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EP weight limit


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After reading thru the threads today i noticed a comment on EPs stating that a particular brand of EP was too heavy to be used on a dob, now i was contemplating matching the skywatcher Nirvana range with the 250PX truss but now im considering the afore mentioned issue. The Nirvs come in at 1000g top end, is that going to be too much?

What do you guys think on this??

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I think the key is indeed BALANCE. You can buy nifty little weights (tho' usually rather expensive!). My experience, but obvious really: If the Eyepiece is on the top of the tube, add weights at the opposite end, preferably *under* the tube. Overall, think "see-saw" (with fat and thin persons?) and you can usually achieve near perfect balance. :icon_eek:

The main hassle arises if your eyepices are of different weight...

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I've been using the Nirvana 28mm and Nagler 31mm (both 1kg eyepieces) in my 12" Meade Lightbridge and I have needed to add weight to the bottom of the tube to keep things in balance - the altitude brake fitted to the scope is pretty puny !. I think the 250PX Flextube is natually better balanced than the Meade is but, as Brian says, you will need some counterweighting to avoid "nose droop".

I tried a Skywatcher Aero ED 30mm a while back and, while it's not as well corrected as the Nirvana / Naglers it's a nice 70 degree FoV eyepiece for it's cost and much much lighter.

John

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The dob can have counter weights added to the bottom of the tube, Steve (Albedo0.39) replaced one of the feet at the bottom of my wifes dob tube (Liightbridge) with a counter weight and held it in place with a correctly threaded bolt. It still leaves enough clearance for the tube to swing in alt without fouling the dob mount. To say it is brilliant would be an understatement, she no longer uses the supplied friction brake when using heavy eye pieces. When reverting back to lighter eyepieces she can either use the friction brake or remove the counter weight, easy peasy and a very simple solution.

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It's an old Meade system that was intended for SCT's. The weights are 1, 2 and 3lbs respectively (only 2 shown in the pic) so that plus the adjustable positioning makes it a versatile solution. I'm not sure now that I've got it in the optimum position though ATM - more research leads me to think the weighting ideally should be positioned on the part of the tube opposite the focusser. I've got to see if the system will fit there without hitting the rocker box.

John

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....But 2lbs for an eyepiece is ridiculous .... does it come with its own wheeled trunk for transportation?

I agree that it does seem extreme but it seems to be the going rate for well corrected 30mm-ish 80+ degree AFoV eyepieces. The Meade 5000 UWA 30mm weighs even more than these - almost another 1lb more :icon_eek:

I think it's not just the number of lens elements in them, but the size of those chunks of glass - the Nagler 31 has at least two elements around 75mm in diameter - which explains it's girth as well as it's weight.

John

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