Robert Chozick <rchozick@...>
Ok. The only way I know to do that is Dropbox. I’m not sure if that can be used for a group. What is the max file size we should send?
On Feb 28, 2020, at 11:04 AM, Mike Shade <mshade@q.com> wrote:
Please do not send big files
to the group. Some people live rural and DO NOT have fast speeds. Provide a
place where people can see them if interested.
Mike J. Shade: mshade@q.com
Mike J. Shade Photography:
mshadephotography.com
In War: Resolution
In Defeat: Defiance
In Victory: Magnanimity
In Peace: Goodwill
Sir Winston Churchill
Already, in the gathering dusk, a few of the stars are turning
on their lights.
Vega, the brightest one, is now dropping towards the west. Can
it be half
a year since I watched her April rising in the east? Low in the
southwest
Antares blinks a sad farwell to fall...
Leslie Peltier, Starlight Nights
International Dark Sky Association: www.darksky.org
From:
main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of Robert
Chozick via Groups.Io
Sent: Friday, February 28, 2020 8:33 AM
To: main@ap-gto.groups.io
Subject: Re: [ap-gto] Close up of M81 without CCDT67
I took the test shots you suggested. I used Pollux and
shot 1,3,5,15.30 sec exposures inside and outside of focus. The 1 and 3
sec seemed to look the best but tell me if you want the 5, 15 and/or 30 sec
shots. Nebulosity saves in 32 bit fits so let me know if you need it
changed. The secondary vane that is wider is where I have tape to hide
the wires for my secondary dew heater. Please let me know if you think I
should take them off and if they may interfere with my images. I did not have
much focus left inside of focus so my outside version is further out of focus
than my inside version.
On Feb 15, 2020, at 4:52 PM, uncarollo2 via Groups.Io <chris1011@...> wrote:
One
thing would be interesting, before you mask it down. Aim the scope at a medium
bright star, defocus the star image until it has a diameter of about 150 pixels
and take a 16 bit Fits image but don't let any of it saturate. Do one for both
inside and outside of focus. Crop it, 16 bit Fits and post the results (or send
me the images). This will tell right away what the state of the correction is
and if there are any edge zones.
-----Original Message-----
From: Robert Chozick via Groups.Io <rchozick@...>
To: main <main@ap-gto.groups.io>
Sent: Sat, Feb 15, 2020 4:45 pm
Subject: Re: [ap-gto] Close up of M81 without CCDT67
Thanks. I have a pier set up in my backyard
and can do testing. With the scope tilted up I can just lay the mask over it
for the test.
Well,
sometimes I don't think things thru when i suggested tape over the edge of the
mirror. That, of course is bad advise.
I
may be wrong about what I am seeing in your bright stars, and it may indeed be
the very high gain of your camera. Here's what I would do: just try a thin
cardboard mask over the edge and compare the result with no mask. If you don't
see any difference, then your edge correction is fine and you won't need to
mask it down.
-----Original Message-----
From: Robert Chozick via Groups.Io <rchozick@...>
To: main <main@ap-gto.groups.io>
Sent: Sat, Feb 15, 2020 11:11 am
Subject: Re: [ap-gto] Close up of M81 without CCDT67
Thanks for the optics lesson.
Actually
it is not a good idea to put any tape on the reflective surface. On the Lomo RC
scopes they used a metal disc which was on standoffs that were attached to the
rear cell. I would make a paper disc and carefully lay it on the edge of the
mirror and attach it to the side of the mirror with Scotch tape. Being careful
to not rub the aluminum surface.
-----Original Message-----
From: Robert Chozick via Groups.Io <rchozick@...>
To: main <main@ap-gto.groups.io>
Sent: Fri, Feb 14, 2020 9:57 pm
Subject: Re: [ap-gto] Close up of M81 without CCDT67
If I were to attempt to mask the edge what
kind of tape can you use that wouldn’t harm the coatings?
On Feb 14, 2020, at 8:40 PM, Robert Chozick
via Groups.Io <rchozick@...>
wrote:
Can you start making some smaller RC’s😀Thanks for the suggestion. One
of the problems is how sensitive the CMOS cameras are. It is very easy to blow
out stars. With my FSQ at f/5 I can’t shoot over 2 1/2 -3 minutes before bright
stars are blown.
I
worked hard on my collimation and it seems to have paid off. I bought a
focuser collimation ring and used a laser to collimate.
I
like the resolution on that Running Man image. Very nice.
Try
masking down the outer 1/8 inch of the mirror, see if that reduces the spray of
light around the brightest stars. If that works, think about adding a disc in
front of the mirror with a diameter perhaps 1/4 inch smaller than the mirror.
I
have seen this on all Russian RCs (RC Optical scopes) where a disc of slightly
smaller aperture really helped. Most of the RC mirrors from Lomo had turned
edge and were only spec'd to 95% of the full aperture. The very outer part
produced a heavy spray of light around bright stars.
-----Original Message-----
From: Robert Chozick via Groups.Io <rchozick@...>
To: main <main@ap-gto.groups.io>
Sent: Fri, Feb 14, 2020 3:47 pm
Subject: Re: [ap-gto] Close up of M81 without CCDT67
So,
would you say the new advantages of the small pixel CMOS cameras is that they
bring high sensitivity to small pixels?
I
also got a shot of the Running Man with the 1600mm setup:
https://pbase.com/rchozick/image/170381415
I
got M101 at 1600 but the seeing was worse and guiding not as good.
https://pbase.com/image/170399423
On
Feb 14, 2020, at 3:10 PM, uncarollo2 via Groups.Io <chris1011@...>
wrote:
You
are running 0.6 arc sec per pixel, which to me is not oversampling for high
resolution imaging. In fact, for galaxies i prefer 0.3 to 0.4 arc sec per pixel
which really brings out fine detail. My 17"F8 astrograph and the QSI 683
has such pixel scale and really does a superb job on small faint galaxies, even
here in Northern Illinois. You have to have good tracking, of course, and on
the best nights I can get below 0.15 arc sec RMS with the 1600 encoder mount.
I
see a lot of images that are way undersampled (3 to 4 arc sec per pixel) with
poor guiding that produces thick stars and very little resolution. To me these
images resemble Brownie camera snapshots versus images taken with an 8x10 view
camera. (shows my age, doesn't it) :^))
-----Original Message-----
From: Robert Chozick via Groups.Io <rchozick@...>
To: main <main@ap-gto.groups.io>
Sent: Fri, Feb 14, 2020 2:14 pm
Subject: Re: [ap-gto] Close up of M81 without CCDT67
Thanks
Roland. My last dark sky outing was my first use of this scope and
camera. I am really confused on the whole image scale question. I
bought this camera because it has the largest pixels of any of the CMOS
cameras. The image scale is .6 with this camera and 1600mm. My scale is
about 1.8 with my FSQ 106 - 530mm. If the recommended guidance of a scale
of 1-2 for image scale is used the 1600mm should be too small an image scale.
Most CMOS cameras have only 2.5-3.5 micron pixels vs 4.63 on my ASI294.
Is oversampling bad? The .6 scale in my image sure looks ok.
What about .4 or .3? I intentionally did not get larger than a
1600mm focal length because of this issue (and yes, guiding issues are not as
bad vs 2000 and over). Everyone asks why I got an 8 RC instead of a 10 or
12 inch RC. The above reason is why. Each new CMOS camera that
comes out still has really small pixels. How good would 2.5 micron
pixels look on a 2500 mm scope?
On
Feb 14, 2020, at 1:18 PM, uncarollo2 via Groups.Io <chris1011@...>
wrote:
That's
really nice. Sharp and great color.
A
question: do you think that 1600mm is a sweet spot for all kinds of deep sky
imaging, especially for high resolution work? Especially since the newer Cmos
cameras have such small pixels and would be able to take advantage of a high
resolution optic for small faint galaxies.
-----Original Message-----
From: Robert Chozick via Groups.Io <rchozick@...>
To: main <main@ap-gto.groups.io>
Sent: Fri, Feb 14, 2020 12:06 am
Subject: [ap-gto] Close up of M81 without CCDT67
I
got another shot of M 81 on the same trip as the M81-82 image, this time at f/8
1620mm.
https://pbase.com/image/170419535
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