Focuser upgrade for Starhopper dob

[DougAdams]

Well, it's been too long but I got the scope out last night and had a great two hours. Saturn was wonderful - although the ring plane has closed up a lot since I last viewed it. Six stars popped up in the Trapezium, and I fancy I even glimpsed the G star once. A pleasant hour with O'Meara's book on the Caldwall objects around rising Crux.

Anyways, the clunky old focuser on the clunky old Starhopper (the old cardboard tube model) is annoying me. Compared to the Crayford on my refractor, it's stiff and sticky.

What are some focuser upgrade options for this Dob? Suppliers? Easy to do yourself?

Cheers
Doug

[avandonk]

I recently bought one of these for a refractor. The are very nicely made.
http://www.scopestuff.com/ss_fnc2.htm
The compression ring locking is good too.

Bert

[iceman (Mike)]

The GS crayford for $99 is a good replacement. Someone was asking about it recently - do a search for crayford in this forum and you'll find it.

[barees63]

The Orion Accufocus might be an option also if the focuser is similar to the typical Chinese R&P found on Orion and GSO scopes, turns the old R&P into an accurate, vibration-free motorised focuser for AUD$95. See the thread in this section..

[rmcpb (Rob)]

I put the GS Crayford on my scope, really easy upgrade and, for the price, its absolutely great. I think these are handled by both Andrews and Bintel.

[DougAdams]

Thanks guys. Bintel have the Crayford and offered to see if it's compatible with my Dob. I'll take it on a daylight field trip sometime this week.

[stringscope (Ian)]

Doug,

I wouldn't knock an old cardboard tube Starhopper. Having had the opportunity to compare 8" Starhopper next to steel tube 8" GSO side by side in middle of winter here in Canberra, I reckon they are OK:

No cold air tube currents.
Primary and secondary don't dew up.
Unique thin mirror that cools really quickly.
Sliding altitude bearing.

I have fitted a Kine Optics HC-2 helical crayford focuser to mine. It is OK but it doesn't like the heavier 2" EP's. Have fun with the mods.

Cheers,

[mickoking]

Originally Posted by stringscope

Doug,

I wouldn't knock an old cardboard tube Starhopper. Having had the opportunity to compare 8" Starhopper next to steel tube 8" GSO side by side in middle of winter here in Canberra, I reckon they are OK

The telescope I miss the most is my old Meade 200mm 'cardboard tube' Dob. Sure it only had a 1 1/4" plastic focusser and would become unbalenced when using heavy eyepieces but it was one great 'scope. All I have left to remember it by is the 25mm modified achromat e/p that came with the Dob.

[janoskiss (Steve H)]

Good to hear from you Doug. GS crayfish does okay, and it is a big improvement over the standard 2" rack-n-pinion. Bit the crayford has only 35mm travel, and a bit lower profile than the R&P. So you might need a barrel extender to reach focus with some EPs. Re fitting it, it would be best if you could take your OTA to Bintel and get Roger to take a serious look at how to go about it.

[Roger Davis]

The Starhopper requires serious modification to fit a 2" focuser using the existing hardware. The secondary mirror cell is supported by a single vane spider that anchors to the 1.25" focuser by the same screw that holds the focuser in place on the tube. The focuser can be removed and the spider reanchored with a lockwasher and a nut. But a new hole would have to be drilled through the tube to accommodate the 2" focuser. To accomplish that and retain a comfortable viewing position, you would have to fit the focuser on the other side of the tube. The secondary cell can be rotated in the spider hub to access the new position. Then you have to fill the old focuser hole. Sorry Doug, thought of this after you left yesterday, but it is a major reconstruction.

[ausastronomer (John Bambury)]

Doug,

The "g" star in the trapezium was 1st discovered in 1888 by A.G.Clark using the 36" refractor at Lick Observatory. It is not possible to see this in an 8" dob.

CS-John B