Altair 80mm Maxi-Finder Finder Scope Package
The Altair Maxi Finder will suit customers who want even more aperture to see fainter objects in their finder scope.
The 80mm optics will drink in those photons offering 2.56x more surface area than a 50mm guide scope with a corresponding increase in brightness.
In fact the Altair 80mm Finder Scope is a mini-telescope in it's own right, with the advantages of being light weight at about 1.2kg, and having a short optical tube about a foot in length.
This is no cheap plastic optical tube with wobbly rack and pinion focuser or a plastic lens cell. Instead you get a machined aluminium tube with a nice finish and the Altair logo engraved on the dewshield. The eyepiece is a good quality unit with independently focusing reticule and illuminator port. The contrast is very good due to matte black internal surfaces and a fully multicoated objective lens.
A right angled star diagonal prism is included with a 1.25" helical focuser. If you want to use the guide scope for straight through viewing with a 1.25" eyepiece, or autoguiding with a guide camera, you can add the 1.25" Lockable Auto-guider Focuser Adapter. This is a very good price for a very versatile system.
The Altair Maxiguider 80 Finder Scope Package Code "AF80-VISUAL" includes the following:
- 80mm F4.1 (328mm focal length) multicoated achromat lens in an all-metal optical tube assembly with dew-shield.
- 1.25" image erecting prism diagonal with full multicoatings and helical focuser, allowing use of most 1.25" eyepieces.
- 23mm 1.25" illuminated reticule finder-eyepiece.
- Reticule illuminator with a variable brightness red LED to fit the eyepiece.
- Silicon rupper objective cap and 1.25" plug for diagonal.
- Tube rings with 6x Nylon tipped screws, and a robust CNC machined finder bracket.
- Altair universal finder base (code: UNIFBR) with two clamping screws (also available separately to use your finder with more scopes).
- Cardboard box with shaped foam inserts to protect your tinder scope when not in use.
The Altair Maxiguider 80 Finder Scope Package Code "AF80-VISUAL-GUIDE" includes the following:
- Includes the all items in package "AF80-VISUAL-GUIDE" above.
- Includes the Precision 1.25" Micro Focuser for Guide Cameras with 3x thumbscrews, brass compression ring and threaded locking ring for Guide Camera. Can be used for autoguiding or straight-through use with a 1.25" eyepiece. (See detailed images for more info).
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 the Altair Maxi Guider 80mm optical tube:
Q: Can I autoguide with the 1.25" or 2" helical focuser, or do I really need the optional locking straight-through focuser?
A: You can try but we wouldn't recommend it. The 2" or 1.25" helical focuser is not rigid enough for autoguiding and the focus can drift because it doesn't have a lock. It's more than enough for visual use however.
Q: Why should I buy this all-metal guidescope instead of a cheap plastic ST80 or other Achromat with rack and pinion focuser?
A: Metal bodied scopes can accept dew heaters (this one works with the DewZapper 3-4" heater code DEWH-34) and transmits 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 2-5 micron pixels - in fact, that's why we at Altair invented the locking guide scope straight-through adapter. Finally it's a very light rigid tube - essential for long focal length guiding.
Q: Are the default finder scope rings in the visual package strong enough for autoguiding?
A: Yes they are, however only for imaging scope with up to about 700mm focal length. If your mail imaging scope has a longer focal length, then you should buy the Altair Astro TMS 100mm or Starwave 110mm machined guidescope rings and 80mm OTA packages we offer.
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?
A: 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)?
A: 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)?
A: 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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