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Old 14-04-2015, 12:32 PM
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graham.hobart (Graham stevens)
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back focus again!!

My mate has kindly lent me a WO FLT 132 with FF for a trial spin. I am trying to work out if I can fit the Microline 8300 plus filter wheel into the back focus needed by the field flattener.
The diagram is here http://www.williamoptics.com/accesso...ChiptoLens.jpg

As can be seen the optimal distance is 46.45mm which makes it ideal for DSLRs plus T ring.
The back focus of the microline is 24.96mm. THe SX filterwheel is 25mm in width. Hence 49.96 which puts over the 46.45mm FF spacing required.
Any ideas?
This not including any special connectors/adaptors etc
Thanks for advice folks
Graham
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Old 14-04-2015, 01:17 PM
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Amaranthus (Barry)
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A narrower filter holder? I use the TS filter slider, which has an optical length of only 15mm. (That would give you 6.5mm spare.) It's terrific, but there are compromises. It can't be automated.
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Old 14-04-2015, 01:33 PM
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graham.hobart (Graham stevens)
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back focus

Hi Barry- can you get a slider that holds four 2" filters?
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Old 14-04-2015, 01:34 PM
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graham.hobart (Graham stevens)
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back focus

I have also found this one.....
any one any experience?http://www.optcorp.com/xagyl-five-po...el-5125v2.html
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Old 14-04-2015, 01:52 PM
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Amaranthus (Barry)
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My slider changes out single cartridges.
http://www.teleskop-express.de/shop/...w-profile.html (this is 2", I use the 1.25" version)

In theory you need 2 drawers (you can buy extras), one in use and the other to load out (so your filter swaps are rapid). Probably better is to get 3-4 of them and have your filter run setup for the night.

These work great if you're not trying to automate, and are happy to run sequences rather than loops, e.g. 10 x L subs, 10 x R, 10 x G, 10 x B - if they were 5 min subs you'd be swapping out every hour or so, which is a good time to re-focus! That's my MO, anyway.
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Old 14-04-2015, 01:52 PM
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rustigsmed (Russell)
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Quote:
Originally Posted by graham.hobart View Post
Hi Barry- can you get a slider that holds four 2" filters?
Like Barry I also use the TS filter slides - they are pretty handy. (although I find the filters hard to unscrew!) - but as Barry mentioned its all manual - I don't mind as I haven't got focus automated.

http://www.teleskop-express.de/shop/...w-profile.html

edit:
- barry just pipped me with his response
- I use the 2"
- like he suggests one slide per filter is more ideal - I will be getting more as only use the 2 slide setup.
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Old 14-04-2015, 02:24 PM
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Graham,

The backfocus of the Microline 8300 is 16mm from the sensor to the faceplate. See here:

http://www.flicamera.com/microline/index.html

You must have measured to the top of the dovetail fitting on top of the camera which goes into the filter wheel or female dovetail adapter that you may use. Unless you have screwed a T thread adapter into it in which case that sounds about right.

I'd also check with users if 1.25 inch filters are large enough. Usually its 36mm. QSI cameras filter wheel is closer to the sensor and that's how they are able to use 1.25 inch filters. Even so 36mm no doubt has less vignetting.

Greg.

Last edited by gregbradley; 14-04-2015 at 05:48 PM.
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Old 14-04-2015, 02:30 PM
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I might also add in my experience flatteners are not super sensitive to spacing, reducers are. 4mm may not mean much especially on a KAF8300 sensor.

If the flattener is meant for a full frame sensor like the KAI 11002 then the 8300 which in digital camera terms is a Micro 4/3rds sensor should be fine. It may not even need a flattener as many scopes only require a flattener for APSc (25 x 16mm) or larger sensors.

The KAF 8300 is 17.96mm x 13.52mm.

Greg.
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Old 14-04-2015, 02:30 PM
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I thought that camera backfocus sounded large! My QHY22 is 15.5mm and SSG3 is 19mm.

Note that the TS filter slider gets the 1.25" filters really close to the T-threads -- much like the QSI design. As a result, there would be virtually no vignetting on a KAF-8300. (I use a smaller ICX694, and there is none.)
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Old 14-04-2015, 02:35 PM
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if you feel you need to go bigger than 1.25" there is a unmounted 36mm slider (10mm width) https://www.teleskop-express.de/shop...low-profi.html
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Old 14-04-2015, 03:42 PM
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graham.hobart (Graham stevens)
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back focus

That's very encouraging news actually thanks Greg and all
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