DRAWTUBES for your MicroGlide Omicron Focuser

VSI's 2" inside diameter drawtubes for Omicron focusers [only] are available in various lengths to accommodate any scope, from SCTs to refractors. Calculating which length is right for your scope is easy. Just determine how far a 2.25" outside diameter tube can be inserted into your telescope's visual back, then add the Omicron's overall profile of 2.5 inches. If it's an SCT, you would probably want to use our Epsilon which has no built-in drawtube capability, but you could also use our Omicron with a standard 2" SCT drawtube (DWT2). Remember, if the Omicron is being used as a secondary focuser on an SCT, you don't really need any drawtube extension but, with the Omicron installed, you will acquire an extra [redundant] inch plus of back focus adjustment, without sacrificing profile. However, you can not use longer than 2" drawtubes if you are installing your Omicron on a commercial SCT.

With refractors, or any other non-SCT, that have no obstructions in their visual backs, a longer drawtube should be used to obtain maximum backfocus range. In many cases, a longer drawtube is absolutely necessary because you have no primary focus to change your back focus. Your long drawtube gives you the focus range you need to accommodate any observing or imaging profile. Just don't get your drawtube too long or vignetting may occur, although you do have a full 2" clear aperture. If you have a [say] fast refractor, consider the shortest drawtube you can utilize effectively. Don't just "pop" for the longest one available.

VSI also offers a special threaded drawtube (item AMGST below) specifically for the SBIG STL11000 CCD camera (pictured below left). This threaded 2.25" OD x 2" ID insert drawtube replaces the standard drawtubes. Installing this threaded drawtube provides the necessary 2" internal clear aperture reguired for the STL's large chip. 

IMPORTANT: Omicron focusers are designed to be used with these optional drawtubes, individually priced below. This drawtube option provides your Omicron focuser with more back focus versatility [and the shortest profile possible] than any other focuser available today, and gives you a selective choice of back focus travel, depending on which drawtube you choose. You can also switch MicroGlide focusers between different scopes, or retain your MicroGlider when you sell your old [say SCT] scope and use it on your new [say refractor] scope, with only a drawtube and ring adapter upgrade. Without the optional drawtube inserted in your Omicron focuser, you'll need non-standard 2.25" barrel nose eyepieces [that don't exist], and you won't have any focus range, except for the intrinsic half-inch travel of the micrometer head itself.

• 2" Standard SCT Drawtube, 2.25" OD, Item DWT2: $49

• 6" Extended Drawtube, 2.25" OD, Item DWT6: $89 (not for SCTs)

• SBIG STL 2.156"-24tpi Threaded Insert Tube for Omicron only, Item AMGST: $99