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Dimensions and Specifications

Straight-vane secondary mounts

The following specifications are provided as general design and planning aids, and can be particularly useful when determining how a ProtoStar secondary mount will fit an existing telescope.

0.75", 1.00", and 1.30" models

The 0.75", 1.00", and 1.30" secondary mounts are all available with 3-vane spiders, and the 1.00" and 1.30" models are available with 4-vane spiders. The antidew heater option is not available on these smaller secondary mounts.

Metric spider versions use M5-0.8 threading for both the collimation screws and the vane lugs (see options).

mirror
holder
size

A
overhang
(incl. mirror)

B
max vane
width

C
stem size
& thread

D
lug
thread

lug
length

no. of lugs
per vane

approx
weight
w/o mirror

0.75"

1.88"
(48 mm)

0.9"
(22.9 mm)

1/4-20 tpi

#8-32 or
M5-0.8 (metric option)

0.5"
(12.7 mm)

1

30 g

1.00"

2.13"
(54 mm)

0.9"
(22.9 mm)

1/4-20 tpi

#8-32 or
M5-0.8 (metric option)

0.5"
(12.7 mm)

1

42 g

1.30"

2.25"
(57 mm)

0.9"
(22.9 mm)

1/4-20 tpi

#8-32 or
M5-0.8 (metric option)

0.5"
(12.7 mm)

1

76 g


1.52", 1.83", and 2.14" models

The 1.52", 1.83", and 2.14" secondary mounts are all available with 4-vane or 3-vane spiders. The antidew heater option is available on all models. The spiders have one lug per vane for tube diameters under 12", and two lugs per vane for larger spiders.

Metric spider versions use M5-0.8 threading for both the collimation screws and the vane lugs (see options).

mirror
holder
size

A
overhang
(incl. mirror)

B
max vane
width

C
stem size
& thread

D
lug
thread

lug
length

no. of lugs
per vane

approx
weight
w/o mirror

1.52"

3.00"
(76 mm)

1.4"
(35.6 mm)

5/16-18 tpi

#8-32 or
M5-0.8 (metric option)

0.5"
(12.7 mm)

1 up to 12" tube
ID; 2 for larger IDs

140 g

1.83"

3.25"
(83 mm)

1.4"
(35.6 mm)

3/8-16 tpi

#8-32 or
M5-0.8 (metric option)

0.5"
(12.7 mm)

1 up to 12" tube
ID; 2 for larger IDs

190 g

2.14"

3.63"
(92 mm)

1.4"
(35.6 mm)

3/8-16 tpi

#8-32 or
M5-0.8 (metric option)

0.5"
(12.7 mm)

1 up to 12" tube
ID; 2 for larger IDs

260 g


2.60", 3.10", 3.50", and 4.00" models

The 2.60", 3.10", 3.50", and 4.00" secondary mounts are available with 4-vane spiders. A 3-vane spider is available for the 2.60" mount for tube diameters up to 18". The antidew heater option is available on all models. All models have two lugs per vane. The 3.50" and 4.00" models are heavy duty versions.

Metric spider versions use M5-0.8 threading for both the collimation screws and the vane lugs (see options).

mirror
holder
size

A
overhang
(incl. mirror)

B
max vane
width

C
stem size
& thread

D
lug
thread

E
lug
spacing

lug
length

no. of lugs
per vane

approx
weight
w/o mirror

2.60"

4.63"
(117 mm)

1.8"
(45.7 mm)

1/2-13 tpi

#8-32 or
M5-0.8 (metric option)

0.5"
(12.7 mm)

0.5"
(12.7 mm)

2

350 g

3.10"

4.88"
(124 mm)

1.8"
(45.7 mm)

1/2-13 tpi

#8-32 or
M5-0.8 (metric option)

0.5"
(12.7 mm)

0.5"
(12.7 mm)

2

510 g

3.50"(1)

na (2)

3.0"
(76 mm)

1/2-13 tpi

#8-32 or
M5-0.8 (metric option)

1.25"
(31.8 mm)

0.5"
(12.7 mm)

2

1005 g

4.00"(1)

na (2)

3.0"
(76 mm)

1/2-13 tpi

#8-32 or
M5-0.8 (metric option)

1.25"
(31.8 mm)

0.5"
(12.7 mm)

2

1160 g

Footnotes:

(1) Heavy-duty spider design features wider vanes, thicker vane material, and larger spider hub.

(2) For the 3.50" and 4.00" mounts, mirror thicknesses vary too much from different manufacturers, so this dimension should be measured directly with your secondary mirror installed.

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