The Centre of our Galaxy

[gregbradley]

Every year I decide to do widefield Milky Way imaging and a mosaic of the whole thing and I've missed it for the last few years.

I got prepared a bit earlier this time.

There's a little bit of time left to image the Milky Way in its widefield glory.

The setup is a FLI Proline 16803 camera, with a Losmandy D mount on a double sided dovetail. A FLI colour filter wheel, FLI PDF Focuser and a Precise Parts adapter to take Pentax 67 (medium format film size) lenses. Autoguiding using an SBIG ST402ME and efinder mounted using a Losmandy D adapter and double sided dovetail plate.

Richard Crisp put me on to this setup as the Pentax 67 lenses are designed to illuminate 60 x 70mm film which is bigger than these large CCD chips plus they have about 87mm of backfocus which is unusual for lenses.

They are also fiarly "cheap" on Ebay and reasonably plentiful (except the rare 300mm 67 F4 EDIF).

I have 55mm F4, 165mm F2.8 and 300mm F4. The 55mm F4 tends to give some coma which weakens with 2x2 binning and stopping it down to F5.6.

This image is with the 165mm F2.8 which seems best wide open which is fantastic. Stopping down a lens tends to reduce the aberrations but it causes those multiple diffraction spikes on bright stars which I am not a fan of.

This one ideally would be a mosaic but only one night was available due to moon and weather.

HaLRGB 10 30 10 10 10. Luminance was shot 1x1 (it is noticeably better at 1x1 than 2x2 with this lens). Colour and Ha was 2x2. There is very little Ha blended in as it did not add much except a bit more depth and contrast to the dust areas and a bit more colour to the Lagoon area.

I intend to do a series of lens widefield images next no moon and probably several mosaics.

I am very pleased with this lens.

http://upload.pbase.com/image/137896676 large

http://upload.pbase.com/gregbradley/image/137896676/large regular

Here is a photo of the lens setup:

http://upload.pbase.com/image/137897274


Greg

[RobF]

Top shot Greg. VERY nicely done. Really appreciate the detail you've put into describing the gear used too thanks. It's certainly done the job nicely here. Do you think you'll be off into mosaics next?

[Ross G]

Hi Greg,

That is an impressive shot of the Milky Way.

So much deatil and I love the colours.

I really like your widefield setup. Clever how the guidecamera balances out the imaging camera.


Thanks.

Ross.

[multiweb]

Lovely saturated colors and great dynamic range. I like it. :thumbsup:

[atalas]

Greg,love the field but It looks like some bad shadows clipped and color balance off to much mate....sorry,feel like the ogre.

[Tom Davis]

Lovely!

Tom

[Stevec35]

That's a nice shot Greg. I think that setup is a definite keeper.

Cheers

Steve

[gregbradley]

Thanks Rob. Its first light for that setup with that lens so its always a discovery about what works and what doesn't.

I planned to do a mosaic with this one but it was too low in the sky by the time I finished with this one. I do plan to do
mosaics.



The little efinder is handy. I see SBIG has a new efinder and lens for their STi guider that looks very good.



Cheers Marc. Its a bit light on exposure time but it came out well enough I thought.



It could do with some extra exposure regarding the dark areas. As far as colour balance I am not so sure what you are referring to there. These lenses do give chromatic aberration so I did have to correct for too much magenta in the stars etc. I think I need an additional filter for the lens. You get spoilt by our ED glass telescopes and lenses tend to be cheaper glasses unless you get ED ones which are telescope prices. So its a bit of a compromise there.



Thanks Tom.



Thanks Steve. I was happy with it. This is its first light and the fact it gives round stars fully open with such a large chip is very good.

Greg.

[Martin Pugh]

Thanks for posting a pic of the set up Greg...its always very interesting to see how folk configure their kit.

I really like the result you have produced from this.

Did you ever find one of those special Pentax lenses that Marco uses?

cheers
Martin

[Leonardo70]

Fantastic realization Greg ... i found it very very nice.

Ciao,
Leo

[strongmanmike]

HI Greg

Nice start with the Pentax lenses mate, looks very promising and the setup looks capable that's for sure. Not much CA to be seen..? Did you do anything to mitigate this?

This is first light for the Pentax lenses is it..?

Mike

[gregbradley]

Yes I have come across 3 actually. I nearly bought one but someone was just ahead of me. 2 others were more expensive at about US$2000 each and I didn't have the dollars.



Thanks Leonardo.



Yes there is a bit Mike. I found, as I noticed in a few others widefield lens images lately, that magenta seemed too high. I had brighter stars looking magenta and some a bit too red. But its processable although I would prefer a fringe killer filter to see if it stops it without needing processing.

It makes you appreciate that nice ED glass that is in our APO lenses.

Greg.