Chromosphere using a PST and DSLR...

In this tutorial, we will be looking at how to take a one shot full disc image and turn it into a Chromosphere using a standard PST and Canon DSLR. The main problem when trying to image using a PST is the fact that there is not enough 'in' focus.  To overcome this problem you need to use a barlow or powermate, this also has the added benefit that you get a larger image on the chip.

A good start is to screw the lens of a barlow onto the end of a standard 1.25 nose piece, above is a Tal x 3 barlow lens screwed onto the nose, it only screws on about the first couple of threads as they don't match up, but it does work very well but only gives a 3/4 full disc image.  Another one that my friend Grant found to work is the Meade #140 x2 barlow.
(If you have got others to work, please let me know and I can add them to the list)...
The filter in the pics is
a 'Baader Neodymlum & IR Cut Filter' I love this filter as it cleans and sharpens the PST image.
(really gives a WOW factor....)
If using a barlow lens that has no filter thread on the front (such as the Tal x 3) a nifty little tip is that you can screw the filter into the back of the nose... (pic below)
Just make sure that it does not stick out past the t adapter as if it does it can damage the flip of the mirror in the camera, the neo filter as show below is fine on the Canon 1000D. (Also make sure it's secure so it does not fall off and smash the flip mirror)....

Sometimes this still does not give enough 'in' focus, so the only way to get that extra bit is to find a nose piece that has a very thin lip on it, as in the photo below.

Or you can file/dremmel off the lip of a standard nose fitting to get the barlow/powermate to fit as flush to the t mount as you can. This then gives the extra needed to get focus. 

For a full disc image I use a tele vue 2.5 x Powermate.

As you can see from the photo, the powermate/barlow fits right up to the t-mount adapter.  The 2.5x powermate give a nice crisp image and also a full disc.   This setup gives a full disc and also allows you to keep the filter in place.

With the 2.5x powermate you can buy the extra T ring to attach it direct to the t mount, this is great as you don't have to file/trim or find a nose piece with no lip, the only drawback is that you can't use the filter, as the powermate does'nt have a filter thread.
Once the DSLR is fitted into the eyepiece holder of the PST (don't forget to put the strap of the DSLR over a secure part of the mount/over the PST tube etc., this stops the DSLR dropping to the floor when the mount is moved).
In full Sun light it is very hard to see the screen of the DSLR, so a towel or blanket placed over the head and covering the DSLR cuts out all the stray light and makes it a lot easier to view, as they used to do with the old plate cameras..
Using a ISO of about 400 + it's easy to see the Sun on the screen. 
Set the colour to Mono in the menu as you're imaging in narrow HA so no colour is needed.
Using the zoom function, locate the rim or prom on the disc and get fine focus on this.
Play with the exposure and ISO until you have a good image of the disc. (The sample here is on a poor seeing day with light cloud, but shows you the basics)

This is the sort of image you should have once downloaded to the computer.   You will notice the sweet spot of the PST shows up as a lighter halo to the left on this image, but can be anywhere depending on how the PST is tuned.   In the liveview you can move the image round the screen to get the best overall image.
After rotating and cropping the image, play with the brightness and contrast sliders in your editing software (I use Gimp as it's free and does a good job) until you get a nice even balance of colours.

Next is the use of the magic wand selection tool, try setting it to 15 and feather the edges by about 10. Then click inside the disc near to the rim, and it should mask the inside edge of the disc, if it doesn't, try setting it to 15 and try again. Once it has a circle that you're happy with, use the bucket fill tool and colour to black, and click inside the disc, this will then blacken out the inner circle.  Click the merge images and then flatten them.

Now the colour part, this is down to personal taste, but a good start is to use the colour balance with the settings at Cyan 17, Magenta -1 and Yellow at -61.....Then  Hue-Saturation, in this set the Saturation to -30 and Hue and Lightness to 0....... Once you get a colour you like, this can be saved for future images.
That's about it, you can if you want create a frame to put it in and add data to it.....

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