Travelscope finished (well almost)

GraemeT (Graeme) · #1 22-01-2014, 09:59 PM

I've just got around to finishing my version of the Gary Seronik travelscope. I've used an f5/200 mirror and a helical crayford focusser. All that remains is to figure out the best way to nest the components into the rocker box.
Sourcing teflon for the bearings was a problem until I was wandering through the big green shed and found selfadhesive SlideGlide, 60mm x 200mm, for less than $10, more than enough for both alt and az bearings.

mercedes_sl1970 · #2 23-01-2014, 09:10 AM

Looks good - a very neat job. I'm curious about the inserts you've used in the tubes - did you make them yourself or buy the press-fit nuts (whatever they are called...).

Cheers, Andrew

alistairsam · #3 23-01-2014, 10:31 AM

Nice work Graeme

Do you have a pic of it stowed away? Which helical focuser is that?

Cheers
Alistair

GraemeT (Graeme) · #4 24-01-2014, 08:43 PM

Andrew, for the inserts in the ends of the tubes, I used propell nuts from Carbatec, forced into wooden blocks cut to fit into the tubes and glued with araldite. I also used the propell nuts to mount the alt rings with a wooden block pushed up inside the tube to take the crushing forces.
Alistair, the helical crayford is from Kineoptics in the US. I initially bought the 2" unit but have decided that the lighter 1.25" would be better. It will not be a big deal sticking to the smaller barrel eyepieces, and will make balancing the scope easier, I haven't a pic of it stowed as I'm not sure how far I want to dismantle it. The major sticking point is the secondary mirror mounting - if I don't mind a major recollimation, it's a doddle!

barx1963 (Malcolm) · #5 25-01-2014, 12:21 AM

Lovely job Graeme. Much neater than my version!
Are the tubes square or round? It is hard to tell in the photo.

Malcolm

GraemeT (Graeme) · #6 25-01-2014, 10:37 AM

Malcolm, the tubes are black anodised 1" square section, from Bunnings.

mercedes_sl1970 · #7 25-01-2014, 01:48 PM

Quote:

Originally Posted by GraemeT

Andrew, for the inserts in the ends of the tubes, I used propell nuts from Carbatec, forced into wooden blocks cut to fit into the tubes and glued with araldite. I also used the propell nuts to mount the alt rings with a wooden block pushed up inside the tube to take the crushing forces.
Alistair, the helical crayford is from Kineoptics in the US. I initially bought the 2" unit but have decided that the lighter 1.25" would be better. It will not be a big deal sticking to the smaller barrel eyepieces, and will make balancing the scope easier, I haven't a pic of it stowed as I'm not sure how far I want to dismantle it. The major sticking point is the secondary mirror mounting - if I don't mind a major recollimation, it's a doddle!

Graeme - thanks for the extra info. Had to look up "propel" nuts - that's a clever way of using them. I also have a Kineoptics focuser - good, simple and light weight units.

Andrew

GraemeT (Graeme) · #8 26-01-2014, 10:19 PM

Clear skies for the first time since whenever, so I thought I'd try it out. M42 was overhead and Jupiter was just in the field provided by my terrace. A shroud will make a distinct improvement and I will need to develop a light touch on the helical focusser as there is significant flexure in the OTA. Otherwise my calculations for the focusser position are spot-on. I will also need a variable tension control on the alt rings to allow for the eyepiece mass variations.

barx1963 (Malcolm) · #9 27-01-2014, 10:11 AM

Graeme
I had the same issues with tube flexure and the tension control. The OTA is so light that there is insufficient friction to hold it in place. The main reason I went to a Crayford (base model Moonlite actually) was because using a helical would move the OTA too much while focusing I thought.
I installed a DSC that I had lying around and putting a bracket connecting the alt encoder to the base aneabled me to apply a little downward pressure on the alt bearings. This had 2 instant beneficial effects. One is stiffened the OTA slightly and significantly reduced the flexure. Two is that I can use a range of eyepiece without worry. I have used a 15mm GSO Superview, not sure if its weight but is is very light, and all my Ethos up to the 21mm which weighs over 1kg with no problems.
I think Gary Seronik from the emails I exchanged with him has a spring attached to do thsi job. Looking at the bottom of this page (http://www.garyseronik.com/?q=node/206 ) you can see a disc and spring on the far side of the scope, and he has a fair sized Nagler in the eyepiece!

Cheers

Malcolm

GraemeT (Graeme) · #10 28-01-2014, 09:55 PM

I was thinking along a different track to solve the alt bearing drag control and came up with this gizmo. Essentially a rubber pad bearing on the inside of the ring, with the tension controlled by the knob. Seems to work well.