Nightskyhunter Q&A

I decided to add this new section due to the prolific number of emails I get from readers looking specific information on various astronomical and weather subjects. In order to save time I will address the most common questions I get on here, hopefully the answers I give will be sufficient enough to satisfy your curiosity or at the very least guide readers in the appropriate direction with enough information to act as a primer for further research.

I'm new to Astronomy, what telescope should I get?

This is the most common question I get asked. I should state from the start that a telescope is not required to enjoy the night sky, in fact, the majority of the most spectacular events are easily visible with the naked eye or through a simple pair of 10x50mm binoculars. However the desire for a telescope is often a strong one and an individual will not feel satisfied until he or she has a telescope all of their own. I always give the same answer every time I get asked this question - without doubt the best telescope one can get is a Newtonian Reflector on an alt-azimuth mount, such as a dobsonian. An aperture of at least 6" is all one needs to see a good representative example of planets, double stars, deep sky objects, and the brighter comets. A Newtonian Reflector is simple to use, reliable, offers decent wide angle contrasty views, and allows you the greatest aperture for your money. You can always change to a different kind of telescope at a later date as your observing interests become more specific. A good reflecting telescope can cost you anywhere between £120.00 and £400.00 depending the quality, brand, aperture, and whether it is new or second hand.

Should I get an Alt-azimuth or Equatorial mount?

It all depends on what kind of observing you intend to do the most. Are you the kind of person who will be spending a considerable amount of time studying a single object?, would you like to sketch what you see through the eyepiece?, would you like to get involved in astrophotography at some point?. If the answer is yes to these then an Equatorial mount is perfect for your needs as you will be able to align your polar axis with Polaris (the Pole Star or North Star) which will allow you to guide your telescope, either manually, or via a motor drive/sidereal clock, and follow your object for an extend period of time. Make sure to study your user manual and become proficient at Polar Alignment.

An alt-azimuth mount is beautiful to use with simple altitude (up-down) and azimuth (left-right) motion made by your hand movements so you can guide the telescope to any position in the sky at your own speed. This method is by far the most traditional and no different from the way in which observing greats like Charles Messier would have used a telescope. With this kind of mount, particularly the Dobsonian variety, an observer will feel completely free and develop a keen communion with the sky. I highly recommend a good 8x50mm finder scope or a 1x reflex sight such as the telrad finder as an necessity. If you are the kind of person who will be spending your sessions covering many objects in the sky, variable star observing, or comet hunting then this is the type of mount for you.

Should I get a Go-To telescope?

Absolutely not!!, if this is going to be your first telescope then I can't underscore enough the importance of avoiding a Go-To robotic/computer guided telescope. The reason is that you will learn nothing at all if you let the telescope find objects for you. Holding a keypad and typing 'M42' or 'Orion Nebula' then letting the scope slew its way across the sky and centering M42 in the FOV is paramount to rape of the night sky in my opinion. So if you are just starting out get yourself a reflector, refractor, or S.Cass and manually guide the telescope by using traditional star hopping methods to find the object you want, and belief me, there is no better feeling in the world than having a working knowledge of the stars in your mind, a true sense of satisfaction and connection with the sky can only be obtained from knowing the sky in this manner - this is the product of passion.

Imagine being at a star party and witnessing two kinds of people, one spends over one hour setting up their fancy scope and mount, polar aligning, checking encoders, leads, and eventually after 60 min's of preparation the telescope is finally pointed at the sky just in time to greet a blanket of cloud which has covered the sky for the rest of the night. The other observer needs no preparation, he has an internal map of the sky in his mind and during that hour has looked at dozens of galaxies, nebulae, supernova remnants, double stars, the cloud belts of Jupiter, open clusters and perhaps even a comet wandering through the solar system that night. Which of these two would you rather be?, I have experienced this example many times before in reality and have always been the latter!

This is not to say that Go-To telescopes do not have their place, in fact quite the opposite with the result that most amateur astronomers own one or more of these telescopes. If you are an experienced observer or have a specific observing programme which involves checking or imaging many faint objects then a Go-To telescope is essential. If you are into astrophotography or undertake a CCD search for asteroids, comets, supernovae etc then this is the instrument to be using!.

Reflector, Refractor, Cassegrain - what's the difference?

To be honest this question really bugs me because it indicates at once that the individual lacks any really passion, desire, or motivation to make the simple step of typing these words into a search engine and getting the answer within seconds. This is a question I get asked time and time again and my emotional response is often somewhere between frustration and anger because, at the end of the day, I am really wasting my time replying due to the fact that the asker has such little self respect that he or she cannot look up the answer themselves. In my opinion if they lack the motivation to do this then they will not make a good astronomer and more than likely will pack up their brief interest and pursue some other plan which often indicates an unsettled and restless mind unsuited to observation of the heavens. However I am a patient person and like to help people out, after all not everyone is internet savoy so here's my short answer...

Refractors: Most expensive per inch of aperture, usually small to medium aperture and best suited to high power work such as double star splitting, lunar and planetary observing. They used to have long tubes and narrows fields however a new breed of refractor is now very popular among observers known as a 'Rich Field Refractor' which sport shorter tubes, smaller focal ratios, and when used in conjunction with sophisticated eyepieces can yield outstanding wide fields of view suitable for deep sky work and general wide angle viewing. Refractors are the typical kind of telescope most people think of, however a high quality instrument will cost you alot of money.

Reflectors: Most affordable per inch of aperture, simple design, light path reflects of a primary mirror and gets re-directed via a diagonal into the eyepiece so the light only encounters a small number of optical surfaces which means that eyepiece views are cleaner, brighter, flatter, and more natural. Reflectors often have moderate to very large fields of view which are perfect for deep sky and comet work with focal ratios between F/4.2 and F/8 offering a wide range of specific configurations for observers in different fields. From years spent observing the night sky and using different telescopes I can honestly say that the reflector is my absolute favourite telescope. Keep in mind though that small focal ratios can easily get knocked out of alignment and require regular collimation, however with practice this is quick and easy to do.

Cassegrains: These are also known as 'compound' telescopes and are without question the most popular kind of telescope in the world today. They are made from a combination of mirrors and lenses which fold the light path allowing for a long focal length inside a compact tube making them ideal for portable use at home or when traveling to star parties in your car. The most common focal length is F/10 however visual and photographic focal reducers can be purchased to reduce the focal length to F/6.3, F/3.2, or even F/1.3. Cassegrains are moderately priced good all-round telescopes which do a decent job on both DSOs and high power planet work. This kind of telescope is almost always accompanied by motor drives, encoders, Go-To, GPS etc. The most common aperture is 8" however amateurs have been using everything from 5" to 16". These kind of smart telescopes, in conjunction with CCD cameras, have changed the world of amateur astronomy forever.

What telescope should I use for visual comet hunting?

There is no perfect telescope for comet hunting, many types have been used successfully over the years such as reflectors, rich field refractors, cassegrains, and even a humble pair of binoculars. The majority of modern day visual comet hunters use moderate to large aperture reflectors on an alt-azimuth mount with a fast optical system and wide field eyepiece. An optical system at F/4.2 to F/6.3 is a good range which will generate a wide field of view and better contrast between a comet and the background sky. An aperture of at least 6" is a good start however if you wish to compete on the world wide stage then acquiring an aperture of 16"-20" would be desirable to see fainter comets, however keep in mind that larger apertures will provide smaller fields of view. It all comes down to a balance between light gathering ability, portability, and field of view because if you can see more sky in one glance then you will be able to sweep a larger area and hence increase your chances of finding a comet. More important than the instrument you are using is patience, dedication, a dark sky away from light pollution, and having a thorough knowledge of the sky. The subject is too in-depth to cover here so check out my visual comet hunting article.

Where in the sky do I need to search to find a new comet?

Comets are at their brightest when near the Sun so logic would indicate that the best place to search to find a bright new comet is within the vicinity of the Sun during astronomical twilight for an hour or so as darkness falls. The typical comet 'haystack' region is within 90 degrees solar elongation which involves searching the evening sky for 1-2 hours after sunset in the west and again for 1-2 hours in the east before sunrise, you can begin searching when 4th magnitude stars are visible with the naked eye. The northern sky near Polaris and low on the northern horizon is also a good location as some of the robotic surveys don't cover this region. Again, check out my comet hunting article for more info.

How long have you been comet hunting?, how many comets have you seen?, and what telescopes have you used?

At the time of writing (2011) I have been searching for comets on and off for 11 years and have spent 1073 hours 24 min's at the eyepiece specifically in pursuit of new comets. To date I have visually observed 54 comets (list) and have independently found 8 known comets while searching. For comet hunting I have used a 16" F/4.5 reflector, 10" F/6.4 reflector and a 8.5" F/7 reflector - all on dobsonian mounts, I have also done alot of searching using my trusty 8" F/6.3 S.Cass. On occasion I even did a little light-hearted sweeping using a 4.5" TAL reflector and 3.5" ETX M. Cass along with 7x50mm and 10x50mm binoculars. Read more on my article called Chasing Tails - The 1000 Hour Journey.

Do you think we will ever get to see a Great Comet in our life time?

Absolutely!. Great comets appear on average once every decade or two so we are long overdue another. Hale-Bopp put on a splendid show back in 1997 then in 2007 the remarkable great comet C/2006 P1 McNaught appeared which was actually brighter than Hale-Bopp, however it was very close to the Sun and it's appearance was subdued by the twilight sky for those in the northern hemisphere. However for those in the southern hemisphere it appeared in the evening sky as a proper Great Comet with a Peacock-shaped dust tail sporting multiple synchronic bands, this comet truly was a jaw dropping sight and the first comet in the 'great' category to be photographed widely with digital cameras. The next Great Comet is due anytime, in an ideal world it would be a negative magnitude naked eye object with a large and active dusty nucleus and extensive curving dust tail located close to both the Sun and Earth yet positioned at a decent elongation from our star and visible for an extended period against a dark sky background during evening hours. Such a sight in this modern era would be extraordinary. We can always hope to witness a sight like that of Donati, Ikeya-Seki, or the stupendous de Chéseaux of 1744.

What camera and lenses are you using?

At the moment I'm using a Canon 450D DSLR, also known as the Rebel XSi in the US. I currently have the 18-55mm kit lens, Canon 100-400mm IS USM, Canon 24-70mm F/2.8, Canon 50mm F/1.8 and Canon 10-22mm F/3.5 lenses. I bought a remote shutter which is essential for long exposure photography and also use a suction window mount (and window clamp version) for attaching my camera to the car window/body for storm chasing. I also use a Samsung HD video camera for taking film of storms and other interesting daytime phenomena.

What camera settings did you use for this image?

This is a question I really do not like to get because the answer is of no use to the reader at all. Knowing a specific list of settings which I used won't get you a similar result with your own camera, and besides, the way I take an image is my way of expressing myself so it should be different from your own style. There is no such thing as the perfect setting for a certain scene which will apply to all cameras and all photographers because everyone is different. The scene, camera, light level, subject brightness, motion, lens size, sensor sensitivity etc never will be the same as what someone else gets at any given moment so studying camera settings is really quite trivial. The best thing to do is be yourself, shoot the scene the way you think you should in the style which matches your own personality because you should shoot for yourself and no one else. I wrote this simple article on the basics of camera settings for bridge cameras which might come in useful for beginners.

How do I take images of the night sky?

You need a DSLR or bridge camera capable of taking a time exposure, most entry level cameras nowadays can take exposures between 15-30 sec's which is sufficient for most bright phenomena. Attach your camera to a tripod, keep the aperture wide open, eg: F/2.8, switch to manual mode, select exposure time, eg: 30 sec's, select ISO of 400 or 800, use your 2 sec or 10 sec timer or cable release/remote shutter if you have one to avoid vibration, then take the exposure. Preview your image on the LCD screen. Bracketing your exposures is a good policy, by this I mean taking several images at different settings, say a slower or faster shutter or by changing the aperture/ISO to get different results, this way you are more likely to get an image which looks good.

I have tried taking images of the night sky with my camera however the stars look like big blobs or wobbles, what am I doing wrong?

If the stars in your images look like blobs this means that your camera is not focused on infinity. Most good DSLRs on the market have live view, if you have it then use it, believe me, it is an excellent tool and will save you valuable time getting focused at night. Simply activate live view, magnify the image either 5x or 10x times and manually focus your camera on a bright start or planet until the blob becomes a point of light which means the camera is focused on infinity. If you don't see stars on the screen then try using a man made source such as a distant light on the horizon. If your star images are wobbled this means your camera has moved during the exposure, to prevent this attach your camera securely on a tripod and use the 2 sec or 10 sec timer in conjunction with a cable release/remote shutter and don't forget to enable the mirror lock up. If you don't have live view then use the conventional view finder to focus on a star or distant light. Alternatively you can focus the camera manually or on auto mode at infinity during daylight hours and leave the camera undisturbed until nightfall.

Do I sell images?

I'm amazed by the amount of times I get asked this question. The answer is YES I do sell images. The images are available as digital files or prints and also for image licensing use. I have sold many images to newspapers and magazines over the years so I am competent in this area. I use paypal and direct bank transfer and prices vary depending on the image format and what it is being used for, eg: educational or for commercial use. If you are interested in purchasing an image then check out my image licensing page or simply email me for further information. To see my images browse the Nightskyhunter Stock Gallery or the Images Per Year section.

Do I write articles?

I periodically write articles for web sites, newspapers, magazines, both locally and internationally on the subjects of astronomy, photography, and severe weather. I do charge a fee however.

Am I available to talk with the media?

This is an area I have been regularly involved in for many years. I am available to talk on a particular subject of interest to the media via telephone or in person. I also do live and recorded radio interviews if an appropriate fee is offered.

I see you captured the aurora borealis, I heard they are very rare in this country, is this true?

It astonishes me how little the public know about the prolific number of aurora displays which actually appear over UK and Ireland. Thinking that one needs to be located at a high northern latitude to see the northern lights is a significant misconception. In truth aurora displays are fairly common in northern UK/Ireland, this is especially so during solar maximum. Every 11 years the sun alternates between high and low levels of activity known as solar minimum and solar maximum. During the latter the sun becomes violent and produces a large number of sunspots, solar flares, and coronal mass ejections which generate a high number of aurora displays on Earth at mid northern latitudes. To date, April 2011, I have observed 85 aurora displays so I can tell you from personal experience that the northern lights are a familiar and welcome visitor in the skies over N. Ireland!

I live in south Britain, I will never see the aurora unless I get a KP of 9

To be frank, this statement is absolute rubbish. There is so much nonsense on the internet about the aurora charts and KP values in relation to latitude-derived aurora activity that I want to put an end to it here and now. If you think aurora displays at specific latitudes require a certain KP value then you have been badly misinformed or know very little about the subject. I have considerable real time experience in this field (this is an understatement) and I can tell you that aurora activity is a product of many different factors, or even a single factor, happening in tandem with the correct geomagnetic conditions. A high KP value is a good thing however you may be surprised to learn that a deep southerly tilt in the Bz component (Interplanetary Magnetic Field or IMF) is the most significant factor in the appearance of lower latitude aurora displays. For the record, I have seen auroras here with a KP value of 2.

Only Solar flares and CMEs are needed to get an aurora, is this correct?

No!. Although Solar flares and Earth-directed Coronal Mass Ejections (CMEs) are the main the source of aurora activity they are not the only kind. By far the greatest number of auroras are caused by solar wind streams from coronal holes in the sun, these often produce surprisingly good displays at mid northern latitudes on a regular basis throughout the year, even during solar minimum with the geomagnetic field being enhanced by a south tilting Bz component, increased solar wind speed, and pressure, or by the natural ebb and flow of the Earth's magnetic field. An especially good time to look is during local 'magnetic midnight'. In summary, one doesn't need a CME or even sunspot activity at all to get the aurora. I intend to do an extensive article on aurora activity in the future so stay tuned.

What aurora charts do I use?

If you are unsure which aurora sites to be checking simply have a look at the aurora links I have posted in the Astro Links section of my site. Below are the main charts I use for monitoring geomagnetic activity and forecasts...





Can I send in my images to your website?

Yes you most certainly can and I always welcome seeing images taken by readers. I usually display images as a NSH POD or Nightskyhunter Picture Of The Day which can be found on the Sky Events Page. I feature images which have an obvious astronomical, weather or photography theme. I post images at 980 pixels wide however if you don't know how to resize your image then just send in the original file and I can resize it for you. On occasion I will feature one or more readers images as a news item on the Sky Events page and even on the homepage if the event demands coverage or is of local interest. Any images I use will be credited to the photographer/source with a website/blog link if one is available.

Can I use your images on my website or forum?

Yes most certainly, I have no problem with people using my images for websites and forums as long as my URL is left unaltered on the image and no processing has been used to modify the image (except resizing). I also expect the image to be credited with my name - Martin McKenna - with a link to this site.

Do you do link exchanges?

Yes I do, if you would like to exchange links then drop me an email and we will take it from there. Links should be related to my own interest fields, however I am choosy about which links I use.

Can I advertise on your website?

I try to avoid accessive advertising on my site however on occasion I will accept an appropriate fee for a text advert/link included within the Astro Links section, in image reports, or more rarely on the homepage. Homepage links require an expensive payment and should be associated with the subjects of astronomy, photography or weather.

What is a fireball?, How bright can they get?, Do they drop meteorites & Can you hear sound?

A fireball is the name given to any meteor which has an apparent magnitude (brightness) equal to or greater than planet Venus. This means a meteor has to be at least magnitude -5.0 to be a true fireball. Fireballs can be so bright that they cast shadows, dazzle the eye, and on occasion surpass the magnitude of the full Moon and even have been known to match the brightness of the Sun (Mag -27) turning night to day. On more rare occasions fireballs have been seen in broad daylight. In general any fireball brighter than mag - 10 is capable of producing one or more meteorites and should be reported to Armagh Observatory, Astronomy Ireland, or to myself and I can forward the report to the appropriate authority. Fireballs can produce very obvious sound, in the past I have heard whistling, sizzling, and even loud rumbles similar to thunder which were astonishing.

What's the difference between a meteor, meteorite & meteoroid?

This mistake is very common and can be seen most often in newspapers and Hollywood movies. A meteor is an event, that's the streak of light you see in the night sky caused by a particle of cosmic dust glowing due to friction with the Earth's atmosphere and becoming briefly visible as a form of light. A meteoroid is this very same dust particle moving through space before it enters the Earth's atmosphere. A meteorite is the solid lump of rock or iron which falls from the sky after the meteor and hence surviving its fiery passage through the atmosphere to reach the Earth's surface.

How did you get interested in the night sky?

There were two important events in my life which triggered my passion for the night sky. The first was on a freezing Winter's night at my old home. I was standing on top of our large oil tank at the back of the house thinking about life and what it meant. I looked up and was simply astonished by the view of the sky which seemed to be filled with millions of stars, some of these were so bright that I felt I could have jumped up and touch them. The view of these countless diamonds sparkling against a backdrop of black country sky changed my life forever. I decided then and there that I was going to learn the sky in a serious way and become intimate with everything it had to offer, I can recall thinking that I wanted to know the stars so well that if a new star suddenly appeared in the sky I would recognize it in an instant. I was buzzing with energy and couldn't wait to get started on the project. The next day I walked to my local library and borrowed a book on Astronomy and eagerly waited for nightfall to learn my first constellations and life has never been the same since.

The second event sealed the deal for me. A friend and I were having a great chat inside a car during the early morning hours of yet another frosty Winter's night when our conversation got distracted by the utter brilliance of the stars and Milky Way from our pitch black location. Just before dawn my friend and I stepped outside, looked to the E, and saw a remarkable sight rising among the pre-dawn stars, it was great comet Hale-Bopp, the brilliance of the coma and curving dust tail had a profound affect on me, I couldn't decide if the comet was more beautiful or frightening and it was this confusing range of emotions associated with the icy visitor that got me hooked on comets forever! You can read more about this in the About Martin section.

How did you get interested in comet hunting?

My love for comets began with my first ever sighting of a comet back in the Winter of 1997 when great comet Hale-Bopp put on a stunning show in front of the entire world. My first sighting of this comet followed by the wild media fixation about the visitor really had my attention. Stories of comet impact, armageddon, tsunamis and public comet fever made the entire period feel like a surreal dream, I knew back then that comets were special and had a history of influencing mankind on so many levels so it was obvious that comets were both beautiful and powerful in equal measure. When the comet retreated so did the media attention and I came to the conclusion that comets were rare and it would be a long time before I could saw another. I didn't even know they could be discovered, that was until I read David Levy's 'Guide To The Night Sky' which was another major event in my life. David Levy's passion for the night sky was very contagious and on parr with my own and as I read through the pages it became clear that we had alot in common. When I encountered the chapter on how he discovered his first comet I was hooked. I decided this was for me and the very thought of discovering my own comet and getting it named after me quickly became my passion and obsession. I like to work hard for results so I was attracted by the extreme challenge and commitment involved so from that moment on I began searching for new comets.

How did you get interested in storm chasing & what was your first storm chase like?

My friend Conor McDonald got me interested in storms and severe weather. We would spend alot of time together out at night watching the sky and over the years he would learn about the night sky from me and I would learn about storms from him. At the beginning I really didn't get what all the fuss was about until interesting events unfolded and Conor pointed out mammatus clouds, cumulonimbus cells and talked about the chance of tornadoes and I quickly began to feel the feel thrill which he had. My first chase was on July 16th 2007 (see report), Conor and his girlfriend picked me up and the three of us went chasing to the top of Slieve Gallion, the chase was exciting and action-packed with flooded roads, heavy rain and hail with countless cloud to ground (c-g) lightning bolts hitting at close range to us, at times it was frightening but this was when I realised what it was all about - enjoying mother nature at her finest and feeling scared and excited at the same time and knowing you are not in control at all which felt fantastic. Also I was aware that others were either seeking shelter or hiding indoors while we deliberately chased the storm to seek out the worst it can do which really felt exceptional and different. It was a successful first chase and it wasn't long until the next one, in fact it was the following day!

On July 17th 2007 Conor, his girlfriend, and I met again during the late afternoon from near my home. We where surrounded by a group of massive cells, one of which was producing continuous thunder however it was the cell to the E which stood out from all the rest. As we watched a very large funnel cloud formed from the belly of the storm and for the next 15-20 min's it twisted and rotated in front of us while trying to make ground contact on several occasions, at the time we thought it was a tornado (almost was) so the event was investigated by TORRO (see report). The experience with the three of us watching that funnel, like a scene from tornado alley, with the hot sun burning our necks was absolutely incredible!!!. I decided then and there that I would be storm chasing for the rest of my life with my main goal focused on photographing more funnels and even a tornado on the ground in N. Ireland.

* More to come....


Martin McKenna

Sky Events Now