Michael‘s Astrophoto Blog

I am a big fan of galaxies. During spring, when a large of them are visible, I used to spend many nights watching them. Most of them are just fuzzy patches, but if you try a little you can see a bit of structure in some of them. If that doesn’t work it is still fun to see if any small companion galaxies are visible and to check their magnitude on a star map. So I was really looking forward to my first galaxy season as a photographer. Some of the reason why I directly tried to make astrophotography work with my SCT, rather than using smaller focal lengths initially, had to do with my hopes of being able to photograph galaxies.  Fortunately there were a couple of clear nights beginning of March and I went a bit crazy imaging all the objects from my usual observing list.   I started with relatively small numbers of frames per object, in order to get some first overview of all the items on my list, what is possible and which objects are good. That way I took pictures of 40+ galaxi...

Using the L-eXtreme dual narrowband filter allows taking quite impressive pictures of various nebulae. However, it will create quite unnaturally looking star colors and will filter out features of the object that are not particularly emitting the spectral lines of Ha or OIII.   Some objects, due to their physical structure, look quite different in the narrowband than in images taken over the full RGB continuum. The crab nebula M1 is a good example for this. M1 the crab nebula in HaOIII, 40x90sec C9.25 on EQ6-R Pro, ASI294MC PRO, L-eXtreme M1 the crab nebula unfiltered RGB image, 40x60sec, C 9 .25 on EQ6-R Pro, ASI 294MC Pro It is interesting to look at and compare these pictures individually.    However, I wanted to try combining them in a meaningful way. Basically I had five different "channels" - red, green, blue, Ha and OIII and was looking for good ways to compose an image from that. There are several ways for doing that, some more flexible than others. I ended u...

When taking my first pictures with the L-eXtrem dual narrowband filter I was quite pleased with the results I was able to get. This filter passes only the Wavelengths of the Ha and O III spectral lines that are very prominent in may nebulae. It turns out being a good tool to expand imaging time beyond just the moonless nights.  Core of M42 Orion Nebula im HaOIII, 50x10sec C9.25 on EQ6-R Pro, ASI294MC PRO, Reducer 1/6.3, L-eXtreme IC405 in HaOIII, 30x300s,  C9.25 on EQ6-R Pro, ASI294MC PRO, Reducer 1/6.3, L-eXtreme IC433 in HaOIII, 40x120sec C9.25 on EQ6-R Pro, Reducer 1/6.3, L-eXtreme Filter Detail of NGC2246, Rosette Nebula in HaOIII, 30x90sec C9.25 on EQ6-R Pro, ASI294MC PRO, Reducer 1/6.3, L-eXtreme However, I noticed that particularly the pictures that were taken with both the reducer/corrector and the filter showed some light color fringe around the stars. I assume that something in the geometry of the imaging train wasn’t quite optimal. As I didn’t have to many opti...

Last week we had a couple of beautiful winter days with reasonably clear nights. Unfortunately, it was almost full moon with the moon lit to 80-90%. However, with the enthusiasm that is typical for beginners I didn’t want to use the night exclusively to test equipment - I wanted to get a few pictures as well.  Star clusters are an object type that I used to observe visually at such nights as they are usually reasonably bright and have good contrast. So that ist what I try first.  NGC457, The Owl cluster 30x10sec, C9. 25 with reducer 1/6.3, ASI 294MC Pro on EQ6-R Pro M35 (right) with NGC 2158 (left) 30x10sec, C9. 25 with reducer 1/6.3, ASI 294MC Pro on EQ6-R Pro I think these came out quite nice. With so much moonlight it is hard to take longer exposures to get deeper. However, the brighter stars are starting to saturate anyhow, so these settings are probably ok. Most deep sky objects are looking way more impressive on a photograph than visually. However, while I like...

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 ...