Friday, November 10, 2006
Crayford focusser Orion Optics UK
I have received a few questions about the height of the Crayford focuser on my 300mm Orion Optics UK Dobson. Here are three images that show the Crayford in its different positions. On the first image you can see the height of the focuser when it's inside the tube, 6 centimeters. The second image shows the focuser when completely outside, 9 centimeters. So you only have 3 centimeters of travel. On the third image you see the focuser with an extension and completely outside. The total height is 14 centimeters. I have to use the extension on all my 1.25 eyepieces as well as on the Zeiss zoom-eyepiece. For my 32mm Televue plossl, the extension is just a few millimeters to short. I have to pull the eyepiece a little out to get it into focus.

Image 1

Image 2

Image 3

Posted by Math on 11/10 at 07:06 AM | (1) Comments | filed in: Equipment | Print
Tuesday, October 24, 2006
My new toy
A few weeks ago my new telescope arrived, a f/5.3, 12-inch Dobson from Orion Optics UK, equipped with a 9x50 finder and a Crayford focuser. At the moment I am adding a few extras, like the Argo Navis Digital Telescope Computer, a fan behind the primary, some flocked paper in some parts of the tube and a tube extension to prevent stray light coming into the scope.

I will keep you updated, and of course I will publish my observing reports with this scope in the next few months (weather permitting). I also will publish some technical details (mount, tube, mirrors) and some test results for the primary by Orion Optics UK.

Click to enlarge

Posted by Math on 10/24 at 02:49 PM | (5) Comments | filed in: Equipment | Print
Sunday, October 22, 2006
Comet Swan and some deepsky tourism
On Monday the 16th of October, Leo and I got out to our new observing spot to have a look at Comet Swan. We arrived at 20.15 hrs local time, and the sky looked pretty clear and transparent. We could see stars right down to 15 degrees above the horizon, which is very good in our area.

Leo set up his 4-inch Takahashi and the Argo Navis. I got the 15x80 binoculars (with mirror mount) out of the car. I also got my 7x50 binoculars with me. We were ready to go within five minutes, and after searching for another two minutes we already had Comet Swan in both the 15x80 and the 4-inch Tak. Swan looked like a big fuzzy snowball, diffuse on the outer edge, gradually getting brighter towards the center. We could not detect a tail. Leo also tried higher magnifications with the binoviewer, but it did not really change compared to what we saw with lower magnifications.
Posted by Math on 10/22 at 10:50 AM | (0) Comments | filed in: Deepsky log | Print
Sunday, September 10, 2006
Observing the Sun in different wavelenghts
Yesterday I observed some interesting active regions on the Sun, especially AR 908. I used the 4-inch refractor and the Baader Herschel Wedge (with the Baader Continuum and ND 3.0 filters) for "white light"? observing and the Coronado PST for the H-Alpha line.

I tried different eyepieces with the 4-inch TAL: the Vixen LV's, the Zeiss vario zoom-eyepiece and a 32mm Televue Plossl. The best overall view I got was from the 32mm Plossl. At a magnification of 30x the granulation was at its best, even better than in the Zeiss zoom. I noticed that the granulation gradually fades away with increasing magnification. I also compared the Zeiss zoom eyepiece (25-10mm) with the Vixen LV's (20, 15, 12, 10, 9, 7 and 5mm). Although the views through the high quality Zeiss zoom were slightly sharper and clearer than through the Vixen LV's, I still prefer the LV's for their great eye-relief of 20mm. With the Coronado PST I only used the 15mm LV. This eyepiece showed me the most pleasant view, and higher magnifications added almost nothing.

The visual impression you get from Sunspots with the Baader Herschel Wedge and the 4-inch refractor is hard to describe. No image I shoot comes near the sharp and detailed view I get live at the eyepiece, but I always shoot a few images to document the observing session in my observing log. The image below was shot with the Nikon Coolpix mounted on the Herschel Wedge using the 32mm Televue Plossl. The camera settings were 100 ISO, f 5.1, 1/125s and 4x optical zoom.

Click to enlarge!

In the centre of the image you see the active region 908. The more or less pear-shaped group has an area with a few umbra’s that seem to form one large umbra in the form of a cloverleaf. To the left of this almost circular feature lie several smaller dark umbra-like areas, divided by one or two light-bridges, I detected at a magnification of 100 times. The whole group is surrounded by a penumbra, which is also breached by the Lightbridge’s. The Lightbridge’s are not very clear on the image, but visually they where absolutely visible, as where the inner and outer bright ring around some parts of the umbra / penumbra. There where no faculae around AR 908 or on any other part of the Sun.

In H-alpha, the darker umbra’s where very easy to see, but I detected no bright patches in the AR 908 area (plages or flares). I did see two large bright areas around AR 907 and AR 909 (the two smaal groups towards the right edge of the image). Between 907 and 908 I detected a long, snakelike bright area. There where only a few smaller prominences visible. Between AR 908 and the edge of the solar disk I detected two dark filaments.
Posted by Math on 09/10 at 02:47 PM | (6) Comments | filed in: Solar log | Print
Sunday, August 20, 2006
On the wing of the Swan: The Veil Nebula
After three heat waves and weeks of hot and sunny weather in June and July, August brought nothing but clouds and rain. Last night however, from 23.00hrs until 00.30 (local time) large gaps started to appear in the cloud cover. The sky looked very transparent, so I got out my 20x80 binoculars and the 85mm Zeiss. I first scanned the Milky Way in Cygnus with the big binoculars, and the amount of stars visible was simply stunning, indeed a very clear and transparent sky.
Posted by Math on 08/20 at 02:54 PM | (3) Comments | filed in: Deepsky log | Print
Friday, August 18, 2006
A quick look at the Sun
In the afternoon the Sun came out for a few minutes, so I quickly got out the 4-inch refractor and the Herschel-Wedge. There was a wonderful active region visible, AR 0904. The umbra looked jet-black against the "Green" Sun. I use the Baader Herschel-Wedge combined with a 3.0 neutral density filter and the Baader Continuum Filter. Simply beautiful. For visual observing of the Sun in white light, I never had any better views than with this fine piece of equipment. The image does not come close to what I really observed, but it should give you an idea. I stacked it from 235 frames from some video-footage I shot with my Canon camcorder. I used Registax for stacking.

Posted by Math on 08/18 at 05:17 PM | (0) Comments | filed in: Solar scraps | Print
Friday, August 04, 2006
I made it into NightSky
I just got a preview-copy of the September/October issue of NightSky magazine. My “Clavius” close-up was published in the “Skyscapes” section. Click on to image below to enlarge. It’s a scan from the entry in the magazine.


If you are interested in NightSky magazine or Sky and Telescope, click on this link to get to their new website.


Posted by Math on 08/04 at 05:07 AM | (2) Comments | filed in: Books and magazines | Print
Thursday, July 27, 2006
Observing the Sun from the shade
I have been observing the Sun for over a year now, using the Coronado PST and TAL 100RS (combined with the Baader Herschel Wedge). One of the problems I noticed during all the observing sessions was getting a good view of the Sun while you are sitting in the direct sunlight. I used to put a black T-shirt over my head, but I can tell you, you feel like your head starts to melt within a few minutes.

Two months ago I decided to try a big plate of Styrofoam. I just cut two holes in it with a box cutter, so it fits over the PST and the 4-inch refractor. To be honest, it works perfectly for me. Now I sit much more relaxed behind the eyepiece. The views are much better, and the white Styrofoam keeps of the heat as well. If I want to have a real good view through the PST, I still use the black T-shirt, but because I do not get direct sunlight on my head, this isn’t a problem anymore. My advise for solar-observers: get behind some kind of white plate, and of you are looking in H-alpha, make your surroundings as dark as possible. I personally get much more contrast when I view with the black T-shirt draped over my head and over the telescope.

Here are two images of the telescopes and the Styrofoam plate, and two images (from the first week of June) I shot during that observing session, one with the PST and one with the Herschel-wedge. Click on the images to enlarge!


Posted by Math on 07/27 at 06:13 AM | (0) Comments | filed in: Solar scraps | Print
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