No telescope drive can eliminate the need for guiding in long exposure astrophotography. Guiding is necessary to correct for small tracking errors caused by the periodic error of the gear, atmospheric refraction, inaccurate alignment of the telescope mount and flex of the telescope structure. There are two choices to make the tiny corrections needed: Using a separate guidescope or use an off-axis guider.

I use an off-axis guider. With a dobsonian telescope or a Newtonian telescope in general, flexure of the telescope structure is likely to occur during guiding. A separate guide scope cannot account for all the flexure, especially when working with long focal lengths (in my case: 2070 mm for the 16" f/4.5 Ninja and 2300 mm for the 16" f/5 Zambuto). Off-axis guiders divert a part of the light cone of the main imaging telescope to a separate ccd camera. The ccd camera analyzes the position of a star ("guide star") in that light cone and sends correcting signals to the motors of the mount.

guiding setup image
Fig.1 - From left to right: Coma corrector (TeleVue Paracorr Type-2 VIP-2010), M65-M48 adapter ring (Teleskop-Service TSTV-M48a), Lacerta Off Axis Guider for Canon EOS cameras.
guiding setup image
Fig.2 - Coma corrector (TeleVue Paracorr Type-2 VIP-2010), M65-M48 adapter ring (Teleskop-Service TSTV-M48a) and Lacerta Off Axis Guider for Canon EOS cameras mounted.

I first used the well-built TSOAG9-EOS off-axis guider. It performed flawlessly but in order to save weight (69 g instead of 149 g), to get a bit closer to the coma corrector (by 2 mm) and to have fewer screws to accidentally loosen, I switched to the Lacerta off-axis guider for EOS cameras. Both off-axis guiders can be purchased at Teleskop-Service in Germany.

As for the autoguider, I chose the Lacerta MGen standalone autoguider from Hungary. It guides the equatorial platform without a PC or a laptop and can control the Canon EOS 450D camera (number, time and pause time of the exposures, waiting time after camera mirror lockup) at the same time. One 7 Ah lead acid battery feeds the MGen autoguider, another one the equatorial platform.

guiding setup image
Fig.3 - From left to right: Astro-modified Canon 450D, coma corrector with mounted off-axis guider, Lacerta MGen autoguider.
guiding setup image
Fig.4 - Canon 450D, coma corrector with mounted off-axis guider and autoguider.
guiding setup image
Fig.5 - The complete guiding / imaging system consisting of a Canon 450D, the coma corrector, the off-axis guider and the autoguider mounted. The whole unit (camera included) weighs 900 g (31.68 ounces).
guiding setup image
Fig.6 - The complete guiding / imaging system consisting of TeleVue Paracorr Type-2 coma corrector VIP-2010, M65-M48 adapter ring TSTV-M48a, Lacerta Off Axis Guider for Canon EOS cameras, Lacerta MGen autoguider and astro-modified Canon 450D disassembled.

Short focus Newtonians show off-axis aberrations known as "coma". Stars in the center of the field are not affected by coma, but the effect grows stronger toward the edge of the field. Stars affected by coma are shaped like tiny comets instead of points. To prevent this, a coma corrector has to be used.

I started with the TeleVue Universal Paracorr PLU-1106 coma corrector. Unfortunately this correcting lens cannot be used visually, so I later replaced it by the new TeleVue Paracorr Type-2 coma corrector VIP-2010, which can be used both visually and for imaging. The VIP-2010 is longer (80 mm instead of 50 mm) but slightly lighter (200 g instead of 204 g).

guiding setup image
Fig.7 - Upper tube of the Ninja 16" f/4.5 dobsonian telescope with Starlight Feather Touch 2" Crayford focuser.
guiding setup image
Fig.8 - The complete guiding / imaging system attached to the focuser.

Until 2012, I used a Canon 20Da camera for astrophotography. The Canon 20Da was based on the successful Canon 20D camera. It was released in 2005 and had a modified low-pass filter with increased hydrogen-alpha sensitivity. In addition, it offered a live view mode. It had an 8 megapixel APS-C sensor (15.0 x 22.5 mm) with a pixel size of 6.4 micrometer. It was a very good camera for long-exposure deep-sky photography. Unfortunately, when stacking a large number of Canon 20Da images, the stack exhibited significant amplifier glow which was almost impossible to remove, even with a large library of dark frames.

In 2012, I acquired a second-hand, astro-modified Canon 450D. It has a Baader BCF H-alpha intensifier filter for enhanced hydrogen-alpha sensitivity. The 12 megapixel APS-C sensor is 14.8 x 22.2 mm across with a pixel size of 5.2 micrometer. The Canon 450D shows no signs of amplifier glow and produces less noise than the Canon 20Da. In addition, it is a bit lighter (524 g / 18.48 oz instead of 770 g / 17.16 oz).

Fig.1 - Fig.8 show my current guiding / imaging setup. Further down the page, you will find images of the guiding / imaging setup which I don't use anymore but which did a good job as well.

Previous guiding setup (not used anymore, but worked perfectly)

guiding setup image
Fig.9 - From left to right: TeleVue Universal Paracorr PLU-1106 coma corrector, M65-M48 adapter ring (Teleskop-Service TSTV-M48a), off-axis guider (Teleskop-Service TSOAG9-EOS) and Canon EOS ring.
guiding setup image
Fig.10 - TeleVue Universal Paracorr PLU-1106 coma corrector, M65-M48 adapter ring (Teleskop-Service TSTV-M48a), off-axis guider (Teleskop-Service TSOAG9-EOS) and Canon EOS ring mounted.
guiding setup image
Fig.11 - From left to right: Canon 20Da, coma corrector attached to off-axis guider, Baader T2 extension tube (7.5 mm, #25C), Lacerta MGen autoguider.
guiding setup image
Fig.12 - Canon 20Da, coma corrector with off-axis guider and autoguider mounted.
guiding setup image
Fig.13 - The complete guiding / imaging system consisting of Canon 20Da, TeleVue Universal Paracorr PLU-1106 coma corrector, M65-M48 adapter ring TSTV-M48a, off-axis guider TSOAG9-EOS, Canon EOS ring, Lacerta MGen autoguider mounted.
guiding setup image
Fig.14 - The complete guiding / imaging system consisting of Canon 20Da, TeleVue Universal Paracorr PLU-1106 coma corrector, M65-M48 adapter ring TSTV-M48a, off-axis guider TSOAG9-EOS, Canon EOS ring, Lacerta MGen autoguider disassembled.
guiding setup image
Fig.15 - Upper tube assembly with MoonLite Crayford focuser.
guiding setup image
Fig.16 - The complete guiding / imaging system (consisting of Canon 20Da, TeleVue Universal Paracorr PLU-1106 coma corrector, M65-M48 adapter ring TSTV-M48a, off-axis guider TSOAG9-EOS, Canon EOS ring, Lacerta MGen autoguider) mounted.