6" F/4 imaging Newtonian optical tube

by Astro-Tech Print

What would you like to print?
(Reviews and Documents/Videos will not be printed)

Basic Product Information
Full Description
Tech Details
Supplied Accessories
Recommended Accessories

More product information
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.
Highest Useful Magnification:
This is the highest visual power a telescope can achieve before the image becomes too dim for useful observing (generally at about 50x to 60x per inch of telescope aperture). However, this power is very often unreachable due to turbulence in our atmosphere that makes the image too blurry and unstable to see any detail.

On nights of less-than-perfect seeing, medium to low power planetary, binary star, and globular cluster observing (at 25x to 30x per inch of aperture or less) is usually more enjoyable than fruitlessly attempting to push a telescope's magnification to its theoretical limits. Very high powers are generally best reserved for planetary observations and binary star splitting.

Small aperture telescopes can usually use more power per inch of aperture on any given night than larger telescopes, as they look through a smaller column of air and see less of the turbulence in our atmosphere. While some observers use up to 100x per inch of refractor aperture on Mars and Jupiter, the actual number of minutes they spend observing at such powers is small in relation to the number of hours they spend waiting for the atmosphere to stabilize enough for them to use such very high powers.
Focal Length:
This is the length of the effective optical path of a telescopeor eyepiece (the distance from the main mirror or lens where the lightis gathered to the point where the prime focus image is formed). Focallength is typically expressed in millimeters.

The longer the focallength, the higher the magnification and the narrower the field of viewwith any given eyepiece. The shorter the focal length, the lower themagnification and the wider the field of view with the same eyepiece.

Focal Ratio:
This is the ‘speed’ of a telescope’s optics, found by dividing the focal length by the aperture. The smaller the f/number, the lower the magnification, the wider the field, and the brighter the image with any given eyepiece or camera.

Fast f/4 to f/5 focal ratios are generally best for lower power wide field observing and deep space photography. Slow f/11 to f/15 focal ratios are usually better suited to higher power lunar, planetary, and binary star observing and high power photography. Medium f/6 to f/10 focal ratios work well with either.

An f/5 system can photograph a nebula or other faint extended deep space object in one-fourth the time of an f/10 system, but the image will be only one-half as large. Point sources, such as stars, are recorded based on the aperture, however, rather than the focal ratio – so that the larger the aperture, the fainter the star you can see or photograph, no matter what the focal ratio.

This is the ability of a telescope to separate closely-spaced binary stars into two distinct objects, measured in seconds of arc. One arc second equals 1/3600th of a degree and is about the width of a 25-cent coin at a distance of three miles! In essence, resolution is a measure of how much detail a telescope can reveal. The resolution values on our website are derived using the Dawes’ limit formula.

Dawes’ limit only applies to point sources of light (stars). Smaller separations can be resolved in extended objects, such as the planets. For example, Cassini’s Division in the rings of Saturn (0.5 arc seconds across), was discovered using a 2.5” telescope – which has a Dawes’ limit of 1.8 arc seconds!

The ability of a telescope to resolve to Dawes’ limit is usually much more affected by seeing conditions, by the difference in brightness between the binary star components, and by the observer’s visual acuity, than it is by the optical quality of the telescope.

0.76 arc seconds
Visual Limiting Magnitude:
This is the magnitude (or brightness) of the faintest star that can be seen with a telescope. The larger the number, the fainter the star that can be seen. An approximate formula for determining the visual limiting magnitude of a telescope is 7.5 + 5 log aperture (in cm).

This is the formula that we use with all of the telescopes we carry, so that our published specs will be consistent from aperture to aperture, from manufacturer to manufacturer. Some telescope makers may use other unspecified methods to determine the limiting magnitude, so their published figures may differ from ours.

Keep in mind that this formula does not take into account light loss within the scope, seeing conditions, the observer’s age (visual performance decreases as we get older), the telescope’s age (the reflectivity of telescope mirrors decreases as they get older), etc. The limiting magnitudes specified by manufacturers for their telescopes assume very dark skies, trained observers, and excellent atmospheric transparency – and are therefore rarely obtainable under average observing conditions. The photographic limiting magnitude is always greater than the visual (typically by two magnitudes).

This is the diameter of the light-gathering main mirror or objective lens of a telescope. In general, the larger the aperture, the better the resolution and the fainter the objects you can see.
Heaviest Single Component:
The weight of the heaviest component in this package.
9 lbs. 10 oz.
Based on Astronomy magazine’s telescope "report cards", scopes of this size and type generally perform as follows . . .
Terrestrial Observation:
Observing terrestrial objects (nature studies, birding, etc.) is usually possible only with refractor and catadioptric telescopes, and convenient only when the scope is on an altazimuth mount or photo tripod. Most reflectors cannot be used for terrestrial observing. Scopes with apertures under 5" to 6" are generally most useful for terrestrial observing due to atmospheric conditions (heat waves and mirage, dust, haze, etc.) that degrade the image quality in larger scopes. 
Lunar Observation:
Visual observation of the Moon is possible with any telescope. Larger aperture scopes will provide more detail than smaller scopes, thereby getting a higher score in this category, but may require an eyepiece filter to cut down the greater glare from the Moon's sunlit surface so small details can be seen more easily. Lunar observing is more rewarding when the Moon is waxing or waning as the changing sun angle casts constantly varying shadows to reveal craters and surface features by the hundreds.  
Planetary Observation:
Very Good
Binary and Star Cluster Observation:
Very Good
Galaxy and Nebula Observation:
Terrestrial Photography:
Photographing terrestrial objects (wildlife, scenery, etc.) is usually possible only with refractor and catadioptric telescopes, and convenient only when the scope is on an altazimuth mount or photo tripod. Most reflectors cannot be used for terrestrial photography. Scopes with focal ratios of f/10 and faster and apertures under 5" to 6" are generally the most useful for terrestrial photography due to atmospheric conditions (heat waves and mirage, dust, haze, etc.) that degrade the image quality in larger scopes.
Lunar Photography:
Photography of the Moon is possible with virtually any telescope, using a 35mm camera, DSLR, or CCD-based webcam (planetary imager). While an equatorial mount with a motor drive is not strictly essential, as the exposure times will be very short, such a mount would be helpful to improve image sharpness, particularly with webcam-type cameras that take a series of exposures over time and stack them together. Reflectors may require a Barlow lens to let the camera reach focus. 
Planetary Photography:
Star Cluster / Nebula / Galaxy Photography:
1 year
There are currently no Cloudy Nights reviews associated with this product

User Ratings/Reviews from our Customers (www.astronomics.com)
Overall Product Rating: AstronomicsAstronomicsAstronomicsAstronomicsAstronomics(5.00)   # of Ratings: 4   (Only registered customers can rate)

(Only registered customers can rate)

5 - Great (100.00%) (4 users)
4 - Good (0.00%) (0 users)
3 - OK (0.00%) (0 users)
2 - Bad (0.00%) (0 users)
1 - Very Bad (0.00%) (0 users)
0% 50% 100%
astronomics image

Sort Ratings: 

  Show these ratings: ALLGreatGoodOKBadVery Bad

loading request
Showing comments 1-4 of 4
1. Roger on 1/7/2015, said: AstronomicsAstronomicsAstronomicsAstronomicsAstronomics
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. http://www.astrobin.com/full/146461/0/ 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.
Was this comment helpful? Yes No   (5 people found this comment helpful, 1 did not)
2. David on 11/4/2014, said: AstronomicsAstronomicsAstronomicsAstronomicsAstronomics
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!
Was this comment helpful? Yes No   (5 people found this comment helpful, 0 did not)
3. Obin on 5/16/2013, said: AstronomicsAstronomicsAstronomicsAstronomicsAstronomics
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!
Was this comment helpful? Yes No   (18 people found this comment helpful, 0 did not)
4. Daniel on 4/30/2013, said: AstronomicsAstronomicsAstronomicsAstronomicsAstronomics
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.
Was this comment helpful? Yes No   (29 people found this comment helpful, 0 did not)
Showing comments 1-4 of 4
General Accessories
Dovetail Plates (2)
7.9" Losmandy-Style "D-plate" short universal dovetail plate, black
by Astro-Tech
7" Short universal dovetail plate for Vixen-style mounts, black
by Astro-Tech
Photographic Accessories
Camera Adapters (1)
2" Prime focus adapter, needs T-ring
by Astro-Tech
Coma Correctors (1)
Photo-visual Coma Corrector & field flattener for fast focal ratio Newtonian reflectors
by Astro-Tech
T-Rings (2)
T-Ring for Canon EOS 35mm autofocus and DSLR cameras
by Various Manufacturers
T-Ring for Nikon 35mm and DSLR cameras
by Various Manufacturers
This product does not have supplied accessories... or supplied accessories have not been assigned.
No documents have been associated with this product.
No videos have been associated with this product.
There are currently no formulas associated with this product
Astro-Tech - 6" F/4 imaging Newtonian optical tube

Click icon(s) below & hover image above for zoom

Astro-Tech - 6" F/4 imaging Newtonian optical tubeMike Scroger's AT6IN image of the Horsehead and Flame Nebulas. Mike Scroger's AT6IN image of M31 and its companions M32 and M110.
In Stock
 AstronomicsAstronomicsAstronomicsAstronomicsAstronomics (Average: 5.00 | Users: 4)  Only registered users can submit ratings - Register Here
Our Product #: AT6IN
Price: $299.00  FREE ground shipping - Click for more info
Congratulations. Your order qualifies for free ground shipping within the 48 contiguous United States.

 E-mail this product to a friend E-mail this product to a friend

Your Email:  
Your Friend's Email:  
Confirm Friend's Email:  

  200 characters or less

An email containing a link to this product has been sent to the email address you provided.

Clear Skies!

 Have a question? Do you have a question about this product?
 Found a better price? Found a lower price? Click to let us know... or call 800-422-7876 before you buy.

If you’ve found a lower delivered price on this product, let us know about it below. We’ll do our best to meet or beat that price and will get back to you within one business day with our best offer. Thanks for giving us the opportunity to give you a better deal.

Your Name:  
From Who:  
Context:  Magazine AdOnline
Website Address:  
Cut and paste the web address into the box above
Your Email:  
Confirm Email:  

We’ll do our best to meet or beat that price and will get back to you within one business day with our best offer. Thanks for giving us the opportunity to give you a better deal.

Clear skies,

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 38th year