A right angled star diagonal prism is included with a 1.25" Lockable Auto-guider Focuser Adapter with three clamping screws to a brass collar that threads to the rear flange eliminating any chance of flex. This is a very good price for a very versatile system, for owners of high quality telescopes the finder is often a weak point, this unit is a no compromise addition with the added benefit of being a quality guider solution..
Included in the package:
80mm F4.1 multicoated achromat lens in an all-metal optical tube assembly with dew-shield and objective cap. (328mm focal length).
23mm 1.25" illuminated reticule eyepiece.
1.25" image erecting prism diagonal with full multicoatings and helical focuser, allowing use of most 1.25" eyepieces.
Straight-Through 1.25" Lockable Auto-guider Focuser with 3x clamping screws
Reticule illuminator with a variable brightness red LED to fit the eyepiece.
Tube rings with 6x Nylon tipped screws, and a robust CNC machined finder bracket.
Altair Universal finder base with two clamping screws (also available separately to use your finder with more scopes).
A sturdy cardboard box with shaped foam inserts to protect your tinder scope when not in use.
Included: Straight-Through 1.25" Lockable Auto-guider Focuser with 3x clamping screws. Can be used for autoguiding or straight-through use with a 1.25" eyepiece.
Dimensions & weights
OTA length without focuser or diagonal: 312mm
OTA diameter: 84.5mm
Dewshield diameter: 90mm
Weight optical tube only: approx. 0.9kg
Rings & hardware weight: approx. 0.3kg
Here are answers to common questions about autoguiding with this optical tube:
Q: Can I autoguide?. Yes - this package includes Straight-Through 1.25" Lockable Auto-guider Focuser with 3x clamping screws. Can be used for autoguiding or straight-through use with a 1.25" eyepiece
Q: Why should I buy this all-metal guidescope instead of a plastic one with rack and pinion focuser? Metal bodied scopes can accept dew heaters (this one works with the Kendrick 3" heater) and transmit heat to the optics. Plastic is an insulator and doesn't work well with dew heaters, if at all. What's more, the focusers on cheap scopes aren't up to the job of holding a guide star steady on a guide camera with 3-5 micron pixels. That's why we at Altair invented the locking guide scope straight-through adapter.
Q: Are the default finder scope rings strong enough for autoguiding? Yes they are, however only up to about 700mm focal length on the main scope. Customers keep sending us good results at longer focal lengths and guiding quality has a lot to do with mount, hardware, camera, software, computer, cabling, and so-on - so we can't quote an exact focal length limit.
Q: Is the 80mm Maxi Guider optical tube with 328mm focal length accurate enough for guiding up to 2 metres? A: Yes indeed. This is the ultimate guidescope package for imaging up to 2 metres focal length and even beyond. Customers send us good results at longer focal lengths, and guiding quality has a lot to do with mount, hardware, camera, software, computer, cabling, and so-on - so we can't quote an exact focal length limit - but if you have a guide camera with pixels around 3.75 microns and manage your cables properly, it will perform very well.
Q: Is the 80mm Maxi Guider optical tube compatible with Sharpcap Polar Alignment routines? Yes the 80mm works very well - in fact, too well, bearing in mind Sharpcap was designed with the Altair 60mm Miniguider 200mm focal lengths. Therefore you may get very close but never achieve "perfect" polar alignment. That's because the backlash in your mount base adjustment screws might make it impossible to place the pole position "perfectly". This is not a disadvantage, but more a pitfall for perfectionists who will waste imaging-time trying for "perfect" polar alignment (we've all been there!).
Q: Is the 80mm Maxi Guider optical tube comparable to an OAG (Off-Axis-Guider)? It's impossible to compare two different systems. OAGs are better suited to telescopes where flex in the focuser or optics is likely so for example SCTs, metal tube Newtonians, and so-on. For refractors and RCs with a good focuser, the Maxiguider is all you need. Guide software and small pixel guide cameras have taken a lot of the hassle out of guiding with short optical tubes and the short focal length improves exposure times, allowing you to pick up fainter stars and more of them too.
Q: Is the 80mm Maxi Guider optical tube easier to use than an OAG (Off-Axis-Guider)? Yes, without doubt. OAGs are difficult to use and in our opinion should only be used when there's no other option as explained above. Finding guide stars at long focal lengths of the main scope can be difficult, and exposure times are always longer. The pickoff-prism in an OAG has to stay at the edge of the field so it doesn't block the main imaging sensor. That means it's often positioned too close or too near the flattener (or other corrective optics), and the spot size is therefore usually larger, being outside the design criteria of your scope. That means it picks up all sorts of optical aberrations and distortions. The further off-axis you move the prism, the more aberrations are amplified, so stars are never very round. To compound matters, flex in the prism housing and OGA body can be a problem too, causing tilt, and finally, the OAG often takes up space needed for filter wheels and so-on. Having said that, there are situations where only an OAG will do - see answer above.
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