Product Description
**Please allow 2-4 weeks for assembly and testing of each individual unit..
Stellarvue's universal field flattener is designed for cameras with sensors that are full frame and smaller. These flatteners are made here and designed and fabricated to tight tolerances to minimize spherical issues that are all too common in mass-produced flatteners. This flattener will work with all of our current model telescopes but will require different extensions when you switch from one size telescope to another. So, we offer each flattener with different extensions based on the telescope used.
Choosing the Correct Flattener Option:
1. From the listing above, first select the telescope you will be using the flattener with. If you have an older (non-SVX) telescope, simply select its size under Universal Flattener Options. So, if you have an SV102ED telescope it will work with the SVX102T flattener and so on. When you select the telescope, you will be using the flattener for, we will provide it with the proper extensions you will need.
2. Check the camera literature to determine the camera's attachment thread size. Choose the correct thread attachment size of your camera. This will permit us to use the correct adapter that will fit your camera.
3. Choose your focuser. Different focusers use different size attachment threads. We will provide the field flattener with the appropriate threaded adapter based on your selection. This way, the flattener will thread into your focuser.
Attaching the Field Flattener:
This field flattener will thread directly into Stellarvue 3" focusers using its M68X1 thread. If you have a 2.5" focuser, a 3" Feather Touch or Moonlite focuser and you indicated that above it will come with the needed adapter.
Refer to the picture on the right:
1. Remove the 2" adapter assembly from the focuser by unscrewing it using your hands.
2. Thread the field flattener into the focuser
3. Thread the camera onto the rear of the field flattener. The camera can either be a DSLR with t-ring as shown in the picture or it can be an astronomy camera with accessories like a filter wheel and/or off-axis guider.
Back Spacing:
Back spacing is also referred to as back focus. This refers to a distance in millimeters and has nothing to do with focus per se. To get the sharpest correction out of your field flattener, it needs to be placed the proper distance from the camera's sensor. We adjust the back spacing of the field flattener to match your camera's back spacing using a series of extension tubes that are placed between the field flattener and the camera.
Our field flatteners are normally assembled assuming that your camera has the standard 55 mm back spacing. DSLR cameras with t-rings, mirrorless cameras with long t-rings, ZWO and many other brand astronomy cameras use this standard 55 mm back spacing. If your camera has a different back spacing, we will gladly adjust the number of extensions we provide you to match your camera. Contact us at (530) 823-7796 or email us at mail@stellarvue.com and we will be happy to assist you.
The picture to the left illustrates how back spacing works. A camera such as the DSLR camera in this case normally has a sensor that is 55 mm from its front attachment thread. The field flattener comes equipped with one or two extension tubes so that the field flattener produces the flattest field at 55 mm. The flattener shown in this example is set up to work with our 80 mm f-6 telescope. For this telescope we use a 33 mm and a 15 mm extension tube. These two extension tubes and the adapter are added to ensure the best flattening is 55 mm from the base of the field flattener adapter.
Now if an astronomy camera you are using has a sensor that is more or less than 55 mm from the attachment thread, we change the extension tubes on the flattener to compensate for this. Let's say the sensor in your camera is 60 mm from the camera attachment thread. In this case we will change the 15 mm extension tube on the flattener to a 10 mm extension tube. This will make the flattener perform best when the sensor is 60 mm from the base of the M48 adapter on the field flattener.
Since the SFFX-1 flattener is universal, it can be used with different focal length telescopes, but the size of the extension tube must be changed to match the telescope.
Here are the extensions we provide with the SFFX-1 flattener based on the telescope used. These extensions when used with the flattener and the telescope listed will provide the best image at 55 mm from the base of the thread on the field flattener adapter.
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SFFX-1 Back Focus (BF) Reference Data
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| Telescope used | Extensions Provided for 55mm BF | BF without extensions/adapter |
| 80mm f-6 | 15mm and 33mm | 106 mm |
| 90mm f-6 | 40mm and 7mm | 104.8 |
| 102mm f-7 | 40mm | 97.8 mm |
| 130mm f-7 | 21mm and 15mm | 93.9 mm |
| 140mm f-6.7 | 21mm and 15mm | 93.7 mm |
| 152mm f-8 | 33mm | 90.5 mm |
| 180mm f7 | 33mm | 90.5 mm |
Extension Tubes:
Stellarvue produces numerous extension tubes and spacer rings for photographic field flatteners. Our SFE-M69 extension tubes are compatible with this flattener. These extensions are placed between the flattener and the camera adapter. These extensions are not for the focuser side of the flattener. The thread on the focuser side is M68 so these extensions will not work on that side of the flattener.
Stellarvue produces numerous extension tubes and spacer rings for photographic field flatteners. Our SFE-M69 extension tubes are compatible with this flattener. These extensions are placed between the flattener and the camera adapter. These extensions are not for the focuser side of the flattener. The thread on the focuser side is M68 so these extensions will not work on that side of the flattener.
Adapters:
We have numerous adapters that thread onto these extensions to allow the use of various cameras. Cameras come with a wide variety of thread sizes. Our available camera adapters include the following thread sizes: 3"-24, 2.156"-24, M68, M54, M48 and M42. If you purchase a flattener for a camera that uses a particular thread size and then you purchase another camera with a different size thread, you can merely replace the adapter.
Filters:
If you need to use a 2" filter with this SFFX-1, you will need to use the SFE-M63F48-005. This will fit on the side of the adapter that is inside. The 63 to 48 threaded adapter allows you to thread on a 2" (M48 thread) filter inside your field flattener.
