Bosma Omega MC6 150mm F12 Mak

[RichieP]

Recently I saw a listing on eBay for a Bosma Omega MC 6 Maksutov Cassegrain. I have had a Skywatcher Skymax 127 for a few years now, and been very happy with it, but apeture fever strikes, and I have been hankering for a larger, but still portable, mak for a little while, so have been looking out for a second hand Orion Optics OMC140 or Skymax 150.

Along comes this scope, listed as new and in a sealed box. I put in a starting bid of £300 and was the only bidder. So have I got a bargain, or does everybody know something that I don't?

There is not a lot of information out there on these scopes, apart from a Dutch website selling them, but from what I can make out, these Chinese 150mm F12 Rumak scopes are also marketed as the Altair MC6 in the UK and iOptron MC6 in the US. The only difference I can see is that the other two have dual speed focus knobs. The retail price would seem to be in the £500 - £700 range.

The scope arrived a couple of days later. I haven't had a chance to use it yet, but here are my first impresssions.

The scope arrives, well packaged containing the following:

- OTA

- Dewshield

- 2" visual back with 1.25" adapter

- 7*50mm finder

- 2" SCT adapter

- Another adapter, not sure what, perhaps T-ring?

It is a 150mm Maksutov with a focal length of 1800mm (F12). It is a Rumak Maksutov scope i.e. the secondary is not a silvered spot on meniscus as per Gregory Maksutovs like the Skymax 127, rather the secondary is a seperate piece of glass glued onto the meniscus, allowing it to have a different curvature.

The first impression is the weight. At 7.5Kg, this scope feels very sturdy. It is nicely finished in a white powder coating. If the dewcap is of the same thickness as the main body (and it feels like it is) then the body is a pretty sturdy 3mm in thickness. The matching dewcap is 6" long (a few more inches would have been nice!) and attaches with a bayonet fitting. Both dewcap and main body are nicely matted.The central obstruction is 46mm which is about 30% of diameter, but only 9% of area.

Focussing is the usual mirror shift system via a large aluminum knob at the rear and it is here that there is a little disppointment. The knob is a bit stiff. It can be loosened, but loosening gives some mirror shift. I will have to play around with this to see if I can get a reasonable compromise between the two.

A 2" visual back is supplied, with 1.25 adapter and these are of reasonable quality, with brass compression rings. If this is removed, a supplied adapter can enable the fitting of standard 2" SCT accessories. Also at the rear, there are three plastic caps. I haven't tried removing these yet, but apparently they cover the colimation screws. From what I can see at the moment, colimation looks good, but I shall need a start test to be sure.

The finder is a good quality, 7*50mm straight through finder which reminds me very much of a Meade finder I used to own, pretty sure it is identical in fact. The finder bracket has fore and aft adjustment bolts and a Vixen compatible finder shoe. The bolts are a little fiddly.

Finally there is a Vixen compatable dovetail plate, attached directly to the tube. A nice feaure is a pair of little bolts on the side of the plate which can be unscrewed to prevent the scope falling out of the mount should the worst happen.

Attached are some pictures of the scope including one next to the Skymax 127 which gives you a sense of the size of the scope.

In summary, focusser issue aside, things are looking good. If things work out, I am happy to spend the dosh to get a 2 speed crayford which should fix that issue. Can't wait to get outside and try this out to see if I really have got a bargain!

Rich

[Earl]

I have not been able to find any reviews of this scope, it is for sale for around 600 Euros, if it does what it should id say a very nice bargain.

[laser_jock99]

Gotta be worth a try- should be a usefull planetary focal length.

[Cornelius Varley]

This is the review of the Altair Astro version with the dual speed focuser http://www.altairastro.com/public/reviews/Altair-105-Rumak-Maksutov-Review-Astronomy-Now-Magazine-2010.pdf

[RichieP]

I have not been able to find any reviews of this scope, it is for sale for around 600 Euros, if it does what it should id say a very nice bargain.

The Bosma badged version is 600 euros on the Dutch website. I have also seen it advertised for $999 (plus $59 extra for the dewshield). The Altair version (with dual focusser) is £699

So if it works out this will be a nice bargain at £300!

[Brian Nordstrom]

Australian "Sky and Telescope" Nov/Dec 2011 has a good artical on this OTA on an Ioptron IEQ45 GoTo mount .

I was that impressed I grabbed me an IEQ45 GoTo , best mount I have ever owned , the 150mm Mak gets a good review as well .

Try a Google ,,,?

Brian.

[Brass n glass]

The French magazine Ciel Espace did a Bosma review quite a few years ago. It's now in their test archive at http://cieletespace.fr/files/InstrumentTest/BosmaMK18015.pdf They liked the OTA but didn't care much for the mount that came with it - Hugh

[Brass n glass]

Whoops, I don't know what happened to that link. Maybe better to go to www.cieletespace.fr and click on "Instruments" at the foot of the home page. The Bosma test was in 2007.

[RichieP]

Just wanted to give you an update on how I have been getting along with this scope over the last few months.

Firstly a few notes about the build.

I had said that the finder shoe was Vixen compatable. On close inspection it isn't, it just looks similar. I have replaced the finder, good though it was, with a Skywatcher 9*50 RACI finder. Due to the incompatability with the finder shoes though, I have had to use the original bracket, which just about fits.

The focusser, although I have adjusted it, still shows a minor bit of mirror shift. I have fitted a Skywatcher dual speed SCT crayford to this and am now perfectly happy. The extra weight at the back has also helped with the balance of this very front heavy scope. Because you have to use the SCT adapter rind to fit SCT accessories, the focusser doesn't fit flush with the back of the tube, but this is only an asthetic annoyance.

Here are a couple of photos of it mounted to a GM8, with the aid of an ADM Losmandy to Vixen adapter.

So how does it perform? Chances have been pretty limited, but allowing for a two hour cool down, I am very happy with it so far. I am no expert in star tests, but I see nice concentric rings which at least proves it is colimated okay. As you would expect from a Mak, I have had some great views of Jupiter and the moon, seeing detail I don't believe I have seen before.

Stars look pin sharp across the field and I have had some lovely views of open clusters, especially M35, I can't wait till M13 comes into view again (my favourite DSO). M42, M57 and M27 are also looking great.

Loads more to see. In short, I am enjoying this scope very much.

Richard

[RichieP]

Total fail on the picture posting!

I will try again.

[RichieP]

Try again, if this fails you will just have to use your imaginations!!!

[Brian Nordstrom]

That's a nice looking scope Richie , Bosma get a good review every where , a bit of an un-known quantity here in Australia tho .

Glad you like it and hope the weather in better for you soon .

Brian.