3.5" Prime Focus Field Flattener for 130GTX serial #130GTX-600 to 130GTX-899 (13035FF-2)
3.5" Prime Focus Field Flattener for 130GTX serial #130GTX-600 to 130GTX-899 (13035FF-2)
3.5" Prime Focus Field Flattener for 130GTX serial #130GTX-600 to 130GTX-899 (13035FF-2)


3.5" Prime Focus Field Flattener for 130GTX serial #130GTX-600 to 130GTX-899 (13035FF-2)

Regular price
$ 969.00
Sale price
$ 969.00
Unit price

This item is out of stock but you can place an order now and we’ll ship when it becomes available.

December 2022 - Two new field flatteners were introduced to optimize performance of all 130GTX scopes and 130GT scopes (upgraded to the 3.5" focuser).

Field flatteners are designed to accurately compensate for the inherent field curvature of a refractor lens. For each lens design there is an optimal spacing that works best for sharp focus over the specified field size. When the refractor lens design changes even slightly, the field flattener may need to have different spacing for highest performance. This is now especially important when using the newest CMOS cameras with pixel sizes of 3.76 microns and smaller.

When producing refractor objective lenses we make the best design possible using the glass index data supplied to us. For the first 3 runs of the GTX lenses (serial# 600 to 899) the glass was the same and we designed the field flattener for those lenses. In the latest runs starting in 2020 (serial# 900 to 1088 and later) the glass data was slightly different and produced a design with slightly different field curvature. Therefore the field flattener for these later production lenses is internally adjusted to produce the same high correction over the specified field size. This allows the external spacing to remain the same at 80.8mm with the supplied adapter. The flattener bodies will be labeled accordingly.

Choose the appropriate version for your refractor

For the 130GTX, look closely at your dew shield to determine which version you need. The serial number is difficult to see. 

Part # 13035FF-2

  • 130mm StarFire GTX serial # 130GTX-600 to 130GTX-888. These were shipped from 2015 to Dec 2019. The dew shield does NOT have a thumbscrew for lockdown.

Part # 13035FF-3

  • 130mm StarFire GTX serial # 130GTX-900 and higher. These were shipped from October 2020 to the present. The dew shield includes a thumbscrew for lockdown. 
  • 130 StarFire GT scope that has been upgraded to our 3.5" focuser. (04-22-23: Correction made to show that 13035FF-3 is the correct version for these scopes)

Backfocus spacing from the rear flange for both 13035FF-2 and 13035FF-3

With included 17mm Backfocus Spacer - 80.8 mm +/- 2.5 mm
Without included 17mm Backfocus Spacer - 97.8 mm +/- 2.5 mm

Conveniently, it uses the same camera adapters as the QUADTCC (and those of the flatteners and TCCs of the 160 and 175 Starfires). 

Field of View with 130 StarFire GTX or GT (with 3.5" Focuser)

Fully Illuminated Circle
35 mm Full Frame CCD

2.6” (65 mm)
18.0 x 13.5 mm
22.3 x 14.9 mm
36 x 24 mm
36.8 x 36.8 mm

4.3° (256 min.)
1.2° x .88° (71 x 53 min.)
1.5 ° x .98° (88 x 59 min.)
2.4° x 1.6° (142 x 97 min.)
2.4° x 2.4° (146 x 146 min.)


35mm SLR or DSR Camera - For full-frame Canon and Nikon DSLRs, we offer our large DSLR adapters with their large 1.875" (47.6mm) inside diameter bayonets: ADATCCEOS and ADATCCNIK.

CCD Camera - Choose the appropriate adapter to space the field flattener properly with your CCD camera. Consult the Diagrams and Instruction Sheets below for a wide variety of options.

13035FF-2 Includes

  • Field Flattener housing with optics optimized for this version
  • EXT327-17.0, 3.27" Backfocus Spacer Extension, 17mm
  • Two beautifully machined and black anodized covers
  • 13035FF-2 Decal to differentiate from similar assemblies

Select the Appropriate Adapter to use with Your Camera

These adapters are no longer available, but shown here in case you already own one. 

Diagrams and Instructions

Custom Adapters

If you need an adapter that is not listed above, we recommend that you contact PreciseParts.  Refer to the link for the spacing requirements document above.

Personal Upgrade Path

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