Dobsonian Adjustable Tension Knobs

[esky]

Hey guys,

Great info so far and have found this site to be a great resource for buying my first scope (since the folks did about 15 years ago anyway). I'm starting to narrow it down and its probably going to be 8" or 10" Dob.

Anyway, my question is in regard to the tension control. Is it really necessary for the scope to have this control? Some models have them and some don't, it seems. I can see their benefit in theory, but in practise, just how much benefit does it provide for the added price?

This issue came up when looking at GSO scopes on the Andrews website and they have different builds of the same scope, ranging from limited to adjustable super deluxe.

Cheers

Craig

[joecool]

There are a few other features of the Andrews GSO Adjustable Super Deluxe model that the base models do not have.

Right-angle correct image 8 x 50 finderscope.
This is much easier to use than normal 8x50 which gives inverted images. Real quick you will want to get a Telrad though, and moving your eye from the telrad to the finderscope to the main eyepiece is easier with upright images in the finderscope. The Telrad gets the main tube aligned onto a target and then the finderscope gives you an idea of what might be in your magnified view and nearby in the main scope and tweaks your alignment to the object.

1:10 crayford focuser is easier to get to focus and feels smoother than a single speed focuser.

Fan - important to get all that glass of the main mirror down to near ambient temperature so you can get observing earlier with clearer images with less collimation adjustments through the night. Mine is a large computer fan with 8xAA batteries.

Knurled collimation knobs - Using a screwdriver underneath the scope in the dark just plain sucks and you will be doing this as a modification if you get a scope without these.

Adjustable tension - If this is like those on my 16" Bintel (made in the same factory as GSO and re-badged as near as I can tell from other peoples reviews) then they make pointing the tube up and down buttery smooth. I like to run the tension off with larger eyepieces, but it feels too slick with smaller, higher magnification eyepieces. Change from big to small eyepieces and the tube can tip up, so give the side knobs a bit of a tweak to hold the scope in place. And check if they can be adjusted along the tube to balance the tube. If they can then this is sweet. Adjust them for your most used eyepieces with the finderscope and Telrad fitted.

Mark.

[joecool]

Oh, and the Super Deluxe comes with the extra 6mm eyepiece for better views of planets and a 2" SP (Super Plossl). They don't say which one though?

Mark.

[esky]

Oh nice, that clears it up for me. Thanks for your help :)

[barx1963]

I have the 12" GSO with the adjustable tension, Bintel do the exact same scope just rebranded. The adjustable tension knobs are easy to use and make balancing the scop a breeze. They can be moved up and down also to get the balance correct. IMO a really nice feature.

Malcolm

[big_dav_2001]

Ive got the standard basic bed-spring style tension on my 12" GSO, and it can be a bit of a pain at times, kinda jumpy when fine movement is needed.

Is it possible to buy the adjustable tension knobs as an after-market mod?? if so, any idea where??