Atik Cameras

Author Topic: 383L Optical Back Focus  (Read 5447 times)

Dave Watson

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383L Optical Back Focus
« on: January 09, 2013, 06:33:00 pm »
Hi,

With regard to the 383L+ camera Atik specify the following

      Distance from top of T-thread to focal plane: Approx 17mm
      Optical window thickness: 2mm

You would normally add 1mm to the back focus of a scopes reducer for the refractive index of the glass filters, the question is should you also add ~1mm to compensate for the cameras optical window?

QSI, for instance, don't actually quote a mechanical sensor distance from the front of the camera, they actually quote the "Optical" distance which takes the refractive index of the optical window into account.

Regards,
     Dave
Takahashi FSQ-85EDX on EM200 Temma-2M mount, SSAG on ST-80 Guide Scope, Atik 383L mono camera and EFW2 Filter Wheel, Baader 2" filters, Lakeside Astro Focuser
Cartes du Ciel, PixInsight, Astroart, Artemis Capture, Photoshop CS5, Noel Carboni's Actions, Nik Software Tools

chrisjbaileyuk

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Re: 383L Optical Back Focus
« Reply #1 on: January 14, 2013, 02:42:11 pm »
I would say yes BUT I have always found it pays to experiment with FF distances by +/- 5mm as the quoted ideal spacing has never given me iideal flatness.

Chris

Dave Watson

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Re: 383L Optical Back Focus
« Reply #2 on: January 20, 2013, 05:58:32 pm »
Hi,

I have just been checking the mechanical drawings for the 383L camera and I have noticed that the wording used is "Optical Backfocus = ~17.5mm".

Can someone from Atik confirm that this OPTICAL backfocus does or does not take into account the reflective index (0.68mm) of the cameras optical window.

I am using a Tak FSQ85EDX with a the Q-Reducer that needs a metal backfocus distance of 72.2mm and with the Baby-Q this distance is very critical, a tolerance of +-0.5mm had been banded around but not confirmed.

Can anyone help.....thanks.

Regards,
   Dave
Takahashi FSQ-85EDX on EM200 Temma-2M mount, SSAG on ST-80 Guide Scope, Atik 383L mono camera and EFW2 Filter Wheel, Baader 2" filters, Lakeside Astro Focuser
Cartes du Ciel, PixInsight, Astroart, Artemis Capture, Photoshop CS5, Noel Carboni's Actions, Nik Software Tools

ruitripa

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Re: 383L Optical Back Focus
« Reply #3 on: January 22, 2013, 08:34:07 am »
Hi Dave,

Yes, it's optical distance, with both optical windows taken into account (CCD and camera's).

I find it very unlikely that a 0.5mm tolerance is required for a reducer...
Rui Tripa

Dave Watson

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Re: 383L Optical Back Focus
« Reply #4 on: January 22, 2013, 09:14:29 am »
Hi Rui,

Brilliant, thanks for your answer.

I agree with you about the 0.5mm, however, Tak America say it is very very critical but won't say exactly what the tolerance is.

Regards,
   Dave
Takahashi FSQ-85EDX on EM200 Temma-2M mount, SSAG on ST-80 Guide Scope, Atik 383L mono camera and EFW2 Filter Wheel, Baader 2" filters, Lakeside Astro Focuser
Cartes du Ciel, PixInsight, Astroart, Artemis Capture, Photoshop CS5, Noel Carboni's Actions, Nik Software Tools