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Old 21-01-2015, 02:50 PM
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Clancy Lane (Phil)
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TSA120 Accessories

I would like to know which reducer or flattener you are using with your TSA120.

There is conflicting information on the various web sites as to which reducer or flattener suits the TSA120.

Also, the back focus distance being used for best results would be handy.

regards,

Phil
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Old 21-01-2015, 05:38 PM
garymck (Gary)
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Hi,
on my TSA120 I use the TOA35 Reducer at a distance of 83.7mm

With TOA35-RD reducer
Focal length 672mm
Focal ratio F/5.6
Image circle 40mm (60% non-vignetted)
Photo field 3.4░ @ 40mm image circle
Spots size 4Ám RMS @ center of field
6Ám RMS @ 10mm off-axis
13Ám RMS @ 20mm off-axis

specs here:
http://www.buytelescopes.com/t/takahashibackfocus
System chart here:
http://www.takahashi-europe.com/en/T...stemcharts.php
There appear to be a couple of versions, mine is cat no: TKA31580S
The difference is a sort of extension on the reducer.
Fields are essentially flat and stars are round to the edge of my ST8300C camera. I haven't tried any bigger chips.

Hope this helps
cheers
Gary

Last edited by garymck; 21-01-2015 at 05:50 PM.
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Old 21-01-2015, 06:30 PM
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Clancy Lane (Phil)
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Reducer

Thanks Gary,

I am using the same reducer with a STF8300 but not getting round stars at the edges.

Back focus is 83.7mm less 17.5mm for distance to chip.

Claude is sending me a flattener to see if that makes a difference.

cheers,

Phil
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Old 21-01-2015, 09:11 PM
garymck (Gary)
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Hi Phil,

where are you measuring the spacing from?

I have seen varying ideas about where to measure.

I can take a pic of my setup if you'd like and show you how mine is arranged.

The reducer should work properly. If you are not getting round stars at the edge, either the reducer is faulty or the spacing is incorrect.

cheers
Gary
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Old 21-01-2015, 10:44 PM
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Clancy Lane (Phil)
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Spacing

Gary,

A picture is worth a thousand words!

Thanks,

Phil
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Old 22-01-2015, 10:04 AM
garymck (Gary)
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Phil,

will post pic tonite sometime

Gary
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Old 22-01-2015, 11:20 AM
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Clancy Lane (Phil)
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Great!
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Old 22-01-2015, 06:06 PM
garymck (Gary)
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Hi,
pic attached - if its not clear enough let me know.

Also remember that if a reducer is too close, stars will look like spokes radiation from the centre of the pic. If the reducer is too far away, stars will look like arcs...

Hope this solves your problem.

cheers
Gary
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Old 22-01-2015, 07:39 PM
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Clancy Lane (Phil)
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Thanks

Thanks for going to all that trouble Gary!

I can now get the correct spacing happening and see if that makes an improvement.

I am sending the camera down to Peter Ward for a dessicant bake and Argon gas charge to overcome a frosting problem.

Hopefully, all should be sorted out before the next dark sky.

regards,

Phil
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