Astro-Tech 8" F/4 imaging Newtonian optical tube


Availability: More on the way

Sky & Telescope said this Astro-Tech AT8IN Imaging Newtonian "wins the biggest-bang-for-the-buck award," and Astronomy named it a Star Product for 2010 award winner. Its contrast-enhancing extended nose and 15 internal knife-edge baffles are just what the imaging doctor ordered to improve the looks of your deep space photos . . .
Our Product #: AT8IN
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Product Description

A review of three Astro-Tech astrographs (the AT6RC and AT8RC Ritchey-Chrétiens, as well as this AT8IN Imaging Newtonian) in the December 2009 issue of Sky & Telescope said "While all three of the Astro-Tech scopes represent excellent value, the AT8IN, with its 8-inch aperture and $499 price tag, wins the biggest-bang-for-the-buck award . . . there's a quality to this scope that seems contradictory to its relatively low cost."

This Astro-Tech Imaging Newtonian optical tube has:

• very fast f/4 focal ratio 8" Newtonian reflector optics
• contrast-enhancing extended tube length with 15 internal baffles
• built-in cooling fan for faster primary mirror cooldown
• 2" dual-speed Crayford focuser with 2" and 1.25" compression ring accessory adapters
• 8 x 50mm finderscope in a quick-release bracket
• dual split hinged mounting rings

This 8" Astro-Tech AT8IN optical tube is a very fast focal ratio f/4 reflector that has been optimized for wide field deep space imaging. It can be used with 35mm cameras, DSLRs, web-cams, DSI-type cameras, and large format CCD cameras alike.

Astronomy named the Astro-Tech AT8IN a Star Product for 2010, saying "Astronomy Technologies has optimized the AT8IN for astroimaging, but the scope is just as adept for backyard viewing . . . a versatile instrument that will take you into the depths of the universe in style."

The light weight standard equipment mounting rings of the Astro-Tech Imaging Newtonian allow you to use it on a wide variety of dovetail plates and German equatorial mounts - from the most basic to the most elaborate high payload go-to system.

In addition to deep space imaging, the Astro-Tech AT8IN is also usable for solar system imaging as well as deep space and solar system visual observing. Solar system visual contrast will be somewhat reduced compared to a longer focal ratio reflector because of the AT8IN's larger secondary mirror that has been optimized for full-field photographic illumination. However, the visual performance will still be much more than acceptable, and the 800mm focal length of this Astro-Tech makes it quite possible to achieve the high powers needed for detailed lunar and planetary observing. Simply add optional 1.25" or 2" eyepieces, and perhaps an optional Barlow lens, and this Astro-Tech Imaging Newtonian will provide you with crisp and sharply detailed close-up views of the Moon and planets.

This Astro-Tech Telescope's Optical System . . .

Newtonian reflector optics: 8" aperture, 800mm focal length, f/4 focal ratio, parabolic primary mirror; 70mm m.a. elliptical diagonal mirror. The mirrors are ground and polished under computer control for guaranteed diffraction limited performance, coated with 91% reflectivity aluminum, and overcoated with a protective layer of silicon dioxide (quartz) for long life.
The mirrors are made of B270 "water white" optical crown glass that is free of internal stress and striae. B270 glass is equivalent to BK7 in performance and optical quality. The thermal stability of B270 glass is generally better than the soda lime float glass used for the mirrors of most reflectors in this reasonable price range. For maximum contrast, the four secondary mirror spider vanes have been optimized to be as thin as possible without losing stability.

No-tool push-pull mirror cell: The die-cast aluminum primary mirror cell has six large hand adjust push-pull collimation knobs. These make it easy to collimate the primary mirror without tools, even while wearing gloves or mittens in cold weather. To further ease collimation, the primary mirror is precisely center-spotted. The Sky & Telescope review praised the "solidly made" primary mirror cell and secondary mirror holder.

Built-in cooling fan: A low-vibration/high CFM fan is mounted on the primary mirror cell. The fan is powered by a supplied battery pack that uses eight user-supplied AA batteries. Alternatively, the fan can be powered by a 12 VDC rechargeable battery if one is being used to power your mount's drive system.

Extended optical tube with 15 internal baffles: To increase the contrast, the optical tube of the Astro-Tech AT8IN is extended 8.75" forward of the focuser centerline to act as a lens shade to keep ambient light from hitting the diagonal mirror. In addition, there are 15 internal knife-edge baffles installed down the interior length of the optical tube to eliminate any stray light that might get past the extended optical tube and lower the contrast. The baffles and tube interior are finished in matte black to further absorb stray light. The result is exceptional contrast, far better than a conventional reflector for both imaging and visual observing.

The white-painted 32" long x 9" diameter (with 9.25" diameter front and rear cells) Astro-Tech optical tube is fabricated of rolled steel, to allow the mirrors to cool to ambient temperature more quickly. While the rolled steel optical tube is a little heavier than a more-costly aluminum tube, the Sky & Telescope review points out that "it also helps make it a very rigid setup, which is a good thing for astrophotographers." The scope's tube end rings are sturdy die-cast aluminum, to protect the tube during transport and provide exceptionally rigid support for the optics, "adding to the scope's overall rigidity," according to the Sky & Telescope review.

For essentially coma-free imaging with the AT8IN, consider adding the Astro-Tech ATCC coma corrector. This imaging accessory essentially eliminates the coma inherent in all fast focal ratio reflector telescope designs, so that the coma-free star images remain point-like all across the field.

2" dual-speed Crayford focuser: The precision-made 2" Crayford focuser drawtube ends in a 2" accessory holder. A 1.25" accessory adapter is standard equipment. Both the drawtube's 2" accessory holder and the 1.25" accessory adapter have non-marring compression ring eyepiece/accessory holders.

The focuser has two coarse focusing knobs. One knob also has a smaller concentric knob with 10:1 ratio reduction gear microfine focusing. This provides exceptionally precise focus control during critical CCD imaging. The focus knobs have ribbed gripping surfaces so they are easy to operate, even while wearing gloves or mittens in cold weather. A drawtube tension knob on the side of the focuser lets you adjust the drag on the focuser drawtube to hold various equipment load weights while focusing. A second knob lets you lock in a precise photographic focus.

The drawtube has 34mm (1.35") of travel. There is 80mm of back focus available from the top of the focuser's 2" accessory holder to the image plane. A 2" diameter x 35mm long extension tube is provided to match the back focus requirement to your particular photographic application. The 35mm extension tube has a non-marring compression ring eyepiece/accessory holder.

Split tube rings: A pair of die-cast aluminum hinged split tube mounting rings are provided. Each ring has a flat boss on its underside with a 1/4"-20 thread mounting hole, flanked by two 4mm metric holes on 30mm centers, for installing the ring on a Vixen-style or Losmandy-style "D-plate" dovetail mounting plate. This lets you mount the scope on virtually any equatorial mount. In addition, there is a flat boss with a 4mm metric hole on the top of each ring. This allows you to install a separate dovetail on top of the optical tube for mounting photoguide rings and a guidescope or similar accessories piggyback on top of the AT8IN. The lightweight optical tube (18 pounds tube only; 21.6 pounds with rings and finderscope) rotates in its felt-lined die cast cradle rings to bring the focuser and finder to the most comfortable viewing position.

Finderscope: 8x 50mm straight-through dark crosshair achromatic design, in a spring-loaded quick-release mounting bracket. The finder has a long and comfortable 13mm eye relief. To focus the finder, loosen the trim ring behind the objective lens cell, screw the lens cell in or out to focus, and tighten the trim ring to lock in the correct focus.

Tech Details

Aperture 8"
Binary and Star Cluster Observation Very Good
Focal Length 800mm
Focal Ratio f/4
Galaxy and Nebula Observation Very Good
Heaviest Single Component 18 lbs.
Highest Useful Magnification 320x
Lunar Observation Great
Weight 21.6 lbs.
Planetary Observation Very Good
Resolution 0.57 arc seconds
Visual Limiting Magnitude 14
Warranty 1 year


Review by:
Excellent astrograph for those deep objects. I debated on what kind of Newt I should get for a long time and I'm happy I settled on the AT8IN. Sharp optics and an awesome price! Despite several other reviews, I've had no troubles with the stock focuser. It seems plenty strong enough for my bulky NIKON D5300. I love this scope, it's not too heavy, not too bulky and plenty of size to reach and touch those deep space objects. (Posted on 1/14/2019)
Review by:
I wrote an earlier review that is posted above. Upon reflection there are a couple of additions that I would like to add to my review above. First the scope is not hard to collimate if you have a good laser collimater. I used a cheap one that was not centered correctly so had to live with slightly out of line optics. Eventually I got it close using an old pin hole cap that was around 35 years old but a laser would have made it a snap. Getting a fast F/4 mirror aligned is pretty important for image quality. This size reflector fits very well on a Sirius/Atlas mount and probably could be used on an AVX weight mount if you had a lightweight camera and guider. Still a great deal! (Posted on 1/11/2019)
Review by:
This is a mid-level imaging scope and it is brilliant. It's fairly light weight and you can tell they put a lot of thought into the engineering. The tube is a little long up top which is a bonus because it blocks stray light very well. The focuser is quality made and good materials. The optics are very good.

I agree with all the rest of the comments who like this scope. It's a slam dunk purchase. (Posted on 1/3/2019)
Review by:
I stuffed this on an Explore Scientific EXOS 2 GT Equatorial Mount
To push the limits
I love it (Posted on 11/29/2018)
Review by:
I bought my AT8IN used, moving up from a department store 4.5" Newtonian. The AT8IN was a huge step up and has not disappointed. I especially like its fast optics and large field of view, which make this scope very good for imaging emission nebulae. Originally I had a small-chip camera (Meade DSI IIc) on the scope and never noticed any coma, even when using a 0.5x focal reducer, but when I moved to a larger chip (ASI1600MM-C) the coma became apparent and I added an inexpensive coma corrector. As others have noted, the weakness of the AT8IN is its focuser (and this is the reason for 4 stars rather than 5). The tension settings need to be adjusted very carefully to allow smooth focusing without slippage. I use the focuser with a home-built stepper motor-driven automated focusing setup, and it works reasonably well although there is some backlash. Most of the images on my Astrobin account ( were taken with this scope. (Posted on 10/14/2018)
Review by:
This is my first telescope specifically for astrophotography and I was definitely not disappointed. The optics are designed for the focal point of a camera which does make it tricky sometime to use visual eyepieces but that means I don't have to get extenders and jump through other hoops to get my camera to focus. The images I've been able to capture so far as great (given my skill level of course)! (Posted on 8/4/2017)
Review by:
I think the AT8IN accomplishes its intended task, that is, provide a fast, reasonably easy to use focal length telescope with generous aperture at an affordable price. To use this scope to its potential you will need a coma corrector and you will need to upgrade some of the hardware. You will need to learn about critical collimation at f/4 and out of the box the collimation adjustment hardware is frustrating at best. The secondary holder's design makes it difficult to collimate properly and most users find that they need to replace pieces of hardware to get it adjustable. The focuser also exhibits a bit of flex and it can be difficult to keep the imaging sensor orthogonal to the image plane. Now having said all that, this can be a fun scope to image with if you are willing to understand what it takes to make it perform. Personally, I would gladly pay a little extra if some of these issues were addressed from the factory so that the out-of-box experience was a little more rewarding. (Posted on 8/4/2017)
Review by:
Good scope for the money. With Bader MPCC corrector you can cover most of a full frame 35mm with round stars. Gives excellent image over full area of a KAF 8300 ccd. Really needs an upgraded focuser ( Moonlite , etc.) but you can get by with the supplied focuser with light loads. (Posted on 8/4/2017)
Review by:
Drove up from Dallas to get one of these, well worth the trip. Probably the most scope available in this price range, has some features you would be paying extra for from some other scope manufacturers. The cooling fan and the focuser are definite upgrades from most scopes in this price range.

Also the CUSTOMER SERVICE IS AWESOME, they only had one left in stock and I asked if they would hold it for me until I could make the drive up there, Mike said it would be no problem to do that and didn't even have to prepay it, just gave him my name and it was there waiting for me when I got to the store. Made sure it was in good shape and even offered to help carry it down to the car for me. The quality of the scope and the excellent customer service have made this an excellent value for the money. The pics and the views are pretty awesome too! (Posted on 8/4/2017)
Review by:
This is a great astrophotography scope, and comes with fine focus setup 2" eyepiece. So you can get full frame photos with a DLSR. My only negative is mounting the DLSR requires an extension tube of rather great length on my Canon. Other than that, it is finely engineered and at a great price for the optics (Posted on 8/4/2017)
Review by:
Currently this telescope is the heart of the Temple Research Observatory. It has been modified for robotic operation and it's full capability is not being used due to a small CCD Chip. However, it does an outstanding job of wide field photometry and imaging.

The 4 star rating is simply due to the weak focuser. In it's current configuration a Robofocus unit has been added and with it's addition has overcome the focusers weakness. When you added a heavy camera ST-7E to the stock focusing unit it would not stay focused and would experience drift. This would cause you to have to refocus quite frequently. Without a Robofocus type unit the problem made it hard to do long time series which is a major part of the work of TRO1. The focuser is adequate for visual and light cameras. In it's visual configuration the views are quite spectacular but need a field flattener.

The OTA has been modified to provide the maximum stability and rigidness to the system. The spider and mirrors were moved to allow the heavy camera assembly to be used without an extension. This has also helped with the balance issue since balancing this unit with a heavy camera can be a challenge. In fact balance was achieved by adding a weight extension on the opposite side of the OTA from the camera, hanging off the bottom of the tube. This allows the unit to reach acceptable balance. It has, however, caused a problem with collimating the mirror. It was much easier to collimate in it's stock configuration. In fact collimation was very easy in it's stock form and unless you need a fully robotic telescope I would not recommend making this kind of alteration.

TRO1 is currently involved in researching fast Eclipsing binary systems. This requires a precision of .01 magnitude and this scope is more than capable of this level of precision. Overall, it is hard to beat the cost vs aperture that you get with this scope! It is highly recommended for anyone needing a large aperture, wide field scope. (Posted on 8/4/2017)
Review by:
Very nice astrograph for the money. Very hard to beat at this price. Only 4 stars because the focuser leaves a bit to be desired but still for this money you can buy a Moonlite for it and have an excellent f/4 astrograph. Oh, also for visual use it needs a longer extension tube than the included 35mm tube. I have to pull mine out a fair amount to reach focus. Needs a longer extension tube. (Posted on 8/4/2017)
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Supplied Accessories

  • 8 x 50mm finderscope in quick-release bracket
  • Cooling fan and battery pack
  • Hinged split tube rings
  • 35mm x 2" compression ring extension tube
  • 2" and 1.25" compression ring eyepiece/accessory holders
  • Dust cover