Astro-Tech 6" F/4 imaging Newtonian optical tube


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This new light weight 6" f/4 Astro-Tech imaging Newtonian reflector makes serious very wide field astrophotography possible with even a small equatorial mount, and at a lower cost than ever before . . .
Our Product #: AT6IN
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Product Description

This Astro-Tech Imaging Newtonian optical tube has:

Very fast f/4 focal ratio 6" Newtonian reflector optics
Contrast-enhancing extended tube length
2" dual-speed linear bearing 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 6" Astro-Tech AT6IN optical tube is a very fast focal ratio f/4 reflector that has been optimized for very wide field deep space imaging. It can be used with 35mm cameras, DSLRs, web-cams, DSI-type cameras, and large format CCD cameras alike.

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 AT6IN 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 AT6IN'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 610mm 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: 6" aperture, 610mm focal length, f/4 focal ratio. Parabolic primary mirror. Both primary and diagonal 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 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 center-spotted.

Extended optical tube: To increase the contrast, the optical tube of the Astro-Tech AT6IN is extended 7.25" forward of the focuser centerline to act as a lens shade to keep ambient light from hitting the diagonal mirror. This results in higher contrast than a conventional reflector for both imaging and visual observing.

The white-painted 22.5" long x 7" diameter Astro-Tech optical tube (with 7.25" diameter front and rear cells) 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, a Sky & Telescope review of the AT6IN's 8" big brother AT8IN pointed out that a steel tube "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. 

For essentially coma-free imaging with the AT6IN, 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 linear bearing Crayford focuser: The precision-made 2" linear bearing 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 dual-speed focusing. There are two coarse focusing knobs. The knob facing the rear of the scope also has a smaller concentric knob with a 10:1 reduction gear microfine focusing ratio. This provides exceptionally precise image control during critical imaging. All focus knobs are ribbed, so they are easy to operate, even while wearing gloves or mittens in cold weather. A lock knob underneath the focuser lets you adjust the tension on the drawtube to accommodate varying equipment loads. A large lock knob on top of the focuser lets you lock in your photographic focus. 

The new linear bearing focuser has a polished stainless steel drive rail that runs the length of the underside of the drawtube. The focuser's stainless steel drive shaft presses on this drive rail to move the focuser, rather than having the hard steel drive shaft press directly on (and wear out) the softer aluminum drawtube as with conventional Crayford focusers. The steel drive rail rides in a self-lubricating track that extends almost the entire length of the focuser body. The drive rail and its attached drawtube are thereby supported over most of their length at all times, rather than by a conventional Crayford focuser's two sets of small contact area roller bearings. This system distributes the drive force evenly over the entire drawtube, without concentrating it on a few small contact points. The result is a very rigid drawtube with essentially zero flexure and no wear (much less flat spots or uneven wear) on the focuser drawtube. 

The focuser drawtube has 51mm (2") of travel. A focusing scale on top of the focuser drawtube is marked in inches and millimeters to make it easy to return to the approximate correct focus when setting up to image or observe each night.

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 AT6IN. The lightweight optical tube (9 pounds 10 ounces without finderscope) rotates in its felt-lined die cast cradle rings to bring the focuser and finder to the most comfortable viewing position.

Finderscope: 8 x 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 6"
    Binary and Star Cluster Observation Very Good
    Focal Length 610mm
    Focal Ratio f/4
    Galaxy and Nebula Observation Good
    Heaviest Single Component 9 lbs. 10 oz.
    Highest Useful Magnification 203x
    Lunar Observation Great
    Planetary Observation Very Good
    Resolution 0.76 arc seconds
    Visual Limiting Magnitude 13.4
    Warranty 1 year


    Review by:
    Used with my Canon SL1 to get great pictures of the eclipse. It performed flawlessly. Focal length works well with the cropped sensor. The focuser is substantial and well suited to supporting the coma corrector and DSLR solidly. You get a respectable aperture at F/4 to give fast wide field views in an instrument capable of top quality astrophotography at a very affordable price. (Posted on 8/21/2019)
    Review by:
    For what you pay, you get a good focuser and nice mirror, but this thing is a bear to collimate good enough for round stars for photography. Maybe it was just the one I got, but this is a fairly common complaint on some of the forums, but to be fair is also inherent in any fast Newtonian. I will also say the dovetail bar is a waste. Maybe they have changed it since I bought mine, but the one which came mounted with the rings was chamfered along part of, not all of, the length. This made it challenging to balance as you had very limited length to work with. I swapped out for a different dovetail almost immediately. (Posted on 1/13/2019)
    Review by:
    I got to use this telescope two nights ago so I just want to share my two cents on this telescope. The reason to why I love Astro-Tech telescopes is due to the fact that they operate the same as some of the bigger companies like Orion, and the price is still at a low price when comparing to Orion telescopes. I decided to image with my Celestron AVX Mount which wasn’t the best because that mount does not operate the best with larger telescopes such as this, but smaller light weight telescopes such as the Explore Scientific ED80 Essential Edition telescope, and more. The contrast of my image of the Orion Nebula came out amazing from a relatively dark sky and is definelty worth buyind if you want a good 6” telescope. (Posted on 1/1/2019)
    Review by:
    For the money, this has got to be the best astrograph around. Like other reviewers, I use it on a Celestron AVX with a Baader Multi Purpose Coma Corrector and DSLR. Collimating can be tedious but that's to be expected with a scope like this. The tube is solid and I have no complaints about the focuser. I use it visually as well and I think it does a fine job. The size and weight make it easy to carry to a dark site. (Posted on 10/30/2018)
    Review by:
    I've used the 6" f/4 astrograph for a couple of years now, and have gotten some very respectable results. Using with a Canon APS-C DSLR give nice, wide-field views. As others have noted, a good coma correcter and collimation tool are must-have accessories. I knocked one star off because the focuser is good-not-great and it is tough to balance in declination with a DSLR attached. I have to move the OTA as far forward as possible to just barely reach balance.

    I couple this OTA with a Celestron AVX mount, and it's a good combo!
    (Posted on 10/14/2018)
    Review by:
    I purchased the Astrotech AT6" F/4 telescope for a friend several months ago. Had the opportunity to borrow it for an evening of imaging. The scope was easy to set up and use. The optics are superb! Highly recommend it for a travel scope. (Posted on 10/7/2018)
    Review by:
    This is an amazing astrograph. With the fast focal ratio of f/4, it makes an excellent imaging platform for One-Shot-Color cameras, as well as deep sky mono cameras. I bought this telescope in 2014 and have imaged nebula, star clusters, and galaxies with it. When coupled with the Baader Multi-Purpose Coma corrector for f/4 Newtonians it delivers a surprisingly large image circle, flat for the entire APS sized camera chip. I definitely recommend this incredible telescope for fast and deep imaging pursuits. (Posted on 10/6/2018)
    Review by:
    Some caveats:
    Supplied screws and dovetail just aren't up to long-life snuf. Dovetail is hollow cast aluminum and the reach of the optical path to any high-end camera is gonna stress the hell out of the metal.

    Only has center-point holes on each side of the clamps. The bolts that came with it are finer thread than what 99% of the industry uses - they are good bolts, just keep track of them!

    Collimation WILL shift with temperature, handling, presence of cats in area and several other variables I was unable to track down. Use a good laser collimator.

    So what did I like?
    Push-pull knobs have different shapes, work fine by fingertip.
    Secondary screws are big enough to hand adjust!
    Tube is solid and didn't expand/contract much over a 15C range.
    Clamps fit snug to creaky-snug on the tube, turning the scope with them closed isn't really possible.
    Large gentle locking knob is opposite the focus tension knob, no more confusion.
    Firm latchy feel when clamping in my STF8300 with OAG and CC.

    The first thing I did with it was go after LoveJoy Q2 (which hates me) and after finding it and deciding not to keep the shots I went over to Oldrion Nebulol. Mind Blown. Single 240s stf-8300C exposure with Baader moon/skyglow/uv/ir filter and coma corrector. I was NOT expecting to pick up that much color and striation with the moon in 3rd quarter and light overcast. For any scope this fast to even come close to performing that close to the edge of a big chip is very nice.

    It even provided enough light for my Sbig OAG-8300 to pick up and guide, something I sometimes have trouble with in my AT6RC.

    If you get a useful collimation tool and have the right mount and add an after-market rail (I used a massive Losmandy from ADM that let me clamp right inside both end-caps) you'll have a hard time not liking this astrograph.

    WARNING: So lightweight that I had to add weight on the scope side WITH my camera/OAG in piggyback on my CGEM-DX. Even with that massive 2kilo 3/4 by 21" Losmandy bar. (Posted on 8/4/2017)
    Review by:
    I purchased this scope in March, 2014 as an upgrade to a 114 X 1000 reflector I own. After putting it on a Celestron AVX mount I must say, I couldn't be happier. Would suggest to anyone considering this to also purchase the Coma Corrector in the recommended accessories. The included 35mm plate is a must in order to reach focus for visual observation. A laser collimator is also a plus. Currently using a Zhumell 8X24 zoom for most observing sessions as a matter of convenience but I bought this thing in order to image so my next step will be an Orion Mini Deluxe Pro AutoGuider and Canon DLSR. Can't wait to see what this little baby can do! (Posted on 8/4/2017)
    Review by:
    The AT6IN is simply an excellent astrograph for the money. Due to the fast optics it is compact, but not too heavy. It is a PERFECT match for my Skyview Pro equatorial mount. Planets and DSOs look great through the eyepiece and even better with a camera attached. Astro Tech has already marked the center of the primary mirror which makes precision collimation even easier. I personally use a laser to collimate and I would recommend the same to anyone else who purchases the AT6IN.

    I would recommend the AT6IN to any beginner who seeks to get into astrophotography. The dual speed focuser makes precision focus a snap. When you add up the cost of the mirrors, the focuser, the finder, and the OTA the AT6IN is one of the best bargains in astrophotography. It is amazing to think that equipment of this high quality can be obtained for such a bargain price. Highly recommended! (Posted on 8/4/2017)
    Review by:
    I bought this scope from Astronomics and have been very happy with it. I use this with a Canon DSLR. This is not designed for visual use, although it is possible (I had to use the included 35mm spacer and a Barlow to reach focus with a standard Plossl). But it does have plenty of focus travel for DSLR. The focuser has two tension screws for the 2" size. Adjusting focuser tension and lock is easy. Fine focus is...fine.

    A coma corrector is a must (I use a Baader Rowe), and I also highly recommend a laser collimator. Collimation will change with swings in temperature, so be prepared to check and adjust a couple times perhaps over the course of a night's shooting. Finally, a Bahtinov mask is a highly useful accessory.

    For the price, this is an awesome little imaging scope. I run it on a Celestron AV-X mount. It is lightweight, compact, sturdy, and gives sharp, bright images. (Posted on 8/4/2017)
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