Argo Navis/Giro II Review

[Stu]

Preamble! :-)

I've been using a few different mounts over the years. I bought a Vixen Spinx EQ mount with my mak about six years ago, and use this combination fairly infrequently now because of setup time. As a travel setup I use a Mini Giro on a Berlebach 2022 Report tripod which works well with my TV76. I also use a Giro II with my Astrotech 106mm triplet and this is probably my most frequently used setup.

I've been gradually improving the Giro II setup over the last year. Initially I had an old surveyors tripod, which was surprisingly wobbly. I swapped this out for an EQ6 tripod and the difference is amazing; rock steady views now. More recently still I added an 8" half pillar which definitely improves the observing position, particularly at the Zenith.

I've been observing for over 13 years now so am fairly familiar with the sky and can find my way about without needing Goto, but I'd been thinking of some form of 'in between' system for a while, and when an Argo Navis DTC came up on the forum for a good price I picked it up. I then needed to add the encoders which I ordered from Teleskop Service, and they duly arrived, nicely packed in a small box.

Box opening and fitting

The kit consists of an encoder for each axis of the Giro II with a plastic toothed wheel attached, and a mechanism for securing it to the body of the Giro. This is a slightly Heath Robinson affair using circlips but it works well.

Paired with each encoder is a toothed ring which in the case of the Alt axis slips over the shaft of the axis and tightens with a grub screw. It involved removing the arm/clamp section of the mount but this was just two allen bolts, very simple and it fitted quite nicely. The Az ring fits over the main body of the Giro, sitting on the lower part, whilst the encoder is attached to the upper, rotating part. This one I found a little strange in that it seemed slightly too big. When I tightened the grub screw it distorted the ring into an oval, making the movement awkward and causing the encoder to move in and out in its bracket. I took off the ring and added a few turns of insulating tape to make it a snug fit, and now everything runs much better.

There are a few tools included, everything you need in fact to fit the kit. This is basically a small, thin spanner which is used to fine adjust the position of the encoders, and Allen keys for the grub screws.

Once fitted and adjusted, the encoders make no difference to the movement of the giro, you would not know they are there in fact.

From there, it is a simple matter of plugging in the network cable correctly to each encoder, and then into the DTC unit. The DTC comes with a handy holder which velcros firmly to a leg of the tripod, it even included a piece if foam to wrap around the leg to stop it slipping. All very simple and effective.

So...once fitted the system does not look particularly pretty, but does not affect the mount in any negative way.

Kits are available for a wide range of mounts including dobsonians and manual EQ's. I believe it is also possible to add servos to make a goto dob for example but this is not something I have explored.

Operation

The DTC unit is battery powered. Although there is an option for a 12V DC input, the usage rate is so low that batteries last for a decent amount of time so I have not bothered with this. The unit itself has two buttons, for Enter and Back, plus a main selection wheel which allows you to scroll through menus or select the targets you want to pick. Quite easy to use once you've got the hang of it. The display itself is a two line red LCD screen which works well and has brightness and contrast adjustment so you can make it just readable in dark conditions, great for maintaining dark adaptation.

There is a very comprehensive user manual available (which I downloaded off the website) and this covers all the various modes of operation. I won't go into too much detail here, or try to replicate the manual, but will just give an overview of calibration and the modes I have tried out.

Initial setup prior to first use involves inputting various parameters into the DTC unit. This includes the type of encoder ie how many steps per revolution, the direction they are operating in so the mount knows up/down, east west rotation, and the type of mount it is fitted to. These are all quite straightforward to enter, I just found it wise to be methodical and to follow the instructions carefully.

Calibration

Calibration is a very straightforward procedure involving an initial start position, followed by a two star align.

The start position is very simple, and just involves positioning the scope vertically, and ensuring it is perpendicular to the mount top. If the mount isn't level, you use the mount as the datum, not a horizontal plane. Once the scope is in this position, turn the DTC unit on and it will go through a brief boot up sequence. After this you select the Catalogue mode and choose Bright stars. I have been using Vega and Arcturus as initial ones but obviously any one will do. Each star selected gives an indication of the accuracy level reached, so long as it falls within a certain range things will be found ok.

After the alignment is done, the mount is ready to use. There are a number of different catalogues including bright stars, Messiers, NGC/IC, double stars, planets etc. With each, it is a simple matter of entering the target and the unit then presents you with two numbers for Alt and Az with arrows indicating the required direction. You simply move the mount as indicated until both numbers reach zero and the target should be in the eyepiece.

Practical use

I have found that accuracy is greatly enhanced by aligning on more targets. You can basically align on any number, and I certainly find that accuracy improves by doing this, particularly if moving to the opposite side of the sky for instance. I often move to the constellation I am observing and align on a known star, this then gives sufficient accuracy in that area to find all objects located near to it. I end up just aligning on any target I find for the first 10 or so objects and after that, accuracy it very good.

There are a wide range of modes to use. The catalogue mode I've mentioned, two other good ones are identify and tour.

With identify, you specify an area of sky (and this can be the whole sky) and the mount will identify whatever you are pointing at which is very handy.

The tour mode can take you through a list of objects within a certain area of sky, or the whole sky. You can also do things like 'show my all the globular clusters above mag Y within this constellation, or within x degrees of where I am currently pointing'

Pros and cons

Pros

- Very simple to use and setup

- One handset and one cable

- Silent!

- Gives you ideas as to what to look for, or what is visible in the area you are observing

- There when you need it, or ignore it if you want to star hop yourself

- Very quick, you can slew the mount far quicker than a goto!

- Potential to add servos for full goto

Cons

- Not cheap

- Encoders are not pretty and look a little vulnerable to a knock (Note that you can buy mounts with the encoders built in which are much nicer to look at and more robust)

- Doesn't track targets, just helps you find them!

I am really beginning to enjoy this system as it means I can get more out of short sessions. I know how to star hop, but actually seeing and studying the objects is what I enjoy. In my light polluted skies, having a little help when you need it makes my sessions more enjoyable. It also stops me wasting time looking for stuff which is not visible with my scope! I recently found Uranus and Neptune in a short session when otherwise I might not have managed it.

So, not for everyone, but an interesting solution which fills a gap between manual and goto.

If you've got this far, well done!!

I will post some pictures of the kit soon.

Cheers,

Stu

[emadmoussa]

Very detailed review, Stu. Look forward to the pictures.

[faulksy]

very good stu , looking foward to the pictures

[Pig]

Very interesting read Stu, it is nice to read about other peoples setups