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Old 28-11-2021, 02:38 PM
Rod-AR127 (Rod)
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Focuser Talk - Beginners Style

You may have read that l damaged my focuser some time ago, destroyed the star diagonal (SD), finder scope bracket and Barlow lens as well.
In short, temperature dropped, dove tail became loose, OTA and everything attached hit the ground, expensive end first.
New GSO 2" diagonal, finder scope bracket sees me back in the game.
My Bresser Hexafoc rack and pinion focuser "absorbed" some of the impact but is now missing teeth on both the pinion gear and rack, good job me.

So, what should l do?
I will contact Bresser.de to ask about parts, they don't list them but worth a try as they have been helpful in the past. I could also contact Explore Scientific for the same. Unfortunately postage cost these days are just ridiculous.

New focuser? This is where my questions start.

The same focuser or better quality, a statement not question.
I have the 8:1 upgrade for finer control, l would like 10:1.

The current advert for the AR 127L states "Very high quality Hexafoc focuser with 2.5" free inner diameter."
The hole in the end of the OTA is 3 3/16", the hole where the SD goes in is 2". I'm guessing the bit in between is 2 1/2".
Is the Hexafoc focuser a non standard size?

Is the 3 3/16" hole in the end of the OTA standard size?

Do l have a standard 2" focuser?

Is there a benefit to having 2 1/2" inner diameter when you throttle it down to 2" for the SD? More room for screws and brass rings to keep that 2" clear?

Is 2 1/2" inner diameter standard, good, bad or gimic?

As for which focuser should l buy, l will most likely get a Crayford style over rack and pinion and not go too expensive as my OTA is only worth so much.

I could buy a high quality focuser knowing in the future l will buy a high end APO, one more portable than my current behemoth, but that won't be for quite a while yet.

Ok then, reading back through l see my main concern is, "is my focuser a standard size and can l replace it with any 2" style focuser for a frac?

Next, extension rings!
Why?

The distance the focuser moves?
Is this because of EP FL? 5 mm EP and 45mm EP being able to work in the one focuser?

Thanks in advance, off to Mr Google and YouTube now.
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  #2  
Old 30-11-2021, 08:13 PM
Rod-AR127 (Rod)
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Well, after some serious google foo, I'm not surprised to hear crickets from the forum.
It's funny you can get a 1.25" or 2" focuser (even 2.5"in my case) and they are all measured in mm.

Grrr.

If Bresser cannot supply the rack and pinion, I'm up for a rather large bill.
The gear and rack are only stiff in one place, right on the focus point.

Grrr.
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  #3  
Old 05-01-2022, 12:58 PM
Rod-AR127 (Rod)
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Sorted, mostly.

I'd like to shout out a BIG THUMBS DOWN to Bresser.de for being the most pig headed, stubborn and self righteous pricks I've ever had to deal with.
The three online shops l contacted wanted to help but all recommended l go to Bresser.de and it all became to painful.

I have a Bintel Crayford style focuser enroute, and a HUGE THUMBS UP to Bintel and Don for the time on the phone, both of us with tape measures in hand and we're confident I'll be focusing properly once l have an adaptor made up.
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Old 14-01-2022, 01:37 PM
Rod-AR127 (Rod)
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New focuser arrived, exciting but l still need to do a comparison with the old one to ensure it will work correctly with my scope.
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  #5  
Old 14-01-2022, 02:12 PM
AdamJL
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Nice work, Rod. That looks like a nice focuser
Why two locking screws on the bottom?
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Old 14-01-2022, 03:58 PM
Rod-AR127 (Rod)
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It's the 112mm Bintel/GSO 10:1 Crayford style focuser.
One screw is locking, the other is tension.
So much smother than the Bresser Hexafoc R&P.
Can't wait to get an adaptor made to fit my OTA, but I'll have to.
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