During the last
sessions I slowly build up the dream of autoguiding my images. There
are many advantages of having a guidecam with a guidescope attached
to your main scope.
to use the guidescope for advanced polar alignment in phd2. There
you use the attached scope to trace movements of stars to determine
the polar alignment offset. Phd2 is then able (because it’s
clever) to give informations about with direction you need to nudge
the scope in order to perfect the alignment.
to use the guidescope with its cam to plate solve. Plate solving is
the ability of the PC to count the stars on a given image and
compare it to a given database in order to determine the current
position of that image in the night sky and give a set of
coordinates as an output. Some of you might ask: Why not use the
main camera for that? Well, upon now I used the old Olympus E510.
This camera can not easiely be controlled by a PC. So in order to
use the main imaging cam for plate solving I would have to take a
picture, grab the CF-card, transfer the image to the laptop… Long
story short: once set up, I don’t want to touch the main camera
any more (focus!). Problem is: I need to align the polar scope and
the main imaging scope properly in order to use the plate solving
Last but not
least: The ability to guide with phd2 to
exposure time! I was up to 60 seconds on lucky sessions, others
were more like 50 seconds.
the framing. Without guiding I had the problem that the image would
shift ever so slightly. Even when 60 seconds would give me pin
point stars, a night long session would result in a noticeable
movement of say half a screen! So I needed to go out and slew back
to the original position from time to time. With guiding phd2 would
check that for me.
reliability of the system. Without guiding I used say 1/3 of the
images max! Some sessions were down to one image out of every 5
frames or so. That was due to bad alignment and other imperfections
of my mount. Increasing this quota would give me much more data on
a given target!
This time I wanted to
capture tow cool galaxies in one frame. I searched Stellarium the day
before and found those two beautiful galaxies. They fit into the FOV
of my camera/scope as I use an old Olympus E510 and a Skywatcher
150/750 Newtonian reflector. Challenge was to frame the objects right
into one frame and not accidentally cut one galaxy off. So I chose a
high ISO 1600 (max with my camera) and like 60’ test frames to
locate the galaxies. Due to my little mount with high inert slewing
errors I had a hard job of even finding the two of them. After that I
needed to fit them into one frame. My sister and her fiancé can tell
the story of me trying to move the scope just ever so slightly than
taking a test shot, wait for 60’ then reslew. Than me realising I
slewed in the wrong direction. Me reslewing again. Taking another
test shot. Off again. Where are the galaxies at all? Reslew. Test
shot. Searching….. Uff! It was tough.
This two images of the Orion Nebula
were taken using a smartphone hand-held in front of the 2” lens.
This evening I observed a few DSOs with my Skywatcher 150/750
Newtonian on my little Skywatcher EQ-3 Pro mount. Doing visual
astronomy is normally not really my thing but I wanted to give it a
try. I was surprised, how much of M42 the Orion Nebula was visible
trough my little 6” newtonian scope. But than I couldn’t resist
to hold my LG G6 in front of the lens to shoot some images. I then
tried to get the exposure time of that single frame exactly in such a
way that it would match the experience with the eye. So here they
I took video files of both
planets on the morning of the 23th of January. It was a
Wednesday so I was (again) in a hurry. Setting up the scope was not
that hard but keeping the last trouble with the moving Venus in mind
I took one more look through the polarscope to align a bit more
properly than last time. Then I searched and found Venus. Again the
planet was so incredible bright, that was not able to choose the
right settings for exposure and focus. I tried my best ether way.
Jupiter was a more easy part. I did some over exposes videos to
capture the moons of Jupiter and then fiddled around to find the
sweet spot for exposure, gain and “brightness” (whatever this
item means). I finally managed to grab three files before I had to
end the session. Focus? A nightmare!
This time I had one target
and one target only in mind (finally managed to obey my own rule!):
M42. The last session gave me 32x1min light frames to work with and
hence a lot of noise in the image. After setting up the scope I was
about to frame the image. This was my first do-over of an object
where I was about to ADD data to my already captured data-pool. I had
already framed an object to my wishes as I framed M31 (Andromeda) to
snugly fit into my DSLR frame. This time I had to match the previous
image framing with enough precision to be able to add the two
sessions together. My problem about this was that my mount tended to
move even so slightly from frame to frame. So first and last frame
and all the counter-re-framing had to fit as well. I did my best and
framed M42 after focussing on a nearby star with my bartinov-mask.
Then I hit the “run” button.
New aspect: Revisiting a
target to improve quality and seeking for the next
Venus: This was a shot in hurry. On morning the 5th of December I set up the scope in a hurry to capture Venus. Polar alignment, balancing: All quick and dirty because of the limited amount of time. The result was a hard job to even find Venus with the scope and the attached webcam. After finding Venus I struggled with the right driver-settings. Venus was so incredible bright that even focussing was a nightmare. The bad polar alignment made I just worse. Venus, taken with a 3x barlow, hurried to leave the FOV whenever I thought that I got the settings right. Then I needed to reslew and start all over again. I managed to capture one video file with a very unstable Venus and an unclear focus.
The image was taken at
dawn right before sunrise. Moon was three quarters on its way to new
moon and Venus was very very bright standing next to the Moon.
Because sunrise was close the dark side of the moon was lit enough to
see some details. Catching both the bright and the dark site of the
moon with the old Canon compact camera was not possible but I took
some images of the bright side showing some craters and some images
of the dark side (longer exposures) so faintly show some surface
details as well. The view of the two bodies in the night sky was very
pretty to watch.
I really want to do a stitching of both sides of the moon – dark and bright side!
This are two images taken
by my brother in Denmark. They show parts of the Milky Way and the
Pleiades with my brother standing in the foreground. As the stars
shine for him he uses his searchlight to connect with them.
Acquisition and Processing can be told by himself.
New aspect: Taking the first close up surface images of the moon with a modded Logitech webcam
When imaging the Mars with the modded webcam in the last session I recognised just how hard it is to get the focus right. So a member of a astro forum (Hi Carole!) pointed me towards the moon. Focusing the moon with its sharp crisp contrast is much more easy than focusing wobbly blurry planets. So I tried the moon as a target for this session. Finding the moon, aligning finder scope and main scope, getting the polar alignment roughly working: all that was done in a minute. Fining the right balance between exposure time, gain, “brightness” and stuff was a completely different story. The Logitech webcam can only be set through the Logitech driver interface and that doesn’t really work smooth with SharpCap, the image acquisition tool I used (and still use). For changing any of the parameters above you have to switch from SharpCap to the driver interface. Gain is called something like “sensitivity” and nobody knows what “brightness” really means… SharpCap has no authority/ability to access the settings of the webcam directly. That’s a shame. So after fiddling around with the settings I tried a few video-files with and without barlow lens. Some were dark, some too bright.
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