Imaging can be one of the most rewarding aspects of this hobby! 

      Ask your self, what do you want to image, planets, nebulae or galaxies? Each one of them may require a different camera or at the least a different telescope set up.  To get started let's assume you want to image nebulae and galaxies, I'll start with my set up.  I chose a 12" LX90 GPS on a wedge and a piggybacked Astro-Tech 66mm refractor.  Why did I pick this set up?  Well, first the 12" scope will offer great close-ups of nebula and galaxies and the image scale I wanted.  Second was admittedly the ease of use when capturing images since I was new to the hobby.  Here is my advice; Do some homework and pick the correct camera for your scope, in my case the 12" LX90 was a good pick for the SBIG ST-2000XCM Single shot camera I bought.  I should point out that I recently purchased an Astro-physics Mach1 GTO mount to replace the LX90 mount and it is OUTSTANDING! 

     For the definitive book on in the astrophotography I would highly recommend that you buy Ron Wodaski's New CCD astronomy, this book is without a doubt the most comprehensive guide to imaging, telescope set up, camera selection and image processing that's currently available.  Ron has even created a free downloadable program to help get a feel of what scale you will have with your telescope and chosen camera.  You can download the program at CCD Calculator. Deciding which camera to purchase is not only a choice of what you want to image but you need to match the camera with a telescope in terms of the image scale. I will give you a simple example.  The SBIG ST-2000XCM has pixels of 7.4 microns, a little on the large side of pixel size, CCD Calculator shows that my image scale with the 12" scope is .81 arc seconds per pixel with a small 16.1 by 21.5 arcminute field of view.  .81 arc seconds is not a lot of space per pixel which could lead to graininess in the image.  A quick look at the 2nd screen shot reveals an image scale of 2.18 arc seconds per pixel, with a field of view of 43.6 by 58.1 arcminutes, a rather generous field of view with better resolution.  The focal length of the telescope you purchase will have a significant impact on the images are able to obtain.  Shorter focal lengths are much more forgiving when imaging than long focal length telescopes because of their relatively wide view of the sky when compared to a long focal and telescope.  Here are screen captures from CCD Calculator:

Notice the scale of the image and field of view when I switched from a 12" Telescope with an 1890mm Focal length (image one) and a 4.92" refractor (125mm) with a 1000mm focal length.

    Think of it this way: when you are using high-power binoculars how difficult is it to zoom in on an object like a soccer ball from a distance of 100 yards and focus only on soccer ball?  Compare that to another pair of binoculars where you just want to be able to see the soccer ball in the field of view.  In the first example where you only want to see the soccer ball and nothing else, even if you move the binoculars slightly you will probably lose sight of the soccer ball.  With a wider angle in the second example you will be able to move binoculars around without losing soccer ball in the field of view.  I'll give you real-world example, when I began imaging I remember trying to image the Orion Nebula with my 66 mm telescope and I had plenty of room to fit the nebula in the field of view; however, when I tried the image with my 12 inch telescope the field of view was only the Orion Nebula and nothing else, the scale of the image had changed significantly.

      Purchase a small telescope (refractor) with a short, 400-800 mm in focal length this will give you a wide field of view with an image scale that it's for giving should you have tracking issues on your mount.   Unless you purchase the 8" Astro-Tech Imaging Newtonian do not purchase a reflecting telescope.  It's not that reflectors aren't acceptable but there is problem with focusing a reflecting telescope, the rack and pinion focuser they use are not always capable of achieving focus for CCD cameras. 

Crayford Type Focuser

 What is 'Guiding' when you are imaging? 

    Here are the BASICS, plan on either purchasing a guide camera or a camera with dual chips where one acts as a guider.  What is a guide camera?  Here it is in plain English; if you have ever looked through a telescope you may have noticed that objects in the field of view tend to move out of the eyepiece over the course of viewing.  Here is the issue, telescope mounts are only so accurate, the more you pay the more accurate the mount and so as time goes on the mount can't accurately keep up with the object you are looking at with the exact rate that the Earth rotates and so your object moves out the field of view.  Here is where guiding comes in, when you guide a telescope a camera targets a star on a small pixel level (very close) and moves the telescope mount to automatically keep the object within tight tolerances and hence in the field of view.  Here is a simple example, let's say I am looking at my guide star and it moves slightly to the left, the guide camera tells the mount to very briefly pause the imager and move the mount right to compensate for the movement.  Immediately after the guider corrects for the drift, it sends a signal to the camera to continue the image.  Here is an example:

You may want to take a 4 minute image of the Orion Nebula and you would set the imaging camera to shoot for 240 seconds (4 minutes) and set the exposure of your guider to 10 seconds.  Here is what happens, the imager doesn't care about the guide camera, it will be imaging for 240 seconds but the guide camera takes images every 10 seconds, evaluates how far the guide star moved and stops the imager to make it's movement corrections and then allows the imager to continue imaging so in actuality the 240 second image may take 245 seconds when you account for the corrections the guider makes.  

   Here is an example of the guide menu with Maxim DL version 4.5.  The best part of this software is that the guide star is automatically chosen as the brightest star in the guider image.  For quick start, set your guide exposure time to 10 seconds (the declination is automatically set if you have your mount connected to Maxim DL).  Click start, the imager takes a picture with the guiding chip and displays the image. 

   At this point the imager will automatically pick the guide star and you will be ready for the next step, calibrating. 

   When you calibrate your imager with your mount the camera uses the guide star to tell the mount how your mount moves when it follows the stars, does the correction start slow and accelerate. Or does the mount axis move up and then downward to keep objects in the eyepiece.   In any event the camera and mount work with the software to 'learn' the behavior of the mount when it moves (just keep in mind, the mount moves differently in different parts of the sky so re-calibrating is not only a good idea when moving to a new target it may be necessary).  When you calibrate, the camera takes an image of the guide star and marks it current position; it then moves the mount in the X axis and then takes another image marking how far the star moved and how far and how much it may have moved off the X axis in terms of a straight line.  The software then moves the star back to the original position the star began from (or as close as possible) which when calculated by the software, it creates a model of the mount movement in that axis. If you look at the image below you will see red lines in the Autoguider Image which represents the path of the mount during the guider calibration process.   The process then repeats in same manner for the Y axis and hence completes the calibration of the mount.

12" Scope, 1890mm Focal Length

 So, when you are imaging here is what happens, one camera (or in the case of the Dual Chip camera a single camera with TWO chips), the imager is only concerned with capturing the object you want to capture.  Meanwhile, the guiding camera is ONLY concerned with keeping the selected 'guide star' from moving a significant amount while it is working; this is imaging while guiding at the most basic level.  The guider tries to hold the star from drifting which allows imagers to capture Deep Sky Objects with little to no star drift in their pictures.  

        You may be thinking what kind of guide camera will I need.  The most common guide camera is a camera mounted on a separate scope from the imaging camera and even though the cameras are looking at the same object the guide camera is not physically looking through the same Aperture as the imaging telescope.  In this set you would literally have two different telescopes looking at the same object but in almost every case the guide telescope would be quite small compared to the imaging telescope.  I have tried to set up several times and not been very successful at it but I must admit the times that it was successful my results were outstanding.  The problem with this set at in my opinion is that the telescopes must be perfectly parallel or orthogonal to each other, and when I say perfect it must be perfect.  I spent a lot of time trying to get telescopes to perfectly aligned with each other and took a lot of time before this actually worked. 

       I actually became frustrated enough to buy a Santa Barbara instruments ST-2000XCM single shot color camera with dual CCD chips, one of course for guiding the telescope and the other for imaging.  The results from this the new camera Greatly increased the quality of my images.  For this camera, the guide chip and the imaging chip are perfectly parallel to each other and look down the same optical pathway while imaging.  Because of my experience that this camera and the success that I have had with it I don't believe I would ever go back to a separate camera for my guiding.  There are a couple of external guiding cameras that are excellent but at this point I can only think of one that I would highly recommend, the Santa Barbara instruments SG-4 auto guiding camera.  This camera costs about $1000 and does not require computer to operate.  Recent reviews of this camera have revealed that it is highly accurate and easy to set up.

       I remember when I first started taking images of the stars I had no idea about guide cameras or exposure times or even color imaging.  I was really trying to just take 30 second images and combine them later in the computer to create a master color image.  It may seem like a lot of effort to take on Astrophotography as a hobby but the rewards are truly great and can be quite addictive.  I would highly recommend not even attempting to get into Astrophotography if you don't use some kind of guide camera because your results are likely to be so poor you will quickly become frustrated and drop the hobby altogether.  If you are serious about getting into this hobby, spend the money on a dual chip Santa Barbara Instruments camera.  The camera that I have now costs about $2900 but it is a single shot color camera with a guide chip built in, both factors greatly speed up the time that is required to capture images.  This is not a cheap hobby by any means but at the same point it offers the rewards of capturing incredible images of deep sky objects.

  What are 'Darks?'

Dark frames are best explained as taking an image (either with a CCD camera or DSLR) with the shutter closed or lens cap on.  Why do this?  The simple answer is that when you take an image with any digital camera or CCD camera there is a small amount of noise that is present due to the inherent heat build up from electronics, as well as atmospheric temperature variations.

 Hot chip, Cold chip and imaging?   Heat produces noise on imaging chips by causing 'graininess' and making an image look out of focus (if you are lucky).  Heat is not really a problem with very short images of a DSLR during the day but leave your shutter open a little longer and the problem becomes obvious, hot chips add graininess to images.  The hotter the chip, the more noise you will have in an image so cooling is imperative. A little tip: DON'T buy a camera without carefully considering if the camera is cooled and the manner in which it achieves cooling.  Meade imagers for instance use passive cooling which may be very difficult to use during the summer in South Texas since there is no fan to actively cool the chip.  On the other hand, SBIG imagers as well as other brands use a small cooling fans to cool their  chips down to -30ºC below ambient temperature in some cases.  A simple rule for CCD chips, colder is better!!  Many SBIG cameras also come with internal water channels for adding a water cooling capability to your camera which can lower your chip temperature a further 9º to 10ºC.

Image processing

    Processing CCD images can actually take just as long as capturing the images in the first-place.  Because of the sensitivity in cameras today there are actually several steps that you need to take to correctly process images and make them look good enough to list on your web site.  I initially began processing astrophotography pictures with Meade software that came with my first CCD camera (The Meade DSI-Pro Camera).  The software did provide the basic steps for processing pictures but I was never able to capture and process images that I thought would be acceptable.  To further process your images make sure and get a copy of Adobe Photoshop.  I use Photoshop CS2 and have been able to download very useful Plug In tools from ProDigital Software where you can automatically make stars smaller, increase their color, remove light pollution and even synthesize Green channels using the Red and Blue channels!  I realize that Photoshop is expensive but don't fool yourself, you need it!  If you can't purchase the latest version of Photoshop that's not a problem, I use CS2 and until it becomes impossible to process my images with that version, that is where I am staying.

    I purchased Maxim DL software by Diffraction Limited and my image processing became much better but because the camera was not high quality (the Meade DSI-Pro), my images only improved slightly.  When I purchased my first Santa Barbara instrument camera I was very pleased with the camera quality as well as the image processing software.  My images quickly became much higher quality than before and I was able to quickly process them using the Santa Barbara instrument and Maxim DL software.  The basic software that Santa Barbara instrument provides is called CCDOps and it does a good job at the initial processing of images but is limited by adjustments that are able to be performed on the image.  Even though I use Maxim DL for my guiding, telescope control and image acquisition is still do my initial processing with CCDOps and then take the images to Maxim DL, adjust the images, use appropriate filters on them, align and stack them. 

     Here is a screen capture of the start of the Maxim DL alignment process.  The user picks two stars for each image (if using the manual method) and the software automatically aligns all the frames on the stars you selected. 

The tutorial will be completed soon!!

 

Meade Reflecting Telescope - Not typically able to image