New aspect: better polar alignment & comparing two cameras
The first camera I used was an Olympus E-5II. Then I had to change
to an Olympus E510. This day I wanted to compare this two cameras by
returning to M101. In the last weeks I had worked on polar alignment.
Skywatcher offers a tool on their mounts to refine the polar
alignment without a polar scope. In this procedure you slew to an
alignment star and the mount will push this star out of the centre of
your FOV. You then use the ALT/AZ knobs to recentre the star. Your
polar alignment will then be refined. By fiddling with this tool I
was able to refine the polar alignment in a way that makes 120 second
exposures possible. Even on my small and overloaded mount like my
Skywatcher EQ3 -Pro. I was quite impressed. Unfortunately something
like half of the frames were wasted due to star stripes. But I tried
my best and took a total of 40 x 120 second = 80 min. Cutting the
‘bad’ light frames out I was left with 17x 120 sec = 34 min of
integrated exposure time on M101. Way to little for that tricky
target. With 15 darks and 30 bias frames I tried to settle the noisy
New aspect: Coming back to already visited objects to enhance the quality
M31 – Andromeda Galaxy: First I tried a second round on M31. As you might remember, M31 was one of the first DSO my brother and I visited. Back then we took little time to capture this beauty. I had recently switched the camera to an Olympus E510 and this session I wanted to give this camera a try. The idea was not to touch exposure length (60’) and ISO (400) but to increase the amount of overall exposure time. I got 75min of exposure time and thought that would be OK. As you see, it took me a while to grasp on the fact that exposure time can’t be to long. Thumb rule for me now is: one hour for basic structure of the object – two hours for increased details and >2h for smother background and finder structures….What ever. Back then I violated the “no more than one object a night”-rule every night.
In northern Germany there are a few dark sky locations where population density is low enough. I spend a few days with my family in a holiday resort in exactly on of those dark spots. Before that occasion I never had appreciated a real dark sky from an astronomer perspective. But this time everything was different. There was a huge difference! I mean: nights are dark. But it’s a big difference between a dark night near a city and a really dark night. This was, when I googled the Bortle scale. This scale gives you an idea, what your sky is like at night. It takes different aspects your can observe under account. Things like cloud illumination or domes of light at the horizon, visible DSOs. From this list, my home sky is Bortle 6. The sky at my holiday apartment was more like Bortle 3. And that makes already a huge (!) difference.
New aspect: Finding DSOs in Stellarium and plan a DSO session
M101: The days before this session i considered what DSO target to capture next. There are many factors I hadn’t figured out back then:
Where is your scope placed?
This is important for setting up. You don’t want to set everything up and running and then realising that your target will be well behind the neighbours garage all night. That’s just frustrating. So check the position of the object well before your session. See my DIY tutorial “getting your backyard into Stellarium” for further advice.
When does a “Deep Space Object” appear on the sky?
Here you use Stellarium or similar apps to figure out when to image. You want to use the precious time you have as good as possible. So planing the session in advance is important. When do you need to be ready? Where do you need to point?
When does it cross the meridian and you are forced to do a ‘meridian flip’?
A meridian flip is a manoeuvrer you are forced to preform, when the captured object crosses the north-south-axis on the sky. At this point the weights on your counter weight bar will rise higher and then above the scope. To avoid that and to keep the scope always above the weights, the scope will stop and you have to rotate 180° and then just keep on tracking. That is a hurdle in the middle of the night. You have to find the object again, align everything and then keep on capturing. I always try to avoid that manoeuvrer, but sometimes it’s inevitable to do so. Back then I really was trying not to… Too many factors.
What are good alignment stars for locating the object?
Errors in the mount will cause errors in the GOTO functions of the mount. So for my cheap SW EQ3 -Pro mount it means that you add together a lot of errors when slewing to a DSO from a distant alignment star. I therefore choose a nearby alignment star to reduce the amount of slewing error. So therefore I am forced to use a different set of alignment stars for every new DSO.
For this target I met with a good friend of mine right in the middle of nowhere. The goal was to flee from city lights, so we chose what seemed to be a place, right in the middle of german no man’s land. It was the first time I packed the rig into the car and assembled it far away from the known grounds of my own backyard. There are multiple factors involved in doing so: where is flat ground? Where is north? Is the power supply line from the car to the scope long enough? Can we build the rigs right here, or is it property of someone else?
A few days before this session I purchased a T2-4/3 Olympus adapter ring to attach the old Olympus E510 DSLR (my brother lent me) to my Skywatcher 750/150 PDS. With such an adapter you can detach the lens of the DSLR and attach the scope instead as it will act as a lens for the DSLR.
this new equipment I aimed for my first deep sky object M31 the
Andromeda Galaxy. I still had troubles polar aligning the mount but I
found a Skywatcher procedure where one can first do a rough polar
alignment, then tree-star star align the scope and then use a given
guide star to refine the polar alignment. The mount slews to the
guide star, then you correct for the occurring error and finally the
mount reslews again and shifts the guide star out of the center. With
the AZ and ALT bolts you then just recenter the guide star and refine
polar alignment. A clever trick for users unable to see Polaris or
users without a laptop and therefore without programs like phd2. With
the refinement of the polar alignment I was now able to take 60
second long images without star trails.
New aspect: First images taken with the old Canon SX240HS
So after a while the sky cleared. I had some friends on board and after viewing some targets of the late summer (M31 and M13) we switched to the planets. First we found Saturn on the sky. If you see Saturn and its rings for the first time you will know what I mean with ‚we gazed at Saturn‘. It was a breathtaking view. A tiny dot on the sky turns into a rotating planet with moons and a beautiful ring! In a hurry I pointed my smartphone above the eyepiece and see: the first astro photo of my life was taken!
In summer 2018 I began my journey with the purchase of a Skywatcher 750/150 PDS on a Skywatcher EQ3 Pro mount. It came along with a 2″ 26mm eyepiece, a small finder-scope, a 3x Barlow lens, a small 1 1/4″ 10mm eyepiece and other minor equipment. I added an adapter for compact cameras to try some ocular projection images. Basically you just hold the camera in front of the eyepiece and take a picture. The adapter helps keeping the right distant and the camera stable.
Why the skywatcher scope? I did a basic research and found that reflector scopes seems to be the best fitting beginner scopes. With a focal length of 750mm you can fit the moon in one frame but will still be able to capture distant galaxies as well. The diameter of 6″ and the EQ3 Pro was manly due to financially reasons. I found the scope as a set on the web store of a german retailer. It was all in all below 1k and seemed to be a good but inexpensive scope. The 750/150 OTA is still great but the mount will cause trouble in the future nights to come…
Assembling the scope was a nightmare. It came in two big boxes witch contained hundreds of small paper boxes, plastic bags, papers, instructions, info material, cables and other stuff. I had literally no idea what to expect and what to assemble. After a while I managed to get every pace into place and managed to get an idea of the movement of equatorial mounts. You can’t just turn them like regular camera tripods (alt az)… So without any idea I thought I would be ready for the first clear sky.
These are the very first words for my new blog. What do I aim to do with these blog posts? First of all I want to give the readers the opportunity to follow me on my astronomy path. They might be able to learn from mistakes I made, to feel the excitement I still feel with this hobby and just to have a second pool of experience. There are very few useful nights with clear skies. If one is able to read along a second set of nights that might be helpful.