The globular cluster M13 in constellation Hercules - and a telescope first light

M13 ist probably one of the most well known globular clusters of the northern hemisphere and very simple to find in the constellation Hercules. When it is comfortably warm in the northern hemisphere in spring and early summer the cluster stands high in the sky and is a popular object for observation. For its high stellar density and apparent brightness astronomical photographers often choose it as a reference object to test a new optical setup for its image quality. This was my major motivation for this image, too. In the end the result was convincing and I chose to present it on this page.

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Image data: M13 and surrounding f=430mm, f/3.3 20x180s, 30x120s, 30x60s als HDR


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Magnified cutout - the image was not drizzled nor sharpened during the processing to be able to judge the quality of the optics

For this photo sets of exposure times of different lengths were used to account for the large variation of brightness between the centre and the outer regions of the cluster. By this measure a saturation of the centre could be avoided. The rest of the processing was rather a basic approach within PixInsight and it was abstained from any sharpening or artificial improvement of resolution to get an impression of the imaging quality.

Until now most of my pictures from my backyard were taken using a triplet (3 lenses) refractor with a focal length of 560mm and an aperture of 80mm - meaning at an aperture ratio of f/7. With reducer factor 0.8 a focal ratio of f/5.6 at a focal length of 448mm could be reached with some penalties on the quality of star images. But in the end the refractor did not satisfy my demands on the field of effective luminosity and image quality. Therefore after some years of longing I surrendered to my wish for a high quality telescope for rather short focal length of 430mm suitable for larger emission nebula and narrow band imaging. And I purchased a Takahashi Epsilon 130d. In the photo below one can see my preliminary setup that was used for the presented image of M13.

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Setup used for the test exposure of M13, Takahashi Epsilon 130d, Lacerta MFOC, EOS 60Da auf Skywatcher EQ8R-pro


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kurz vor "Arbeitsbeginn"


Luckily the telescope reached me in a well collimated state.

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Sehr guter Kollimations-Status bei Auslieferung - die Spiegelmarken wurden natürlich auch genau getroffen

This was not only confirmed by the collimation laser but also by a star test.


Beyond the telescope the Lacerta MFOC was tested in conjuction with my Linux based setup using INDI on a Raspberry-Pi 4. The latter works as a host for the indiserver process. All clients are running on a separate Laptop nearby - but not near enough to keep USB3 connections at sensible lengths if used directly with the setup.

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Automatic focus operation using the Lacerta MFOC with KStars/EKOS Client and INDI