ONAG®: ON-Axis Guider for your best images yet
   

 

The new standard in guiding

                    patent pending

ONAG® and now the new ONAG® XT

- Finding a guide star has never been easier!
- Presenting your scope's field of view to your guider.
- No more differential flexure even with long focal.
- Integrated X/Y stage for your guider.
- Reduce seeing effect by guiding with near infrared (NIR).
- Ideal for medium to long focal scopes, such as RCT and SCT.
- ONAG®  for chip diagonals up to 28mm, KAF8300,
   KAI10100..., and now ONAG® XT for diagonals up to 50mm.
- Accept most focal reducers.
- No extra load for your mount, weight only 0.8 kg (1.8 lbs).
- No rotation necessary for finding a guide star.
- Enjoy reusing your flat frames over and over again.
- No filter in the way, ideal for narrow band imaging!



Introducing ONAG® XT (up to 50mm diagonal)




The ONAG® XT features:

- Rigid 59mm dovetail system for scope and image ports
- Tilt/tip user adjustable dichroic mirror (laser aligned at factory)
- Guider port with corrective optics providing seeing limited guide stars
- 68mm imager back focus (compare with 66mm for the ONAG®)
- Compatible with AO units, including the AO-L from SBIG
- Same X/Y stage as the ONAG® with a T-thread M42 x 0.75mm connection as well as 1.25" nosepiece compatible

"I feel this is the ultimate design in guide star tracking and imaging. I am a firm believer in the system and plan on solely using this type of tracking from now on. My only problem now is... I need to re-image the entire sky to upgrade my stock of sky images!"

Owner of a f/6 32" relay telescope

Dr. Mario Motta

Read more at our user feedback page.

Click here to read more on NIR guiding and seeing effect reduction using the ONAG technology on Dr. M. Motta's scope.



            Download the ONAG® 3D drawing 


                
 
                   Find out what our customers have to say


"After working with the ONAG® for many nights last fall, I can certainly say it's easier to use than any off-axis systems I've tried (and that includes the few that I built myself). It also produced some of the most accurately guided image sequence I've ever obtained."

"The guiding was remarkably accurate during all my testing".

"A clever as the concept behind the ONAG® is, the devil is on the details, and that's where the ONAG® really shines.
The device,... , is extremely well engineered and, more importantly, well made."


Dennis di Cicco, Sky & Telescope December 2012


                                    ONAG® (patent pending)

                 

As pointed out by Sky and Telescope ONAG test report:

"Observers, have been guiding their telescopes since the dawn of long-exposure astrophotography. It's a need that arises from a very long list of mechanical, optical, and atmospheric factors that makes it all but impossible for a simple telescope drive to precisely follows a celestial object for more than a minute or two as it moves across the sky."
"Enter the ONAG®. Because digital detectors in today's autoguiders are sensitive to near-infrared (NIR) light beyond the visual spectrum, the ONAG® works by sending a telescope's visible light to the imager camera and the NIR to the guider system..."
"...Ingenious!" And it works because digital technology has given us the opportunity to easily use NIR light for guiding."

(Dennis di Cicco, Sky & Telescope December 2012, pages 60-63)

Guiding for long exposures is challenging, yet a critical task. Astronomy is one of the most demanding field in photography (see how much guiding error is too much). 
Astrophotography for deep space objects, associated with medium to long focal length such as SCT or RCT scopes, requires high precision accurate tracking and active guiding. Classical techniques suffer from various issues and limitations.

Guide scopes are prone to differential flexures, which are very difficult to track and fix, they also add an extra load for the mount. Another issue happens when used with SCT telescopes a possible principal mirror motion, this could happen slowly over the time of an astrophotography session due to gravity and load transfer. Even a scope with locking  mirror mechanism could still exhibits some left over motion, and it does not take much more, with a long focal, to end with elongated stars.

"The ONAG® has a very rigid connection, and it's especially noteworthy because the device has an adjustable X-Y mounting for the guide camera , which helps in the search for suitable guide stars."

(Dennis di Cicco, Sky & Telescope December 2012, pages 60-63)

 

Also most guide scopes have small apertures limiting the starlight energy available for the guider chip. Unlike extended objects, such as galaxies or nebulae, a star remains a point source at any magnification, at least for amateurs.
The start apparent size on the sensor is only related to the seeing, or at best the diffraction limited optics.
Therefore as far as energy budget goes the scope F-number ("speed") does not play any role here, only the aperture diameter D is relevant in the calculation of the star energy received by the sensor.
The larger D is the better and since the energy is proportional to its square, D is a key figure of merit in the guide star magnitude limit.
This means that a 8" scope will gather [(8*25)/80]^2 = 6.25x more signal than a typical 80mm guide scope. This is a gain of 2 magnitudes, and a 11" scope will results to almost 3 magnitudes.

While off-axis guiders (OAG) solve most of this issue they only provide access to a small field of view, making the search for a guide star challenging at best, often a significant source of frustration and time consuming. OAG pick-up prisms may lead in starlight energy loss, limiting the usable maximum guide star magnitude. Since by nature they are looking well off-axis, guide stars could exhibit extreme deformations  with some scopes.
Self-guided cameras are much like OAG, with an even smaller field since there is no position adjustment possible, beside the rotation of the whole camera body.

Our on-axis guider ONAG^® solves those problems, providing you with easy access to a wide field of view without any differential flexure or significant extra load for your set-up. The ONAG® weights only 770 grams (1.7 lb).

"As mentioned above, there's an X-Y stage one the (ONAG®) guider port that allows the user to move the center of the autoguider's view 28 mm horizontally and 23 mm vertically , so you can explore a 46 mm diameter area of your telescope focal plane to search for appropriate guide stars. This area is huge compared to what is available with most off-axis guiding systems."
"But there's another aspect of the ONAG® that further improves the efficiency of finding a guide star..."
"...The guide stars available to the ONAG® are closer to the telescope's optical axis and are thus of much better quality for guiding."

(Dennis di Cicco, Sky & Telescope December 2012, pages 60-63)

Since it uses the same scope, and optical train  than your imager it provides maximum light to your guider camera. The ONAG® works by splitting the light into two components.

The visible range, from 370nm to 750nm, is sent to your imager camera, while the near infrared (NIR) range, above 750nm, is transmitted to the guider camera. This patent pending design uses a dichroic beam splitter, basically a selective mirror, set a 45 degrees. The light received by your imager is reflected, this insures there is no optical aberration involved in the process, this is no different than a star diagonal.
Our dichroic mirror is made of high quality, very low thermal expansion, optical grade glass and will not experience any deformation even when exposed to an extended temperature range. Our goal and commitment has been not to compromise with your image quality, ever.
Unfiltered CMOS, CCD cameras are sensitive in NIR. More than 76% of the main sequence stars have surface temperatures lower than 3700K (red) radiating large amount of infrared energy. Therefore they are a good candidates for NIR guiding. Indeed this is the technology used by the professionals, now made available to you as well. Guiding in NIR offers a unique opportunity to improve accuracy. Longer wavelengths are less sensitive to atmospheric turbulences (seeing), therefore the ONAG technology can improve your active tracking performance by as much as 20% to 30%.

Want to know more about guiding error and near infrared (NIR)?

Visit:

"Guiding with NIR" and "How much guiding error is too much?"

If you want to use a light pollution reduction filter (skyglow imaging filter) please visit our FAQ page for further information.

                         ONAG® Basic Principal

The visible-NIR cut-off wavelength at 750nm gives full access for imaging using H Balmer alpha band. The new dichroic mirrors have an extended NIR range up to 1800nm this allows the ONAG® to be used in NIR spectroscopy (in such case the guider port is used to image, and the imager port to guide).
In the visible range the reflection is better than 99% in average, as it can be seen in the coating inspection report above (with a minimum reflection of 96.4% @ 370.82nm).
Since filters and filter wheels are placed in the imager's optical path, they will not interfere with the guider camera. Therefore even narrow band imaging will not make the guide star too dim to use anymore.
The ONAG® will work well with many scopes, refractors as well as reflectors, it requires only 66mm (2.6") of back focus for your imager (see our product page or ONAG® user manual for further information).
It excels with long focal such as Schmidt Cassegrain type scopes (SCT), such as Celestron, Meade, ... 
The ONAG® works with almost any focal reducers (FR), a NIR optimized adjustable focal reducer (AFR) using aspheric optics is also available from IF for your guider. The AFR is designed to be used with your FR/corrector when the later is placed in front of your imager, at the ONAG®'s imager port (IP). Alternatively you can place most FR/corrector in front of the ONAG®, see the FAQs section and the ONAG® user manual for further information.

The ONAG® is made of high quality aluminum and stainless steel. The optical beam splitter is fully multi-coated and protected with a transparent layer of quartz to provide a long life.  

                ONAG® a flexible and versatile solution

   

 

ONAG® mounted on Hyperion 12.5".
Imager: Apogee U8300 + filter wheel.
Guider: SBIG ST402. 
Credit: Frank Colosimo, Blue Mtn Vista Observatory

 

ONAG® mounted on C11-CGE with SBIG AO8 adaptive optic module and an OPTEC TCF-S focuser
Imager: ST4000XCM with focal reducer f/6.3 and filter wheel (skyglow imaging filter).
Guider: Home made guider.  
Credit: Dr. Gaston Baudat, IF's CTO. Glenmoore observatory PA - USA

The ONAG® has been optimized for CCD imagers using large format APS-C chips with a diagonal up to 28mm (1.1"), such as the Kodak KAF83000 and Kodak KAI-10100. The imager camera can be attached to the ONAG® imager port using a standard T-thread (M42x.75mm) connection.
Searching for a suitable guide star has never been easier thanks to its wide field of view and convenient quick set-up X/Y stage, providing an exploration circle up to 46 mm (1.8”) in diameter. This is more than 1.3 arc-degrees for a two meters focal length scope.
The guider camera is attached at the ONAG® guider port with a male T-thread . However the ONAG® build-in focuser drawtube can be removed allowing to use any standard 1-1/4" nosepiece instead*. This is particularly handy if your guider nosepiece can not be removed. See FAQs for guide star focusing procedure and comments.
Should you have an adaptive optic modules, such as the SBIG AO8, you can use it with our ONAG®, see the ONAG® user manual for further information. We also offer an AO8 adaptor plate for the ONAG®.

* An extra 1-1/4" extension tube could be necessary to reach focus.

                              
                              ONAG® with DSLR 
 

SLR and DSLR cameras can be easily mounted on the ONAG® using a standard T-thread connection. This make the ONAG® a very versatile tool. whatever you use a astronomical CCD or a DSLR camera.

 

ONAG® mounted on ORION EON apochromat refractor with a DSLR (Canon EOS) 
Guider: ORION Starshoot autoguider

The ONAG® comes with a variety of extension tubes, which associated with a compressed ring focuser at its guider port, allow a very large range of imagers and guiders to reach focus.
See the ONAG® user manual for further information.
The ONAG® is attached to your scope using a standard T_thread. For convenience it comes with a low profile male T-thread to female SCT adapter, as well as male T-thread to 2" tube adapter.
IF offers also a compact AP 2.7" adaptor.

            ONAG® unit, extension tubes, and scope adaptors
 

ONAG® unit and the included parts.

                      ONAG® and spectroscopy
 

Astronomical spectroscopy requires to keep the object under analysis, star, nebula, ..., centered on the spectrograph slit.
Here the ONAG® can be used as well for precise guiding, allowing to track the analyzed star, or another one with the same scope focal  and optical train than for the spectrograph.

Most of the spectral features happen between 350nm to 750nm. This is also the range for most of commercially available spectrograph for amateurs.
The ONAG®'s dichroic beam splitter has been designed to keep this spectral range available to your imager, and spectrograph as well. The ONAG® mirror's cut-off wavelength is set at 750nm.

The next picture shows the ONAG® used for spectroscopy with a C11, a SBIG DSS-7 and associated ST7 camera.

                        ONAG® with spectrograph

ONAG® with a SBIG DSS-7 spectrograph + ST7 camera on C11