Re: [APML] M51 & M97

["Volker Wendel" <volker@spiegelteam.de>]

Great shots, Brian,

what kind of Corrector do you use for this large field and for f/4?

I made my first CCD shots with a Lumicon Barlow optimized for f/4,5 and for
the small field of a ST7 the stars look o.k. with my 15"f/4,6 newtonian. I
also want to use a Paracorr corrector soon.

Volker




> Hi,
>
> Tony's M51 was an inspiration to all imagers to go deeper than usual to
extract as much
> info as possible in the image field. I was intrigued to see how deep I
could go in my
> moderately light polluted area near Worcester MA. Limiting magnitude is
4.9 - 5.0 at my
> site in the area of M51 reducing to about 3rd mag  25 degrees above the
horizon in the
> south. Seeing was about 6 the night I took these images with transparency
about 8. I took
> the images just after Tony posted his luminance image I but it took me a
long time to get
> my M51 image to a half decent point and post today.
>
> M51 and M97 are both (L)LRGB's with 90:24:24:30 minute respective total
exposures using
> 10 minute individual exposures for the L frame in 1x1 bin mode and 5
minute individual
> exposures in the RGB frames in 2x2 bin mode. The L and RGB's were combined
in MAXIM
> using average and bicubic resampling for each set.The luminance for M51
was also slightly
> DDP'ed ( custom setting of 20) and 0.8 gamma stretched before importing
into PS6for
> further curve work. Both images were (L)LRGB' in Photoshop using the
double layering
> techniques that Rob Gendler prepared on his website with considerable
lassoing,
> feathering, curve adjustment and star shaping ( thanks Matt!) techniques
used to enhance
> local features.
>
> M51 is almost a full field image using a Finger Lakes IMG6303E CCD (2K x
3K x 9 micron
> pixels) camera on my 20" homemade F/4 Newt while M97 is a subframe.
>
> I tried the "Mike Cook" technique on both images today to reduce the "fat"
stars using the
> radius at 1 and adjusting the fade to somepoint between 40% and 70% but
noted it also
> eroded finer detail in the spiral arms and eliminated faint stars. Bloated
stars are one of my
> biggest challenges in imaging and I was hoping for a silver bullet fix.
Are these effects
> expected or did I do something wrong in the execution?
>
> You will note some astigmatic effects in the stars images on M51 from the
cooldown
> problems with the 20" pyrex Galaxy primary as it chased thermal
equilibrium all through
> that particular night.
>
> The new images are at:
>
> http://www.heavensgloryobservatory.com/Color_Jpegs/m51FRGB04-6303Eweb.jpg
>
> and
>
> http://www.heavensgloryobservatory.com/Color_Jpegs/m97FRGB01-6303Eweb.jpg
>
> M97 shows additional faint galaxies through the nebula in addition to the
6 stars that form 2
> distinct triangles.
>
> I had considerable problems to remove the magenta from the HII regions in
M51's arms.
> Any ideas how to accentuate these with more "accurate" color?
>
> Thanks, Brian Lula
>
>
>
>
>
> Brian Lula
> Polytec PI, Inc.
> (508) 832-3456
>
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