Astronomy and DSLR Astrophotography Blog

A lot of astrophotograpers decide to make a modification of their cameras. The reason is that filter in front of CMOS or CCS sensor blocks almost all the H-α part of spectrum due to balancing the colors for daylight photography. But this is not suitable for astrophotography because almost all the nebulas consist of the Hydrogen and this light is cutted off just some millimeters in front of the sensor. If we remove that filter then we get much better response of the red color.

Since the Canon Rebel is the most common camera used between enthusiastic astrophotographers I’ll try to suggest some good links of step-by-step tutorials which guide you thought the process.

1. Canon Digital Rebel (300D) Modification
   Good tutorial with sample images before and after modification. For Rebel (300D).
2. ash’s Modified Digital Rebel XT Page
   Very nice tutorial for modification of Rebel XT (350D). I have done modification of my Rebel XT with this guide and he survived the operation!
3. Canon Digital Rebel XSi (450D) Modification
   Good guide with pictures and everything well explained for Rebel XSi (450D).
4. Canon Digital Rebel (300D) Peltier Modification
   Guide how attach Peltier cooling element into Rebel. Works good for long-exposure astrophotography.
5. Another Digital Rebel XT (350D) Modification
   Just another Digital Rebel XT mod. Maybe someone finds it useful.

For the end I am presenting one of my images after the modification. The Veil Nebula, NGC 6992:

The Veil nebula (NGC 6992) @ Primož Cigler

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Canon’s low-priced range of Digital Single Lens Reflexive (DSLR) cameras are extremely popular between amateur astrophotographers. In this group we can find the following cameras as they appeared on the market:

• Canon Rebel (300D)
• Canon Rebel XT (350D)
• Canon Rebel XTi (400D)
• Canon Rebel XSi (450D)

The first Canon Rebel was published in 2003 and since then the astrophotography began also more popular and reachable to everyone.
There is a lot of reasons why Rebels are so popular. I’ll try to emphasise the most important:

1. PRICE
   Until the announcement of Canon Rebel there were no other cameras for the reasonably good price delivering all the specifications that are needed for astrophotography. There were only a few astronomy CCD cameras available for high prices. With the Rebel everything changed. It has all the main features needed for astrophotography and it is providing excellent picture quality for low amount of money.
2. SENSOR SIZE
   The Rebels’ sensors are the APS-C size (22.7 x 15.1mm) witch works pretty well for astrophotography because it covers a large area on the sky with any optical instrument.
3. PREVIEW ON LCD
   We are always able to check the focus, the object, field of view etc. on the LCD. It’s one of the most useful things and here DSLRs beats even much more expensive CCD cameras.
4. HIGH SENSITIVITY
   The ISO setting ranges from ISO100 to ISO1600 and more. The picture quality is still OK at high ISO settings and with combining we can get practically noiseless images.
5. PICTURE QUALITY
   Picture quality is just outstanding for this price. At high ISO setting and long exposures the pictures are still useful.
6. DAYLIGHT PHOTOGRAPHY
   The camera you use for astrophotography can still be used for daylight photography unless you modified it. That saves you a lot of money since you don’t need two cameras – one for astrophotography and another for daylight photography.
7. DIGITAL FORMAT
   It’s quite obvious that images from digital camera are in digital format, isn’t is ? Digital pictures are much more fond for post-processing then scanned film.
8. MODIFICATION
   With modifications we can get out even more from Rebels – if we remove the filter in front of the CMOS sensor the camera becomes much more sensitive for H-α part of spectrum and we are able to get more information with shorter exposures.
9. VIEWFINDER
   Viewfinder is extremely handy when we are positioning the camera to deep-sky object. It saves us a lot of time. With the CCDs we are forced to take multiple exposures just to specify the right location and angle of the camera and that’s really time-consuming.
10. CONNECTIVITY WITH PC
    All the Rebels can be remotely controlled with a PC. They comes with the most basic software but on the web you can find a software that turns your Canon Rebel to the fully remote camera!

Of course, there are not only advantages of DSLRs. They have many cons and their quality is not on the same level as CCDs but with some skills we can turn them for really good astrocameras.

Thanks for reading!

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The light pollution is becoming more and more annoying thing more or less all over the world. Astronomers are the ones who suffers due to that more than any others. The problem is that there are every year less locations for observing and photographing the untouched sky. Well, some manufactures of astronomy equipment decided to produce filters that suppress the light pollution.

On the beginning of summer 2008 I figured out that the situation from the point of light pollution from my backyard is so bad that I need the solution. On the web I found some filters that suppress the light pollution but no one good review of them.

In the end I decided for IDAS LPS filter of Hutec. Because I was pretty sure I will be using just for astrophotography I decided for front-filter (look at this figure) which can be placed directly in the camera’s body so I can use it with lenses also and not just with the telescope. The version of filter is P2, that means that is the most suitable for astrophotography in prime focus.

The filter arrived on June and costed approximately 250 eur here in Europe, in USA it’s a bit cheaper. The first impression was something like: “250 eur for such a piece of glass?!??”. But after a first-light I changed my opinion. It is worth every single pennie! It works just the best for me, my backyard turned to the very good astrophotography place. It has no affect to sharpness of the image. I use it with my Canon 350D (Baader mod.) and also both sample pictures are captured with this equipment. The telescope was William Optics SuperAPO 80/480 with TeleVue reducer/flattener 0.8x. The picture without filter is out of focus because when I removed the filter I didn’t refocused. Anyway, it represents the affect of filter. Both pictures are captured at the same settings: f/4.8, ISO1600, 120s, RAW, WB(2850, -30), imported and exported with Lightroom.

The image without Hutech IDAS LPS filter

The image with Hutech IDAS LPS filter

It’s quite obvius what the filter does.

I have also measured the Mean of these two pictures. The median value for the picture without IDAS LPS is 118 whereas the median for picture with IDAS LPS filter is 52.

That’s all, hope that this article will help someone to decide what to buy or not to buy.

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