Latest Posts

GMN - Global Meteor Network

Published: 20 January 2026

Background

I am interested in most things astronomy related and this caught my attention a couple of (or perhaps more) years ago.  At the time, I thought it looked an expensive project and it went on the backburner for a little while. I really should have read the GMN WiKi a little more closely. In the scheme of things, this is really not an expensive project, especially when you consider the return and involvement in a true Global Citizen Science project.

What is it?

Broadly the system consists of a (very) low cost security camera with a very wide angle lens, LAN connected through to a Raspberry Pi 4 or 5 with an external internet connection to central data processing servers for the GMN, plus, for UK users, connection to the parallel UKMon (UK Meteor) infrastructure. I have assembled two camera systems - one pointing South West (identified as UK00DA) and the other pointing North West (identified as UK00DE).Their purpose is to detect and record meteor trails accurately enough, so that (with other remote systems) an accurate trajectory of the meteors original orbital path can be calculated. An additional and very important benefit is that any likely meteorite falls can be tracked and the meteorites recovered

The continuous (hours of darkness) image data collection from the camera is processed by the Pi identifying apparent meteor trails against a stellar background. There are two levels of data analysis, a quite intensive pre-upload processing phase that is carried out on the Pi. This involves eliminating anything that does not appear to be a meteor, for example aircraft trails, satellites. A meteor has a quite distinctive visual trail, it is normally very short duration, typically less than 2 seconds plus the visual cue of a trail that 'fades in' to maximum brightness then either terminates abruptly or "fades out" back to nothing. This contrasts with aircraft (usually flashing lights and a trail duration of many seconds) or satellites that may have a trail duration of several minutes. Once a valid trail has been captured, it is possible to backtrack this trail establish the meteor shower source or whether the meteor was sporadic.

The camera is set to have a fixed shutter speed. What this means is that each sequence  is formed from a set of frames of CMOS Camera rows and columns of data captured contiguously at a fixed timing. This allows the processor to determine the apparent velocity and direction of the trail against the stars that are captured within that sequence of frames. Frames are analysed in blocks of 10. Each frame is analysed, if there are insufficient stars visible (a minimum of 20 required for astrometry purposes) or no trail detected, the frame is nominally discarded.

Before you can start, the camera needs to be located, fixed and then prepared. There are 2 aspects of this, the first is very simple. From an image produced by the camera, simply create a mask, blacking out everything that isn't sky. The second task is to calibrate the direction that the camera is pointing. From an image previously captured on a clear night showing lots of stars, create a calibration file that fits matched stars to those on a downloaded star map. The process compensates for distortion  induced by the use of a very wide angle lens. This is a very worthwhile and enjoyable task

Walkthrough

This is a walkthrough of events that occurred on the night of the 2025 October 25-26.

A typical stacked image of all captured frames for that night looks something like this. You can see that the image is swamped by aircraft trails. 

This image is a stack of the 104 detected objects that were shortlisted as meteors. There are a few aircraft trails, but possibly, they just happened to be in frame at the same time that a meteor appeared.

After filtering, the image looks like this. Star trails can be seen as an arc of dots against the black sky background. Clearly, there are some aircraft visible but nothing resembling a satellite. This is a filtered image from all the objects detected that night:

Each trail is then compared against a map of background stars and its apparent velocity and position is calculated. The Pi then identifies the likely cosmic source and if possible, the 'parent' meteor shower source. 

This is a visual report of the meteors detected on the night of the 2025-10-25/26 with the source shower identified or the number and source of any sporadic meteors. 

The following day,  after the capture phase and initial processing has completed, the data is then uploaded to the central data processing servers and each potential meteor is compared with other cameras that may have detected the same trail The system has the capability to detect meteor trails up to about 300km distant and down to about magnitude 4. Aircraft and other flying objects that remained following the local processing phase are now eliminated as these fly much lower (usually less than 10km altitude) than meteors. Satellites orbit at a minimum altitude of about 160km and these are easily isolated and are now eliminated as accurate height information cannot be determined from a single camera.  Meteors burn and form trails somewhere between 75km and 120km altitude. The elimination phase is performed by triangulating the trajectory with 2 or more RMS systems pointing in the direction of the meteor.

The data is then processed and orbital parameters determined. This ongoing iterative process allows the real scientists to determine, with a great deal of accuracy, the source of the meteor and record this accordingly. The Global Meteor Network home page details how the data is captured and compiled.

the UKMon archive website has a search facility that enables a user to examine the meteors detected on any specific date (or date range). The data for my camera UK00DA for the night of 2025-10-25 provides this result.

Selecting the match for 2025-10-26 04:16 provides a detailed analysis for a particular meteor including (where the meteor was bright enough), the image that was captured by my own camera.

Captured moving from the SW to NE with Orion nicely framed.

Next stage in this project will be a 3rd camera pointing East. One for the spring.

 

 

 

 

 

Deep Space imaging with a Small Telescope

Published: 20 November 2025

Background

Small in this context means a 80mm F7 refractor, focal length of 560mm. I appreciate that many 'smart' telescopes have much smaller objectives, but this is my experience of imaging with a fairly conventional astronomical set-up.

Most of my imaging with this telescope has been of the sun, either white light for observing and capturing sunspot detail or with my Spectroheliograph which I use for imaging the sun at very narrow spectral bandwidths.

Last night, 2025-11-19 was actually quite a decent night for observing, the moon was almost new, it had been clear and cold all day with quite a fresh wind although seeing was not perfect when I started setting up at 19:15, it improved as the evening progressed.

My original intention was to do some Spectroscopy but I decided that as I had my 80mm refractor setup and polar and 3 star aligned, I would tackle some of the larger Deep Space objects that would be too big to fit on the sensor of my old SXVR-H694 cooled mono camera if using a telescope with a longer focal length.

The selected targets were M31, the Andromeda Galaxy, M33, The Triangulum Galaxy and M45, Pleiades.

All 3 objects would have 100 exposures of 30 seconds each - about the limit for unguided exposures - with slight variations (between 5 and 15) in Digital Gain adjusted to suit the surface brightness. 

A bit of a false start as I managed (but was unaware) to knock the mount after alignment but before I started the first imaging pass on M31. I couldn't understand why the tracking was drifting slightly giving me elongated stars. A quick check on the polar alignment and I was about 1 degree out, so realigned and restarted.

My setup was as follows:

• SvBony 80mm F7 ED Refractor#
• Starlight Xpress SXVR-H694 Camera cooled to -20C
• Orion EQ-G mount (with GoTo) and tripod (rebadged EQ-6 mount).
• No guiding. I had forgotten that I had taken the guide telescope bevel mount off my refractor.
• Lots of warm clothing and hot tea, it was very cold.

The tracking was remarkably accurate, there was no obvious drift or elongation of star images. After almost an hour, the same peripheral stars in the capture area were all present. It really is worthwhile (essential!) setting up a good polar alignment if you are operating unguided.

Processing was very simple:

• SharpCap v4.1 (Binning 2x2)
• AutoStakert! v4 (Stacking 90% of the images)
• Registax v6 or GIMP

Note: this post is best viewed on a PC screen

M31, the Great Andromeda Galaxy

I have never successfully imaged this galaxy before. M31 is a huge object, several moon widths across the major axis and the only thing I can usually capture is an over exposed core with a hint of a dust lane somewhere.

With M31 centred in the eyepiece, I could see a fuzzy core but not much else. Connecting the camera and focussing and suddenly the dust lanes were just visible. Digital Gain was set to 10.

After realigning the mount, I started the long exposure sequence. 

After processing, I had this result.

I don't think that is too bad for a total 50 minute exposure time. The 2 dwarf galaxies, spiral M32 to the lower right and elliptical M101 to the left of centre. A few processing artifacts due to trying to get the detail in the dust lanes but I am quite pleased with that. It is certainly far better than I have achieved previously.

M33 - Triangulum Galaxy

This was not visible through the telescope eyepiece but was instantly visibly as a faint fuzzy when using the camera. I have noticed this before when imaging M51 and the Flame nebula. It makes a heck of a difference having a better eye attached to the telescope.

It is also an object that I have never managed to image in the past, I am not sure why, its a lovely face on spiral galaxy with lots happening.

As the surface brightness was lower with this object, the digital gain was increased to 15 (100 is max).

The ragged appearance of the galaxy is quite noticeable. However the amount of detail that I could capture is limited with only 100 exposures and an 80mm aperture. Very pleased with that and one to have another crack at with my 200mm F5 reflector.

M45 Pleiades

If you have read any of my earlier blogs you will know that all I wanted to achieve with this was to capture some of that wonderful reflection nebula wispiness that is the main characteristic of the Pleiades.

Digital Gain was reduced to 5 for this as it is obviously the brightest of the 3 targets for the evening.

My main criticism with this was that I didn't centre the object very well. It also very slightly out of focus which is rather irritating. I will have to go back and do it again! The nebula is visible, it is a shame it is not colour  as the nebula has a lovely blue tint.

 

So, all in all a good evening, from start to finishing pack-up it was almost exactly 5 hours. The temperature continued to fall with nearly everything covered in a fine layer of frost at the end of the evening. The dew shield on the telescope was very effective, no condensation at all, all evening.

Lessons learnt:

1. I need to improve my focussing technique. I'll try a Bhatinov mask next time.

2. The results were all better than expected. I am not a Deep Space imager but it is nice to have record of objects that you can't quite see.. I now have to decide what is the longest exposure sequence that I can live with.. Probably not much more than an hour at the moment.

 

 

Choosing a Telescope System

Published: 04 November 2025

This page takes the form of a presentation that I was asked to give at very short notice (3 hours!) at the Monday evening club night of South Cheshire Astronomical Society. Literally just a few thoughts, ideas and anecdotes for a presentation not to last more that 20 minutes.

Trying to avoid real money discussions as I didn't want to get into a 'How Much?' or 'You can buy it cheaper at another emporium' type responses. 

So, making a start...

I always introduce my talks with a brief explanation of what we are going to talk about. I opened with a question ' How many here own a Telescope?' Most people put their hand up. The second question was 'How many people use their telescope regularly?'. Most hands stayed down and a few embarrassed chuckles. 

 

A decent telescope is usually an expensive investment for most people. My view is that first telescopes are often purchased on a whim without any thought of the suitability of the instrument bearing in mind the capabilities of the owner, what the telescope will actually be used for and how practical it will be to use in the owners local environment. I was hoping to get people to think about what they really need before they buy.

My response is to create a check list.  Clearly, budget is a factor, but be realistic, once the novelty of the initial purchase has been made just how often and what opportunities will you have to use the telescope to become proficient. While thinking about this, think about obstacles that will prevent you from getting maximum enjoyment or will limit the range of celestial objects that you would like to observe. For example if your garden is North facing with a limited southern horizon, choosing a telescope to observe planets may not be the best idea - unless you are prepared to travel - which in itself would probably be a hinderance to using a telescope. You may need to swap North for South if you are reading this in the Southern Hemisphere.

When you have a good idea what you think you will use your telescope for then you can now think about the specification of the instrument that you would like to buy. I explained a few key phrases that you will come across. 

Broadly, my recommendations would be - especially for those will a limited budget:

• Always choose optical quality over aperture.
• Unless you really want to do planetary and lunar observing, then always choose aperture over focal length.

Then see what you can buy within your budget. Stick to the well known names where possible or better, discuss with someone with experience.

Don't forget the mount - I discussed mounts later in the presentation.

Finally - where will you keep your instrument. Ideally somewhere secure, dry but unheated. The telescope should always be kept at outside ambient temperature if possible.

So, lets have a look at the type of instruments that you are likely to come across. I cover each of these options in the next few slides.

These should be mandatory for all beginners. Most households already have a pair lying unused in a cupboard somewhere. Learning to find your way around the sky - especially in typical light polluted areas - is so much easier with a pair of binoculars. However holding a pair of binoculars, trying to keep them steady while not getting severe neck/back/arm/shoulder ache can be a challenge. Easily alleviated by using a binocular mount. Older binoculars may have different fitting types, you will need to check your binoculars before you buy. The tripod should be rigid enough to support the binoculars without juddering every time that you want to move it. Something like this with a long arm to move the binoculars works well. I was asked to suggest a binocular size - 10x50 will enable you to see the four Galilean moons and with a weight and size that is easily manageable.

Moving onto telescopes and starting with Newton type reflectors. In many respects these make ideal starter telescopes with an aperture diameter of about 150mm (6"). Compared with similarly sized Refractors, they tend to be cheaper. I have a 200mm (8") Blue (that dates it!) SkyWatcher reflector - similar to the image, that I have owned for about 25 years (purchased in 2000 or 2001 and funded by a bonus). It's 1000mm focal length and therefore has a F5 focal ratio. I can't see me selling it any time soon. The downside of reflectors is that they need fairly frequent (every few months) collimation. This can be a bit nerve wracking and a challenge for a beginner but with a little bit of guidance it becomes a simple routine maintenance task. They tend to be fairly light weight compared with a refractor. I mainly use mine for Deep Space work but it can also give excellent views of the moon and the planets. One benefit for those who may have mobility issues is that the eyepiece is usually around eye level when standing up or sitting on a high stool.

On to Refractors. These are the telescopes that most non astronomers think about when you tell them you are an Astronomer.

My first telescope was a small Tasco refractor, purchased when I was 11 years old - about 1967. I remember standing out on the patio at my parents house observing Saturn. The image quality was awful but I could see the rings of Saturn nicely merged into the planet.

Lets have a think about Refractors. Providing you look after them, they are essentially maintenance free. However, a decent quality refractor will always be more expensive than a Newton reflector 30% bigger. The reason is that the optics are made of high quality glass, optimised to minimise (never eliminate) chromatic dispersion, the effect of seeing a colour halo around bright point objects - like stars. With modern optics using ED (Extra low dispersion) glass or APO technology (Apochromatic - corrects both chromatic and spherical aberrations) unwanted colour is almost insignificant. Chromatic dispersion is caused by light of the three different primary colours (Red, Green and Blue) that make up white light being refracted differently as it passes though the glass.

They are usually a safe bet if buying second hand - see my caveats later - but can be heavy. 

I purchased a SvBONY 80mm refractor about 4 years ago. This is my first choice everyday telescope, it has ED optics and fits well on a EQ-5 Equatorial mount. It goes with me whenever I travel (in my car). I use the telescope about 250 days every year. Although not cheap (it cost me about £450 at the time), it is far and away the best value instrument in terms of usage that I have ever owned.

By Hybrid I am talking about Cassegrain derivatives that use glass 'correctors' to simplify the very complex construction of a traditional Cassegrain telescope.  The most common variants are Schmidt Cassegrain (SCT) or Maksutov Cassegrain (MAK) types. The advantage of these telescopes is that due to the light path, they pack a long focal length in a very short tube. The downside is that due to the optical complexity, they can be expensive and also very heavy. When I returned to optical astronomy 4 years ago, I treated myself to a Celestron Edge11HD as a retirement gift to myself. (Along with a second hand Orion EQ-G mount).  For planetary and lunar work it is superb but it really needs a permanent observatory mount to get the most out of it. This is something for discussion with your (my) household chief planning officer.

I have two equatorial mounts, an EQ-5 that came with the 200mm Reflector that I mentioned earlier and the EQ-G (similar to an EQ-6) mount that I bought second-hand. Being totally honest, the EQ-5 is too small for a 200mm reflector, The tripod is fine but the equatorial head is not really rigid enough for a telescope of that size. However, I managed to cope with it for over 20 years but it was very frustrating at times.

Most beginners/starter type telescopes are supplied with a tripod and Alt/Az (Altitude (tilt) and Azimuth (rotating around a vertical axis)) fork mount with the telescope tube (also known as an Optical Tube Assembly) sat within the fork. There is nothing inherently wrong with this type of mount except they tend to be a bit too flimsy. If you are considering a telescope with a mount like this, check that it is stiff enough with the legs extended. It really shouldn't move or flex at all when you move or focus the telescope.

Our club has a 200mm SkyWatcher Reflector - a bit more recent than mine with a Dobson mount that is in my care at the moment. It is so easy to use, I can set it up within a minute and be observing. With a low power eyepiece, image drift is not a problem.

The downside of a normal hand powered Dobson is that it is not really suitable for astrophotography unless the exposure is very short - for example, lunar or solar observing. However, some users cope remarkably well with this limitation.

A Dobson mount is inherently very rigid. It is an excellent mount for casual observing and also learning to navigate around the celestial sphere. A nature of the design is that they can only be used with Newton reflector type telescopes.

My anecdote about mounts is perhaps more of a lesson learned. When SkyWatcher released their 'Black Diamond' series of telescopes about 18 years ago, I decided that I would buy a SkyMax 180 Maksutov telescope. It was a beautiful looking instrument and I duly mounted it on my EQ-5. It was totally unusable. The MAK180 was far heavier than the 200mm  reflector and the mount simply couldn't cope with the additional mass. I eventually sold the MAK180 at a loss and really felt quite peeved about the experience. 

There is no point buying a mount that is not strong enough or rigid enough to support the telescope. It is the quickest path to disillusionment there is. Always go one size bigger if that is an option and you can afford it.

Buying Second Hand. Undoubtedly, there are some very good deals on the second hand market. However, there is also some rubbish out there. I do buy second hand, but, unless it is something low cost, I stick to established Buy and Sell sites that specialise in Astronomical equipment like the (UK) Stargazers Lounge and UK Astronomy Buy and Sell websites. You will be buying from established Amateur Astronomers who will be very concerned about their reputation. Again, stick to well known brands - unless you are taking sound advice from a local experienced amateur.

My anecdote for buying second hand is also not a good story. I purchased an Orion Optics OMC-140 Maksutov telescope about 20 years ago from that well known internet auction site. It wasn't cheap. I asked for evidence of optical quality - I was sent photos of Saturn showing the Cassini division. It all looked good. "Buy now" was duly pressed and I excitedly waited delivery.

The telescope arrived a few days later, wrapped in a single layer of thin bubble wrap - which had come undone. It was left on the doorstep. Although there was no visible damage it was clear that the optics had been damaged or knocked in transit. The optics were dreadful. I had no comeback, the seller had arranged delivery and because there was no visible damage, I was 'stuck with it'. I passed it to an experienced friend of mine who declared 'there was something wrong' but couldn't say what. I took it to Orion Optics (the manufacturer/supplier) and they charged me £70 to look at it and declared it was irreparable but they also couldn't say specifically what was wrong. I tried to collimate it but got nowhere and eventually sold it for spares back on the some auction site.  Read my guidance above and take heed.

And that was that, apart from a few questions.

Presentations like this make you think. I hope that this page will be of use to any newcomers out there.

 

Enjoy your Astronomy.