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Originally Posted by carthick1000 This is worrying to see such unsafe pictures. Every small object sitting unsecured is a projectile in a crash. No matter how many airbags you have, it is not safe at all. |
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Originally Posted by itwasntme Axe77/graaja: I think BMW sells cargo nets as does Skoda. Why not pick up a set because I think the attachment points are already present in boot floor and walls? Just a thought - could be worth it given the steady outstation trips you guys do. |
Thank you for pointing this. I usually take care not to leave lose objects lying around. But still this is a very valid point. I will look into getting cargo nets and packing things more safely.
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Originally Posted by slayer23 Fantastic post. Learned a lot of things across topics. |
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Originally Posted by AKSarkar1 Loved this thread! Awesome to see your BMW being actually used and not just sitting in a garage, kudos to you for that! ... |
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Originally Posted by Arjun Bharadwaj The last I remember seeing these kind of photos was probably in a science textbook or an encyclopedia and most times I used to think these galaxy photos are imaginary/theoretical... |
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Originally Posted by gulerianeeraj What lovely photographs. Kudos to you and heartiest congratulations on the GT. ![Clapping](https://www.team-bhp.com/forum/images/smilies/Clapping.gif) |
slayer23, AKSarkar1, Arjun Bharadwaj, gulerianeeraj, Thank you so much for your kind words
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Originally Posted by adi_sun Jaw dropping photographs !!
The gear in the first few pictures all packed up made me thing what dinosaur are you packing !! Do share some more photographs and some details on what goes in to get these clicks; if not in this thread a new thread would be helpful. |
I will try to give a high level description of the equipment, software and the process involved in shooting photographs of deep space objects.
In astrophotography, we are photographing objects that are astronomically far away from us. The objects we see today are from light rays that left the objects thousands, hundred thousands, millions and billions of years before. These objects are so faint that our eyes - even when we view these through powerful telescopes, cannot resolve the color information. To resolve color information, we have to collect light for long durations, sometimes in hours. To do this we do multiple exposures of shorter durations like 2 minutes, 3 minutes or 5 minutes etc. and add all these pictures. The equipment we use in astrophotography work together to achieve this. Below is the picture of the setup I use. I would call this is somewhat in between a beginner to intermediate setup.
Equatorial Mount: All celestial objects move across the sky due to the rotation of earth. If I do a 3 minute exposure of an object, it will have moved a lot in that 3 minutes. Because of this stars will not be a point, but will be a line. So we need to move the camera at the same speed as the objects move in the sky. This is called tracking. The equatorial mount does this. The mount also rotates at the speed the earth rotates, thus keeping the objects in the same place on the image sensor of the camera. A good equatorial mount can keep the objects within a pixel for as long as 1 minute or even more. The particular mount I have is EQ6-R Pro made by a company called Skywatcher. It is an excellent mid segment mount.
Main Scope: This is the telescope that collects light from the objects and focuses on to the sensor of the camera. There are many types of telescopes like Newtonian reflectors, refractors, schmitt cassegranian etc. These telescopes come in various sizes and focal lengths. The larger the focal length, the farther the telescope can see. The larger the aperture, the more light they can collect. In general, for wide field astrophotography (shooting large objects like nebulae, large galaxies etc), refractor telescopes are preferred. For smaller objects like planets and distant objects we need longer focal lengths. Refractors become prohibitively expensive at these focal lengths and reflectors are used. The telescope I have is Gran Tourismo 81 (yes, another GT) made by William Optics. It has a focal length of 480mm. I also have a 6" Schmidt Cassegranian telescope which I will be using for shooting smaller objects.
Main Camera: The camera records the light collected by the telescope. We can use a cell phone, or a DSLR or a dedicated astrophotography CCD/CMOS cameras. As we are shooting very faint objects with very long exposures in minutes, the noise performance of the camera is very important. Cell phone cameras can be used to shoot bright objects like moon or planets. But to shoot dull deep space objects like nebulae and galaxies, we need good DSLRs or dedicated CMOS/CCD cameras. The camera I have is ASI 2600MC Pro, a dedicated astrophotography camera made by a company called ZWO. It has an 26 megapixel APS-C sensor, and a cooler that can cool the sensor to 35 degrees below ambient. This is an important feature in astrophotgraphy cameras. The lower the temperature, the lower the noise and better the picture. We usually shoot pictures at 0, -5 or -10 degrees depending on the ambient temperature.
Guide scope and guide camera: Though a good equatorial mount can track objects within a pixel for long durations like a minute, they will still have some drift and this drift will become noticeable when doing exposures like 3, 5 or 10 minutes or more. This is where a guide scope and a guide camera come in. The guide scope has a shorter focal length and the guide camera has a smaller sensor size. A software chooses some random star from the guide camera and keeps tracking how the star is moving in the frame. Whenever the star drifts on the frame, it issues a correction signal to the equatorial mount. This correction signal along with the equatorial mount's tracking will keep the objects in the same place even for an hour. Below is a graph showing the guide setup working. The solid lines show how the equatorial mount is drifting off in two axes. Whenever there is a drift, the guide software issues the correction pulses (the short +ve and -ve pulses ). As soon as the pulse is issued, you can see how the solid line turns back.
Electronic auto focuser: For good photographs, we need to get a perfect focus with pointed stars. We generally use a manual focus technique using something called a bahtinov's mask. When doing multiple exposures throughout the night, it is sometimes good to check the focus after say every two hours, or between objects etc. An electronic auto focuser can be used to achieve this. An auto focuser has a motor that is coupled to the focus shaft of the telescope. A software will occasionally analyze the focus of the acquired image and and drive the motor to get the perfect focus.
Mini PC: To control all these equipment many software are required. We can either use a laptop running these software or use a mini PC or even a Raspberry Pi to control the equipment. I have chosesn to use an Intel Mini PC with an i7 processor to run all the software. Once I set up all the equipment in my terrace, I can access this Mini PC through remote desktop from inside my home and control the equipment to point to various objects in the sky, set up exposure times etc.
What I have described above is the hardware part that is used to acquire the images. We also use many software.
Some software are used to control the hardware during image acquisition. Some well known software for image acquisition are SharpCap Pro, APT, N.I.N.A, SGP (Sequence Generator Pro). These software are used to turn the telescope to any chosen object (it is very difficult to manually point to these objects as they are so small), focus on the object and program the exposure sequence like how many exposures to take, length of the exposure, camera settings during the exposure etc. I use a software called N.I.N.A. Below are a couple of screenshots of the software that I access using remote desktop from my PC.
This shows the sequence of exposures. In this case, I have programmed 30 exposures of 120 seconds, 20 exposures of 30 seconds and 20 exposures of 15 seconds.
This screen shows the status of image acquisition.
Once image acquisition is complete, we use other software to integrate multiple images. This is called stacking. Some software used for stacking are Deep Sky Stacker, Pixinsight etc. They integrate multiple exposures, align all the images using reference stars and create a single final image. After this we do some post processing on this integrated image to remove noise, adjust histogram etc. This can be done using software like Photoshop, Gimp, Pixinsight etc.
I use Pixinsight as a single tool to do both stacking and post processing. Below screenshot is a "work in progress" of processing in Pixinsight.
To close this post, here is an image I took over the last two days. This object is called Rosette nebula which is a birthplace of many stars and lies about 5200 light years from the earth. This means what we see in this picture is actually what this nebula was 5200 years back, essentially history. This image is an integration of 90 x 3 minute exposures captured over two nights.
![A GT joins a GT - Estoril Blue BMW 330i GT M-Sport comes home - EDIT: 100,000 kilometers up-rosette-nebula-v3.jpg](https://www.team-bhp.com/forum/attachments/long-term-ownership-reviews/2134599d1688021317t-gt-joins-gt-estoril-blue-bmw-330i-gt-m-sport-comes-home-edit-100-000-kilometers-up-rosette-nebula-v3.jpg)