ASTRO: M-61, Spiral Galaxy in Virgo

I took this image on a night of really awful seeing. 30 minutes of total
exposure with an STL-1301E CCD thru a 20-in F/8.1 RC Cass. The field of view
is 13x16 arc minutes with North at the top.

For more on M-61, see: http://www.kopernik.org/images/archive/m61.htm

George N

George Normandin wrote:
I took this image on a night of really awful seeing. 30 minutes of total
exposure with an STL-1301E CCD thru a 20-in F/8.1 RC Cass. The field of view
is 13x16 arc minutes with North at the top.

For more on M-61, see: http://www.kopernik.org/images/archive/m61.htm

George N

Seeing looks better than it was the night I took it:
http://www.usenet-replayer.com/2/7/4...383472.18.jpeg

Though I used no LR deconvolution. That gives me nasty rings on stars
when I dig deep as I usually do so I put up with bloated stars but no
rings. Though I've now changed my technique for digging deep so should
give it a try again. Maybe the rings won't be so bad now.

Rick
--
Correct domain name is arvig and it is net not com. Prefix is correct.
Third character is a zero rather than a capital "Oh".

What a pity that bad seeing hit you there. Otherwise a very nice picture.
The old picture you posted with the SN looks like it had better seeing.
M61 is one of those objects I have to reshoot, maybe next year.

Stefan

"George Normandin" schrieb im Newsbeitrag
...
I took this image on a night of really awful seeing. 30 minutes of total
exposure with an STL-1301E CCD thru a 20-in F/8.1 RC Cass. The field of
view
is 13x16 arc minutes with North at the top.

For more on M-61, see: http://www.kopernik.org/images/archive/m61.htm

George N

"Rick Johnson" wrote

Though I used no LR deconvolution. That gives me nasty rings on stars
when I dig deep as I usually do so I put up with bloated stars but no
rings. Though I've now changed my technique for digging deep so should
give it a try again. Maybe the rings won't be so bad now.


Rick,

This is the first image I've ever taken with a FWHM of seven something!!
It was clear (sort of) so I just kept going. That night Saturn looked like a
blurry thing with ears!

Both IRIS and AIP4Win v2 have second LR routines that have an adjustment
that prevents operation at certain count levels (for 'anti-ring' purposes).
I believe that the ring problem comes when a star gets max'ed out and LR
starts moving "count" out of the star instead of in. Both IRIS and AIP use
real numbers, and AIP has no "upper limit" on number size, so stars never
max-out. With IRIS I divide by two (or some other constant) before using LR
to prevent too many stars from max'ing. There is no loss of info because
IRIS uses real numbers. Together these methods reduce the 'ring effect',
which I have no problem with anyway as long as it's only a few stars. I'm
use to star rings because all the kids at Kopernik always have their fingers
on the eyepiece lenses!

George N

"Stefan Lilge" wrote
...
What a pity that bad seeing hit you there.......

Stefan,

The seeing was the worst I've seen while still being able to image.

George N

George Normandin wrote:

"Rick Johnson" wrote


Though I used no LR deconvolution. That gives me nasty rings on stars
when I dig deep as I usually do so I put up with bloated stars but no
rings. Though I've now changed my technique for digging deep so should
give it a try again. Maybe the rings won't be so bad now.



Rick,

This is the first image I've ever taken with a FWHM of seven something!!
It was clear (sort of) so I just kept going. That night Saturn looked like a
blurry thing with ears!

Both IRIS and AIP4Win v2 have second LR routines that have an adjustment
that prevents operation at certain count levels (for 'anti-ring' purposes).
I believe that the ring problem comes when a star gets max'ed out and LR
starts moving "count" out of the star instead of in. Both IRIS and AIP use
real numbers, and AIP has no "upper limit" on number size, so stars never
max-out. With IRIS I divide by two (or some other constant) before using LR
to prevent too many stars from max'ing. There is no loss of info because
IRIS uses real numbers. Together these methods reduce the 'ring effect',
which I have no problem with anyway as long as it's only a few stars. I'm
use to star rings because all the kids at Kopernik always have their fingers
on the eyepiece lenses!

George N

7"! I've never had it that bad. Nor have I been able even with AIP's
LR get stars as small as you did after deconvolution. I must be doing
something wrong. I haven't tried it in months. Guess I should go back
and have another look.

I use AIP Version 1. Maybe I need the later version.

At Hyde we have had little trouble with kids fingers on eyepieces. When
we opened in 1977 I figured it would be a major problem as would
eyepieces disappearing when an operator left one out on a counter but
only one eyepiece has every vanished. Fingers are rarely a problem
though putting the eyeball right onto the eyepiece happens all too
often. Usually because a parent insists on holding the kid rather than
using our perfectly safe lift system for the kid. They then push the
kids eye right into the eyepiece causing the kid to start crying and a
gooey eyepiece. Then there was the parent that licked an eyepiece at 20
below. His tongue froze instantly to it. Rather than wait for the hair
dryer to thaw it out he pulled it off sending blood everywhere. The
blood caused two elements to separate and the blood replace the cement.
That was the only other eyepiece we "lost". Usually they stay clean
enough we clean them only twice a year. I figured it would be a nightly
chore but the kids have been excellent. It's the parents that are the
problem.

Rick
--
Correct domain name is arvig and it is net not com. Prefix is correct.
Third character is a zero rather than a capital "Oh".