MLx814 to ZTA. When attached to the camera it leaves a tiny gap between the adapter and the front plate of the camera and it is very difficult to see if that gap is uniform all the way round so I'm going to have a shim made to fill the gap and ensure uniformity all the way round. This is of course not an issue with the PL16803 as it has a purpose built ZTA front plate
Best wishes
Gordon