NGC 3918 Blue Planetary

Lester · #1 15-05-2011, 11:04 AM

Hi all, got this one last weekend, it is a very bright small planetary in Centaurus. This is 58 x 30 second exposures at ISO 400 with Astro 40D and 14" LX200 at F6.3 . It has a diameter of 20" and magnitude of 8.1 . Being only 3.5 degrees from Delta Crucis.

The first image is a crop from the full size image and the second is the full field of view showing the distortion/out of focus stars I am getting around the edges. It seems more pronounced on the right side of the image, but is still evident on the left. Is this to be expected from SCT type scopes, or is it something else? Thanks for your constructive knowledge on this question.

http://i638.photobucket.com/albums/u...s/6388dba6.jpg

http://i638.photobucket.com/albums/u...s/f5b084c9.jpg

joecool (Mark) · #2 15-05-2011, 01:34 PM

I can confirm that mine does the same. It is an older LX200 10" f6.3 (classic) so no ACF. In prime focus with t-adapter and 450D I have lovely comets all around the edges. They look like arrow heads with bubble tails all pointing into the center. When I use the Meade f6.3 focal reducer they look like what you have with the pac-men, only they extend about 50% into the center. The reducer is called a "corrector" and I suspect it works on an f10 scope, but it is over-correcting on mine. Probably works OK with a smaller CCD, but that is like cropping a larger sensor anyway... With the f3.3 reducer I get VERY long spikes and it is un-usable. haha good for a laugh though.

I have found one fellow who uses a MPCC corrector on his f6.3 to good effect so I'm going to try it. I've got the corrector already, but it needs a 2" eyepiece holder so I've got a JMI EV-1cM focuser clearing customs as we speak. (Lets hope it even comes to focus haha. Can't find much info on a configuration like this so just went and ordered it...)

Mark.

joecool (Mark) · #3 15-05-2011, 01:43 PM

Oh, nice image by the way. I like how it shows the lighter haze around it with the bright spots at each end. (I googled it and got the Hubble shot which shows these features). Sweet to get such features from a telescope at home.

As I am early in my learning about processing I am intrigued by the bright orange star to the right with the hard core. Is this from something like an un-sharp mask causing donuts? Some of the smaller stars show it too.

Mark.

Lester · #4 15-05-2011, 01:45 PM

Thanks for the reply Mark. I will be interested to find what others have experieced also.

Hope the corrector works well for you.

Lester · #5 15-05-2011, 01:47 PM

Thanks again Mark, I did a unsharp mask, perhaps too much.

Bassnut (Fred) · #6 15-05-2011, 02:01 PM

Thats excellent Lester, and good res.

CoolhandJo (Paul) · #7 15-05-2011, 07:50 PM

Nice one! Colours and detail etc.

Lester · #8 15-05-2011, 08:41 PM

Thanks Fred and Paul for your comments. All the best.

Lester · #9 15-05-2011, 08:44 PM

Here is a brighter version.

http://i638.photobucket.com/albums/u...s/20628763.jpg

Hagar (Doug) · #10 16-05-2011, 10:57 AM

Very nice Lester, boy is that a tiny target. A bit small for my rig.

Lester · #11 16-05-2011, 10:30 PM

Thanks Doug, yes it would be the smallest planetary I have tried so far. All the best.