Introduction

Despite there are not many Losmandy G11 users in Poland and it is generally  underestimated, I think that it is a piece of equipment that can deliver results which are comparable to much more expensive mounts. The second-hand mount can be bought at a relatively good price. My thesis is that it might be a serious alternative for those astrophotographers, who expect really accurate tracking and, at the same time, can’t afford such mounts as AP900 or similar.

Losmandy G11 have been produced since 1992. It is an old and heavy duty construction, that had to prove itself on the field of astrophotography long time before the software guiding become a standard. I am not going to write a review of this mount here – it has been done many times already and you’ll find easily a lot of reviews, tests and opinions on this mount in the Internet. That’s it as for the introduction and let’s proceed to my upgrades.

Upgrade 1.

Tracking quality, precise guiding capabilities and the construction of the mount

G11 has a lot of  pros but at the same time has its cons. The most of G11 units have PE oscillating around +/- 10 arcsec. However, these mounts are not even – there are some units that have PE around +/- 5 arcsec whereas the others are as jerky as +/-30, up to 50 arcsec. Needless to say that the astrophotography nowadays assumes the use of autoguiding, in most cases via computer and software. Therefore the amplitude of the PE is not a key factor anymore as opposed to the micro-characteristics of PE itself (I call it ‘granularity’). And it is the granularity of the PE that decides whether guiding is successful or not.

How G11 performs?

From my experience, G11 can be guided quite precisely, but there’s one exception. The PE curve is generally smooth except for one fundamental of a ~76s period or 1/3rd of the main gear period, that is in fact unguidable. In case of my setup (5.4 micon pixel) this gives visible 2px radius blur in RA axis. It is something one can live with, but willing to achieve predictable results it needs to be improved sooner or later .

The graph below shows the 10-15 minutes guided exposure at bin 2×2 and the problem is clearly visible.

Losmandy G11 76s peak error

Shat causes the issue? Let’s have a look at the frequency spectrum and identified fundamentals contributing to the G11′s PE curve.

Losmandy G11 PE Frequency spectral analysis

1. 239,34 – Worm period – 1x
2. 76,00 – RA worm bearings rolling past a tight spot in the bearing race 3,15x
3. 31,91 – Intermediate Gearbox – if present gearbox is suspect
4. 9,58 – Motor – if present may be a bent pinion.

A detailed analysis of the harmonic fundamentals shows (apart of worm period) clearly visible fundamental of a 76s period.

Interpretation of the data

The construction of the mount has one serious flaw – the main RA worm bearings. The worm is held by two separate bearings in 2 separate points and this, sooner or later, results in non-coaxial worm bearing. This is the reason for 76s fundamental peak and obviously affects the mount’s performance significantly.

Solution – The Ovision NS Kit

The well known solution is provided by a French company Optique et Vision (Ovision.com). Ovision offers much more precise worm that is held within an unibody block with 2 coaxial bearings.

http://www.ovision.com/Losmandy_PresentationNS.html

What I’ve got after ordering a Losmandy G11 NS Kit from Ovision was one perfectly machined unit including the housing and a new precise worm. It goes right in place of the default G11 worm and bearings and can be mounted very easily. It is accompanied by convenient adjustment bolts to get rid of any possible backlash. The kit costs a lot, but makes a very good impression from the very beginning. Well designed, high quality of materials used, precise machining. The unit is delivered with a chart graph showing its individually tested performance. There also comes a lot of detailed instructions explaining mainly how to avoid accidental damage to the kit.

My NS kit was ordered on thursday and I got it in about a week. I have to admit that the company support and customer service is of high standards. However the site looks a bit ancient and archaic, my emails were replied very quickly and the NS kit is available in stock.

The upgrade proceeds as follows and takes not more than 10 minutes.

1. Balance your mount
2. Turn the OTA to the side and stabilize it (I put it against the pier body)
3. Disassemble the worm housing (2 bolts)
4. Unmount the worm coupling (2 bolts)
5. Unmount the worm and bearings (2 larger bolts)
6. Mount the NS kit module
7. Put all stuff back in a reversed order.

I already mentioned the high quality of NS kit. In addition it is worth mentioning that the Losmandy worm module is very likely to disassemble and fall into few separate parts – housings, bearings, the worm.
There is a quick comparison of the original Losmand G11 worm and a new Ovision Kit.

Losmandy G11 Original worm and housing

Losmandy G11 worm and housing - The Ovision NS Kit

The results

After having the new kit mounted it turned out that the tracking precision is highly increased. I did not perform measurements nor tests, but it is visible at a glance with a naked eye that the quality got much better. The graph speaks for itself.

Losmandy G11 with Ovision Worm - Tracking Log

15 minutes of a guided exposure under Maxim DL, bin 2×2, 4.7 arcsec/px. The graph is more stable and the amplitude is much lower. There are no more jerky moments that were unguidable.

To summarize, we can confirm the statement mentioned at the very beginning of this post, that the upgraded G11 can compete with much more expensive mounts. Also I personally think that the Ovision kit is definitely worth it price. At last it is worth mentioning that the Ovision company also offers the additional G11 module that shifts the declination axis slightly (about 10cm offset) – this allows to track past meridian a few minutes longer without the necessity to flip the mount.

Upgrade 2.

New firmware – Losmandy Gemini Level 4.

My G11 unit was manufactured in 2004 and was equiped with Gemini v3 firmware. It is possible to live with the older version but it is better to upgrade it.

You can download the new firmware free of charge from the manufacturer’s website, but you need to be have the necessary skills and equipment to reprogram the EPROM. I don’t have such skills nor the equipment, so I decided to order the firmware upgrade at already preprogrammed EPROM from  Graeme Coates at chromosphere. It costed me  just a few pounds and the new chip shipped in a few days.

Losmandy G11 - Gemini V4 firmware EPROM

The EPROM chip is nothing particularly special. But during the installation I was very positively surprised with the quality of the Gemini housing, which (similarly to new MacBooks) is an alu monolith. In case of Gemini housing it is covered by a bolted steel cover. I guess It would stand even throwing it around the room. The quality and durability of the Gemini board is really impressive. I switched the EPROMS and after restarting my Gemini reported a new firmware properly.

The first impression? Gemini seems to start a bit faster, and the whole user interface seems much faster. There are no more lags and there’s a lot of new features. In Gemini firmware v4 we have a few interesting features worth to mention here:

1. V4 allows us to save in the memory up to 4 predefined locations that can be swapped easily later.
2. There’s much better improved mound limits management.

Some other features:

1. There are many more stars available for the alignment
2. There are 2 sync modes available at the hand controller: standard sync and additional sync that affects the model – that was not present in previous version and is really convenient.

The full list of features may be found at the manufacturer’s website.