Laser cap for Polarscope - iOptron CEM 70 equatorial mount

Purpose

First step when aligning an equatorial mount is a rough alignment of the rotational axis, polaris in the northern hemisphere. The more precise the better for next steps. With a laser beam exactly along the axis of rotation rough polar alignment can be done easier, more comfortable and faster.

Dimensions

Designed for iOptron CEM 70. Maybe it suits on other iOptron CEM mounts too, measure the hole and compare it with the drawings.

If it you can use it on other model than a CEM 70 mount please leave a comment.

For use with a Laser with diameter 12 mm.

Usage

With this designed laser cap you'll get a laser beam in direction of the rotational axis of the mount. Switching on the laser and following the beam (with the head just next to the laser) and you can see the laser point “in the sky” (of course not, due to fine particles or [hopefully not too much] vapour/water droplets). Rotating the tripod that the laser beam points near polaris and do a finer adjustment in azimuth and altitude and you are ready for either align more exactly with the polar scope or for two/three (recommended for more precise tracking) star alignment.
 

Laser

Take care that the laser light does not shine in your eyes! Even tough only 1 mW is allowed in the EU which (usually!!) does not harm eyes, don't look in a laser. The risk of eye damage is not worth it.

I like green lasers best for using in the night sky. According to EU-law 1 mW is allowed, that is enough. I can't imagine that there is a benefit with more laser power. Imagine that a laser with 5 mW is eye safe after about 16 m (52 ft) for unintentional exposure! With the head near the laser and following the beam a 1 mW Laser is good to see and does what it should. 

I bought a laser module with diameter 12 mm and connected it to the battery pack with a connector. For example this one by Amazon: Green laser 12mm
 Of course you can find a lot of lasers at Chinese shopping sites (aliexpress). Be careful, you do not always get a safe product or exactly what it was specified. You can easily order a 35 mW laser for less than 10 €. In EU it is forbidden to import laser with more than 1 mW, the buyer is responsible not the seller! If delivered to EU it also happens sometimes (often) that products are labelled with the CE and therefore appear to be compliant with the law but in reality they are not!

Probably even Amazon orders from China.

Print

PETG recommended, weight ~ 30 grams

Nozzle 0.4 mm, Layer height 0.2 mm, Variable layer height recommended (Thread), 3 Wall lines, 3 top and bottom shell layers, infill 10 %, no brim, no support.

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