MiniGuider 60 Guide Scope OTA 110mm Rings & Mini Losmandy Clamps
60mm Autoguiding Kit includes:
- Altair 60mm MiniGuider Guide Scope, 225mm focal length with lens caps, and Precision locking 1.25" focuser with brass clamping ring and 3x thumbscrews.
- 2x 110mm guide scope rings,
- 2x Mini Losmandy-format clamps, each with 2x stainless steel M6 cap head set-screws for attachment to any Starwave or Altair TMS guide scope rings.
Mounting the guide scope on your telescope: The two 110mm Guide Scope Rings and 2x mini Losmandy dovetail clamps are used to attach the 60mm guide scope to any inverted Losmandy dovetail plate as found on most RC telescopes or medium size refractors. This is the perfect way to mount your guide scope "piggyback style" on top of your Altair RC or Refractor for flex-free autoguiding.
Attaching and balancing your guide scope: Simply loosen the Losmandy-format clamps and slide them back and forth to adjust the spacing between the rings. The guide scope can easily be positioned and moved back and forth to achieve the best balance along the full length of the Losmandy Dovetail Plate.
What focal lengths can I guide with? You can use the 60mm Mini Guider at focal lengths beyond the usual recommended 1.2 metres, because the 110mm guide scope rings, and the precision locking focuser make for a completely flex-free system. This system can be used for any refractor or RC up to 2 metre focal length with a good quality, sensitive guide camera with small pixels of around 4 microns and guide software which uses pixel interpolation. A Barlow lens can help increase the focal length of the guide scope to acommodate guide cameras with larger pixels.
What's the benefit of this ring and clamp design? There is no possibility of "lateral twisting" with this 2-screw attachment method. Differential flex is therefore not an issue - unlike with cheaper rings. Two steel guide-pins are installed on each clamp, with one on each side of the main clamping thread. This maintains clamping strength and rigidity. This makes the mini-Losmandy dovetail clamp perform just like a small precision vice, without causing "differential flex" like with cheaper clamps and rings.
What's the total weight? The whole system weighs 1380 grams.
How does this compare to an OAG Off Axis Guider unit? There is little if any difference in performance provided everything is mounted correctly and the dovetail plate you're mounting the guide on has a rigid connection with the optical tube. Cheap OAGs often have poor prism mountings with the guide camera sitting on top, a design which introduces a lot of flex, and which is difficult to focus. OAGs introduce complication to the imaging train, causing you to use many spacers and adapters to achieve perfect spacing with your flattener, resulting in the whole lot protruding quite far from the focuser. The more threaded connections you introduce, the more flex on the camera-end which causes tilt error. Consider a typical imaging train with focuser, flattener, OAG, filter wheel, and the various spacers needed to make it all work, and finally the camera. That's a lot of threads. OAG bodies (especially the cheaper slim-line ones) are often quite unstable in themselves. An OAG uses a "pickoff prism" which has to be manually positioned at the field-edge (in order not to block the main imaging sensor).. Aside from actual Vignetting caused by incorrect positioning of the pickoff prism, finding a suitable star for guiding is often quite challenging and time consuming. Finding a sharply focused star at the edge of the field can be challenging because most telescopes show coma or other aberrations at the very edge of the field, which smears or distorts the star-image. This obviously depends on the optical design to some degree. By comparison, a guide scope can easily be re-pointed and can even act as a "digital finder" for remote use. When one considers these factors and their low cost and flexibility, guide scopes are often much "easier to live with" than an OAG. On the other hand, they can introduce more weight than an OAG, so this should also be considered if you are pushing the capacity limits of your mount and you are using a very light camera train and filter wheel. Generally though, you cannot go wrong with a good quality purpose made guide scope and being less complicated, it's our preferred solution for beginner imagers.
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