ISS and Sun (10th Nov 2012)

Another alarm again, from CalSky service. This time ISS would have passed in front of Sun disk at Espoo / Finland, on 10th November 2012. Estimated time was approximately 12:33. I tried to follow, also this time - plans were not successful. Sky was full cloudy...

Nikon DSLR battery project, converter selection

Some background investigation is done now. Few samples from couple of DC/DC converter manufacturers, seems a good solution. One that I first noticed, was 75Watt series from Meanwell. Type MHB75-12S12 provides conversion from 4S LiPo cell voltage to constant output voltage. Most important spec are:

Half-brick size (2.28" 2.4" 0.5")
2:1 wide input range
Protections: Short circuit / Over current / Over voltage / Over temperature
High efficiency up to 89%
Built-in remote ON/OFF control
Built-in remote sense
Trimming output 10%
Five-sided shield metal case

For more detailed information, check MHB75-12S12 specs here. This type of converter, is in sale at Elfa Distrelec.

Images from Utö, Messier 27

Another image from trip to Utö... This time one planetary nebula (Messier 27), as wide angle image. It is visible in image upper left corner, as green dot. Difficult imaging indeed, conditions were windy and I had to struggle keeping my tripod on the ground. Image taken with Nikon D200, Nikkor AF-S G 50mm, at f/1.4, single 8s exposure at ISO2500. Unfortunately sensor produces lot of noise :-(

Nikon DSLR battery project, converter specs

This battery project, requires some additional electronics. Main purpose is to keep output voltage stable as the input voltage changes (depending on the amount of 4S LiPo cell discharge level).

There is many options and manufactures to look at... First I will check what local stores (like YE, Partco and Elfa) are selling. I will make later decisions, what voltage converter to use. Because of efficiency requirements, converter module based on the linear technology, is not an option here...

requirements:

-typical input voltage 14.8…16.8V DC

-output voltage 12...13.5V DC

-output current 6A continuous

-efficiency bigger than 80%

-input low voltage cut-off @ 14V => 4*3.5V for 4S LiPo

-output short circuit protected

-preferred as PCB model

-small size recommended

-small heatsink usage - ok

Seawater bow at Utö

My company photography club made a trip to Finland archipelago / Utö, at October 2012. There I got captured few images, related to optical phenomenon. Origin of seawater bow is same as in normal rainbow, light is reflected inside of seawater droplet.

Nikon DSLR battery project, 4S LiPo testing

Project test continues with 4S LiPo battery (Orion 14.8V 6400mAh). Only D200 camera was powered. I used four diodes as voltage dropper (1N3879 switching diode). This solution is only temporary, more sophisticated one would be low loss switch mode voltage converter....

camera setup
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Nikon D200
300/4.5 lens (at max aperture)
raw images used
ISO800
menu: high ISO NR, off
menu: long exposure NR, off
"M" mode used
bulb exposure selected
camera at room temp, approx +23C

exposure setup
************************
MC36 trigger used
delay 10sec
exposure 60sec
interval 62sec
no limit in image count

Results (27th Oct)
*******************************
Diodes heat up a bit during testing, without heat sink used. Test was stopped, when voltage per cell approx at 3.5V level (some cells were 3.2/3.3V, two last at 3.6V, slightly uneven discharging). Totally 472 images were taken. It corresponds to three times more images, than in 3S LiPo 2100mAh test setup.

Utö nightsky, milky way

In the the beginning of October 2012, we had a company's photography club trip to Utö. It is a small island, in southern Finnish archipelago.

Expected clear sky there, for astro imaging. Expectations were not completely fulfilled. Occasionally sky was clear and milky way visible. Definitely a place, where you need to visit again some day...

Milky way, Utö 10/2012