ONAG: ON-Axis Guider for your best images yet
   

The new standard in guiding
  

The technology used by professionals available to you:

- 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.
- Work with refractors as well as reflectors.
- Ideal for SCTs such as Celestron, Meade, ...
- Accept most focal reducers.
- No extra load for your mount, weight only 770 grams (1.7 lbs).
- No rotation necessary for finding a guide star.
- Enjoy reusing your flat frames over and over again.


                               

ONAG (patent pending)

 

 

                
                   The ONAG unit                                                           ONAG + C8 "orange" tube


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, 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.

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 lead to large F numbers, 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). 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.

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

Visit:

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

ONAG Basic Principal

The visible NIR cut-off wavelength at 750nm gives full access for imaging using H Balmer alpha band. 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, provided you have the necessary back focus (see our product page or ONAG user manual). 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.  

Unlike standard black anodizing, which is transparent in NIR, and may break down over time causing lens cloudiness, as well as reduced efficiency, our product is made of optical grade quality anodizing. It absorbs up to 5 times more light than standard anodizing with an extended spectral performance way above 1200nm.

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. 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.

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 with DSLR 
 

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