Category : The Sun

Transit of Mercury 2016

Today was the transit of Mercury 2016. I had two set-ups today – my Coronado Ha PST telescope with my ASI120-MMS camera in it and my Meade 127mm refractor with a white light filter on it, on this scope I tried my Atik 460 and Canon DSLR but none of these images came out that well, these cameras are just not made for solar imaging, all images from these cameras were too bright.

I imaged the transit of Mercury with the PST on its own and with a Televue 2.5x Powermate. The problem with the PST is that it does not do well when trying to image the whole of the solar surface as the etalon does not cover the whole of the solar disc so you can get bright and dim areas of the surface. The Coronado PST works best with the Televue 2.5x Powermate.

Previously I used a lot of the Imaging Source DMK CCD cameras, and I never really suffered from Newton’s rings. Thing is now I have an ASI120 camera which is a CMOS camera, it does seem to suffer badly with Newton’s rings. When trying to remove the rings it seems you can either buy a tilt adaptor or take flat frames.

I have always taken flat frames for deep sky imaging, but never for solar, lunar or planetary imaging. I did try taking some dark frames to remove the Newton’s rings but that never worked. Taking flat frames does work though.

I only tried taking flat frames when I took zoomed in images of the Sun with the 2.5x Powermate. You begin taking your normal video and then keep all the settings the same but just de-focus your telescope and then take a video of exactly the same length of time.

All the work is then carried out in AutoStakkert. Begin by loading your video of the de-focused Sun and select “Image Calibration” > “Create Master Frame” – then you will be asked to name the TIF file. Once completed you can then select “Image Calibration” > “Load Master Flat” and load your TIF file. Then load your AVI or SER video file and process it normally. You will now see all your Newton’s Rings disappear and your dust bunnies or doughnuts will also have disappeared.

It’s a pain to keep having to remember to take flat frame videos all the time, but as long as you don’t change your field of view or exposure, gamma or gain settings you should be OK and be able to use the same flat frames.

Mercury Transit

Solar Surface Details

Mercury on this is at the top right hand corner, taken very close to first contact.

full solar mercury transit

The Sun in Hydrogren Alpha with Coronado PST

This image of the Solar disc was taken on Saturday 6th July 2013. It was taken using a standard Coronado PST and an Imaging Source DMK21 AU618 Mono camera. I did use a Short ‘C’ mount adaptor in order to allow the PST to gain focus, without having to use a Barlow lens.

As the DMK21 is only 640×480 I have to take 4 videos and then process each one in turn using Registax 6. I then imported them into Photoshop and used the Photomerge software to align them all up into one image. I then gave the mono image some false colour.

H-Alpha Image with DMK21-AU618

Received my new Imaging Source DMK21-AU618 camera the other day, today was my first chance to use it. There was a lot of cloud about today and I did not start imaging until 3pm which was a bit late in the day, but I am happy with the images I took.

One thing I did try was a short C mount adaptor, as usually I use a 2.5x Powermate as I thought that was the only way to achieve focus on the Coronado PST. But now the short C mount does allow you to focus on the PST without the need of a Barlow. This now means that I can image a whole solar disc by stitching together just 3 images.

Sun with Coronado PST

Solar Image with Coronado PST and Canon SLR

I decided to have a look at the Sun today whilst it was out for a change and not cloudy. The weather this summer in 2011 in the UK has been terrible cloudy by day and cloudy by night.

I began by putting my standard Coronado PST on my Manfrotto tripod and put in my 9mm eyepiece, I had a good look around and decided to try and attach my Canon 550D to the telescope and take an image. I had not done this before as I usually image with my PST on my EQ6 mount and then use my Imaging Source DMK21 camera to do the imaging. The only problem with doing this is that the CCD chip is quite small at 640×480 so you can never get the whole of the solar disc in the image, you would need to create a mosiac. This is something you don’t have to do the with the large CCD sensor of a modern DSLR camera.

Anyway, I added my T-ring to my DSLR and attached a 1.25″ nosepiece and my trusty 2.5x Televue Powermate. I managed to get the image in rough focus and take a few images, not expecting much. But I was pleasantly surprised to see that I had managed to capture prominances in one image and surface solar detail in the other images.

This was not guided and it was clumsily handheld, I did set the 2 second timer on the SLR to try and cut down on the camera shake, as my Manfrotto tripod could barely hold the weight of the PST, DSLR and Powermate.

Prominances layer: 1/125 exposure, auto ISO (it selected ISO1000)
Surface detail layer: 1/1000 exposure, auto ISO (it selected ISO1600)

The two images were then put on top of each other and tweaked in Photoshop.

So there could be some more work to do in order to lower the ISO setting to try and reduce the noise, but otherwise I was very happy considering it was handheld and not guided.

Click on the image below to enlarge it.

Solar Image with Coronado PST and Canon 550D Handheld Unguided

Coronado PST Images

Well I went out and purchased a Coronado PST from ScopesNSkies the other week and was itching to try it out, but it seems since I have bought it, it’s now cloudy every day – typical! I did get to put it on my NEQ6 mount and do some imaging one Sunday morning though.

I used my Televue Powermate 2.5x with my DMK21 camera for these shots. The video was stacked using Registax 6.

These images show the Sun in Hydrogen Alpha or Ha. I think for the price of the scope it does not do a bad job. This a basic entry level version of the Coronado PST which can be purchased for just over £450 new.

I was not so happy with the first image, I took two images for this shot and then layered them in Photoshop, but to me they still look a bit fake, perhaps because I added the false colour first to each and then layered them, next time I will layer them first and then flatten the image and add the false colour.

Coronado PST Image 2.5x Powermate and DMK21

Coronado PST with Televue Powermate 2.5x and DMK21 Camera

But overall I am quite happy with my first efforts, I have also subsequently learnt how to take flats against the Sun, so I need to subtract the flats next time to remove the dust bunnies. Then I just need more Sun and more free time!

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