What Do I Do? FW Problem....

[PRejto]

So, I've created a problem and now I can't find an answer. The system shown was formerly mounted on my TEC180 which was on an MEII on a pier. For the next year or so that setup is no longer possible and the camera system is now on my TEC140 on an MX+ on a tripod. Clearly I can only get to the meridian with the giant SX FW (7 x 2" filters) with the filter wheel in 2 positions rendering the Gemini rotator moot. I have to say that even my MEII is pretty restricted with this huge wheel so I'd been eyeing the Optec IFW 2" wheel which has interchangeable carousels (without breaking down the system). Sadly it won't take mounted filters and I'd need to buy a new OAG to boot.

The only solutions I can think of are a pier extension (not available from Software Bisque for the Helium Tripod) or some sort of saddle extension the likes of which I've never seen before...or, a different FW similar to the Optec design. The thought of breaking down the system to change filters is extremely unappealing! Smaller 2" wheels only hold 4 filters....

Any ideas appreciated!

Thanks,

Peter

[multiweb]

How about an RA axis extension like what Losmandy did for the G11. That would move the load forward a bit and clear the front leg.

[PRejto]

Thanks Marc.

I was thinking along those lines....but, if I don't lift the mount higher on a pier extension of some sort I'd need to lift the dec axis out about
2.5" min. which seems like a lot. Maybe I could make something out of RHS steel but then I wonder about shear loads on such long bolts?

Peter

[multiweb]

Have you tried the mount manufacturer see what they'd advise. Pretty sure this would have come across before from other PME users.

[Outcast]

Hi Peter,

I'm not familiar with the tripod or mount however, I did a bit of a quick google & am I correct in the fact that the the mount is affixed to the tripod via the two black plates & 4 x bolts?

If this is correct, assuming that you don't need to lift the mount too much to clear the leg with the filter wheel, would it be possible to machine up a billet alluminium plate of appropriate thickness & get 4 x longer bolts to sandwich it all together to act as a very solid pier extension?

Just my thoughts from outside the square... not sure if they are of any use

Cheers

[PRejto]

Hi Carlton,

I am thinking along those lines but lifting alone will not solve the problem. I will also need to lift the dec axis out to have the FW clear the mount at the meridian.

Thanks!

Peter

[billdan]

You may have to ditch the tripod and get something similar to this JMI pier.

[Sunfish]

I have thought of adding an offset pier extension to my pier . So the centre of the mount is offset to the South Pole to ensure better clearance through the zenith for the camera end. In the case of a tripod it would need to be balanced and offset with a counterweight on the North side, but that could be part of the offset plate.

[Joshua Bunn]

Hi Peter.

I reckon a Declination axis extension/spacer is going to be the best option.


Cheers, Josh

[jamespierce]

Paramount makes an extension for the pyramid tripod. The design at the top here looks pretty similar to mine I reckon it would fit.

[gregbradley]

Turn the filter wheel around so when the scope is horizontal the filter wheel is sticking up in the air rather than facing down to the ground.

I have my FLI filter wheel sticking up in the air as it gives a better balance and I hadn't really thought about it but it also gives better clearance.

Failing that, set the parameters limiting the mounts tracking so it stops before it hits the leg and do a meridian flip.

Greg.

[PRejto]

Thanks everyone for your suggestions!

I've been told by Software Bisque that the Pyramid extender will not fit on the Helium Tripod.

Greg, I can't see much point to ignoring the fact that I have an expensive rotator/focuser. This is equipment that I want to use so I think I'm going to go for an extender either under the versa plate, or under the TEC rings.

Once I get this figured out I'll post some updates.

Thanks!

Peter

[gregbradley]

Oh I see, the rotator will rotate the filter wheel around with the camera. I wasn't suggesting removing the rotator.

I have my filter wheel pointing up which I presume would be easy to do with yours. It adds clearance but may not be enough in your situation.

Greg

[Paul Haese]

Peter, a 2 or 3 entension fitted to the versa plate should give you enough clearance. Would a Robin Casady saddle plate be converted? A machined chunk of aluminium will work, but require more counter weight.

[PRejto]

I happened to have two ADM pieces of kit.....a cross bar equal in length to the versa plate and a saddle. I had a local machine shop countersink some M8 holes/threads and added a 25mm (3mm thick) piece of RHS steel between the two. They provided 40mm bolts high strength bolts but I think I'd be feeling safer if they were 45mm (50mm is just a hair too long).

In spite of one photo looking like there is a skew the two plates are parallel. (And, yes, I need new shoes but I've spent too much money on astro gear!)

Beyond this I cannot post a photo of the gear all mounted as I've just sent my rotator and all extension tubes and flattener to Joshua Bunn in WA due to a part from Precise Parts that has never worked properly and a Gemini Rotator that has been nothing but trouble from the day I bought it (tilt on rotation). Maybe some day I will actually take a useful photo. It is now a year and counting.

Peter