The Coma galaxy cluster, Fritz Zwicky, and Dark Matter.

This is an original Hyperstar (no collimation or camera angle adjusters) and SX H9C OSC CCD image of the Coma cluster of galaxies. This galaxy cluster was made famous by Fritz Zwicky who studied the cluster, and by applying the virial theorem to star motion in the galaxies he deduced that there must be some form of Dark Matter present.

There are a number of people attempting to re-write history by stating that Vera Rubin discovered Dark Matter during her work in the 60s and 70s where she also applied the virial theorem to star motion in galaxies. Unfortunately she was around 30 years late in coming up with that one.

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How did it all begin??

As I sit through gloomy days and gloomy nights waiting patiently for this season’s imaging to get underway, I remembered the very odd start I had to this hobby. I don’t think I’ve shared this one before, so maybe now is a good time to do so.

I have always had an interest in Astronomy, my first degree at Sussex University (1975 – 1978) was a B.Sc. in Physics, Mathematics and Astronomy. I must admit that it was a mistake doing something you love as part of a degree as it put me off Astronomy for a good 5 years. At that time I lived in Southwater near Horsham and although the skies were reasonable I didn’t do any Astronomy that I can remember, I didn’t have a telescope anyway, although I did have binoculars.

We then moved to a place just outside of Abingdon, Oxford, and I spent a little more time viewing the skies, through binoculars, mostly from White Horse Hill. Observing as I remember was reasonable from one side of the hill and really bad the other side where the Swindon skyglow lit up the sky. There was still nothing serious going on Astronomy-wise.

The next move was to Lyndhurst in the New Forest and surprisingly there was a slight increase in the Astronomy interest, especially as Halley’s comet was due at the time. I bought a huge pair of zoom binoculars (totally inappropriate for the job) and saw the comet from the open forest just over the road from my house. Seven years in Lyndhurst and nothing progressed much from the occasional night out with the binoculars.

We then moved to just outside Brockenhurst, and it must have been nearly ten years before I realised that for the first time in my life I had a few quid in my pocket and I also had half reasonable skies. I’m going to buy a telescope!! But what scope? There was a huge range of beautiful scopes to choose from back in 2002, so what do I pick? My first thought was I didn’t want a “Go To” scope as I wanted the “fun” of finding all those deep-sky goodies on my own. To that end I bought a Helios 6″ refractor (a truly excellent scope for the price) on an equatorial mount, a mount by the way that I never set up properly as I didn’t know how to. I managed to find the Ring nebula, and the Double Cluster, and I think that was pretty much it. All these globular clusters and other nebulae were completely elusive, I wasn’t having much “fun”. I knew almost immediately that I had made a big mistake in not buying a “Go To” scope, so cutting my losses I went and got one. Again, with such a huge offering of beautiful scopes, which one do I pick? Well I was going to choose the biggest one I could carry in and out of the house, which limited me to an 11″ reflector, and the Celestron Nexstar 11″ reflector (from David Hinds) also allowed you to put a thing called a “Hyperstar” on the front which allowed you to do ultra-fast imaging (so it seemed). Although I had no intention of doing any imaging I bought the 11″ SCT as it seemed to offer great flexibility.

The C11 arrived, and I thought I’d made another (even more expensive) mistake. It looked very complicated to set up, and to be honest, I thought it was beyond me to get it going. Having read the booklets at least a dozen times I got the scope outside on the first clear night and tried to set it up. I did what I thought was a 2-star alignment, but then when I told it to go to the first object, there was nothing in the viewfinder – huge disappointment. I think I must have chosen the wrong star or something because on the second clear night – it all worked!!  I can clearly remember the night of Thursday 2nd May 2002 as if it were yesterday.  It was the first night that I properly aligned my brand new 11″ Celestron GPS scope so that I could automatically go to all the objects I’d read about for many years – but never seen before.  I wrote about the experience in a “Lateral Thoughts” article in the September 2002 issue of Physics World (IOP Publications) titled, somewhat sadly, “The most amazing two and a half hours of my life (so far)”. I had Norton’s Star Atlas by my side and managed to view all the objects on the page that had May objects I could view – astounding.

Now I was away! I was only ever interested in observing, which is why I wonder why I bought the Hyperstar a few months after getting the scope, along with binoviewers and two eyepieces of all the powers I could find. The binoviewers really transformed my observing and made it a wonderful experience to watch the skies. At some point I must have gotten pretty fed up carrying the C11 in and out of doors every clear night, so I bought a Pulsar observatory to set it up in. I removed the excellent tripod and put the C11 on a custom made Aluminium pillar that was anchored to a concrete block that went through the obsevatory floor. Observing was made even better by being in the shelter of the observatory and I spent many happy (freezing) nights observing the heavens.

I guess I must have spent nearly 2 years doing observational work when it struck me that I was always going back to the (very) few objects that looked good through the scope – and I suppose I was starting to get bored. This was bad! However, I had that Hyperstar that had been sitting in a drawer for 2 years, so I bought a Starlight Xpress H9C OSC CCD to go with it and bolted the two to the front of the C11 having removed the secondary mirror. What happened then was an Epiphany. A short 10-second exposure showed an order of magnitude more stars than I could see through the binoviewers, and it got even more exciting. A very short exposure on the Horsehead nebula region showed the Horsehead as clear as day – but I never managed to observe it visually, even using a bunch of different filters. That was the end of my observational Astronomy, and I am ashamed to say I haven’t looked through an eyepiece since. So there I have a padded case full of 2 sets of every eyepiece, binoviewers, and a bunch of other stuff, just sitting there for 17 years.

Things progressed very quickly for the first few months. I was using the scope in Alt-Az mode as the C11 I bought was fork-mounted, and I was surprised to see I got star trailing with exposures much beyond 20-seconds. What was that all about? So then I learnt about Equatorial mounts and bought a wedge to turn the fork-mounted Alt-Az C11 into an equatorially mounted imaging beast. The wedge in turn needed me to get a new Aluminium pillar made up and then I had to go through the painful experience of polar aligning this thing as well – as I said, a lot of progress and a lot of new learning, in a very short time. So then that should be it shouldn’t it? Nope, for exposures of a few minutes the Celestron mount wasn’t up to the job unguided – so I then had to purchase a guide scope and guide camera to lock onto a star to enable longer exposure times. In addition, the wedge had an open box end section which deformed as the scope slewed across the skies. This in turn threw out the polar alignment and required me to “tankify” the wedge by closing off the open box end with a thumping great 5mm thick Aluminium plate. The wedge is now rock-solid wherever the scope is pointing in the sky.

So my imaging proper started in the Autumn of 2004 with this basic Hyperstar setup. I quickly learnt, and overcame, the difficulties of imaging with the original Hyperstar which didn’t have collimation or camera angle adjusters and started to turn out half reasonable (as far as I was concerned) deep-sky images.

And that’s how it all began.

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Polar Alignment using Sharpcap

Unexpectedly clear last night, albeit with a nearly full Moon. Still, that doesn’t matter too much when you’re setting up/tuning a system.

So it was the Hyperstar 4 on the C11 with the ASI2600MC-Pro camera last night. Started off by getting reasonable collimation and then moved on to polar alignment. Now I haven’t touched the polar alignment for what must be going on for 10 years so I was expecting it to be miles out. I bought the Pro version of Sharpcap just for the polar alignment program which looked very good. Well – it IS very good, in fact I would say it is phenomenal. If an idiot like me can get aligned to the Pole within 10-arcseconds in less than 30-minutes – then the product is a good’un!! I of course checked the PA before making any adjustments and was astonished to find it was “FAIR” at something like 4 arc-minutes. Amazing since it hasn’t been looked at for a decade and the mount had taken a good few knocks in that time.

As there was a blazing (almost full) Moon up it was pointless to go for any serious imaging – so I left the scope pointing at the Celestial Pole and took a bunch of 3-minute unguided subs just to see what I got. Collimation wasn’t spot on, but I am very pleased with the result, especially as magnitude 17.5 galaxies are clearly visible – with just 3-minutes exposure time!

Next job (while the Moon is being a pain) will be to get the MiniWASP array polar aligned and then I’m in business for this imaging season. Fingers crossed for some clear skies this year.

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A 10-year Journey on Speed or Why the Hyperstar Really is a High-Speed Imaging System.

No not amphetamines speed, but f# speed, a poorly understood but absolutely critical optical system parameter.

It has been a very difficult decision for me to make on how to tell this story. I have had clues about what’s been going on dating back some 16 years, but for some unknown reason my brain decided it was not going to put all the pieces together, and give me enlightenment. Instead, I have had to wait until just two days ago when I put up 2 images side-by-side, for me to finally understand what’s been going on. So the best way to start the story I guess, is with those 2 images.

Figure 1) Pelican nebula shot with the Sky90 array at the New Forest Observatory using 3 x Sky90s @ f#4.5 and 3 x M26C OSC CCDs with APS-C size image sensors. 12 x 10-minute subs.

Figure 2) Pelican nebula shot with the Hyperstar 4 @ f#2 on a Celestron Nexstar C11 using an ASI2600MC-Pro OSC CMOS camera with an APS-C size sensor. 3 x 10-minute subs.

Take a very close look at the 2 images and compare the differences. The field of view of the Sky90 image is bigger than the Hyperstar because although the sensor size is the same for both systems, the focal length of the Sky90 is less than for the Hyperstar. The colour in the Sky90 image is closer to natural colour, but that’s just because the Hyperstar camera is new to me and I haven’t yet sorted out the colour processing properly. But the BIG difference between the 2 images is the DEPTH of the Hyperstar image. The Hyperstar image of the Pelican is clearly deeper than the Sky90 image. Now that is odd seeing as we have 2-hours of imaging time on the Sky90s and only 30-minutes of total imaging time on the Hyperstar, that is we have 4 times more data in the Sky90 image, and yet the Hyperstar image seems to go deeper. If you are more switched-on than I am, you already have enough information there to see what’s happening. But if you are as slow as me it is worth going back a good few of those 16 years to see some other images that were clearly telling me what was going on, even though I didn’t realise they were doing so at the time.

Figure 3) A four-frame mosaic of the Pleiades using the original Hyperstar @ f#2 and a tiny little H9C OSC CCD. Each frame is an hour’s worth of 60-second subs, so there are 60 subs per frame.

The Pleiades image in Figure 3) should have been my first clue as to what’s going on if I had listened a little closer to Ron Arbour’s comments. I sent the image to Ron as it had an asteroid going through the Merope nebulosity, and I knew that Ron, being a supernova hunter could probably identify it for me. Ron did identify the asteroid, but he also made the passing comment, “Although glassy clean and very low-noise (due to there being 60 subs per frame) your image is not very deep”, which at the time I thought was an odd thing to say. As you can see, there’s plenty of nebulosity in the image, so it didn’t seem particularly “shallow” to me. I completely forgot about Ron’s comment and moved on.

Figure 4) A deep single frame image of the Pleiades using the 3 x Sky90 refractor array at the NFO. Many hours of 10, 20 and 30-minute subs, plus 6-hours of 1-hour long sub-exposures!

The Pleiades image in Figure 4) was taken just a few years ago using the Sky90 refractor array I call the MiniWASP array at the NFO. Well there’s no questioning that this time we have a very deep image, and it is clearly much deeper than the original Hyperstar image in Figure 3). I still didn’t put the pieces together.

I have been running the MiniWASP array for something like 10 years now, this array comprises 3 x Sky90 f#4.5 refractors with M26C OSC CCDs, and 2 x Canon 200mm prime lenses stopped down to f#3.8 with Trius M26C OSC CCDs. I have written an article about the array for Astronomy Now, and I have had many images produced by the array published by Astronomy Now. However, I have kept it rather to myself, that I have not been overly impressed by the images the array produces, certainly not when you compare images produced by the array against Hyperstar images.

For the final bit of the jigsaw you need to go back just over 10 years when I was putting pen to paper and trying to work out what I needed to assemble for my proposed MiniWASP array. I wanted the array to approach Hyperstar performance, and although equalling Hyperstar performance was out of my price range, I thought I could get some way towards it by paralleling up a bunch of Sky90 refractors. So the original thought went something like this. The Hyperstar operates at f#2 and the Sky90s (with reducer/corrector) are f#4.5. In terms of speed this means the Hyperstar is some 5 times faster than the Sky90s, so logic (without much thought) says if I build a 5 x Sky90 array then I will have Hyperstar performance using refractors. I should say at this point that there were other reasons I wanted to use refractors rather than the Hyperstar, and these were that the refractors could image very bright stars (including Sirius) without ANY lens flare. Also, I found the star images from the refractors were just “better” looking than those from the Hyperstar. I don’t know what that undefinable something is, but it might have something to do with the refractors having higher contrast than the Hyperstar as they don’t have a secondary mirror port getting in the (optical) way of the main mirror. As my wallet would only stretch to 3 x Sky90s rather than the 5 required I had expected less than Hyperstar performance, but I hadn’t expected for a moment the actual (highly disappointing) performance I got. Star fields were great, the results for point objects were pretty much as I had expected. But nebulae and other extended objects were another thing entirely. I had to use rather long subs of at least 15 to 20-minutes to get anything I was happy with, and I needed at least 20 of them to get a decent low-noise final image as well. So, where did I go wrong?

Well, if you were more on the ball than I was, the answer was right there with those first two images. A Hyperstar at f#2 is 5 times faster than a Sky90 at f#4.5, we know that. But what that means, and this is the final bit of the jigsaw that only just came together for me, is that an f#4.5 Sky90 needs to take a 50-minute sub to get the same depth of image as a 10-minute Hyperstar sub! It doesn’t matter if you have 5 Sky90s working in parallel, each camera/refractor system is STILL only f#4.5, you WILL need a 50-minute sub-exposure with the Sky90s to equal the depth of image achieved by a single 10-minute sub-exposure with the Hyperstar. You don’t even get the bonus of a lower noise image with the Sky90s. If you produce 5 subs of 50-minutes duration using 5 Sky90s, then you will also produce 5 subs of 10-minutes for the same 50-minute duration using the Hyperstar. So the noise reduction (due to stacking together subs) is just the same in both cases. The only real problem is, you would have forked out on 5 Sky90s together with their cameras, just to manage to get the quality of data you could get from a single Hyperstar 4 with a single camera. This is not really a cost-effective solution to the problem.

You will see people on a number of Forums say that the Hyperstar is a “hype” job, and that this “faster, high-speed” imaging business is just an advertising gimmick. They feel this must be so because you can use the same optical system, say an 11” reflector to image at both f#10 and f#2. Now since the collection optics is the same, an 11” mirror, the thought is, you will get the same photon density in the focal plane in both cases, one is no faster than the other. That train of thought is unfortunately totally incorrect. The f#2 system images a much BIGGER area of sky than the f#10 system, the field of view at f#2 is much greater than the FOV at f#10. Since you are imaging a much bigger area of sky at f#2 it should really come as no surprise to you that the photon density in the image plane is also much bigger than for imaging at f#10. So f#, which is simply defined as the focal length of the optical system divided by the system aperture, REALLY is the “speed” of the system. It does seem to defy common-sense because one’s first thought is that a bigger mirror must put more photons per unit area onto the sensor – BUT – go back to the definition of f#. f# is normalised to the optical aperture by taking the ratio, focal length/aperture. This leads to this conclusion, that I must admit, even I don’t like, and that is the 8-foot f#24 mirror of the Hubble Space Telescope is 144 times SLOWER than the f#2 Hyperstar 4 sitting in my back garden. Strange but true.

CCD = Charge Coupled Device
F# = Focal Ratio = Focal Length/Aperture diameter
FOV = Field of View
Hyperstar 4 = Unity magnification field corrector
NFO = New Forest Observatory 
OSC = One Shot Colour
Sub = sub-exposure
WASP = Wide-Angle Search for Planets

 

 

 

 

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First light for the Hyperstar 4 and ASI2600MC-Pro CMOS colour camera on the C11.

Well I posted up the Second Light image from the Hyperstar 4 so I thought I might as well post up the (less-impressive) First Light image as well. This image comprises of 2 x 1-minute subs, 2 x 5-minute subs, and a single 10-minute sub, so just 22-minutes in total. The gain setting was zero for this image, whereas it was 100 for the Pelican sub.

You will also see that this North America nebula image appears to be almost a square format – what’s that all about? Well somehow the sub-frame box in Maxim DL got ticked and that’s the size of the sub-frame it chose. How did the box get ticked? Not entirely sure, but the last few weeks I have been plagued by the wrong settings appearing in Maxim DL after a Windows Update – so it appears that Windows Updates can somehow screw up Maxim DL – I’m not a software expert so don’t know whether this is possible, or just a coincidence.

Anyway – it’s all systems go for the new kit at the New Forest Observatory and I can’t wait to let it loose on the Winter goodies. Let’s just hope for some decent weather for a change.

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Hyperstar 4 and ASI2600MC-Pro now on the Celestron C11 Nexstar GPS SCT.

Starizona sent me the latest Hyperstar 4 and an ASI2600MC-Pro CMOS colour camera to get me out the door and start doing some work again. How could I possibly say no? So the image below (expertly processed by Noel Carboni) is Second Light for the kit and is a SINGLE 10-minute sub of the Pelican nebula. Well I know enough about this game now to state that this kit is going to produce some SUPERB images – provided I get enough clear night hours to use it to its full potential.

The new Hyperstar 4 completely fills the APS-C size chip in the 2600 camera but there is some vignetting to deal with, easily controlled by taking some flat frames. In addition this image is a single UNCALIBRATED sub, no flats, no darks, no bias frames. Another amazing thing about this camera – there’s virtually no hot pixels to be seen. And all this at a set temperature of only -5C, it’s incredible. You’ll see in a post above, another unexpected bonus. There’s no ghost flaring from the bright stars in the Pleiades – well done Starizona!!!

Provided I can get some clear Moonless skies this season, this remarkable piece of kit is going to keep me extremely busy. I might not have a lot of time to man the MiniWASP array, and that will be a painful experience.

Keep checking in to the New Forest Observatory to keep right up to date with the new Hyperstar 4 adventures.

 

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First image of the season

Managed to get out a couple of nights back, clear AND Moonless, and fired up the Hyperstar III for my first image of the new season. It’s only 6 x 3-minute subs on the Pelican’s head – but at least it shows everything is still working. Also it shows that I need to sort out the collimation again – never mind.

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Absolutely everything I have on the Pelican Nebula combined together.

Every sub of the Pelican Nebula from every imaging system all combined together to give this result.

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NFO reboot image

Here is a an image of the Carbon star X Cancri which lies close to the Beehive cluster in the constellation Cancer.

 

 

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We enter a new imaging season.

Well, finally, we are starting to get a few  hours of true darkness back again – hooray!!

Both the Hyperstar III/814C in the south dome, and the mini-WASP array in the north dome are fully functional (makes a change, usually something isn’t working) – so it’s all systems go for the new season.

I have a few exciting projects listed up on the whiteboard for the coming months, so let’s just hope for some decent imaging weather so I can cross a few of them off.

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