Deep Space Astrophotography Filters for Colour Cameras:
In this article we'll look at some of the popular filter types available for use with colour cameras - both DSLR & Colour Astrocameras. Modern astro filters can be seen as real game changers particularly for astrophotographers based in the city and for most astrophotographers, building up the right filter set is a must have for any serious astro-imager.
Light Pollution Filters (Broadband Filters):
Light waves travel through the air at various frequencies just like radio waves and this frequency changes depending on the light source. The reason light pollution filters are known as broadband filters is because they allow light across a broad range of light frequencies to pass through the filter onto the camera sensor while blocking out just a small amount of unwanted light frequencies (ie. from street lights etc.)
There are many good light pollution filter manufacturers out there and one we recommend is the Optolong range. Optolong not only make great light pollution filters, but also dual narrowband filters, which we'll go into later below. The Optolong L-Pro is Optolong's light pollution filter that is available in both 1.25" and 2" mounted sizes or as a clip in type which clips in front of your camera sensor (Note: these are camera specific).
Tip: When buying filters, we would always recommend getting the mounted type filters because long term they make much more financial and practical sense. The clip in types are designed to clip just in front of your camera sensor on the camera body so if you have a Nikon, you need a Nikon one and likewise for Canon and other brands too. However the mounted types are designed to attach to your telescope, either on the corrector, focus tube or the T-Adapter, meaning you can use the same filter regardless of which camera you have, even if you change camera or upgrade later on to an Astrocamera.
Performance wise, the Optolong L-Pro filter is a really excellent filter for imaging from light polluted skies, and it also has very little impact on natural star colours, something which many other regular light pollution filters can struggle with.
In the image below we took two 150sec photographs of the Orion Nebula from Bortle 8 skies using a standard DSLR camera. In the first image we had no filter and the pink/orange glow from the city light pollution is very obvious, the stars are washed out and the nebula is just about visible. In the second image we took the same photo moments later with the same camera using the Optolong L-Pro filter and the difference is quite dramatic. A lot more stars are visible for one, and the background sky and stars are less washed out and the nebula itself shows a lot more detail, contrast and colour.
The image above will give you a good practical idea of how a good light pollution filter like the L-Pro can really help bring out the details in your astro images, even if you live in a large city like Dublin. The L-Pro filter is also perfectly fine to use on all deep space targets, including Galaxies, Reflection and Emission Nebula. Its also suitable for use with standard (unmodified) DSLR cameras as well as dedicated cooled OSC Astrocameras.
Optolong L-Pro suitability:
Camera Types: Colour Astrocameras and DSLR Cameras.
Galaxies: Yes
Emmision Nebula: Yes
Planetary Nebula: Yes
Reflection Nebula: Yes
Narrowband Filters:
Unlike broadband filters which allow a large range of light through, narrowband work the opposite way and only allow a small range of light frequencies through
while blocking out the majority of all other light sources.
So why is this important? Well most nebula in space (with the exception of reflection nebula) contain large amounts of Hydrogen gas as well as Sulphur and Oxygen - Hydrogen & Oxygen being the dominant ones. By allowing the light from these sources only to pass through, and blocking everything else you are going to be left with a much cleaner and sharper image, even on a moonlit night and from heavily light polluted cities. Its important to keep in mind that while these filters work exceptionally well on a wide range of targets eg. emission nebula, planetary nebula etc., you need to pick your target correctly as some nebula like dark nebula or reflection nebula will simply not be visible through these filters. These filters are also not suitable for Galaxies unless you are using HA data for example, to combine with a regular broadband image, to highlight the areas of nebulosity in the galaxy.
There are 2 popular Optolong narrowband filters in the range (also called Dual Narrowband Filters). These are the L-eNhance & the L-xTreme filters and both are designed for use with colour astrocameras. The main difference between the two is that the L-eNhance is less aggressive than the L-eXtreme filter and it allows HA, Oiii and H-beta light to pass through. Its very effective from light polluted areas and will make a considerable difference to your nebula photos, leaving them much cleaner with lots of detail and contrast.
The L-eXtreme is also a narrowband filter but works at a much tighter bandwidth than the L-eNhance and so its very restrictive as to what light passes through it. It allows only HA and Oiii light sources to pass through at a very small 7NM range and this results in outstanding clarity and detail even from the most light polluted locations. As the L-eXtreme allows such a small bandwidth of light to pass through, you will find the image is very dark when using it and so you will likely have to increase your camera gain and/or exposure times. You will also find the stars are smaller and sharper (which is great!) but you will loose the natural star colour unless you combine it with an RGB version to create a composite image.
The other thing to bare in mind is that these narrowband filters are not suitable for unmodified standard DSLR cameras, as many of these cameras have a built in filter which tends to block out the light that these filters are passing through, so we recommend only using dual narrowband filters with an Astromodified DSLR or a dedicated colour Astrocameras.
The image below is an example of the L-eXtreme filter in action. These images were taken from Dublin of the Rosette Nebula (a nebula rich in Hydrogen gas) and as you can se from the filtered version with the L-eXtreme, there is a lot less noise, much better detail and stronger colour.
Optolong L-eNhance/L-eXtreme suitability:
Camera Types: Colour Astrocameras and Astromodified DSLR Cameras only.
Galaxies: No (unless using as a layer with an RGB image)
Emission Nebula: Yes
Planetary Nebula: Yes
Reflection Nebula: No
So in summary if you are using a either an Astromodified DSLR or a colour astrocamera then we would definitely recommend both the L-Pro and the L eNhance or L-eXtreme filters as part of your astro imaging kit as these will give you lots of options across a very large range of deep space targets, even from cities. However, if you are using a standard DSLR then we would recommend just sticking with the L-Pro as this will work very well with immediate and noticeable improvements in your astro images.
If you would like to know more about these filters or would like some help choosing a filter for your specific setup, feel free to contact us here. or if you would like to view our range of filters Click here >
Happy Imaging & Clear Skies :)
]]>
Following our most recent star test, in this brief review we are going to look at the TS 61EDPH APO Refractor Telescope. TS (Teleskop Service) is a German company based in Ransburg Germany and offer a wide range of premium Astronomy and Astrophotography equipment including telescopes, binoculars and mount accessories.
The 61EDPH is a wide field, 6 element, APO Triplet Refractor which includes a reducer and flattener as part of the package and although it can also be used quite well for visual Astronomy, it certainly excels at Astrophotography.
One thing we noticed about this Telescope is its size, its really short (with the dew shield retracted), this means its going to be great for transporting to dark sky locations or even on Holidays, as you will have no problems fitting it into a small travel bag. At a weight of about 1.8kg its also light and so won't need a very large mount to use it either, even a good star tracker would probably work fine too, making it an ideal travel telescope.
Features & Build Quality:
Apart from its compact size, some of the features we really liked where its graduated focus tube, which is handy to help ensure the same focus during different viewing sessions (You'd be amazed how many high end telescopes don't have this basic feature). The carry handle is also really useful too, not just for carrying the scope (obviously!) but you can also use it to mount a DSLR camera, an ASIAir PRO, a Microcomputer or any other accessory you see fit (we used it to attach the controls for the dew heater.
The other feature which Astrophotographers will really appreciate is the rotating focuser ring which makes framing your target so much easier - Simply loosen the 3 brass screws and rotate the focus tube to the desired angle. There is also a dual speed focuser to help you make minute adjustments to reach perfect focus.
Inside the corrector there is a 2" thread for using a 2" mounted filter but if you use 1.25" filters you will need an adapter to use this feature. What's great about having the filter inside the corrector is that it doesn't affect the back focus to the camera, which in this refractor is 55mm from the last M48 thread on the corrector - the required distance for most cameras.
Overall on first impression the telescope seems extremely well built, you can tell quality was not sacrificed in anyway either in production or the materials used. Even the red anodised tube rings and carry handle looked very clean and well made and the whole setup feels rock solid.
However we did have two small issues with it, although to be fair, these were easily fixable. Firstly the dovetail bar was way too short to get perfect balance, especially with a heavy camera on the end. Perhaps with a lighter camera it would be fine however an extra 2 or 3 inches would give a lot more leeway for getting better balance for heavier cameras. To rectify this we just attached it to a slightly longer dovetail - problem solved.
The second issue we had was the dew shield. As its retractable, it seems to slide very easily and with the dew heater fitted and viewing/imaging close to the zenith, you get the feeling it might slide back under its own weight. A rubber band was a quick and easy fix for this and this seems to be an issue commonly found with many other similar brands using this type of sliding retractable dew shield - again, not a show stopper, but worth a mention.
What's it like for Astrophotography:
We haven't used this telescope for visual purposes because lets face it, due to the cost, you're unlikely to buy a Triplet refractor for viewing purposes as the benefits of having a triplet lens are most evident during long exposure astrophotography, particularly in bright stars.
This particular telescope has a 61mm Aperture and a focal length of 274mm (with the corrector/reducer fitted). This gives you a very wide field of view which makes it a really excellent choice for some of the most spectacular deep space targets in the night sky. Andromeda is one example, its one of the most photographed galaxies but also one of the hardest to frame up because its so big - The TS 61EDPH makes light work of this and even gives plenty of star fields around the galaxy itself for cropping in or just to have a better perspective of this galaxy in space. Other targets such as the North American Nebula, Heart and Soul and the Horse Head all frame up perfectly too and having so much background stars really adds a sense of depth to any astro-photo.
This refractor has a focal ratio of f/4.5, again with the corrector/reducer installed. This makes it a very fast scope and will really help reduce your imaging time considerably, or to look at it another way - collect much more data in longer imaging sessions. In our very short test on Andromeda we found the stars where sharp & round right to the edge of the frame and the image contrast was simply excellent.
We had a look at two popular targets with a total exposure time of just 45mins on each. It should be noted also that these photos were taken from city skies (Bortle 8) and we were using a 2" Optolong L-Pro filter. We have full details and links to the equipment below. So lets get to the results because at the end of the day, the proof is in the photos!
(IMAGE 1) M31 Andromeda Galaxy - Cropped to 90%.
In this very short 45min image of Andromeda we could see some real structure to the galaxy and some of the fine details including dark dust lanes and even some hints of nebulosity in the Galaxy itself.
(IMAGE 2) Flame & Horsehead Nebula in Orion - Cropped to 70%
As there was a layer of high altitude cloud during imaging, this resulted in a large haze visible around the bright star 'Alnitak' however despite this, we were very impressed with the overall image clarity and sharpness at such a short exposure time, particularly for a nebula region as faint as this one.
Equipment Details & Links:
Telescope: TS 61EDPH APO Triplet
Camera: Explore Scientific 16MP Astrocamera
Filter: 2" Optolong L-Pro Filter
Mount: Vixen SXD2
Acquisition details for both targets:
- Total time: 45mins each
- Sub exposure length: 180secs (unguided)
- Location: Dublin City, Ireland (Bortle 8)
So overall we were extremely impressed with this widefield refractor from Teleskop Service both in terms of quality and actual performance under the stars. Its fast focal ratio and wide field of view make it a very good contender for serious astrophotographers looking for an optical systems that guarantees exceptional performance in a very tidy and solidly built telescope.
However if you are looking for something with a smaller field of view and a little more reach, another consideration the very similar but larger TS 94EDPH which offers a longer 517mm focal length at f/5.5, making it ideal for those intermediate sized galaxies and deep space nebula regions.
]]>
The expanse and fascination of space has always been something that has intrigued people for generations. In fact we are living in quite a privileged time where amateurs now have access to extremely high-tech and advanced optical equipment which allows us to see detailed surface features on the moon, or the rings of Saturn (1.4 billion km away), or even distant galaxies and star clusters (billions of light years away) - all from our own back garden.
Astronomy can enjoyed by anyone at any age and can be made as simple or as complex as you like, depending on how deep you wish to go into it. In the field of Astronomy like everything else, using the necessary equipment does come with a learning curve and in this article we will try to cover some of the basics which we hope will offer beginners in this hobby a better idea of what to expect and also offer some advice in getting started in Astronomy.
Choosing your Equipment:
First off, there is a tendency for many people to think you need a telescope with the most magnification you can get, to see the best views of space. This is actually not true, in fact we never recommend purchasing a telescope advertised by its magnification capability. A much more important thing to consider when choosing your first telescope is actually its aperture - We have more detailed information on this topic in our 'Choosing a Telescope' article which you can view here.
But even before you decide on purchasing any equipment, here are some other ways you can begin your journey in the fascinating and exciting field of Astronomy:
Planetarium Apps:
Observing the night sky with just the naked eye and no equipment may seem slightly underwhelming at first but actually with the help of various Planetarium Apps now available on your phone (e.g 'Stellarium'), its amazing what you can see without a telescope at all. For many of us when we look up at the night sky we see lots of stars but some of those may be planets and if you are fortunate enough to live in a dark sky location (eg. away from city lights) our own galaxy the Milky Way and even some of the larger galaxies like Andromeda are also visible to the naked eye as well. - You just need to know where to look and this is where the planetarium apps on your phone will help - Just load them up and hold your phone to the sky and as you move around it will tell you what you are looking at, its that simple.
In fact some of the larger and closer planets such as Jupiter, Saturn and Venus are very easy to locate even from bright city skies and are often mistaken for a bright stars.
Choosing your basic Equipment:
One thing that can be said about Astronomy is that the cost of equipment can ramp up quite quickly for more advanced telescopes and mounts (especially for Astrophotography), however you really don't have to invest much at all to get some fantastic views of the night sky - In fact we would always discourage beginners from jumping in and purchasing expensive equipment from the start, as the learning curve for this is very steep and its easy to become discouraged and loose interest in a hobby which can otherwise provide you with a lifetime of fascination and enjoyment.
Don't rule out the Bino's:
You would be surprised just how amazing the solar system and deep sky objects can look through a good pair of binoculars. There is something quite unique and special about looking at an area of space with such a wide field of view with both eyes. The sheer number of extra stars for one will blow you away, and even the moon and planets like Jupiter will look very clear - with Jupiter appearing as a very small but bright disc and possibly 2 or three of its moons becoming visible. The other great thing about Binoculars is that they take up very little space and you can take them literally anywhere - even on holidays if you will be visiting an area where there is dark skies.
TIP: When using high-power Binoculars, its a good idea to use some kind of Tripod, as this will improve your viewing experience considerably by providing a more steady viewing platform.
Choosing a Telescope:
Choosing a telescope is normally where most beginners feel the most unsure about, especially given the huge range of options now available. The main thing however is not to feel you need to spend a fortune to get started, its better to get something simple that you can really enjoy, rather than a large and expensive Telescope which will rarely be used.
Even with good smaller Telescopes, you can enjoy some really breathtaking views of the Moon such as this photo below sent in by a customer who's 13yr old daughter took using her mobile phone camera and a small beginner Telescope - The Bresser AR80 Nano Telescope.
(Customer Photo: Taken with a Mobile Phone & Bresser AR80 Nano Telescope)
Telescopes are of course a step up from Binoculars and will naturally offer more detailed views of our solar system and deep space objects. There are various types of Telescope you can choose from and some will cater better for different types of viewing - We have put together some slightly more detailed articles below that you may hopefully find useful:
1. Choosing a Telescope
2. Astronomy Telescope Designs
The main thing we would say about choosing your first telescope is to take your time and ask for help if needed. Generally speaking if you are looking for a beginner telescope for just casual viewing of the Moon and Planets, then most telescope designs will work quite well and one with an Alt-Azimuth mount would be a good option as they are cheaper, less complex and much quicker to setup.
If on the other hand you feel you would like to delve a little deeper into the hobby and perhaps try out some astrophotography, it may be worth considering one with a German Equatorial Mount - Either way, if you would like more help we are happy to offer you more tailored advice for your specific needs - so feel free to contact us here.
You can also contact one of the many Astronomy clubs around the country who can also provide a wealth of information and experience. Many of these clubs have outings where you may be able to try out some of the equipment for yourself and meet like minded individuals.
Finally - Managing expectations:
While we may have control over what equipment we choose, one thing we do not have control of is the weather and the seeing conditions. Its important for anyone beginning in Astronomy to be aware of these limitations, as they will determine just how clearly we see objects like the planets and other deep sky objects. The other thing to be aware of is the difference between visual Astronomy and Astrophotography.
Visual Astronomy:
This is simply using an eyepiece to view an object through a telescope. Viewing planets and especially the moon through a telescope in this way is always a memorable experience - even through smaller telescopes.
Astrophotography:
This is where we attach a camera (either a dedicated Astro Camera or a DSLR) to the eyepiece connection point and usually take long exposure images which are later stacked using specialised stacking software.
In the image below we show an example of the Andromeda Galaxy viewed under dark skies through both an eyepiece and also with a camera using long exposure stacked images. While both are impressive, there is naturally a lot more detail visible in the photograph, but saying that, there's also something really special about viewing another galaxy with your own eyes through an eyepiece, regardless of the detail.
The reason for this difference is that many of these deep space objects are so far away (millions of light years) so their light signal is very weak by the time it reaches us - Its a bit like someone holding a bright torch on a hill, as you move further away the light becomes fainter and harder to see, until a point where its not visible anymore. Because modern camera sensors are far more sensitive to light and can also capture even fainter light signals using longer exposures, they are able to collect far more detail and colour than just using our eyes.
The only exception to this is when we view the moon and the planets. As these are so much closer and brighter, its possible to see a lot of detail, even when viewing through an eyepiece using a telescope. This can be even further enhanced by using special planetary filters attached to the eyepiece to further enhance some of their features such as cloud bands on Jupiter and polar caps on Mars.
Seeing Conditions:
The one factor which affects both visual Astronomy and Astrophotography and is unfortunately out of our control is seeing conditions. Cloud is an obvious one, but less obvious is high altitude jet-stream activity, heavy moisture in the air and thermals (warm air rising from roof tops and concrete structures) - and lets not forget the dreaded light pollution from city lights.
This is why most of the worlds large scientific observatories are located in areas of high altitude, well away from large cities - or even better Hubble Space telescope located in orbit, where it has a completely unobstructed view of the universe!
Seeing conditions can make a big difference to our viewing experience, and this becomes even more obvious the higher you magnify the view. For example, you may find on one clear night your view of the moon or planets at high magnification looks extremely sharp and detailed but on another clear night using the same telescope at the same place, you may find the view much less clear - This is not a fault with your equipment, but is because the seeing conditions are constantly changing, even by the hour.
Larger aperture telescopes will help provide decent views at higher magnifications even when seeing conditions are not perfect, but even these have limitations too and even the largest amateur telescopes will always be limited on nights when atmospheric conditions are particularly poor.
If you'd like to know more or need help choosing your first telescope, or a telescope for a child, feel free to contact us here
Clear Skies!
]]>Three important characteristics of a telescopes design include:
Of these 3 characteristics, Aperture is the probably the most important factor to consider. Most telescope designs can in theory provide several hundred times magnification however if the telescopes aperture is not sufficient to gather enough light for a given magnification, you won't be able to get the resolution or sharpness needed provide any detail in the image.
In the images below we show a comparison as to how Jupiter might look at approx x200 magnification through both an 8" and a 4" aperture telescope under the exact same sky conditions. As you can see, at this high magnification the larger 8" aperture gathers much more light and therefore better image resolution to comfortably show a much brighter and sharper image. However pushing the small 4" aperture to the same level of magnification does not offer the same level of clarity as the smaller aperture can't collect the same amount of light needed to offer the same resolution at this magnification.
However, that's not to say you can't see great views of the planets such as Jupiter using a smaller aperture telescope, you certainly can, but just be aware that the maximum clarity and detail that you can see in the image will peak at a lower magnification - See example image below.
© Horizon Astronomy
When it comes to choosing a Telescope, the good news is that most reputable telescope brands of all sizes will generally be very capable instruments and provide you with great views of our solar system and beyond, but its important to be aware of their limitations, and never buy a telescope misleadingly advertised by its 'off the scale' magnification power.
So in a nutshell, when choosing a telescope, we always recommend going for the biggest aperture you can comfortably afford but also keep in mind that the bigger the aperture, the bigger and heavier the telescope will be and its a good idea to consider any space limitations you may have at home for storing and using it, or maybe if you plan on regularly transporting it to dark sky locations.
We find as an entry level telescope, a good place to start would be a 3" to 4" Refractor or Newtonian Reflectors / Cassegrain of 5" to 6" aperture upwards. These will give you some really great views of the night sky and are a great way to enter the field of amateur astronomy.
If you would like to know more about the different specific telescope designs and some of the advantages they offer we recommend reading - Our Astronomy Telescope Designs article here
The Mount:
The Mount is the foundation of your whole setup and is often overlooked when purchasing a telescope. The reality is that a poor mount can render even the best telescopes unusable and its vital to get a mount that is not only suitable for your main area of use (eg. Visual Astronomy or Astrophotography) but also a mount that can comfortably hold the payload weight of all your equipment, including cameras, guidescopes and other accessories you may decide to use down the line.
There are many variations of telescope mounts but the two main types of mounts used in Astronomy are Alt-Azimuth Mounts and German Equatorial Mounts.
These mounts offer a sturdy yet very simple and intuitive way to scan the night sky. These mounts work in 2 axis - Altitude (Up, Down) and Azimuth (Left, Right) and as straight forward as that, you simply move them up, down, left or right to where you want to point your telescope. They are perfect for visual Astronomy and are extremely quick and easy to get setup. They don't require any kind of polar alignment or additional power supply to operate and the lack of motors, counter weights and other accessories mean they are much lighter than German Equatorial Mounts.
The main drawback to these mounts however is their lack of tracking ability and so this rules out any kind of long exposure deep sky astrophotography, however point and shoot astrophotography of brighter objects such as the moon and the larger planets is still possible using a smart phone or camera.
German Equatorial Mounts (GEM) are available as manually operated or fully electric GOTO versions. These mounts also operate in 2 axis RA (Right Ascension) and DEC (Declination). The RA axis needs to be first polar aligned to the north celestial pole (or south celestial pole, if you are in the southern hemisphere) and once setup correctly, these mounts are designed to allow you to accurately track the night sky, keeping your object centered in the telescopes field of view.
A Manual GEM will require regular inputs from the user to keep the image centered in the field of view so we would recommend at least getting a mount with an RA Tracking motor fitted - Many good GEM brands do offer this as an optional upgrade. That way once your target is in the field of view, the motor will track it for you, this means you don't constantly have to manually track it and it will also allow you to begin trying out long exposure astrophotography.
Ideally however, we would recommend a fully electric GOTO GEM. These will have motors on both RA & DEC axis and will also automatically slew the telescope to your selected target by simply selecting it on the hand controller or a laptop.
One important thing to consider when choosing a mount is the payload capacity. For visual Astronomy work, you can operate the mount at its maximum capacity no problem at all, however for Astrophotography it is generally recommended that you operate between 60-75% of the mounts payload capacity as tracking errors may be introduced, because the weight on the mounts bearings and torque required by the motors are higher. These tracking errors can be noticed (particularly in the stars) when taking long exposure photographs.
However it also depends on the quality of the mount, the focal length you are imaging at and the exposure time you are using. For example, if you are at the imaging at the maximum payload capacity of a mount but at a short focal length using 30-60sec exposures, then some minor inaccuracies in tracking might not be that obvious, however as you increase the focal length and exposure times, tracking accuracy becomes more of an issue. So while the 60-75% payload rule for astrophotography is not set in stone, it is a good concept to take into account when choosing a mount as it does give you more options down the line, especially if you plan on using larger telescopes and adding other accessories such as autoguiding equipment at a later stage.
Summary: So when choosing a mount it really depends on your own personal preference. If you know you will just be casually using it for observing the moon and planets and have no particular interest in long exposure astrophotography, then an Alt Azimuth mount would be a very good option, as its light weight and quick and easy to setup.
If you are more interested in viewing deep sky objects and trying out Astrophotography then a GEM is really the only option, ideally a full GOTO version but if not, a manual version with the option to include tracking motors at a later stage would work well too. Just keep in mind the payload capacity if you plan on using a number of different telescopes and camera equipment on the same mount.
For more information or if you would like some one-to-one help and advice in choosing the right telescope feel free to contact us here
]]>Refractor telescopes would be familiar to most people as a typical telescope design. They use a front lens (or series of lenses) to collect and refract(bend) the incoming light through the front of the telescope, re-directing it to a focus point on the eyepiece or camera sensor.
Unlike Refractors, Newtonian Reflector Telescopes do not bend the light but redirect it using a series of mirrors - For this reason they are Achromatic by design (don't suffer from the same level of chromatic aberration as refractors). As the light passes through the front of the tube, the primary mirror at the end of the telescope collects and redirects it to the secondary mirror near the front end and then to the eyepiece or camera sensor - For this reason the viewing end is normally at the front of the telescope.
Suitable for viewing:
Summary: Newtonian Reflectors are an excellent telescope for beginners and experienced Astronomers/Astrophotographers alike. Their larger apertures mean that at higher magnifications, images will appear clearer and brighter thanks to better resolution.
SCT & MC telescope designs are somewhat of a hybrid between refractor and newtonian reflector designs - bringing together some of the positive features of both. The Internal layout of the SCT & MC differ slightly between them but essentially they use a corrector plate or objective lens like a refractor but also have a primary and secondary mirror like a newtonian reflector.
SCT & MC Telescope (Pro's):
SCT & MC Telescope (Cons):
Suitable for viewing:
(Schmidt Cassegrains)
(Maksutov Cassegrains)
Summary: Schmidt Cassegrains and Maksutov designs are generally more robust and more compact than their equivalent Newtonian designs and as their internal mirrors are not directly exposed to the atmosphere, they rarely require cleaning and only occasional aligning. They are a good middle ground choice between high end Refractors and Newtonian Reflectors as they offer extremely sharp optics with wider apertures and longer focal lengths but in a more compact and robust instrument.
]]>