Michael‘s Astrophoto Blog

One of the first images taken with my new Hyperstar.  After long deliberation I bought a Hyperstar system for my C9.25 Schmidt Cassegrain. For quite a while I was torn between the Hyperstar and getting a separate refractor. I did a lot of research and in the end I changed my opinion almost on a daily basis. Finally, I decided that the pros and cons of these two approaches are probably reasonably balanced and that I need to try it myself.   If you are not familiar with it - the Hyperstar is an optical system that is put in place of the secondary mirror of a Celestron Schmidt Cassegrain telescope, basically turning it into a very fast astrograph. For example, C9.25 becomes an f/2.2 system with 525mm focal length. The Hyperstar mounted on top of the telescope  Rough Collimation One of the drawbacks of a system like the Hyperstar is that, like all reflector telescopes, it requires some level of alignment i.e collimation of the optical components in order to perform optimally....

My old NexStar Evolution mount is a really great "grab and go" mount for visual observation. It is pretty light as it doesn’t require a counterweight, it comes with its own rechargeable battery and its own Wlan - so basically everything you need to start observing super quickly. I was surprised how far it took me on my astrophotography journey and it is probably viable with a small telescope or tele lens. However, undoubtedly it has quite substantial limitations when used for photography with my Celestron C9.25: The mount is not really balanced on any axis. So it was very hard to make guiding work in many cases. It usually took a while of adjusting parameters or guiding in only one direction depending on the weight distribution.   For higher declinations guiding did not work at all. Even when it worked tracking and guiding accuracy was not really good enough for imaging at higher focal lengths. Typical guiding errors were in the 3“-4“ range. The mount geometry requires the us...

Since a couple years I own a focal reducer for my Schmidt Cassegrain. It didn’t come with a whole lot of documentation or manuals, but I knew that it was supposed to reduce the focal ratio from 1/10 down to 1/6.3 while at the same time correcting the image. I have used it mostly to visually observe larger objects that wouldn’t quite fit in the field of view otherwise.  The reducer/corrector for changing the focal ratio to 1/6.3 When starting with photography I wanted to give it a try as I was hoping to benefit from the image correction as well as from the fact that a shorter focal length would be more forgiving in the presence of small errors in tracking and focusing. In general that worked as expected, however I was really surprised when the plate solving of my first images showed a focal ratio of 1/4.8 rather than the expected 1/6.3. That is how I started to realize the importance of the backfocus distance of a device. The corrector, like many optical devices, is calculated with ...

Starting with astrophotography was quite a steep learning curve for me. Though I felt that I had a reasonably good grasp of many of the general concepts - the reality of making all components work well together was something different. At the beginning large portions of the observing nights were spent battling all kinds of technical issues with the new equipment.  In this post I want to describe some of the bigger or smaller issues and pitfalls I encountered. Many of them may be specific to my situation and equipment, but perhaps it gives some idea on what to look out for. Don’t trust Indi device defaults The Indi drivers for most devices come with a large number of device settings. As a beginner I was not always clear on what each of them does and/or why I may want something different. My assumption was that the default settings are good enough to get started and changes can be left for fine tuning at a much later point in time. However, when taking and processing the first pictur...

As I described in the previous blog my equipment has improved quite a bit over the past weeks. I got a dedicated, cooled astro camera as well as a separate camera and a little finder scope for automatic guiding. After sorting out the initial technical issues, finally we had    a few clear nights to put the new kit to the test.  M33 30x30sec, C9.25 with 1/6.3 reducer, ASI294MC Pro on NexStar Evolution  M1 Crab Nebula, 28x60sec C9.25 with 1/6.3 reducer, ASI294MC Pro on NexStar Evolution  M27 Dumbbell Nebula, 30x30sec C9.25 with 1/6.3 reducer, ASI294MC Pro on NexStar Evolution  IC5146 Cocoon Nebula, 60x60 sec  C9.25 with 1/6.3 reducer, ASI294MC Pro on NexStar Evolution  NGC6888 Crescent Nebula, 30x30sec C9.25 with 1/6.3 reducer, ASI294MC Pro on NexStar Evolution  As visible in the pictures on close inspection I am still struggling with the autofocus.    The guiding doesn’t work really flawlessly in all cases, particularly in high ...

After the first promising tests I could have continued with the initial equipment setup for a while. However, I had the impression that I am enjoying astrophotography enough to move to a more "final"setup as quickly as possible. I was expecting that a dedicated, cooled astro camera, an auto-guiding setup and a new mount will probably be required. On the other hand I wanted to take this journey in steps so that I didn’t have to deal with too many new things at the same time. So I took the decision to go with the cameras first. That way I would have everything ready to go to test the guiding accuracy of a new mount later. Selecting an astro-camera At first the vast number of different astro-cameras that are being offered is a bit overwhelming. I tried to get some structure in the decision process, while not overthinking it. Here is how I went about the selection: Vendor choice : The first thing I noticed was that a large number of camera variants is basically the same sensor be...

One of the things that made me reluctant to seriously start with astrophotography was the prospect of spending long nights outside in front of a laptop that is tied to the telescope with a long USB cable. Nights that would typically end in disappointment and anger after I inadvertently tripped over that cable - at least that had been my experience in some early attempts.   This time I wanted to take a different approach. The entire setup should be controlled by a little computer that is directly attached to the equipment, while the control would happen remotely over the network.  I guess there are three main technical approaches that you can take to achieve this: mini-pc being controlled over remote desktop; basically using ascom and a similar imaging software as you would use in the "long USB" scenario.  "out of the box" solution from an astronomy equipment vendor like the ASIair Linux based solution using Kstars/Ekos/Indi running e.g. on a Rasperry Pi I am not sur...