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Losmandy vs Vixen Bars and Scope Size

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#1 pubquiz

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Posted 30 June 2013 - 04:48 AM

Hi All

I have just obtained an Altair Astro 8" RC scope for a good price used. I will be upgrading my mount soon and will be getting a side by side scope mount set ..either the Altair TMS or ADM.

Currently I use a solid side by side thick alloy plate bolted to the Losmandy rail for the G11 and the vixen rail on my C8 is bolted directly to this but would like something more adjustable and versatile so will be going to a proper dual mount system.

What I want to know is at what size scope does it become advisable to use Losmandy rails instead of Vixen?

The latest 'fully loaded' RC's come with Losmandy bars top and bottom ...before that it was Losmandy bottom and Vixen top and before that (as mine) Vixen top and bottom.

I will be mounting my Megrez 72 on top of the RC and my C100 alongside.

I realise that the Vixen rail on top of the RC will be fine for the Megrez (I used an even smaller ADM mini dovetail for it on top of my C8 with no problem) but wondered if it was worth changing the bottom rail for a Losmandy which as you know is substantially wider..

Obviously I will need a Losmandy bar to go in the mount saddle but was wondering what to get as saddles for the 2 scopes on the side by side Losmandy bar.

The mount I will be getting is a Mesu 200 so weight will be no problem and who knows in the future I may get bigger/heavier/longer scopes.

So was wondering if it was worth changing the bottom Vixen rail on the RC for a Losmandy one and going All Losmandy since I will be buying the dual mount system new and want it to be future proof.

It will primarily be for imaging so obviously don't want any flex and it will be permanently mounted in an observatory.

Any advice from users of the Altair TMS and ADM side by side system users with similar/bigger scopes will be most welcome.

Tom

#2 hottr6

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Posted 30 June 2013 - 06:00 AM

It seems to me that if your mount can handle the extra weight of the Losmandy rails, "bigger is better".

#3 MikeCMP

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Posted 30 June 2013 - 06:54 AM

You could also get the dual saddles from ADM and not have to worry.

Mike

#4 pubquiz

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Posted 30 June 2013 - 10:25 AM

Thanks guys

Yes good idea Mike ...might be worth the extra £30 for the ADM dual option.

Torn between the 2 ...I like the rings with easier to grip knobs and bigger delrin tips on the Altairs (I have the ADM rings and find the 'splined grip' type knobs not as easy to get really tight)

But I like the way the ADM saddles grip along their full length unlike the Altair ones that just grip in 2 places.

Maybe I'll combine the best of both.

Tom

#5 astrophile

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Posted 30 June 2013 - 06:38 PM

For anything but the smallest & lightest setups, the Vixen bars make me nervous--not so much their width, but the gripping angle in their design is much less secure than that of the Losmandy system. For me, anything over 10 lbs would merit a Losmandy plate. But I'm sure there are other views.

#6 Richard Low

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Posted 30 June 2013 - 11:49 PM

Just to share my expwrience... I have used the Tak Mewlon 210 (ota about 8.5kg) on Vixen dovetail with no issue. I tried the APM 6"f/8 apo (ota about 12.5kg) on Vixen dovetail and it slipped slightly ... no disaster fortunately, but it works well on Losmandy dovetail plate.

#7 yowser

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Posted 01 July 2013 - 07:33 AM

I use the Vixen dovetail on a Vixen VMC260L, weighing in at 30lbs fully loaded, with no problem on an ADM Vixen style saddle. However, since you'll be using it for AP, just go with the Losmandy if it helps you sleep better at night. :grin:

#8 Midnight Dan

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Posted 01 July 2013 - 08:18 AM

Everything has flexure. The bigger you go, the less there will be. Period.

For AP, I'd use Losmandy everywhere you reasonably can. For small scopes like your Megrez 72, it probably doesn't make sense to use Losmandy, but everywhere else I would.

In your side-by-side, I'd probably use one Losmandy saddle, and one dual saddle. You could use 2 dual saddles, but you probably won't have the need for two vixen mounted scopes at the same time so you could save a little money by using one Losamandy-only saddle.

Since weight doesn't appear to be an issue, you might also want to consider the ADM Max Guider aiming device instead of tube rings to align your two scopes. It's not cheap, but definitely more solid and precise.

-Dan

#9 pubquiz

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Posted 01 July 2013 - 11:23 AM

Thanks guys all good info ...a dual saddle and a losmandy only saddle is a good idea.

Tom






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