New Dob owner questions

[Talitha]

When my 16" LightBridge arrived on 9 July () , one of the small boxes that came with it contained a 35mm "extension tube".... i'm clueless.. what is it?

Also, the scope came with a Meade 26mm 2" XQ wide angle ep. If possible, i'd like to use one of my barlows with it for a while before deciding if i'd like to get more 2" ep's (i have a 2x and a 2.8x barlow). There's a 2"-1.25" adapter i can get for less than $30 but i'm curious if the fov of the ep will be decreased by the smaller barlow... should i expect any side effects like kidney-beaning or something similar?

[yeti monster]

Is, perhaps, the extension tube for positioning a digital camera? Rather than a dedicated astonomy camera??? just a thought, as my focuser tube is a stacked one. As for 2" EPs, I am yet to experiment, although I do intend to buy one this trip, just haven't decided which one yet.......... I've certainly not felt restricted using 1.25" EPs in my 2" focuser.

[Talitha]

The "35mm" stamp automatically made me think of a camera, but i suppose there might be 35mm eyepieces, too. But why (if it is indeed for an eyepiece), would i need a separate device?

I might not have explained the barlow question properly. I have two 1.25" barlows and am wondering if the view will suffer if i use the 2" ep in the barlows (via the adapter).

[yeti monster]

2" EP in a 1.25 Barlow? I'm only guessing here, but I think you would suffer horrendously. I'd only use 2" with 2" accessories, otherwise you HAVE to be losing heaps of light cone, surely??? Or put another way, wasting heaps of glass........

I'm only planning to go 2" on wide field EPs, my existing short FL EPs are performing adequately enough for my myopic eyes.

[johninderby]

Would that be a 35mm long by 2" diameter extension tube for giving additional back-focus ?

John

[barkis]

Maybe the scope is setup for AP with a DSLR, and as with the SW Mak Newt, will have a larger secondary fitted. The tube will therefore be for your visual work, so you don't need to rack the focuser too far out to achieve focus.

Ron .

[NGC 1502]

Hi, a clubmate had an 8" Lightbridge, he needed the extension tube to bring

the supplied 26mm QX eyepiece to focus. Perhaps the larger LBs are set up

this way too?

HTH, Ed.

[Doc]

I've never needed extention tubes to bring my eyepieces to focus on my 16" LB.

[RobH]

I don't need extension tubes on our 12 inch LB.

These scopes are built as visual scopes anyway, and as such won't have the oversized secondary required in a photographic newt I wouldn't have thought.

Cheers

Rob

[yeti monster]

Would that be a 35mm long by 2" diameter extension

That's how I interpreted it.

[DarkerSky]

I might not have explained the barlow question properly. I have two 1.25" barlows and am wondering if the view will suffer if i use the 2" ep in the barlows (via the adapter).

The 26mm QX on its own is not the best I have found. It does give a superb wide angle but I do find the edges of the field get distorted - more noticeable in a rich star field in the milky way for example.

I have barlowed the QX using a Meade 5000 2X telextender - that allows for both 2" and 1.25" barrel via a slotted adapter at the top of the unit. There is no noticeable degradation in the view over what you have un-barlowed, but I think the quality of the barlow used could come into play also

[Peter Drew]

It is just possible that being a new 16" LB, the manufacturers have modified the optical set-up to accommodate a DSLR hence the inclusion of an extension for visual use, a tryout should soon determine the outcome.

[Ags]

Congrats on the new telescope!

[Talitha]

Thanks everyone, sorry i'm late but it's been violently stormy all day.. a tornado was sighted not too far south of me.

Back focus sounds a reasonable explanation for the extension tube, but if Mick says he didn't need one, i'm still stumped.. i'll call my supplier tomorrow and see if they know. The scope was drop-shipped from the manufacturer though, so i'm guessing my supplier might not be aware it was in the shipment.

Seb, it would've been great if they'd have sent an Ethos with the scope, wouldn't it? Thanks for the info, is a telextender the same thing as a barlow? Just for grins and giggles, i'll get the adapter and see what happens. It doesn't cost too much and it'll be interesting to see what i can squeeze out of the QX with it... as soon as the weather permits, that is.