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Oct30

Megrez 72FD

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I bought a new telescope a couple of weeks ago (that makes a total of six that I own) and it’s a beautiful piece of work. It’s a William Optics Megrez 72FD and is the best engineered telescope I have used, solid and strong. The focuser is beautiful, it has a 1:10 ratio dual focuser which is just so precise.

It’s only 72mm aperture but the first apochromat (APO) refractor I have owned, this means it is well colour corrected (the colours all focus to the same point) a common problem with cheap refractors is false colour when you observe with them. The Megrez 72 does show some blue blooming but it’s not too bad. The short focal length of 432mm makes it an F/6 which is pretty fast and gives a nice widefield view.

I primarily bought it as a portable scope to take on holidays etc. it comes with a custom backpack to carry it in. I have been doing some imaging with it on clear nights since I got it, the short tube and widefield means it autoguides much better than the large thin-tube reflector and I have been able to do 10 minute exposures with no star trailing at all! You can see plenty of examples of images taken with the telescope in my Astroimages Gallery.

I now want a larger aperture version, maybe a triplet lens William Optics. Unfortunately they are BIG money, the 132mm triplet is nearly £3000!! Where’s my lottery ticket?

Posted: Thursday, Oct 30, 2008 at 02:17 PM by jochta

Sep03

Chrome

2 comments posted in: Buttons

Colour me impressed. I’ve not used Internet Explorer for a long time (other than for testing purposes) and been a Firefox user since it was called Firebird. I found it quicker, cleaner and of course it had tabbed browsing long before IE copied it. However I’ve been a bit mixed over FF3, it’s slower and even more of a memory hog than FF2 was in my opinion and I’ve had a few crashes. Not enough to make me even contemplate using the awful IE7 though.

Now today Google released Chrome and it seems bloody marvellous so far. Boy is it quick as well, makes IE7 and FF3 seem very slow in comparison. It’s worked with every site I’ve tried and I do like the form highlighting. I’m using it right now as a matter of fact! I’ll use it for a few days and see how it goes. One thing I have noticed is it doesn’t seem to work very well with cookies but maybe I need to explore some options.

Posted: Wednesday, Sep 03, 2008 at 01:59 PM by jochta

Jul25

H-alpha

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My latest astroimaging acquisition is a Hydrogen alpha filter. This filter has a very narrow bandpass and only allows light within 13nm of a wavelength of 656nm to pass through it (normal human vision at night is between 400 and 600nm). Some types of nebulae (emission nebulae, planetary nebulae and supernovae remnants) glow particularly strongly at a wavelength of 656nm due to the excitation state of the hydrogen gas in the nebula.

The advantage of using the filter is that it cuts out all light pollution and all ‘visible’ light and only allows the nebula and stars to show. The CCD chips in the cameras are sensitive to this light so you can achieve very high contrast images of nebula, impossible to achieve with filters that allow visible light through. The images are inky black where there is no nebula so even the faintest wisps can show.

Over the coming weeks and months expect to see images taken using this filter appear in the astroimages gallery.

Posted: Friday, Jul 25, 2008 at 01:26 PM by jochta

Jun18

LRGB

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I’ve invested in some colour filters and a filter wheel for my astroimaging setup so I’m going to be posting some colour astroimages up over the coming months, I’ve already posted my first LRGB image of M27 into the gallery.

I thought I’d take a few words to explain how this works. The CCD camera I have is monochrome, these are generally better then singleshot colour cameras as they have a higher resolution and there are no filters in front of the chip. So to get monochrome images it’s just a case of capturing multiple exposures and stacking them in software to increase the signal to noise ratio. To get colour you need to take monochrome images through red, green and blue filters. The filters are very precisely made so they only pass through the correct wavelengths, they also block any infrared light which the cameras are sensitive to and can cause problems. They are also manufactured to ensure that they focus the light from the telescope to the same place, so you don’t have to refocus when you change filters.

The filters are held in a filterwheel, this is a mechanical device driven by batteries that rotates the filters into the lightpath at the push of a button. So there’s no requirement to dismantle the setup to put in the next filter.

So what is LRGB? An LRGB image is made up of Luminance data (monochrome), Red, Green and Blue data. What you do is capture a lot of high quality monochrome data. This provides all of the detail in the final image. You then capture some data through each of the coloured filters, this data can be with much shorter exposures and far lower quality. This colour data can then even be binned, i.e. each square of 4 pixels is summed together to make 1 pixel.  You can also blur it with a Gaussian blur filter to reduce colour noise in the final image. Software is used to combine the three images taken through the coloured filters into what looks like a blurred, low resolution colour image of the object.

Now comes the clever bit, the human eye is really good at picking out detail in monochrome images, it’s rubbish with colour. So what you do is layer the colour behind the monochrome (luminance) data. Lo and behold you have a high resolution colour image!

Posted: Wednesday, Jun 18, 2008 at 01:52 PM by jochta

Apr30

Season Summary

3 comments posted in: Buttons

Now the table tennis season is over (I think) let me summarise how it’s gone this year…

Newbury League
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My 2nd season in the Newbury league and my first in Division 2 and as captain. I was planning on avoiding relegation but we got off to a storming start and we were 1st or 2nd for a good chunk of the season. We ended a bit poorly, losing several matches including a disappointing 10-0 defeat at AWE Aldermaston in a match I thought we had a good chance in. An 8-2 win in the final match means that we end up with a three-way tie on points for 2nd place. In the Newbury league this requires a playoff but I haven’t heard if we need to play this yet. In the cup competition we had a terrific run and ended up in the final of the Pembroke Cup against very tricky opponents. We lost (no surprises really) but a runners up trophy in our first season was a good result. I was aiming for a 33% average for the season and won 19 of 44 matches (43.2%) so very pleased with that.

Didcot League
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Our final league match was last night and we needed an 8-2 win to pip our opponents to runners up spot. It was highly unlikely as they are very strong but we managed to win 6-4 and that was our 16th tie unbeaten for the season. We finish 3rd in Division 3 and it was the first two matches of the season which proved to be costly when we could only put out weak teams. I won 50 of 60 matches (83.3%) which is my best performance for several seasons, playing tougher opposition in Division 2 in Newbury has forced me to be more attacking and seems to have improved my game a bit. This was enough to win the “Best Player” trophy for Division 3 which is awarded to the player with the most wins in the season. I entered the Divisional Championships this season, I usually don’t as I’m not keen on individual competitions, I lost all 4 of my matches in 5 games. In the cup competitions, we lost in the semis in the club competition and we were knocked out in the group stage of the team competition.

Posted: Wednesday, Apr 30, 2008 at 10:40 AM by jochta

Apr10

Star Camp

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Reading AS held their first ever Star Camp last weekend. We took the Eriba and joined some hardy souls on a hillside in Powys on a working farm. Some stayed in the B&B in the farmhouse and others chose nearby self catering accommodation. We were blessed with four clear nights although it was bitterly cold. I managed to get some imaging done on the final night and I will be posting the results in the Astroimages section. It was a really good social weekend and I’m hoping we can make it a regular thing within the society.

Posted: Thursday, Apr 10, 2008 at 01:34 PM by jochta

Mar28

First of the Losers

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Yep, we lost the final which was only to be expected as our opponents were generously handicapped and we went in with just a 28 point lead. Most of that evaporated in the very first match as I lost 21-8 21-12. Needing to stay level to stand any chance from then on, we were dead and buried by the halfway stage. Still not too bad for our very first season in the Newbury league to get to the final. One of our opponents had been trying to win the trophy for 62 years and this was the very first time he had won it! And we get a runners up medal so it wasn’t all for nothing.

Posted: Friday, Mar 28, 2008 at 03:12 PM by jochta

Mar20

New Astrocam

1 comment posted in: Buttons

I splashed out on a new CCD camera for astronomy this week. An Atik 16IC-S which is a 16-bit monochrome camera with peltier cooling, resolution is 782x582 pixels. The chip is progressive scan as well. This is a big improvement over the Watec I have been using, which is great for live views of objects but its 10s maximum exposure and noisy output is restrictive for deep sky imaging. The Atik can do unlimited exposures but since my telescope is not autoguiding (yet) I’m limited to about 30-60s which is about as good as my mount can do. You can see my first efforts from last night in my photo gallery. I’m thinking of splitting off the astronomy images into their own gallery by the way.

Posted: Thursday, Mar 20, 2008 at 12:41 PM by jochta

Mar05

Where’s Mercury?

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This morning was the conjunction of Moon, Mercury and Venus. Due to various astronomical variables which I won’t bore you with, the southern UK was not the best place to see this. However, I got up at 5.30am and drove up to Wittenham Clumps (a nearby Iron age hillfort and just about the highest point within easy reach). The sky was just starting to lighten as I walked up from the deserted car-park. There was frost on the ground and the car temperature was reading -3.5ºC. It was perfectly clear right down to the horizon.

Then I spotted the slender Moon rising, an awesome sight and started snapping off some pictures. Soon afterwards I could just glimpse Venus, easy in binoculars, but couldn’t see Mercury. I continued taking photographs at various exposures hoping that one would capture the inner planet. As the sky began to brighten I knew my chances of spotting Mercury were dwindling, especially as it was 40x fainter than Venus and I could only barely see that. I never did spot it in the binoculars. The sky was by now too bright to even spot the Moon, so I waited for sunrise about 15mins away. It was cold, very cold. And then rapidly the Sun burst above the horizon and on my hilltop perch I was the first to be basked in sunshine as the valley about lay frozen white and in shadow. A glorious experience even if I didn’t quite manage what I set out to do.

Mercury is marginally visible on one or two of my photos, I’m going to have a go at stacking them to try and bring it out. I will post any successful results here

Posted: Wednesday, Mar 05, 2008 at 05:49 PM by jochta

Feb27

Early Start

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Got up at 6am this morning to try and spot the conjunction of Venus and Mercury. Unfortunately it is very low in the sky and the horizon which I thought I might be able to spot them on wasn’t as good as I was expecting. Still, I get another opportunity in early March but I need to find a hill with a good low Eastern horizon this time.

By the way, due to the stupid nature of the handicap system in the Didcot league (which is mainly my own invention) we failed miserably to make the second cup final. The opponents may as well have emailed me their proposed team and saved us the trip.

Posted: Wednesday, Feb 27, 2008 at 03:32 PM by jochta

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