The above SCT imaging train consists of a Meade 10" SCT + A381 (not shown, mounted in base of OMEGATOAD) + 3" OMEGATOAD + A388 + TARGETRON + SR2156 + CCD camera (SBIG STL11000/4020/6303).
Many have said that VSI has too many confusing port rings, adapters and couplings. This is probably true, because VSI has dozens of different adapters that can be installed in various locations along your imaging train. VSI also has the best selection, by far, on Planet Earth (now where have I heard that before?). So your confusion is well justified, but I do believe that a good selection is important, simply because there are so many different types of telescopes and imaging equipment available to the modern astroimager. I hope the following will make your final imaging train decisions easier and less frustrating. After all, that's what VSI components are all about - creating an ultra-low profile, rock-solid imaging train, and removing the frustration from astroimaging. - PVS
QUALITY ASSURANCE NOTE: It has come to my attention that others use less than adequate couplings on their products that induce flexure. They look very similar to VSI's exclusive docking/coupling systems. They are NOT! VSI's exclusive docking/couplings are not like any other flimsy, flexure-ridden connections used on other products. A good anology would be a comparison between a (less than) $50 and a $300 (and up) rifle scope. The lesser rifle scopes looks identical to the more expensive ones but, in operation, the differences are very apparent, optically and [especially] mechanically. Let the buyer beware, you receive quality and functionality only when you are willing to expend an appropriate dollar amount. VSI's proprietary flared flange (circular dovetail) docking inserts have extremely thick-wall construction and are locked in place by three set screws opposed by 120 degrees. When you tighten these set screws against this special [angled] flange, it not only pushes directly against the insert ring, but it also pushes laterally to compress the ring inwards against external and internal shoulders, which locks it in place like a good weld - rock-solid! - PVS
TAK scope+ A384 + 3" ALPHATOAD + A388 + TARGETRON + SR2156 + CAMERA
The following configurations indicate straight-through imaging trains only
TAK REFRACTOR (less focuser) + A384 + ALPHATOAD + A388 + TARG + SR2156 + CCD CAMERA (SBIG STL11 or similar)
AP REFRACTOR (less focuser) + A385 + ALPHATOAD + A388 + TARG + SR35 + 35mm or CCD CAMERA (42mm T-thread)
COMMERCIAL SCT + A381 + OMEGATOAD + A388 + TARG + SR2156 + CCD CAMERA (SBIG STL11000 or similar)
COMMERCIAL SCT + A382 + OMEGATOAD + A388 + TARG + SR35 + 35mm or CCD CAMERA (42mm T-thread)
16" MEADE SCT + A383 + OMEGATOAD + A388 + TARG + SR224 + f/3.3 FR + A2T + 35mm or CCD CAMERA
ABBREVIATION GUIDE FOR ABOVE (click on product code below to go directly to link)
REFRACTOR (no focuser): Visual back ring only, no existing focuser
ALPHA = Any model VSI 3" ALPHATOAD (i.e. ALF1, ALF2, ALF3 or ALF4)
OMEGA = Any model VSI 3" OMEGATOAD (i.e. OMG1, OMG2, OMG3 or OMG4)
COMMERCIAL SCT = Meade/Celestron SCTs 10" and larger, mounts to 3.25" or 3.29" threaded visual back
A312R = 2" Output Reducer w/Quad-Lock for 3" TOADLOADERS (see FOCUSERS link, Output Adapters link)
A381 = Docking Converter for Meade to install OMEGATOAD (see FOCUSERS link, Docking Converters link)
A384 = Docking Converter for Tak Refractor to install ALPHATOAD (see FOCUSERS link, Docking Converters link)
A385 = Docking Converter for AP Refractor to install ALPHATOAD (see FOCUSERS link, Docking Converters link)
MPSW = Mega-Port Sidewinder Optical Manifold (see SIDEWINDERS link)
TARG = Accu-Port Targetron Off-Axis Guider (see TARGETRON link)
ZBR1 = ATLAS 4.5" Zerotator (see ROTATORS link)
SR29 = Coupling Port Ring, 2.9" to 3.1" back-to-back flange (see SIDEWINDERS link, Docking Port Rings link)
SR224 = Docking Port Ring, 2"-24tpi commercial SCTs, female (see TARGETRONS link, Docking Port Rings link)
MR2729 = Coupling Port Ring, 2.9" to 3.1" back-to-back flange (see SIDEWINDERS link, Docking Port Rings link)
A388 = Coupling Port Ring, 2.9" to 3.1" back-to-back flange (see SIDEWINDERS link, Docking Port Rings link)
SR72 = Docking Port Ring to install Sidewinder to your existing Takahashi focuser (see TARGETRONS link, Docking Port Rings link)
SR2724 = Docking Port Ring to install Sidewinder to your existing AstroPhysics focuser (see TARGETRONS link, Docking Port Rings link)
SR2156 = Camera Port Ring, 2.156"-24tpi, SBIG STL11000 (see SIDEWINDERS link, Camera Port Ring link)
SR35 = Camera Port Ring, 42mm-0.75mm, T-Ring (see SIDEWINDERS link, Camera Port Ring link)
A2LT = 2" Threaded Long Barrel Adapter (see SLIDERS link, Adapters link)
A2T = 2"-24tpi Female to 42mm T-Thread Male Adapter (see SLIDERS link, Adapters link)
Remember, a 3" TOADLOADER is a larger than 2" format focuser for larger than 2" format components and cameras, like VSI's Sidewinders and Zerotators (pictured at right). TOADLOADERS are designed for 35mm or CCD cameras (like the SBIG STL11000) that have larger film/chip areas than 2" format. Usually, VSI's smaller 2" format Slider will accommodate up to 35mm format with no vignetting, depending on the f/ratio of your scope, etc. However, you can use standard 2" format components, like our Sliders, by inserting an A312R 2" Output Reducer with Quad-Lock (pictured at left), which will convert the output of the 's moving tube to accept 2" barrel-nose eyepieces and accessories.
Your primary concern will be the type, and number of telescopes you have now, and/or plan on purchasing in the future.
If you have a commercial Schmidt-Cassegrain telescope larger than 8 inches, your back focus is more than adequate for any VSI focuser and/or imaging train, but don't get too involved with add-on accessories (especially in-line filter wheels) that increase your profile and flexure. Most hi-end CCD cameras have built-in filter wheels with interchangeable filters. 3" MicroGlide focusers are gigantic, and are not for 8" or smaller SCTs. If you need a secondary focuser for your 8" SCT, consider our MicroGlide focusers.
If you are going to dock a 3" focuser on a Newtonian telescope, the ALPHATOAD probably has too much focus range (5") and the OMEGA (1") has too little. VSI can custom machine a special moving tube to your needs. Usually a 3" travel range is appropriate for a Newt, but that will be your call. If you need more back focus, the best way to gain back focus is to move your primary mirror forward. Do not move it too far or you will cut off the edge of your primary light cone by vignetting your secondary mirror. If you do cut off your primary light cone, you can install a larger minor-axis diagonal flat, but you will also lose a small amount of resolution, because you will then have a larger center obstruction. This small clarity loss will probably not be noticeable, even when imaging. By moving your primary forward, this will allow you to gain back focus and provide enough profile to use an optical manifold or off-axis guider, etc. in your imaging train.
If you are going to dock a 3" to a refractor, you need the ALPHATOAD model, which is a primary focuser with an enormous 5 inches of travel. Most refractor scopes have stock focusers with very long housings, so you will probably gain some profile by replacing your refractor's existing focuser with a relatively short profile focuser, and you will also gain the capability of autofocus, which is a feature that most refractor focusers do not possess. If you would like to increase your back focus, this would be a good time to do it. You can accomplish this by simply cutting off your tube and remounting your visual back a few inches closer to your objective lens. Use a simple square to make sure that the tube end is perpendicular to your tube assembly after you cut it off. No, this action will not alter your internal baffling because we are not changing your focal point. You are just shortening the hardware around your light cone. This shortening process is easy because most refractor's have visual backs with 3 screws opposed by 120 degree. Just use your scope's visual back as a template and drill three holes in your shortened tube assembly to remount. If your scope happens to have a threaded tube, like the Takahashi scopes, then you simply need to purchase one that has extended back focus, like the TOA-130 mentioned above and not shorten the tube at all. You can shorten your Takahashi tube assembly, but you need [at minimum] a lathe to machine out the visual back threads after you cut down the tube assembly. Then remount the visual back using the 3-screw method noted above.
If you are using a different type of telescope that is not listed above (i.e. catadioptric-not SC, off-axis, folded, etc.), then VSI can create any custom machined docking platform that you require. If you need to check your back focus requirements, you can perform the back focus test noted below and follow the guidelines that apply to your specific configuration above.
The above SCT imaging train consists of a Meade 10" SCT + 2" TOADLOADER + A2LT + SLIDER 1 + AZP2T + CCD camera.
Many have said that VSI has too many confusing port rings, adapters and couplings. This is probably true, because VSI has dozens of different adapters that can be installed in various locations along your imaging train. VSI also has the best selection, by far, on Planet Earth (now where have I heard that before?). So your confusion is well justified, but I do believe that a good selection is important, simply because there are so many different types of telescopes and imaging equipment available to the modern astroimager. I hope the following will make your final imaging train decisions easier and less frustrating. After all, that's what VSI components are all about - creating an ultra-low profile, rock-solid imaging train, and removing the frustration from astroimaging. - PVS
QUALITY ASSURANCE NOTE: It has come to my attention that others use less than adequate couplings on their products that induce flexure. They look very similar to VSI's exclusive docking/coupling systems. They are NOT! VSI's exclusive docking/couplings are not like any other flimsy, flexure-ridden connections used on other products. A good analogy would be a comparison between a (less than) $50 and a $300 (and up) rifle scope. The lesser rifle scopes looks identical to the more expensive ones but, in operation, the differences are very apparent, optically and [especially] mechanically. Let the buyer beware, you receive quality and functionality only when you are willing to expend an appropriate dollar amount. VSI's proprietary flared flange (circular dovetail) docking inserts have extremely thick-wall construction and are locked in place by three set screws opposed by 120 degrees. When you tighten these set screws against this special [angled] flange, it not only pushes directly against the insert ring, but it also pushes laterally to compress the ring inwards against external and internal shoulders, which locks it in place like a good weld - rock-solid! - PVS
COMMERCIAL SCT + 2" TOADLOADER + A2LT + SLIDER 1 + AZP2T + CCD CAMERA
10"+ COMMERCIAL SCT + 2" TOAD (w/f/6.3 FR inside) + A2LT + SLIDER + AZP2T + CAMERA
10"+ COMMERCIAL SCT + 2" TOAD + A2LT + f/6.3 FR + SLIDER + AZP2T + CAMERA
10"+ COMMERCIAL SCT + 2" TOAD + A2LT + SLIDER + A2ST + f/3.3 FR + A2T + CAMERA
10"+ COMMERCIAL SCT + 2" TOAD + A2LT + SR224 + ZEROTATOR + CR224 + SLIDER + AZP2T + CAMERA
NEWTONIAN SCOPE + ANT43 + 2" TOAD + A2LT + SR224 + ZEROTATOR + CR224 + SLIDER + AZP2T + CAMERA
CASS/REFRACTOR SCOPE + ACR45 + 2" TOAD + DT6 (less screw-on knurled section) + SLIDER + AZP2T + CAMERA
ABBREVIATION GUIDE FOR ABOVE (click on product code below to go directly to link)
M3 = Any model VSI 2" TOADLOADER with hidden cavity for f/6.3 focal reducer insertion (i.e. M1 thru M5)
DT6 = 6" Long Drawtube, 2" format, two-part with 2"-24tpi threaded tube end section and knurled 2 thumb screw section
ANT43 = 4" Square to 3.25"-16tpi Male Threaded Converter Plate (see FOCUSERS link, Docking Converters link)
ACR45 = 4.5" Round [flat-bottom] to 3.25"-16tpi Male Threaded Ring Converter (see FOCUSERS link, Docking Converters link)
CR224 = Camera Port Ring, 2"-24tpi standard SCT, male (see TARGETRON link, Camera Port Ring link)
SR224 = Docking Port Ring, 2"-24tpi commercial SCTs, female (see TARGETRON link, Docking Port Ring link)
A2LT = 2" Threaded Long Barrel Adapter (see SLIDERS link, Adapters link)
A2T = 2"-24tpi Female to 42mm T-Thread Male Adapter (see SLIDERS link, Adapters link)
AZP2T = Zero Profile 2" to T-Adapter (see SLIDERS link, Adapters link)
f/3.3 FR = Meade f/3.3 focal reducer (extension drawtube required for top & side ports to achieve parfocus)
f/6.3 FR = Meade or Celestron f/6.3 focal reducer
SLIDER = includes built-in zero profile (2" format) filter slot (see SLIDERS link)
CAMERA = 35mm or CCD camera (with standard female T-thread input)
10"+ COMMERCIAL SCT = Meade/Celestron SCTs and Ritcheys 10" and larger, mounts to 3.25"-16tpi threaded visual back (adapter needed for all Celestron SCTs and Meade 16" SCT, see FOCUSERS link, Docking Converters link).
NEWTONIAN SCOPE: tube with 3" diameter tube hole perforation
CASS/REFRACTOR (no focuser): Visual back only, no existing focuser
All VSI 2" TOADLOADERS screw directly onto any Meade 10" or 12" SCTs and Ritcheys that utilize their standard 3.25"-16tpi threaded visual backs. All 2" TOADLOADERS also have our exclusive focal reducer "hidden cavity" allowing you to insert your f/6.3 Meade or Celestron focal reducer securely inside the moving tube of your VSI focuser effectively rendering your focal reducer's profile to zero.
2" TOADLOADERS are offered in five different models. All models have the Meade 3.25"-16tpi threaded housing base, because they are designed to be secondary focusers mainly for SCTs. However, they can be installed on virtually any scope. Various stock docking converters are available at that specific link or custom machined docking converters are always available. If more than 1-inch of travel is needed, you can use our DT6 drawtube to increase the overall range to about 4 inches.
Your primary concern will be the type, and number of telescopes you have now, and/or plan on purchasing in the future.
If you have a commercial Schmidt-Cassegrain telescope larger than 8 inches, your back focus is more than adequate for any VSI focuser and/or imaging train, but don't get too involved with add-on accessories (especially in-line filter wheels) that increase your profile and flexure. Most hi-end CCD cameras have built-in filter wheels with interchangeable filters. 3" MicroGlide focusers are gigantic, and are not for 8" or smaller SCTs. If you need a secondary focuser for your 8" SCT, consider our MicroGlide focusers.
If you are going to dock a 2" TOADLOADER on a Newtonian telescope, you will need our ANT43 noted above. If you need more back focus, the best way to gain back focus is to move your primary mirror forward. Do not move it too far or you will cut off the edge of your primary light cone by vignetting your secondary mirror. If you do cut off your primary light cone, you can install a larger minor-axis diagonal flat, but you will also lose a small amount of resolution, because you will then have a larger center obstruction. This small clarity loss will probably not be noticeable, even when imaging. By moving your primary forward, this will allow you to gain back focus and provide enough profile to use an optical manifold or off-axis guider, etc. in your imaging train.
If you are going to dock a 2" TOADLOADER to a Cassegrain or refractor, you need our ACR45 noted above. If you are mounting a TOADLOADER to a Cassegrain's visual back, just center the ACR45 on your visual back and mark, drill and tap the holes. You can also drill through holes using bolts and nuts, which are included. Aligning the plate angle with your optical axis is done with the 3 push/pull set screws (see picture at above link). Most refractor scopes have stock focusers with very long housings, so you will probably gain some profile by replacing your refractor's existing focuser with a short profile 2" TOADLOADER, and you will also gain the capability of autofocus, which is a feature that most refractor focusers do not possess. If you would like to increase your back focus, this would be a good time to do it. You can accomplish this by simply cutting off your tube and remounting your visual back a few inches closer to your objective lens. Use a simple square to make sure that the tube end is perpendicular to your tube assembly after you cut it off. No, this action will not alter your internal baffling because we are not changing your focal point. You are just shortening the hardware around your light cone. This shortening process is easy because most refractor's have visual backs with 3 screws opposed by 120 degree. Just use your scope's visual back as a template and drill three holes in your shortened tube assembly to remount. If your scope happens to have a threaded tube, like the Takahashi scopes, then you simply need to purchase one that has extended back focus, like the TOA-130 mentioned above and not shorten the tube at all. You can shorten your Takahashi tube assembly, but you need [at minimum] a lathe to machine out the visual back threads after you cut down the tube assembly. Then remount the visual back using the 3-screw method noted above.
If you are using a different type of telescope that is not listed above (i.e. catadioptric-not SC, off-axis, folded, etc.), then VSI can create any custom machined docking platform that you require. If you need to check your back focus requirements, you can perform the back focus test noted below and follow the guidelines that apply to your specific configuration above.
If you don't have a commercial SCT, you need to check your back focus before purchasing a Slider, Sidewinder or Targetron. I'm finding that many seemingly experienced astrophotographers know very little about their own telescope's back focus (BF). They order an optical manifold, etc. and find that it won't work on their telescope. This wastes my time and yours. Back focus is something that you need in abundance if you're going to do astroimaging. Unfortunately, many telescopes, like refractors and Newtonians, have very limited back focus and are designed for visual observing only. The only telescopes that have near infinite back focus are Cassegrains that move their primary mirrors, like the commercial Meade/Celestron Schmidt-Cassegrain telescopes. For every inch that you move your primary mirror, you get an equivalent of about 6 inches of back focus change, depending on your f/ratio.
If you have a commercial Schmidt-Cassegrain telescope (Meade/Celestron, etc.) you don't need to perform this test. Any Glider/Slider, etc. will work with your scope. If you don't, then Rack [or move] your focuser all the way in. Then rack [or move] the focuser out about a quarter of an inch. Move the imaging camera or eyepiece out from the focuser, without moving the focuser position (a drawtube would be very useful at this point, but not always available), until you achieve focus at the camera/eyepiece. The distance from the outer edge/lip of the focuser's rack [or moving] tube, to the OD T-ring butt plate (not the end of a 2-inch adapter tube) of the camera is the profile (in inches) that you need (see BF diagram above left). To install a Slider or Sidewinder you will need 3.5 inches of profile. If you don't have 3.5 inches of profile, then you can't use a Slider or Sidewinder, or anything else for that matter, until you extend your telescope's back focus. There are many ways of modifying a telescope's back focus. Some of these methods are briefly discussed above. If you need advice, give me [Paul Van Slyke] a call and we'll talk about modifications to your telescope.
Say that three times real quick. Betcha can't without spitting all over yourself? Anyway, I hope this section will provide you with a better understanding of parfocusing any imaging train, not just the Slider or Sidewinder. I selected the [now] discontinued Micro-Slider (MS) and Flipper because they were designed to parfocus "in-reverse" of each other, which should provide you with a better concept of parfocusing principles (oops! there's another P-word). The MS parfocuses [from 35mm to CCD camera] by adding length to the straight through imaging port (noted in red, upper left) which is the most inefficient method of parfocusing (like the Meade flip-mirror devices) because you are increasing your imaging train's profile. The Flipper, Slider and Sidewinder parfocuses [from CCD to 35mm camera] by adding drawtubes to the top flip or slide port (noted in red, lower right) and side pick-off ports (not shown), which is the most effective method to parfocus your system because you are not adding any length to your straight-through imaging train to parfocus your system, it remains the same for either CCD or 35mm cameras. Remember that a shorter imaging train is always preferred because it's simply more solid, eliminating system flexure problems as you move from object to object. After attaching your new Slider/Sidewinder to your scope (addressed above), attach your camera, using the appropriate adapter, to the rear imaging port. Adjust the telescope's focus on your 35mm camera's focal plane, or CCD chip of your imaging camera. Then, insert a 2" or 1.25" eyepiece in the top slide mirror port and focus the eyepiece by push/pulling the eyepiece in and out until adequate focus is achieved.
Typically, with a CCD camera, you should not need an extension drawtube using a Slider or Sidewinder (see lower left Flipper), because most CCD cameras are roughly parfocus with most newer standardized eyepieces. However, with a 35mm camera, that focuses about 1.5" further out from a standard CCD camera, you will need an extension drawtube (item code AD22 or AD21) between the top slide mirror port and your eyepiece (see lower right Flipper, area in red). Although not shown in the pictures at left, side pick-off ports will need to be extended with a simple drawtube, but not on the discontinued Micro-Slider models because of the inferior "reverse" design that Meade has now "adopted" that extends the imaging train profile instead of the top or side mirror port profile. To further reiterate, note the two lower Flippers above. The red area noted on the lower right Flipper is an inserted drawtube that is needed to parfocalize your system when using a 35mm camera, and is not needed when imaging with a CCD camera (see lower left Flipper). Conversely, the upper two Micro-Sliders obtain parfocus by extending the CCD camera's straight-through profile (again, a no-no) noted in the red area in the upper left Micro-Slider image.
NOTE: Flippers were beta tested for nearly 10 years at Black Forest Observatory before a production model was finally offered. We found that secondary helical focusing, offered on other brands is time consuming, awkward and literally useless when attempting to focus secondary eyepieces, since your eye can't observe perfect focus anyway. The push/pull method is easier to adjust, fast, accurate and functional.
Also reference The Art of Astroimaging for more info on parfocusing your imaging train.