New focuser

[Arthur Alchin (Arthur Alchin)]

Suppose hypothetically that i was to replace the standard, no frills rack and pinion focuser on my meade LXD 8" schmidt newtonian (yes the one with the corrector lens on the front) with a nice crayford piece say a 10:1.

Would the removal of the corrector lens be very, very difficult if i took my time and lined everything up properly and secondly can anyone suggest a particular unit that would bolt straight in without having to drill holes in my precious scope.

I would really like a low profile piece if possible, but only if possible (use binoviewers).

Also is there somewhere or someone in the Sydney/Central Coast/ Newcastle area that does this type of work??

Thanks Arthur

[marki]

You might like to look here for starters ...

http://www.focuser.com/cgi-bin/dman....cgi&category=3


Mark

[dannat (Daniel)]

why do you need to remove the corrector? .or are the screws inside the tube? as for the holes i would lay the tube on its side & unscrew the old focuser..check what holes are there..draw it then ask at the shops for the same profile. I would mark the corrector with stickers/tape thay isn't going to rub off so you can line it up exactly. BIntel may do it , contact them

PS if you have the old R&P lying around i would take it off your hands

[TheDecepticon]

I believe Feathertouch or Moonlight do a direct replacement for the SN8 and SN10 Meade scopes.
When you take out the corrector, take the whole cell out by undoing the four Allen head screws in the tube. Make sure you mark the position it came out of the tube, as the are set in the factory for optimum alignment to the mirror.
Oh, and be careful!!

[Garry (Garry)]

I just did this exact modification over the last weekend (Moonlite focuser on a Meade SN8). The difficult part is not removing the corrector, that's easy. All you need to do is ensure that the plate assembly is replaced with the same orientation as before. This is easy since the 4 screws holding it on have very little play and you can ensure a near exact positional replacement by placing some kind of coloured tape across the junction and slitting it with a sharp knife so that you can exactly align the tape edges.
The more difficult part is installing the SN8-specific adapter and the the focuser itself. Moonlite sells the unit (which seems to be very high quality btw...) as an exact drop-in replacement, but it seems that not all units are exact fits (at least mine wasn't...). I had to slightly modify/enlarge the bolt holes to get the adapter to fit onto the scope. I used a drill bit to shave away some metal at the appropriate position. After the adapter could be attached, the next issue was that the original focuser hole on the scope was not quite wide enough for the focuser drawtube to rack down completely. I had to grind down the metal to enlarge the hole for that. Here I used a 1" diameter file drill bit to remove the metal around the circumference. To do all of this you will absolutely need to remove the corrector assembly. I also made sure to place a barrier (crumpled newspaper worked fine...) in front of the main mirror to prevent metal shavings from getting too far into the tube.
I imagine that there's enough variability in the manufacture of these mass-produced scopes that no aftermarket modification like this will be a perfect fit every time. All told, the installation was not hard to do and although I have not had a chance to see how it's working yet, it's a serious improvement over the old focuser.
Hope that helps.
Garry

[Arthur Alchin (Arthur Alchin)]

Thankyou all

Mark: i went looking, the moonlight looks real good and not a bucket load of cash.

Dannat: when done i will get an address and you are welcome to the R&P.

Gary and TheDeception: Thankyou for the advice, i will be carefull, will have to access the "best fit" stuff from the usa unless there is somewhere out here with moonlight gear (i haven't seen one)

I spoke with Bintel a couple of weeks ago, was told they weren't interested in the labour side of it