Losmandy DSBS

[Nortilus]

I finally got my Losmandy Dual Side by Side (DSBS) mounting system today after scrimping and scraping all my spare coins together. Can't wait to get this all happening. Will have a f/10 8" Meade ACF SCT mounted on it with a ST80 guide scope. This is all going onto a NEQ6 Pro mount. Also going to be easily able to swap out the SCT for my f/5 8" Newt now too.

So do many of you have this or similar setup. Any tips and tricks you know that could make life easier. I guess the big thing now is getting the perfect balance setup.

Anyhow...piccys :D

[g__day]

Yes, actually I have a C9.25 on the left hand side of the Losmandy bar and a Williams Optics 110mm FLT on the right hand side (with another WO 90mm mounted on top of the larger refractor).

The biggest tip I can give you if you plan to image is not about balance - I will come to that - it's about eliminating differential flexure in the large, long focal length SCT that is essential to getting long duration guiding right for deep sky objects. It was practically impossible so I went for a Off Axis Guider (OAG) on the SCT (would have loved an On Axis Guider - one day). Differential flexure is minute varying flexure caused by multiple interacting factors at different elevations and temperatures. These mechanical flexures include the scope tube itself, mirror shift and mirror flop, lose fittings, movement of the imaging train due to weight etc. It was truly horrible and after months of trying everything I could imagine I simply gave up in utter despair and then totally bypassed the problem altogether by installing a giant Lumicon Off Axis Guider. As a guide camera first I used a Meade DSI 1 colour - which was total junk as it was not sufficient sensitivite or stable, then I upgraded to a Meade DSI II mono pro (much better). If I bought again today I would go for a Lodestar II or QHY5 guide camera. I used PHD for many years, but recently swapped to PHD2 which seems more intelligent, informative and advanced then Craig Stark's original brilliant product. This setup guides at 2.3 metre focal length (F10) and regularly achieves 30 minutes subs with beautifully round stars :)

On to balancing you gear...

Get a block / off cut of four by two wood of any length from six inches to two feet. Drill two 1/2 diameter holes straight down in the four inch face of the wood anywhere close to the middle. Ideally you wish these holes to be about 1 inch deep and their respective centres to be about 2 - 3 inches apart.

Place your block of wood with its two holes face up on your kitchen table. Get two equal sized marbles or ball bearing that are well larger than 1/2 inch diameter and simply place one into each of the two wells you have drilled into the block of wood. This creates a very simple fulcrum - two very stable but slippery points - you can use to balance your gear on. Using the tops of the two marbles as a fulcrum find the balance point of each respective scope (with all its gear attached)! Mark this point on the bar holding the OTA in pencil. Now slide each OTA into the DSBS so its penciled in balance point is in the centre of each of your DSBS plates. The point of suspension of each scope will now be over the lateral bar that seperates the two OTAs.

Finally lift the entire dual set up onto the two marbles to find the point of balance / suspension along the length of the DSBS bar seperating your two OTA set-ups. Mark this in pencil.

Dismantle it all - slide the gear back into your scope when ready and align your pencil marks - and there you have a perfectly well balanced set up!

[Nortilus]

thanks for that. that makes perfect sense to find the center of balance. will give that ago when i get home from holidays.