Takahashi NJP

2023, Oct 28

The NJP Temma2 is a wonderful mount, with antique electronics. This shows how to upgrade it with a modern TeenAstro controller in a reversible way, without modifying any of the connectors. The original Temma2 electronics box is removed and replaced by a custom box.

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It has a classical gear arrangement. Both RA and DEC axes have the same motor (NEMA17, 200 steps/rev), reducer (18:1) and gears (60:24). The RA axis wheel has 240 teeth, and the DEC has 144 teeth. The resulting gear ratios are:

RA: 18 x 2.5 x 240 = 10800

DEC: 18 x 2.5 x 144 = 6480

The encoders on the worm are ABN type with 300 pulses/rev. At sidereal speed, on the RA axis, we get one A/B pulse every 0.8333 second and one N pulse every 250 seconds.

At this time, I use a temporary aluminium plate with an external TeenAstro. Eventually it will be replaced by a small TeenAstro board attached to the mount.

I made simple 4-wire adapters to plug the motors. The Temma2 has Rose connectors that are mechanically very close to similar Molex models.
The encoders connectors have 6 pins at 1.27mm pitch. It is difficult, but possible to make an adapter to the easier 2.54mm pitch. However I have not yet figured out how Takahashi uses them. Of course they are not absolute, so they cannot be used like modern 10-Micron or Astrophysics mounts, but they might be used to improve tracking (more on this later).

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The mount works fine. The original Temma2 electronics are rated to 350x. I set the maximum slewing speed to 420x, with 16 microsteps (no need to use a bigger value with such a high gear). In Motion Controller mode (SPI only), it would be possible to run faster, but this would push the motors way beyond their rated maximum speed.


M31

2023, Oct 3

M31: Andromeda Galaxy
Nikkor 180mm@F4, ASI533MC, 48x300sec AP600 mount with TeenAstro
UV/IR Filter
PixInsight

This Nikkor lens is pretty good, but it leaves blue halos around bright stars. I need to find out how to get rid of them.


Lunar Eclipse - 16 may 2022

2022, May 16

Borg 90FL@F5.6, Nikon D750, 1 to 2 second exposures





Leo Triplet

2022, Apr 28

M65, M66 and NGC3628: Leo Triplet
Borg 90FL@F4, ASI533MC, 24x300sec
UV/IR Filter
PixInsight