It is always frustrating to see good weather pass without the opportunity to do some photography – especially astro-photography. So even if time does not permit a trip to the darker spots in reasonable distance from my home, it is worth a try to setup the telescope on the balcony.
This time, clouds cleared throughout the day (and happend to reappear before midnight). So I had to take the chance to spot Comet C/2018 Y1 Iwamoto. Unfortunately, I was unable to spot the comet through the eyepiece. The sky was far too bright (approximately 18mpss) watching straight over the citys light dome and having a 60% illuminated moon shining bright. Fortunately, through the camera I could make out a smudge, being brighter than the sky.
Processing the 180s subs with 1 hour total exposure time, I could achieve this result (compare to the unprocessed image!):
Image is a composite of 2 stacks (one aligned on stars, second aligned on comet). The comet moved more than 1.5 degrees during the 1 hour capturing time!
Above the comet: NGC 2903 (mag 9 galaxy)
At left: NGC 2916 (mag 12.1 galaxy)
Imaging setup: 800mm f/4.0 Newton, Sony A6000 full spectrum modified, UV/IR block filter, UHC filter, coma corrector (at wrong distance).
20x 180s @ ISO800, darks and flats
Conditions: +2°C, 60% moon, 18-18.5mpss sky in suburban location (with ample street light)
I had a bit of time to experiment with an H-alpha filter at home. Conditions are limiting astro-imaging as my balcony faces south. Living in the northern outskirts of a city, all the sky visible is significantly affected by city lights. This night, the sky was somewhat OK, reaching up to 18.7 to 19.5 mag/arcsec².
Using narrow band filters, like an H-alpha filter, the majority of the city lights may be cut away. This image (not perfectly focussed) shows, what is possible. It is a result of 12x240s, captured at ISO800 with my modified Sony A6000…
After converting my Sony A6000 camera to full spectrum capabilities, I finally got a sunny day to test the “new” camera, using a 720nm IR filter…
For quite a while I was looking for a camera, capable of better capturing the 656nm light of the H-alpha emissions from deep sky objects like gas nebulae or the suns prominences. Further more I was curious about infra red daylight photography. First, I thought I should buy an astronomy camera with very low noise due to active cooling. Unfortunately, such cameras are with a reasonable price tag. Further more, the astronomical cameras require an external power supply as well as a computer for control and data acquisition. Having such a camera would therefore only be reasonable, when I would spend several nights each month to capture images.
Then I thought, there are several regular DLSR cameras available (directly or by modification) which are capable of infrared or even full spectrum photography. These cameras or the modifications are available at attractive prices. Further more, the camera would be compact, easy to handle and suitable during daytime as well. There are 2 drawbacks in deep sky photography, which only really become relevant, when capturing very faint and distant objects at higher ambient temperatures:
- no active cooling
the camera has a higher thermal noise. To compensate for this, more images have to be captured
- less color or black and white resolution
Astronomical cameras usually have 16 Bits per channel, DSLRs have 12-14 Bits per channel. This is 4 to 16 times less detail, which is not so much of a problem, when capturing brighter objects
The modifications would imply to change the IR filter, which is attached in front of the imaging sensor. The whole procedure requires a service manual or a detailed description of how to disassemble the camera of choice. Fortunately I came across a very detailed step by step description of the disassembly process of the Sony Alpha 6000 camera. The description is (until now) available here from the company Lifepixel. They are also offering conversion services if you are not up to the task. One of the biggest challenges is to cope with the rather delicate ribbon cables. Pay as much attention as possible when disconnecting and connecting these cables! Further more, pay attention to the position of the On-Off power switch! If you change the position before reassembling, you may break the switch or the ribbon cable the switch sits on. If you do break this switch you are in serious trouble!
A hint for organization: During the modification process, one has to remove a whole lot of screws in different shapes and sizes. To keep all the screws and parts organized, I printed the complete step by step instructions with two steps per page (side by side). on the bottom of each page I attached a strip of masking tape, with the sticky side up. So I could place all the screws in the corresponding positions below each steps photo. Et voila! All parts are kept where they should be and matching the sequence.
Hint concerning electronics: You are dealing with highly sensitive electronic parts! You will create enough electrical charge to destroy the electronics when you move around! Use wrist band grounding wires and static precautions when operating with such sensitive devices!