Another tail of woe...

DJVege · #1 28-08-2007, 10:44 AM

I forgot to mention I bought a 10:1 crayford from Bintel...but it has 4 screws in each corner, and my scope is set up for 2 screws along the side!! Doh! Any suggestions to attach this besides drilling holes in my scope? Or is drilling the best option?

rmcpb (Rob) · #2 28-08-2007, 10:52 AM

Just take a deep breath, measure twice and drill once for each hole.

Make sure you take your mirrors out before any drilling!!

Omaroo (Chris Malikoff) · #3 28-08-2007, 11:00 AM

WAIT! The typical Bintel (GSO) 10:1 focusers come with a base plate designed with a 70mm (between centers) hole pattern, and a curvature to fit an 8-10" tube diameter. Before you go whacking holes in your scope do you know for sure that the curvature is going to fit? Looking at the image I've found, it has a hell of a small radius being a 5" incher.

Secondly - the MN56 is a Maksutov-Newtonian that has a meniscus corrector plate at the front. If you remove this plate in order to go drilling and mounting a new focuser I reckon you'll have a great deal of fun getting it back together again without a major collimation effort. The MN56 already comes with a crayford-style focuser - so is installing a 10:1 version going to be worth it to you really? You have to cut holes and take the scope apart to do it... I'm not sure that you gain all that much by doing it.... just my honest opinion and probably only worth 2 cents but there you go.... If you're happy with your ability to take the thing apart (including the mirror as mentioned by Rob) then go for it

One trick when drilling is to hold the whole OTA mirror-up so that swarf doesn't fall back into the optics - but removal is safer.

rmcpb (Rob) · #4 28-08-2007, 11:07 AM

Good points above!!

DJVege · #5 28-08-2007, 11:18 AM

The crayford on there now isn't very smooth and difficult to do fine corrections with. Everytime I touch it, the scope shakes, and it's focusing the finer adjustments is just annoying.

I asked Bintel whether it would fit my scope, sending them a link of my scope's specs, and they said it would.

Omaroo (Chris Malikoff) · #6 28-08-2007, 11:32 AM

Quote:

Originally Posted by DJVege

I asked Bintel whether it would fit my scope, sending them a link of my scope's specs, and they said it would.

Here's hoping......

I've found that Bintel are generally very good at supplying what you ask for - but still make sure the curvature of the base plate is going to fit before you start taking the scope apart....

Shaking of the scope isn't going to change - as soon as you touch any focuser you'll shake it anyway. Smoothness is all that is going to be gained. Are you sure that the current crayford is in correct adjustment? Have you tried the tension adjuster screw?

DJVege · #7 28-08-2007, 11:34 AM

Hmmm....

I think I have...but I'll give it a go when I get home tonight and let you know the outcome.

Thanks mate!

Umm...what IS the tension screw for? What does easing the tension do? Does that lead to smaller increments/decrements when focusing?

DJVege · #8 31-08-2007, 06:27 PM

You were right, Omaroo. This 10:1 focuser doesn't fit.

I've asked Bintel for a refund or if they can suggest an exchange 10:1 focuser that would fit my scope.

Terry B · #9 31-08-2007, 08:21 PM

Have you thought about adapting one of these https://www.bintelshop.com.au/Images/Stock/7439X.jpg
that Bintel has for $59.
This stops the wobbles completely.

DJVege · #10 01-09-2007, 09:39 AM

Hmm...interesting... Thanks Terry. Will check it out!

[1ponders] (Paul) · #11 01-09-2007, 09:54 AM

You beat me to it Terry, I was just going to suggest the motor focuser. If it doesn't work it is still a hell of a lot cheaper than stuffing up the scope.

ausastronomer (John Bambury) · #12 01-09-2007, 10:02 AM

Quote:

Originally Posted by DJVege

You were right, Omaroo. This 10:1 focuser doesn't fit.

I've asked Bintel for a refund or if they can suggest an exchange 10:1 focuser that would fit my scope.

It's quite rare to get an aftermarket focuser designed for a round solid tube telescope that fits perfectly. This isn't an issue in any way.

I assume the issue with the small diameter tube is the plate section where the screw holes are on the focuser sits out from the tube ?

Use some neoprene or steel washers to pack out where the screw holes are and then use some slightly longer countersunk head machine screws to attach the focuser.

Collimate the focuser properly on the telescope and then run some black foam weatherstripping material around the edge of the focuser to block the stray light.

Cheers
John B

DJVege · #13 01-09-2007, 01:24 PM

Thanks for the suggestion John. I'm trying to stay away from drilling 4 extra holes i the scope, though. Plus, there'd be open areas between the focuser and the tube if I kept was to put this new one on.

DJVege · #14 03-09-2007, 02:48 PM

OK. Just letting everyone know that Don from Bintel is awesome. He suggested that if my focuser was a Gueng Sheng or whatever, I might be able to take the base screws off and just swap the bintel one over. Which I did and it fits great! SO! 10:1 focusing, here i come!

The only issue I MAY have, is that my old focuser is sort of low...and the new one is high..I may not be able to focus for the high powered EPs (adding barlows included) that have a short EP focal length. Does that make sense?

But I'll check it out tonight.

DJVege · #15 03-09-2007, 06:47 PM

Update! Works sweet. I can focus even with a 7mm Nagler and a 5X powermate.