July 2017 – BillD's corner of the net

Solar Imaging

Below you will find various images of our sun taken through a specifically designed solar telescope.

Never look at the sun without the right solar filters.

Not too long after I built the Serenity Observatory, they started renovating a block of housing units over the back fence. What do you know, they decided to add bright lights in the driveway that stay on all night. Nooooooo!!!! Bright light is not what I need next to an observatory where I am trying to look at the faintest objects in the night sky 🙁

So I decided to branch out and get into part of the hobby, that can be just as satisfying but less dependent on the nigh time conditions. I purchased a Solar Telescope. A solar scope has a specially designed filter system called an ‘Etalon’, that allows to you view a very specific bandwidth of light from the sun. With this we can view activity on the sun without going blind.

The day my solar scope arrived it was a clear bright sunny day. I walked out into the backyard and yelled “BLOCK THIS YOU BA#%^$DS”.
My Solar Imaging hobby was born.

As a side note, many years later, those lights or not used any more as even the residents thought they were too bright.

Venus Transit

During the once in a lifetime Venus Transit event, I was all setup with two solar telescopes HD recorders and other equipment. However the weather did not cooperate and it was totally overcast :-(.

I did manage to capture a few seconds of video here and there when a crack in the clouds allowed.

I spent most of my time looking at live feeds from other locations around the world.

The image below is extracted from a single frame of the video where there were the least amount of clouds.

Horse Head Nebula

I have tried in the past to get a reasonable image of the horse head nebula, but have never had much success due to the light pollution and lack of experience.

I wanted to take advantage of the relatively nice weather and started trying to image the Horse Head Nebula. Light pollution has become a problem in my area, and after several terrible results in the past using a colour camera, I decided to splurge and purchased a second hand QSI 583 mono camera with filters.

Man I should have done this sooner. This is the result of first light for this camera. The image below is not fantastic and is only monochrome but I am very happy with the amount of detail I can see in this test exposure from a suburb that is heavily light polluted now.

It was windy so the Active Optics unit was working overtime and there was a very bright moon very close to the target, so I used an Astrodon Ha filter. This is the result of 4×10 minute exposures through an ED80. There are many issues with the image for the fussy peeps, but it taken in difficult conditions with new gear and much cussing, as I was working out how to get it all working together. I can see more detail in the nebulous regions then I have ever managed to capture before. In the past the cloudy region around the horse head always looked plain and featureless. This time I have picked up more detail.

I now want to capture much more data as 40 mins is no where near enough for this faint object, but of course its gonna be cloudy for the next week hehe.

My First Narrow-band Colour Image

Here is my First ever colour image in Narrow Band using the Hubble Palette (kind of).
I am still learning how to process images taken through narrow band filters, so I probably got a bit carried away 🙂

Eta Carinae nebula: Total exposure time is approximately 1.5 hours with 6 x 5 minute exposures for each narrow band filter: Ha, Sii, and Oiii Filters.

Hydrogen-Alpha Filter vs Red Filter for Astro Imaging

Hydrogen Alpha Filters

To add to my equipment list (as you do), I decided to get a more sensitive Monochrome camera and a set of Narrowband Filters.

When I first entered this hobby I used one shot colour cameras in the past. Either an Canon 40D or the QHY8 cooled camera.

Mono cameras don’t do colour, as you can see from the images below. But this give a few advantages, such as being more sensitive and give sharper pictures (due to the fact that in colour cameras there are pixels next to each other for each RGB colour, so you get slightly reduced resolution per colour and the camera interpolates the pixels in between).

You still can create colour images with a monochrome camera, but you need to take individual pictures through different coloured filters and merge them, post processing to make the coloured image.

This does mean though that your are not limited to Red, Green, and Blue, light like a colour camera. You can use all sorts of specialised filters to pick very specific bandwidths of light.

What amazed me about using a narrowband Ha (hydrogen Alpha) filter, is that even though the Hydrogen Alpha filter captures a much narrower portion of the red band (hence the name: narrow-band), for the same amount of time it revealed much more nebula data depending on the target you are imaging.

The chart below shows the typical narrowband filters that are used for astrophotography. As you can see they only allow light in from very specific narrow areas of the spectrum. If you have ever seen pictures taken by the Hubble telescope, you have probably seen narrowband images. They often reveal more detail by showing light from specific wavelengths emitted by Hydrogen, Sodium and Oxygen. Colour pictures taken with these filters are often presented in what is called the Hubble Palette.

Below is an image of the Eta Carina nebula taken with a mono camera. There are two variants. Each is a single 5 minute exposure taken on the same night. The first is with a standard Photometric red filter, the second is with an Astrodon 6mm Ha filter. You can toggle between the two images by click on the right arrow on the side of the image.

Although the HA shows less stars, it shows a lot more of the nebula.