Different Types of Imaging & Camera Mounting

PiggyBack – This method simply uses the telescope as a tracking platform. The camera is mounted to the top of the telescope tube using a “Piggyback Camera Mount” and shoots through it’s own standard camera lens. This method does not offer any gain in magnification or light grasp over what your camera lens provides, it simply allows the camera to follow the sky so long exposures do not streak as the earth moves.

See:
We do not currently carry any Piggyback mounts, consult your telescope manufacturer for an appropriate mount as they are typically made to fit a particular scope model.

Prime Focus – This is the purest form in that it uses the telescope as the camera lens. The camera is not fitted with a lens and the telescope is not fitted with an eyepiece. The camera film plane (or CCD) is placed at the “prime” focal point of the telescope. This method offers the widest, brightest fields, moderate magnification and shortest exposure times. Typically used for imaging nebulae, galaxies and other large deep sky objects. To use this method your camera must have a removable lens (SLR/DSLR/CCD Imagers/Some Webcams). This rules out most all point & shoot type consumer cameras (for these see “Afocal” below).

See:
1.25” Prime Focus Kits (for scopes that accept only 1.25” eyepieces)
2” TRUE-2 UltraWide Adapters (for scopes that can accept 2” eyepieces)
C Mount Adapters (for box type cameras)
Webcam Adapters (for many popular webcams)

Barlow Projection – This method is essentially the same as “Prime Focus” above except that it places a telenegative lens (barlow) between the telescope and camera. This increases the focal length of the system which increases magnification.

See:
1.25” Prime Focus Kits (for scopes that accept only 1.25” eyepieces)
2” TRUE-2 UltraWide Adapters (for scopes that can accept 2” eyepieces)
C Mount Adapters (for box type cameras)
Webcam Adapters (for many popular webcams)

Eyepiece Projection & Variable Projection – This method also requires a camera with a removable lens so it is typically limited to SLRs/DSLRs/CCD Imagers. The camera body is fitted to an eyepiece which is placed in the optical train between the camera and telescope. The eyepiece “projects” the image onto the film plane (or CCD). This provides a method of increasing the magnification just as it does visually. Shorter focal length eyepieces provide higher magnification. Often rather simple eyepiece designs work best for this purpose. A “Variable” projection adapter allows you to adjust the distance between the film plane (or CCD) and the eyepiece. This varies the magnification of the system allowing you more flexibility in adjusting the image size when framing your shots.

See:
Eyepiece Projection Kits
Variable Projection Kits
AdaptaView Adapter (fits many TeleVue eyepieces)

Afocal – This method is primarily employed with consumer “point & shoot” type cameras. Since these cameras do not have a removable lens they MUST shoot through an eyepiece to form an image. If you were to try to shoot though a scope without an eyepiece (but with the fixed camera lens) you would simply get a picture of the inside of the scope. Care should be used in eyepiece selection for this method since trying to shoot through an eyepiece with a small lens will result in a lot of vignetting. Vignetting is when the image has dark corners or a dark circle surrounding it. Minor vignetting such as dark corners can almost be expected with many cameras and can be easily cropped out. But excessive vignetting can be like viewing through a soda straw. If your camera has a large lens (generally if its filter thread is larger than 37mm) you should consider a lens made for this purpose such as our Afocal Eyepiece.

See:
Digi-Kits (afocal kits for hundreds of point & shoot cameras)
MaxView Afocal Eyepiece (recommended for cameras with large lenses)
AdaptaView Adapter (fits many TeleVue eyepieces)
Attachment Kits (used to connect MaxView Eyepiece or AdaptaView to your camera)
Universal Camera Mount (for point & shoot cameras for which there is no Digi-Kit)

The best eyepieces for this purpose will have ALL of the following characteristics:
-Low Power (The lower the better, the camera zoom will provide plenty of magnification)
-Large Eye Lens (preferably nearly as large as your camera lens)
-Long Eye Relief (short eye relief will result in major vignetting)
-A non-recessed lens (if the eye lens is mounted deep in the barrel it is the same as short eye relief)
-A method of attaching it to the camera (it is compatible with our Digi-Kits, AdaptaView or Universal adapters)

Tips for Afocal Imaging:
-Make sure the camera lens and eyepiece lens are spaced very closely together.
-Use an appropriate eyepiece as outlined above.
-Generally most cameras will need to operate at or near maximum zoom to reduce vignetting to a minimum. On a camera with a large zoom range (such as 10X) this may cause the system to be “overpowered” unless you use a very low power eyepiece.
-Some cameras may work best in Macro mode, experiment with yours to see which mode works best.
-If you’re shooting a large bright object such as the Moon your camera may adjust its exposure and focus correctly so long as the telescope is near focus. But the best results will be achieved by going to full manual mode and adjusting the exposure time yourself. Focus using the telescopes focus knob.
- If you don’t have a remote for your camera use the built in self timer feature so you don’t have to touch the setup (causing it to shake) when taking the photo.

Focusing Methods

Regardless of the type of telescope or camera focusing is typically done with the telescope focuser knob, not with the camera. Achieving sharp focus can sometimes be a challenge through a tiny viewscreen. There are a number of methods to aid in achieving sharp focus. If your camera is digital you can simply take a picture , then blow it up and see how good the focus is. Some even allow you to zoom in on a live image before you take the shot. However such hit and miss methods can get frustrating when imaging different objects. There are focus masks that can be placed over the front of the scope to aid in focusing but I find these often provide a rather dark image that makes it difficult to judge focus as well. I prefer the “Parfocalizing Ring” method. This method allows you to turn a spare eyepiece into a focusing aid by making it parfocal with your camera (the focus point of the eyepiece matches the camera). Once your camera and parfocal eyepiece have their focus points perfectly matched focusing becomes much easier. Simply focus using the parfocal eyepiece then replace the eyepiece with your camera setup. If you have an ETX or other scope with a built in flip mirror it’s even easier.. simply focus in the eyepiece, turn the flip mirror knob and take a picture. By selecting an eyepiece that has approximately the same field of view as your camera it will aid you in framing the shot as well as focusing. Sometimes a small shake of the camera during the exposure will appear to be an out of focus condition. To reduce shaking use a remote shutter release. If you don’t have a remote simply use the built in timer feature of the camera for “hands off” shake free shots. Some SLR type cameras also have a “mirror lock”, locking the mirror in the up position before taking the shot will also help reduce vibration.

Focusing Issues

Certain types of telescopes tend to have particular issues reaching focus when fitted with a camera. Typically the Afocal and Eyepiece Projection methods will work fine in most any scope since the eyepiece is placed at or near its original position in the optical train. However the prime focus method in particular may require physical or optical extensions to place the camera at the prime focal point of the scope.

Possible focusing issues by telescope type:

Schmidt-Cassegrain (SCT)- Generally these scopes focus by moving the primary mirror, this provides a very large range of focus and reaching focus is rarely a problem. Though some Celestron SCTs (mainly the older 8”) have been known to not have enough back-focus when attempting to use a reducer.

Maksutov (Maks & other mirror lens types)- Again most of these focus by moving the primary and do not have issues reaching focus with a camera. If yours has an external focuser and a fixed primary you may need an extension tube to reach focus.

Refractors- Since a refractors focus range is limited by the length of its drawtube travel an extension tube is often needed. Many short focus refractors in particular will have too long of an optical path when fitted with a diagonal and too short of an optical path when the diagonal is removed to reach its prime focal point. Typically the diagonal would be removed and an appropriate length extension tube will be put in its place. If your telescope manual does not specify the length of the extension tube required you can figure this out yourself by hand holding the camera behind the drawtube to judge its proper length. When doing this be sure the scope is aimed at an extremely distant object to insure it will reach focus at infinity. Ideally you want the focuser to have just a bit of focus range left beyond infinity and a lot left on the near side so you have the widest possible useable focus range for both near and distant objects.

Reflector/Newtonian/Dobsonian- Since a reflectors focus range is limited by its focuser drawtube travel there are sometimes focus issues.. typically a lack of back focus (the focuser reaches the end of its travel but it needs to go in just a bit more to reach focus).

There are a number of things you can do if you experience a lack of back focus:
-Try placing a barlow between the telescope and camera. A barlow extends the focal length of the scope and consequently it moves the focal point rearward a bit, often just enough for everything to work.
-Use a low profile camera adapter. Make sure your camera adapter uses as little of the optical path as possible. Our TRUE-2 adapters use only 12mm of your precious back focus.
-Use a low profile focuser. If your scope has an inexpensive rack and pinion focuser consider replacing it with a more modern low profile crayford type focuser. These will often provide enough back focus since they are lower than most rack and pinion type focusers.
-Move your primary mirror. Some scopes have 2 sets of holes in the tube for the primary mirror mounting screws. The lower position is for visual use and the upper position is for photography, moving the primary forward moves the prime focus point further out. If you really only need a fraction of an inch you may be able to use the collimation screws to raise the mirror up a bit. If building your own scope you should consider designing it so it needs a short extension tube for visual use, and removing the extension places it in imaging mode. If the scope is a truss type you could also make a second set of shorter trusses for use during imaging.