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Recent annoucements from the labour party conference suggest plans for phasing out traditional lightbulbs by 2011I approve of energy saving lightbulbs. I use them in my house everywhere except the bathroom where I like the "instant" light of a traditional bulb. Energy saving lightbulbs also last much longer than traditional bulbs, which means less hassle added to my stressful life worrying about buying lightbulbs.

Attempting to reduce carbon emissions and save energy by banning traditional lightbulbs is also highly laudable. But don't forget, the majority still use normal lightbulbs. A traditional lightbulb factory can only make lightbulbs, and a few other similar things like vacuum tubes. A traditional light bulb factory does not normally make energy saving lightbulbs.

Therefore we have to use up a great deal of energy making factories to keep up with the demand for energysaving lightbulbs. We also have to expend energy dismantling traditional lightbulb factories that are no longer needed, and sacrificing the energy invested in making those factories in th first place.

And are traditional lightbulbs the big culprit? What about halogen spotlights? I know they give you sunburn, so they must waste lots of energy

And the worst one of all1 The 500W halogen flood lights bolted to the side of every body's houses, sports facility and pub car park. License all exterior lighting over 250W - that will really make people think.

As far as astrophotography goes, the big problem is not lightbulbs. It isn't sodium orange streetlights either. It is white light metal halide streetlamps. These are installed because people can see colour - and astronomers can't filter it out using a LPfilter. Because the light from white streetlamps is broadband, our light pollution filters become very ineffective.

Anyhow, I appear to be ranting. In summary I approve of banning the lightbulb. You can't stop the present government mentality of banning anything bannable. So join 'em I say. Just make sure you ban a few other obvious candidates too.]]> General http://astro.neutral.org/astronomy_blog/blog/index.php?itemid=31 Thu, 27 Sep 2007 14:32:45 +0100 http://astro.neutral.org/astronomy_blog/blog/index.php?itemid=28
As the more advanced astrophotographers amongst you will have noticed, we don't stuff our optical tube assemblies with clothes and fill them with water. However, some people in our hobby have a mentality that telescope equipment should be like a washing machine. You bring it home. You install it. You read the instructions, and then it works first time and every time, performing its mundane task without variation.Anybody who has actually done some astrophotography will know that this is simply not the case. It is quite possible to spend many tens of thousands of pounds on equipment and still spend months getting the whole thing talking to itself.

First of all, no astronomer's astrophotography kit is the same. We all started at a different time from a different stimulus. We've all built up our kit from completely different directions. This simple fact alone makes marketing any new astronomy product a minefield of compatibility.

It won't just "work" out of the box without ascending a steep learning curve and more than likely making a few custom modifications or additional purchases to suit you and your location. For example: How many SCTs come with a dew heater as standard? How many SCTs have a label on the box saying "dew heater not included"?

An astrophotograhpy setup is quite unique in the ranks of most hobbyist equipment. I can't off hand think of a hobby where such a wide and varied combination of optical, mechanical, electronic and computer elements must all be brought together and made to work in harmony. All the parts have to work properly. Not only that, they have to keep on working over and over again whilst we reel off a long line of subs over the course of a cold damp, and quite possibly freezing cold night.

Some people in astrophotography world still seem to insist, against all the odds, that everything *should* work first time, and indeed every time. Each time something does not work (or is perceived not to work) they instantly start questioning the item's value, and whether it should be sent away for repair, refunded or simply replaced.

This sort of attitude, although very valid for domestic white goods, is not so relevant for astronomy equipment. This sort of attitude is not going to get you the type of results you see on advanced astrophotographers' websites. Yes, I suppose things should work, and if something is blatantly dead on arrival, then, ok, perhaps it should be sorted by the supplier. However, generally speaking, astrophotography doesn't work out of the box!

Anyhow, nine times out of ten it is probably the user who is at fault.

A little more application to the problems and learning to develop some practical solutions would result in a lot less frustrated astronomers and a lot better astrophotographs.]]> General http://astro.neutral.org/astronomy_blog/blog/index.php?itemid=28 Mon, 24 Sep 2007 23:18:47 +0100 http://astro.neutral.org/astronomy_blog/blog/index.php?itemid=17
It is still a mystery to me why people buy these scopes.

I think it all started with the adverts in the leading Astronomy magazines. In our youth many of us poured over the glossy adverts for a Meade LX200. How great would it be to visit 50,000 different celestial objects in one night?! If only we had the £2999 required to buy one.

Then we all went to university, met women, got jobs and generally lived off beans on toast for half a dozen years. Coming out the other side we suddenly find we have credit cards and disposable income.. and what better way to spend it then on the machine of our dreams from the back page of a ten year old copy of Sky and Telescope?

This might not be exactly the case for everybody... but at the same time I am hoping some people spot the grain of truth in that. Once a newcomer to a hobby sets his or her heart on a particular purchase, it is difficult to deflect them with sound advice.

"It's a great visual instrument"

This is the usual argument. Now, I don't do much visual. In my mind a "great visual instrument" is a 20 inch dob. Preferably one with a with motors to keep the thing pointing in the same direction. Why a 14inch SCT should be so much better than a f4.5 14inch dob beats me.

The F10 SCT is responsible for more beginners dropping out of astrophotography than anything else.

Why?

The reason is quite simple. Any astrophotographic system normally requires two different bits of optics. It needs a primary optic... usually a big mirror or a big APO lens, and it needs a corrector, flattener or reducer type thingy which goes up the camera end at tries to correct for the drawbacks of the chosen primary optic. A refractor normally needs some kind of focal reduction and field flattening, especially for big chips. A Newtonian requires a coma corrector and a thumping great SCT needs a thumping big focal reducer. There are few scopes that take great photos without the bit of glass up the camera end to sort everything out.

Now, when you are new to astrophotography, you generally don't know about the second bit of glass. You assume that the optics will take great photos out of the box. It works fine with an eyepiece, so it should work fine with a camera? Right?

Most of these people who rushed out and purchased the giant SCT of their dreams eventually decide to try some astrophotography. Normally this starts with either the family DSLR or a small chipped entry level camera like the ATIK IC or DSI. At this point the first major drawback of the SCT become apparent. Your ATIK IC running on a F10 10inch SCT with a focal length of 2500mm yields a field of view of 4 arc minutes by 3 arc minutes. Not a lot. And then they wonder why the entire Orion Nebula doesn't show.

This is quickly followed by the second problem. F10. At F10 you gather light on the imaging plane FOUR TIMES more slowly than with an F5 instrument. Ah ha you think - I'll get a reducer! So you spend more money on a reducer and get the bugger down to F6 or so. And then you find the problems with cheap reducers. Focal reducers are very difficult to make. The are expensive. They are very difficult to use as well, and the camera to reducer spacings must be correct.

There is a need for slower focal ratio scopes - but only when your pixel sizes increase. Most entry level camera are in the 6um pixel size range and therefore not suited to imaging at F10.

A F10 10incher running at F6.3 is still a medium speed scope and your ATIK IC is still only going to give 10 arc minutes field of view. Trying to get that sucker to track (or dare we venture autoguide) at that image scale is going to be difficult for the beginner who doesn't know anything about tracking or autoguiding or periodic error. Many of us have forgotten, but most newcomers to astrophotography don't know anything about the difficulty of tracking stars. They just think you slap the camera on the telescope, and it will just work... I remember that I did. I was most disgruntled to learn of the existance of periodic error.

SCTs have these huge plates of glass at the front of the tube corrector plates. Dew delights in settling on this large plate. The longer you are out at night, huffing and puffing around your telescope, the more misted up the corrector plate becomes. The corrector plate is pointing up at the sky, and is doing so at least a foot above your head. You don't notice the slow buildup of water on the front of the SCT corrector plate. How many frustrated beginners out there have got frustrated to the point of packing everything away, only to learn that the front of the scope is completely opaque with condensation? And have you seen how much kendrick charge for their anti-dew systems for telescopes?

And the last one: Wedges. Equatorial Wedges. The delightful SCT usually comes on a jolly fork mount. A jolly ALT-AZIMUTH fork mount. In short, a crap mount for astrophotography. To take long exposure photos with any degree of success your telescope needs to be equatorially mounted. Another set of problems for the beginner to learn about and spend more money trying to solve. Which leads us up another alley - most commercially available wedges of SCT scope are at best poorly constructed and overprice, and at worst downright dangerous. They are comprehensively unsuited to astrophotography unless you spend a great deal of money, or find some of the more niche manufactures.

"It is a great planetary imaging scope"

This is the other one you hear all the time. Long focal length telescopes are fantastic for planetary imaging. The great Damian Peach uses one of the ultimate large SCT scopes: The vast Celestron C14.

There is a problem with planetary imaging. Of the eight planets in your solar system, one of them we stand on. Of the other seven, only 3 of them show very much in the way of surface markings. Of those 3, Mars is a once-every-two-years event, and jupiter and Saturn are either rapidly heading into, or lurking around in some of the least favourable parts of the sky for UK imaging. Most of the upcoming Mars apparitions are fairly poor.

It is a bad time for planetary imaging in the UK. Gone are the heady days of the early part of this decade when Saturn and Jupiter were riding high in the wintertime skies and Mars was making headline rattling appearances. We'd all just learn how to use registax and a toucam. The golden years of planetary imaging. These times will not return to the UK for at least 6 years. It is a bad time to buy a dedicated planetary scope.

So there we have it. A huge focal length and its attendant tracking problems and a focal reducer of dubious quality and operating at medium to slow focal ratios. Add a misted up corrector plate and a equatorial wedge made from rubber metal and it all adds up to a difficult imaging proposition for a beginner.

The F10 SCT is responsible for more people dropping out of astrophotography than anything else.

When is such an instrument good for astrophotography? Take the new RCX things from Meade. put one of these on a great mount and put one of the modern breed of large format, large pixel cameras on the back and put an experienced imager in charge, and you'll be getting some cracking images. Assuming you can afford the 50mm filters.

So there we have my two main scope dislikes. SCTs because they are too slow and have too much focal length and shouldn't be sold to beginners in astrohpotography. 80mm apos because everybody and their dog has one and they are getting a bit tedious.


]]> Buying Kit http://astro.neutral.org/astronomy_blog/blog/index.php?itemid=17 Fri, 21 Sep 2007 12:35:21 +0100 http://astro.neutral.org/astronomy_blog/blog/index.php?itemid=27
I took the opportunity this weekend to install one of these at home. Now my rather confusing backup system (which involved several different computers) is replaced by a simple nightly scheduled task which makes sure my new USB Hdd has a up to date copy of everything on all my other HDDs. I use xxcopy command line.

Hands up who can recover ALL their raw file, images, etc if their Hard Disk dies today?

After years of astronomy I've got over 50GB of astrophotography related file on my hard disk. Personally I don't have the time or energy (or long term faith in the medium) to keep cutting stuff to DVDs... with a USB HDD it is painless...now everything, all my raw images, all those giant photoshop files, everything is safely backuped.

I've also backed up the entire 40GB hard disk on the observatory computer. God only knows how many carefully setup and configured programs are on the computer. If the hard disk goes bang, it would be back to stage one trying to work out the settings for the autoguiding software! Nice to have it backed up.

DVDs and CDs don't last forever. No backup medium lasts for ever, so it is important to periodically review how you are doing backups and take advantage of new techniologies. It won't be long before we are getting 1TB USB hardisks for £75. I also don't thnk it will be many years before USB memory sticks and the like expand to the multi-century Gigbyte capacity. Soon we will be able to carry around all the raw files we have ever taken. Stored on something smaller than mobile phone. Won't that be useful! :-)

Just a little reminder for us all. There are lots of fun and interesting things to spend our pocket money on in the world of astronomy, but sometimes it is worth spending money on the boring things. It is nice that this reminder takes the form of a special offer in a local shop rather than a tale of stife and woe and data recovery.

...and just to shock you further... £75 is just over half what I used to spend a month on cigarettes before I gave up....]]> Equipment http://astro.neutral.org/astronomy_blog/blog/index.php?itemid=27 Wed, 19 Sep 2007 13:52:56 +0100 http://astro.neutral.org/astronomy_blog/blog/index.php?itemid=26
This evening I forced myself to sit down and go back to he beginning of the pile. This is 4 hours of Ha data on the Bubble which was collected during the first major test run of the homebrew off axis guider.

I've done the normal pushed version, and also a more subtle version for the arty types. Both have their merits. (I hope!)

The image of the bubble nebula is under this link..

I'm pretty happy with the level of detail I can now potentially get. Don't forget we are still talking about an LXD55 mount and a bargain basement 8inch F5 newtonian. One which is quite a few years old now as well I might Add.

Taking ourselves back in time to 2 years ago in 2005, we imaged the bubble nebula with our SC3 webcam and got some nice colour and detail. With the Off axis guider working now I am getting the sort of detail using 20 minute subs that I used to get in those heady days of banging off a few billion 30 second subs.

There is another one from last july 2006. What a mess! I made a right pigs ear of that one! Yuck. Still, if we don't have the horrid pictures we won't have any nice pictures! :-)

Shortly after processing this image I found myself looking at the Hubble shots of this region . Wow. They are super hi res. I'm not likely to approach that on my budget (orbital launches are still prohibitively expensive) but it is fun to compre the hubble image with my own after some suitable re-sizeing.

The comparison images below clearly show I need to tidy up my stars. Now I've got my tracking well sorted, and the impending fast guider, it might be time to start thinking about new mirrors and better optics.

hubble curdridge bubble nebula

]]> General http://astro.neutral.org/astronomy_blog/blog/index.php?itemid=26 Sun, 16 Sep 2007 21:28:00 +0100 http://astro.neutral.org/astronomy_blog/blog/index.php?itemid=25
Simply taking RGB astrophotography images of deep space objects is getting a little tiring. Unless you are really good at it, like the Parker / Carboni team the results are a little mundane. If you are really good at it the results are extremely impressive. But, like Greg, a nice dark site does help a lot!

Narrowband astrophotography is very different. We construct the colour image using images captured with narrowband astrophotography filters. These filters allow is to image a very slim band of light centred on the emission from certain elements in our nebula targets. Normally we use H-alpha, OIII and SII.

The secret to a good narrowband astrophotograph is exposure time. Just like Greg with his massive 24 hour+ integrations, a really good narrowband astrophotograph has a massive amount of exposure. Doing 10-15 sub exposures of 20minutes sub exposure time on EACH channel is not unusual. If the target is particularly faint in one or more channels, then massive extra exposure time must be included. Some narrowband astropohotograhers include several days of exposure in a finished image.

A few weeks ago I purchased a OIII narrowband astrophotography filter from Baader so that I could use bicolour techniques to add some interest to my images.

In a stroke of remarkable good fortune, an astronomical acquaintance in the uk offered me an Astrodon SII filter which he'd had for a while, but no real plans to make any use of it. He offered it to me for a price I could not refuse.

SII is sulpher two. This is the emission of sulpher atoms at a wavelength of 673nm. It is deep into the red - even deeper than hydrogren alpha. It is right on the edge of human seeing.

Of course, with all my Heart of the Heart Nebula data from last year, you can guess my first tricolour image... Yesterday I visited Greg in the New forest for a cup of tea, and we were both looking forward to a fine clear night. We were calling it "the last day of summer". So last night I was able to capture 15x1200s of SII data on the Heart of the Heart nebula. Last week I got 11x1200s of OIII data. Now for the processing marathon!]]> Equipment http://astro.neutral.org/astronomy_blog/blog/index.php?itemid=25 Sun, 16 Sep 2007 12:20:23 +0100 http://astro.neutral.org/astronomy_blog/blog/index.php?itemid=24
First, the collimator cross threaded and jammed on to the off axis guider. Using some serious plumbing tools I managed to rip the two appart. However, no hread left on the off axis guider.

So I modified to camera-oag mating so that it was held on by three very iffy and insecure looking screws. Got the whole thing together and the dew heater snapped off the main scope.

Resoldered that back on, and found that the camera was misting up.

20 minutes to find the right allen key to open the camera, and nuked the dessicant and attacked the ccd with a hair dryer.

No luck of course. The camera is still misted over and icing up. I have never, ever had a good solution to keeping my Artemis camera dry. For me this is the biggest failing. Others seem to have no problems, so I guess I am going something wrong. :-/

OAG of course needs re-focusing. I can't dry the camera out. Therefore none of my targets really show up. I either run with no cooling - the noise is a joke, or I switch on the cooling and watch the camera mist over.

Iam always trying to make sure i am well prepared for imaging, but some nights the gods just throw problem after problem at you - I don't really understand what it is that I am suppose to do better.

I am going to give up in a minute - but I've no idea what to do for tomorrow? Perhaps I show take the camera apart AGAIN, nuke the dessicant AGAIN and put the whole thing to bed for a while.

Yours

Fedup of curdridge

]]> General http://astro.neutral.org/astronomy_blog/blog/index.php?itemid=24 Thu, 13 Sep 2007 21:01:29 +0100 http://astro.neutral.org/astronomy_blog/blog/index.php?itemid=11 Canon 350D DSLR camera. Last night Pete and I did the filter swap.

Below is the harmless looking package containing a small piece of glass guaranteed to jangle the nerves of an astrophotographer.



Yup, it is the Baader DSLR-ACF Astro Conversion Filter for Canon EOS 350D/20D.

All digital cameras have a filter to block infra-red light. Digital sensors are very sensitive to IR light which humans cannot see. If the sensor gets hit by too much IR then it cannot find an accurate representation of the colours. The colour balance is a joke.

However, for astrophotography the needs are different. We are interested in wavelengths quite close to IR. Close to 6500Å we find the nebulae transmission lines of Hydrogen Alpha and SII. The typical IR filter found in a digital SLR such as my Canon 350D blocks over 80% of the red light at these vital wavelengths.

Luckily, several manufactures sell replacement IR filters for these cameras. These allow transmission of almost all SII and Ha light, but block off any longer wavelengths. This mean that the camera is able to operate normally in terrestrial situations with a custom white balance selected, but on the telescope, all the vital hydrogen alpha and SII light can get through.
replacement baader IR filter for Canon 350D part number 2459212
The fun part is of course, replacing the filter. Last night Pete and I (well, mainly Pete) completely dismantled the camera, cut out the ir filter, and re-assembled.

An overview of the process of replacing the IR filter in a DSLR canon 350 for astrophotography is found here.

Detailed Infrared Conversion Instructions can be found here.

I've taken a series of photos of our conversion job, but here is one picture for now.

350d ir filter removal

I am happy to say the swap was a success and the camera works fine. Now all we need is some clear skies.]]> Equipment http://astro.neutral.org/astronomy_blog/blog/index.php?itemid=11 Sun, 9 Sep 2007 12:51:58 +0100 http://astro.neutral.org/astronomy_blog/blog/index.php?itemid=19
Direct bias amp off modification for long exposure webcamsThis was an interesting period. Steve chambers was showing off some rather fine dark frames from the then new Artemis 424 camera. This got me thinking... and asking a lot of questions from Steve.

All CCD chips that we use in astrophotography have varying amounts of electrical gubbins alongside the imaging chip. Most of these are to do with amplification of the charge stored on the CCD chip. Now, due to some effect, these components glow very slightly. You can see it on any DSLR. Put the lens cap on and take a 5 minute exposure at ISO 800. You'll see red bits down the side. This is glow from the on-chip electronics. In webcam astrophotography we called it "amp glow".

This "amp glow" limited the faintness of targets for our long exposure webcams . In fact, it was more an issue than light pollution was - at least for me.

We already had some rudimentary methods for reducing this glow. This were based around lowering the supply voltage to the CCD during exposures. Whilst this reduced the amp glow, it still left and uncomfortable amount of residual glow. Proper astrophotography CCD cameras didn't have this problem, so clearly they were doing something we weren't.

This "something" was supplying the bias voltage to the chip separately. The details in are my main direct bias amp off article but in the end I made it work.

Over the last couple of years or so since then I've always had a steady trickle of people enquiring about the mod - but because it came towards the end of the great astrophotography camera revolution, takeup of the mod wasn't very high.

These days it is very easy and cheap to acquire a fairly decent astrophotography camera, such as the ATIK 16IC designed by Steve Chamber. The need to modify a webcam to get a cheap foothold in the ccd camera market is no longer a requirement. Mind you, a black and white chipped long exposure webcam still makes a stunning guidecamera.

philips toucam circuit board
]]> Equipment http://astro.neutral.org/astronomy_blog/blog/index.php?itemid=19 Thu, 6 Sep 2007 21:44:30 +0100 http://astro.neutral.org/astronomy_blog/blog/index.php?itemid=22


This will be handy for holding the camera steading taking pictures of all those small telescope parts!

Using a tripod I can utilise much longer exposures, and therefore use a much narrower aperture, giving more depth of field. This is very useful when taking closeup pictures of astrophotography equipment.

I will use my new tripod in conjunction with my remote shutter release. This helps me to fire the shutter without touching the camera - touching your canon 350D whilst taking an exposure will allow camera shake to creep in and ruin things.

Another clever thing that the 350D canon DSLR does to reduce vibration is Mirror Lock. In the custom functions of the camera, you can program a mirror lock. When you press the shutter button the first time, it locks the reflex mirror out of place, on the second press of the shutter button it actually fires the shutter curtain and takes the picture.

Using a tripod, remote release and mirror lock allows nice long shutters to be used. These techniques are all vital for astrophotography as well as terrestial photography. I will be learning more about this sort of thing once I get this camera onto my telescope!

tripod 350d Canon DSLR jessops]]> General http://astro.neutral.org/astronomy_blog/blog/index.php?itemid=22 Thu, 6 Sep 2007 21:23:16 +0100