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Astrophotography and Sketching >> Beginning and Intermediate Imaging

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WhitenerJ
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Reged: 02/06/12

Loc: Waxahachie, Texas
Got a QHY8L on the way!!!
      #5659013 - 02/02/13 10:20 PM

Finally made the switch to a CCD. I'm getting a mint condition QHY8L and was wondering about spacing. I currently use a Canon T2i DSLR with a Astro Tech FF and IDAS LP filter. I have the T2i screwed into the FF and then the LP screwed into the other side of the FF. Would I do the same with the QHY8L? Just attach the FF to it? Or does it even need a FF? Any other tips for a first time CCD owner is appreciated.

Thanks, Jason


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zerro1
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Reged: 08/02/09

Loc: Smokey Point , 48.12°N 122.25...
Re: Got a QHY8L on the way!!! new [Re: WhitenerJ]
      #5659071 - 02/02/13 10:56 PM

I have a QHY8: yes the field flattener would still be desired. You will need a spacer between the flattener and the QHY8. The backfocus of a DSLR with a T-ring is just about perfect for a flattener, but CCD's don't start out as far back. I don't know the exact length off hand but I think my QHY8 starts out with 24mm from the top of the snout to the sensor surface.

Determine what that distance is, then figure out how much more space you need to equal the proper back focus for the field flattener(wich is probably around 55 to 56mm from lens to sensor surface)


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WhitenerJ
professor emeritus


Reged: 02/06/12

Loc: Waxahachie, Texas
Re: Got a QHY8L on the way!!! new [Re: zerro1]
      #5659075 - 02/02/13 10:58 PM

Yeah its 20mm. I'm not sure how to calculate what size spacer I would need??

Jason


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WhitenerJ
professor emeritus


Reged: 02/06/12

Loc: Waxahachie, Texas
Re: Got a QHY8L on the way!!! new [Re: WhitenerJ]
      #5659094 - 02/02/13 11:09 PM

Here is what Astronomics says:

Spacing from field flattener to film plane: Optimal spacing from the shoulder of the field flattener (where a T-ring threads on) to a cameras imaging sensor or film plane is 57mm +/- 4mm. The following DSLR camera body/T-ring combinations typically all fall within this optimum spacing range and generally should require no additional spacers.

A Canon EOS DSLR/T-ring combination typically has a T-ring front flange to camera sensor spacing of approximately 55.5mm, although this number is dependent on the thickness of the T-ring you use and cannot be guaranteed. (Without T-ring, the distance from the front flange of the camera body to the sensor is approximately 44mm by itself.)

A Minolta/Sony DSLR and T-ring combo typically has an approximately 54mm T-ring front flange to sensor spacing. The exact number is again dependent on the thickness of your T-ring. (The camera front flange to sensor distance by itself is approximately 43.5mm.)

A Nikon DSLR and T-ring combo typically has a total spacing of approximately 56mm. This number is again dependent on the T-ring thickness. (The camera front flange to sensor spacing is typically 46.5mm by itself.)

With CCD and DSI-type cameras, some experimentation with spacers will be necessary to achieve optimum performance, as these typically have much shorter camera front plate to sensor spacing than DSLR cameras.

Jason


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zerro1
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Reged: 08/02/09

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Re: Got a QHY8L on the way!!! new [Re: WhitenerJ]
      #5659106 - 02/02/13 11:17 PM

well you'd probably need something like 35mm to get a total of 55mm. The threads in the front of the camera are T-adapter threads. A 1 inch spacer and a 10mm spacer would get you pretty darn close.ScopeStuff

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CounterWeight
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Reged: 10/05/08

Loc: Palo alto, CA.
Re: Got a QHY8L on the way!!! new [Re: zerro1]
      #5659272 - 02/03/13 01:52 AM

Congrat's on the new CCD, look forward to your images.

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WhitenerJ
professor emeritus


Reged: 02/06/12

Loc: Waxahachie, Texas
Re: Got a QHY8L on the way!!! new [Re: zerro1]
      #5661601 - 02/04/13 11:46 AM

Quote:

well you'd probably need something like 35mm to get a total of 55mm. The threads in the front of the camera are T-adapter threads. A 1 inch spacer and a 10mm spacer would get you pretty darn close.ScopeStuff




Thanks Robert. Just ordered the two spacers. Thanks so much.

Jason


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