New aspect: Imaging under a dark sky – taking an image of the Milky Way
Image acquisition: My family and I were holidaying in France at the western Atlantic coast. The weather was overwhelming and the trip wonderful! Being fairly far away from any major city the camping site and the beach in particular offered my some spectacular views of the night sky. Having Comet NEOWISE peaked its brightness a couple of days ago – read the article about this – I really wanted to capture the faint traveler in France. Unfortunately my only „gear“ I took with my was the lightweight tripod and a smartphone holder, along with my LG G6 (with the ability to take .raw images).
There are once in a lifetime events that no one should miss. Observing a bright comet is one of those rare things. This year we got the chance to witness a very bright and majestic comet: comet NEOWISE.
New aspect: Testing the coma aberration on a Newton Telescope
This time I was testing the errors I encountered during my first light session (M27). I saw the stars in the corners being elongated towards the center of the image.
This elongation was to be expected – it is called „coma“ and is a result of A) imperfections in the mirror and B) a natural effect for parabolic mirrors to focus light in different focal points depending on the distance of the image center. I did a full review of inner light paths inside reflection scopes in this video:
finally everything arrived. My old rig was quite overwhelmed with my
ambitions and had to be replaced. Why so?
First reason was the old mount. The mount is undoubtedly the most
important part of your equipment. No fancy OTA will produce sweet DSO
images without a proper tracking mount. And “proper” means: The
mount must be able to carry the optics with ease.
New aspect: Visualize the impact of seeing while taking images of Venus.
Image acquisition & processing: I took three different images of Venus during the recent few months. All of the images were taken with the exact same hardware and setting – a ASI ZWO120MC-S Color planetary webcam with a 3x Barlow lens on top of my 750mm Newtonian reflector carried by the Skywatcher EQ3 -Pro mount. All images were recorded as .avi files (2min @ 60fps) and stacked (20% best) and sharpened in Autostakkert!3.
& „It’s too much!“ – beginning backlash-errors or the EQ3 -Pro
29.04.2019 – 04.05.2019
New aspects: – first time with an auto-guiding system – Guiding shows first signs of overcapacity – revisited a target for noise reduction – first „proper“ galaxy – longest project so far
Image acquisition: So finally every part of my new guide-scope arrived and I could use phd2 for proper guiding for the first time! Last session I had unsolvable difficulties with the guidecam, the „ToupTek Camera G-1200-KMB Mono Guider“. I stayed in touch with astroshop.de and they finally replaced my guidecam with another model, the ZWO ASI120mm mini-mono. This camera arrived and the current guiding setup now looks like this:
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.