My astronomy project:
TS130 upgrade, 130 mm f/7 APO telescope

Content:

1. Mechanical
2. Electrical
3. Stands
4. Brackets hub and computer
5. Bracket motor focus driver
6. Triple DC/DC converter
7. Power splitter
8. Dew heater and lens cover
9. Telescope unbalance
10. To be continued

Note:
I take no responsibility or liability for what are written here, you use the information on your own risk!

8: Dew heater and lens cover

I want my dew heater to be power efficient, that cause some problem.

Dew heater power:

I use one of the outputs to power the Dew heater. Earlier they were connected direct to the battery power, about 13.6 Volt. I have over sized the dew heater band, for the triple lens APO refractor I get at 13.5 Volt 0.71 Amp or 9.6 Watt. For the guide telescope 0.35 Amp or 4.7 Watt. Together they take about 1 Ampere from the power source, too much if they are connected to a battery. I over size the dew heater because I planed for the future to have some sort of power regulator. Now with the extra Voltage output I can do test with different power to the dew heaters and see how low I can go without dew problem. If I reduce the voltage to 6 Volt I get these figures:

• APO refractor: 0.2 Amp (at 13.5 Volt), 1.6 Watt
• Guide telescope: 0.07 Amp (at 13.5 Volt), 1 Watt

There are of course some losses in the DC/DC converters. Maybe this can be enough to get rid of the dew on the front lenses. The dew heaters sits direct on the lens packet and are thermal isolated on the outside. With this I lower the current from the battery from 1 Amp to 0.26 Amp. If not enough power to the dew heater I can easily increase it.

Dew heater:

The dew heater is placed in the space between the dew shield and the lens cell. With that the dew heater has direct contact with the lens cell and not waste power to heat the whole telescope. The disadvantage is that there is a cable that must have some free space to let it out.

The original lens cover, a heavy peace of metal, 400 gram. It attaches on the dew shield, not the lens. Then there is no space for the cable to let it out.

I can solve it by design a new 3D-printed lens cover. This one attaches direct to the lens cell and then there is a gap between the dew shield and the lens cell where the cable can let out. Must be carefully that there is space enough from the lens cover to the front lens. Plastic is soft and could bend from external force and hit the front lens. I made some extra 3 mm space in the center to handle this.