How do I know if I need a Starlight Instruments 2.5" Diameter Riser for my Dobsonian?
If you find that you have to pull your eyepieces almost completely out of the focuser to reach focus, or if you cannot reach focus at all with a specific accessory like a Paracorr or a camera, you likely need a riser. The best way to measure is to rack your focuser all the way out and see how much more travel you need. This will help you decide between the 1.25" and 2.25" options.
Which height, 1.25" or 2.25", should I choose for my 2.5" Diameter Riser?
Choose the shortest riser that solves your focus problem. The 1.25" riser is the most common choice and solves most eyepiece-related travel issues. The 2.25" riser is typically reserved for imaging setups with long back-focus requirements, such as those including a filter wheel and off-axis guider, or for custom-built telescopes with unique optical dimensions.
Is the Starlight Instruments 2.5" Riser compatible with bases from other manufacturers?
No, this riser is specifically designed to match the bolt pattern and diameter of Starlight Instruments' 2.5" diameter focuser bases. Using it with other brands is not recommended as it may not fit correctly and could introduce tilt into your optical train.
Does adding the 2.5" Diameter Riser affect the stability or collimation of my Feather Touch focuser?
When installed correctly, the riser has no negative impact on stability or collimation. It is machined from solid aluminum to be as rigid as the base itself. It becomes a stable, integrated part of the focuser assembly, maintaining the precise alignment required for astrophotography.
Can I stack multiple Starlight Instruments 2.5" Diameter Risers?
While mechanically possible, stacking risers is generally not recommended. Each additional component introduces a potential point of flexure or misalignment. It is always better to select the single, correct-sized riser for your application. If you need more height than 2.25", you may need to consider a different base or custom mounting solution.
I'm trying to use a Paracorr with my imaging setup on an f/4 Newtonian. Could the 2.5" Diameter Riser help me reach focus?
Yes, this is a very common scenario. Coma correctors like the Tele Vue Paracorr often require additional out-travel compared to a standard eyepiece. If your camera cannot reach focus when attached to the Paracorr, a 1.25" or 2.25" riser will almost certainly provide the extra distance needed to achieve a sharp image across the field.
