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NGC7635 The Bubble Nebula


Darth Takahashi
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This is the first such image from my Mewlon. As most may know I have struggled to use the Mewlon from my location, since it need excellent skys to get the most from it. However, I have spent a lot on this telescope and definately want to get more use under my skys with it, therefore, back in October 2012 I modified it with the new corrector baffle system designed to eliminate coma.

The Mewlon is a Dall-kirham cassegain telescope and these have the best on axis optical performance; however, they do have off-axis coma inherrent in their design. The corrector baffle solves this issue and lowers the effective focal length, which is what I was interested in! With the baffle in place the focal ratio drops from F12 to F10, not much change there? But with the new focal reducer it drops to F7, just a little below 2m focal length and thats the change that I was looking for.

This image of the Bubble is taken a F7 using the Mewlon. The coditions were average (Seeing & Transparency) and yet I was able to use the Mewlon!!!

Its not all be pain sailing, I have also had to learn to drift align on the pole. To do this I use Metaguide since its also used to confirm that the collimation of the Mewlon is spot on. Metaguide is actually able to measure the drift and report back the new value after your adjustments, so you know very quickly if you are going in the wrong direction, which is great.

Anyway the image capture was as follows;

Red 8x300sec

Blue 8x300sec

Green 8x300sec

Lum 8x300sec

HA 10x600sec

So about 4.5hours in total, probably I need another night to get the most from the image?

Another important point is at the moment I cannot flat field the Mewlon, I need to build a light box!!! This would also improve the image quality eventually.

I hope you like it? I'm very pleased with the results.

post-3011-0-69800100-1353157580_thumb.jp

Edited by Darth Takahashi
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Thanks for all the great comments; from another forum I had the comment that there is a little green haze lurking in the center of the image so I have run the SCNR function in Pixinsight to remove it, here is the result, I think you will agree that it has improved the image? The weather looks to be terrible next week so I don't know when I'm going to be able to finish it?

post-3011-0-91686300-1353229754_thumb.jp

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I manage to get a few more hours of H Alpha on the bubble last night before the mist rolled in here in Holland. The weather conditions are making the transparency destinctly average at the moment, so unless I get some clear nights with exceptional transparency I'm calling it quits for now with the bubble.

This image is now approximately 8.5 hours worth of data with 4.5 coming from H Alpha.

Unfortunately, on the second image run I had some rotation between session, therefore, I have had to blend the two successive images together to create the final image that you see here. Can't wait to get my obsy finished.

No flats used, thats not intentional, I just have no way at present to flat field such a large telescope... something for my Christmas list I think! :grin:

post-3011-0-64924600-1353354262_thumb.jp

I hope you like this image as much as I do. I'm very happy in that I now feel that I have a new telescope. I would never have dreamed of using the Mewlon in this manner before the modification. Can't wait to feed it some gallaxies in the spring!!!

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As you know well Martin, imaging with a focal length greater than 1500mm becomes very challenging for lots of reasons, the weather included! The native focal length of the Mewlon is 3000mm which is ideal for planetary imaging but not much else. The original reducer didn't really improve matters either, since it only brought the focal length down to 2500mm. The new corrector baffle already brings the focal length down to 2600mm, a shade over F10 while eliminating off axis coma and give 2 micron stars!!! But the real benefit comes with the new reducer, this take the Mewlon down to F7 or 1750mm focal length, this gives me a much more manageable scope and a very nice image scale for the smaller galaxy's etc...

Take the reducer out and put a barlow in and you have a planetary telescope again... the new system makes it much more versatile overall.

For my part, I have learn't to be a little more patient and to drift align on the pole which is mandatory at these focal lengths... Its a lot easier using short focal length refractors...

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