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Old 16-07-2018, 08:48 PM
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What's a good lens focusing unit?

I use lenses often to image with. I have in the past used a FLI PDF to get accurate focus and to be able to refocus easily. Unfortunately I sold that. It was very good.

I see Robofocus setups where there is a rubber belt wrapped around the lens focus ring and it goes down to a smaller wheel connected to a Robofocus.

The last Robofocus I had was great but old fashioned in that it wasn't USB but serial. Perhaps its USB now.

Any other focus units out there you could recommend?

Greg.
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Old 16-07-2018, 08:58 PM
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Octane (Humayun)
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It’s still serial, meaning that it is uber reliable.

I think the setup you’re referring to is the Mandel kit. I’ve always wanted to do it, but, I don’t have any camera lenses anymore other than my 6x7 stuff and that is probably impossible to mount on any CCD as they are a bayonet design.

H
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Old 16-07-2018, 09:53 PM
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Greg - Robofocus is probably the most adaptable for this purpose

H - I converted all my Robofocus controllers to native USB.

Got a mate to do the first ones.
You have to add another chip (a Max232) into the design and a couple of diodes to prevent power from back feeding from the USB power though the chip and back into your motor controller if the power drops out (learnt that the hard way !)
Its not hard - not sure if I still have the circuit diagram though.

Bojan could do it with his eyes closed !
Its just a simple birdsnest mod.

Rally
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Old 17-07-2018, 08:57 AM
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Octane (Humayun)
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Rally,

I'm a complete gumby when it comes to electronics -- I'd ruin it! The computer I use in my little makeshift observatory has a native serial port so that takes care of that.

H
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Old 17-07-2018, 10:03 AM
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Quote:
Originally Posted by Octane View Post
Itís still serial, meaning that it is uber reliable.

I think the setup youíre referring to is the Mandel kit. Iíve always wanted to do it, but, I donít have any camera lenses anymore other than my 6x7 stuff and that is probably impossible to mount on any CCD as they are a bayonet design.

H
Thanks Humi.

I have an adapter for 6 x 7 lenses that fits them onto my FLI Filter wheel. Easy. 6 x 7 lenses have the longest backfocus of any camera lens - over 80mm (85mm I think) 645 have around 65-70mm.

You get a cheap Pentax 6x7 to Nikon or Canon (doesn't matter which) adapter off Ebay. Probably $30 or less. Most CCD camera manufacturers offer a Canon or Nikon lens adapter for their cameras.

I had Precise Parts make me one to attach the 6x7 adapter to a FLI PDF focuser. Now that was a nice setup with precise focus control.
Mind you lenses are not as sensitive it seems to focus shift compared to telescopes. But they also may not be parfocal to the different coloured filters.

Greg.
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Old 17-07-2018, 10:05 AM
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Quote:
Originally Posted by Octane View Post
Itís still serial, meaning that it is uber reliable.

I think the setup youíre referring to is the Mandel kit. Iíve always wanted to do it, but, I donít have any camera lenses anymore other than my 6x7 stuff and that is probably impossible to mount on any CCD as they are a bayonet design.

H
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Rally,

I'm a complete gumby when it comes to electronics -- I'd ruin it! The computer I use in my little makeshift observatory has a native serial port so that takes care of that.

H
If you get a decent adapter its not really an issue. I forget what brand I have but they work well and they cost a little more but its worth it. The only issue I have with them is its easy for the USB2 plug to pull out a little bit and lose connection. So I tend to check they are snug as part of my routine for starting up or the first thing I check if they won't connect.

Greg.
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Old 17-07-2018, 10:06 AM
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Quote:
Originally Posted by rally View Post
Greg - Robofocus is probably the most adaptable for this purpose

H - I converted all my Robofocus controllers to native USB.

Got a mate to do the first ones.
You have to add another chip (a Max232) into the design and a couple of diodes to prevent power from back feeding from the USB power though the chip and back into your motor controller if the power drops out (learnt that the hard way !)
Its not hard - not sure if I still have the circuit diagram though.

Bojan could do it with his eyes closed !
Its just a simple birdsnest mod.

Rally
Yes Robofocus was reliable for me for years on various APOs. I tended to struggle a tad if you went past focus and tried to go back a few steps but it would get there.

But its US$500 which is pricey for what it is.

Greg.
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Old 17-07-2018, 11:18 AM
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Yep, my AAG CloudWatcher uses the serial-to-USB adapter, as well as my Losmandy Gemini.

As for my 6x7 lenses, they're the Mamiya type. They have a special locking mechanism. Admittedly, it's been a while since I've looked, but, the last time I did search, there wasn't an adapter for Mamiya-Canon lens mount. I've got an STL-Canon mount, and, if there was a Mamiya adapter, I'd be tempted to bung my 180mm f/4.5 on it and have a play! Or, better yet, attach my FSQ-106N to the Pentax RZ67 Professional II. Sadly, I think that's a pipe dream.

H
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Old 17-07-2018, 11:19 AM
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Look what I just found: https://fotodioxpro.com/products/rbrz67-eos-pro

$180 US, though.

H
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Old 17-07-2018, 01:11 PM
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Look what I just found: https://fotodioxpro.com/products/rbrz67-eos-pro

$180 US, though.

H
Woo hoo! Time to go ultrawidefield Humi.

Greg.
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