Astrophotography by Philipp Salzgeber

 

 

Philipp
Salzgeber

Wolfurt / Austria

My Astronomical Equipment

The observatory

Probably the most important piece of equipment right now is our roof-top terrace. While the place where I live has some strong light pollution, and is sometimes plagued with fog. The ability to quickly step outside the house and have access to the whole sky is a big bonus to the hobby. I have put my telescope, mount and accessories in an aluminum box, which up to now has stood up agains the elements. Now I can start observing pretty quickly and even had some success in astrophotography from home.

The evolution of my self-built 6" f/5 Newtonian Telescope:

Travel-Dob

After seeing a very light weight travel-dobson telescope at the Internationales Teleskoptreffen in Carinthia, I decided to build a similar telescope. After lot´s of trial and error I was quite content with my work. You can find the whole story with some pictures of the finished scope, the building process and images from the optical shop (Interferometry, Ronchi, Foucault,...) here: building a 6" dob. While I liked the liitle weight and uncomplicated setup, the fact that I was not able to use it for photography bothered me, to resolve this issue I decided to put it into a tube...

Tube
self-built 6" inch f/5 telescopeA 20cm diameter drainage tube and a Vixen 2" focuser were the start for my project. The tube was cut off squarely and I built a curved spider similar to the one used for the dob. The mount of the main mirror stayed the same, I just made a new baseplate for it. Adhesive black velour was applied to the inner tube, while the outside was lined with blue dc-fix foil. The dc-fix foil is easier to apply than paint and less messy too! After some searching I found the tube rings at a plumbing equipment shop, they are quite heavy - but stable. While the scope looks quite finished I have to fine-tune the secondary holder. While doing a star-test on Vega I noticed astigmatism, maybe the secondary is the culprit, after some research I may have to replace it...

Some first images done with this setup are: M13, M27, M57 and M71.

 
 

Truss-Tube

It turned out, that the pvc tube was too heavy for my Super-Polaris mount, especially when adding a guide-scope to the setup. I decided to rebuild the tube using an open three-truss design. And yes, the secondary was the cause of the Astigmatism, it has been replaced. Using simple tools and materials this is the result:

Eschenbach Novalux 60/415 Refractor

modified Eschenbach Novalux 415I used this scope as a "grab-and-go" scope for quite some time. But after viewing the lunar eclipse in November 2003 with a Orion ST80 (from Florida!) I decided to buy a 80mm GSO f/6 refractor, which is described above....

The Novalux has bad chromatic aberration and quite some astigmatism and spheric aberration, furthermore the tube was too short and demanded lots of extension tubes behind the wiggly focuser. I replaced the original tube with a plumbing pvc tube, and added an adapter to use 1 1/4" eyepieces. While the scope is very bad visually, it tuns out that it is quite usable photographically and I am also able to use it as a guidescope with the QHY5 autoguider.

Vixen R-130S Telescope on Super Polaris Mount

Vixen R-130S on Super Polaris mount, Optus 70/700 "Lidlscope" as GuidescopeTelescope: Vixen 130S, Newtonian Telescope with 130mm (5,1") aperture and 720mm focal length (f/5,5). A drawback of this telescope is the 1,25" focuser, which does not allow unvignetted 35mm photography. The mirror is slightly overcorrected, delivering less than perfect planetary images.

Mount: Vixen Super Polaris german equatorial mount with dual axis drive. While it is too light for this kind of setup, the polar alignment with the built in polar scope is very accurate. Corrections in declination are only needed a few times during an exposure. The yellow/orange surveyor tripod I use is much more stable than the original aluminium tripod.

Guidescope: Optus 70/700 Achromatic refractor. I bought this refractor with a quite reasonable equatorial mount at an outlet of the Lidl supermarket chain. It´s low price makes it quite popular with amateurs in Austria and Germany. I found mine to perform quite well as a Guidescope. It is very light regarding it´s size, which is a bonus for me and my overloaded Super Polaris! I use the Baader Microguide as Guiding eyepiece.

Nikon FM2

NIkon FM2 with eyepiece magnifierThe FM2 is a fully mechanical 35mm camera, it does not need a battery for its full range of shutter speeds from 1/4000s to B. When the self-timer is activated the camera swings up the mirror at the push of the button, so when the exposure starts some seconds later, the vibrations have dampened out. For widefield shots I use lenses from 20 to 105mm, with the AF 85/1.8 and the AF 105/2.8 Micro Nikkor being my favorites. Focusing is difficult, but the 2x focusing magnifier helps a little. So far I this method proved to be sufficient for my purposes.

Pentax 6x7 [sold]

Pentax 6x7 with 400/4.0 Takumar, Nikon FM2 with AF-Nikkor 85/1,8With lenses from 55 to 400mm this should be a powerful camera for widefield shots. I have not used it very much for astrophotography yet. The combo Pentax 6x7 and 400/4.0 is quite impressive! In the picture it is shown alongside with the FM2. The biggest problem with this camera is the current lack of good astro-films in 120 format. The camera is quite old, and I had to replace the shutter (700 € - ouch!) but it works fine and it delivers nice slides.

 

Nikon Coolpix 4500 [broken]

Nikon Coolpix 4500 with Vixen Digital Camera AdaptorMuch more advanced than the 950 this camera is sensitive enough for basic deep-sky astrophotography. You find some deep-sky and planetary images here. I have used exposures of up to two minutes quite successfully. When not using my self build cable release bracket I use my laptop running Snappix and a serial cable.

Nikon Coolpix 950: This digital camera is usable for shots of the moon, planets and the sun.The images are taken afocally, i.e. The camera looks through the eyepiece like an observer. I use a Vixen Digital Camera adaptor to couple the Coolpix to the eyepiece. For use with a cable-release I made a bracket of surplus pci-card slot covers from my computer. I also tried some deep-sky shots with this camera, but the results were not very encouraging.

GSO 80mm f/6 Achromatic Refractor [sold]

Vixen R-130S on Super Polaris mount, Optus 70/700 "Lidlscope" as GuidescopeQuick Look scope: I bought this GSO 80mm f/6 (480mm focal length) refractor used over the internet. The GSO is nicely built. It is much bigger than other 80mm f/5 scopes I have held in hand. The dew-shield is quite large and the tube is also a little wider than absolutely necessary.
The focuser is a very nice rack-and-pinion type. It is very smooth, better than the Vixen 2" focuser on my self-built scope. The optical quality is quite good, I made a direct comparison to a Japanese 80mm f/5, and the GSO had better limiting magnitude, resolution and contrast. The Cassini division was clearly seen, while in the other scope it was quite difficult. Chromatic aberration was a lot less in the GSO.
During the Venus transit, I was able to spot the atmosphere of Venus outside the Sun before second contact.

The star test looked quite funny, so I made some inquiries and at last the telescope was optically tested. The asymmetrical star test stems from a irregulary polished surface of the cemented doublet. Misalignment of the lenses was not the cause, as some people speculated. While optical quality is not perfect, it is better than in the comparison scope. For a quick look at the sun or the moon this scope is exactly what I needed, It will come with us to the camping-holiday to!!

Webcam

Philips Vesta Webcam on  R-130S I found this Philips Vesta 675K for only about 22€ at the local Media Markt. It is well suited for planetary imaging. On my planet page you can find images of Mars, Jupiter and Saturn.

The more expensive ToUCam Pro could give you up to 30frames per second in VGA (640x480) resolution, but because of the compression taking place, it is recommended to use 5fps in any case, so this camera with its limit to 5 fps works just as well.

To increase the meager 720 mm focal length of my R-130S I use a Vixen 3-element Barlow and a Diagonal Prism between the barlow and the camera, which results in a 2.7 increase in f.l.

 


All images Philipp Salzgeber

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