Omega Cent and Cent A galaxy on a tight budget

[janoskiss (Steve H)]

Here is what I managed with a ~$300 camera, an $85 lens off ebay and a 22-year-old Japanese EQ mount worth maybe about $300.

Decent skies in North-Central Victoria did help (the smoke from deliberately lit fires around did not).

I am still not happy with the colours (I am yet to learn about how to properly deal with raw files and colour balance), and the lens has considerable CA till it's stopped down to f5.6 or slower; I think this was taken at f4.7 or maybe f5.6.

Details
Camera: Nikon D3300, ISO 1600, 45 x 30s exposures, 5 x 30s dark frames
Lens: Tamron 135mm, f2.8 (at f4.7?)
Mount: 1994 Polaris EQ with RA clock drive
Software: DSS, Imagemagick, Gimp
Location: Upper Lurg, Victoria

The two close-ups are 100% crops.
Larger image here: https://s6.postimg.org/3oboxdoe7/ome...p_edit_010.jpg

[RickS (Rick)]

Quite nice wide views, Steve.

[Atmos (Colin)]

Nice being able to fit two objects in the one frame
Very nice for such modest equipment

[Mickoid (Michael)]

Great to show people what you can achieve on second hand older equipment. You just can't beat the resolution on some of those older Japanese lenses. You've got yourself a winner at a bargain price with that Tamron. Marry it with modern digital cameras and you have the best of both worlds. Great shots Steve, well done!

[traveller (Bo)]

Very nice Steve, esp given the modest outlay.

[raymo]

Good start Steve. Until you start layering subs in Photoshop or whatever,
you need to take shorter subs when imaging objects with a large dynamic
range such as O.Cent, M42,etc: to avoid burning out the highlights, in this
case the core of O.Cent.
Have you thought about hooking your 3300 up to your Mak. Its very slow
photographically, but would be o.k. with bright objects.
raymo

[janoskiss (Steve H)]

Originally Posted by raymo

Have you thought about hooking your 3300 up to your Mak. Its very slow
photographically, but would be o.k. with bright objects.
raymo

Yeah, I had the Mak on location but forgot to take both the focusser and camera adapter.

In any case it would not have mattered much because I only have the one mount and the camera+lenses alone proved challenging enough. But next time I'll give the scope a go. A focal reducer would be nice though.

Anyway, in a single shot/sub the core of omega cent is resolved and no saturated. And I also had to compromise the image for the jpeg upload and my image processing skills are sub-par.

Here is a single sub 100% crop.

[janoskiss (Steve H)]

And here is what the full uncropped DX frame covers at 135mm.

[Camelopardalis (Dunk)]

Nice one Steve quality kit is priceless

[bojan]

Steve, you mentioned f/4.7... I can't see any traces of difraction spikes on stars?

If you have't already, try to use external aperture instead of internal one - with my manual Canon lenses above 100mm (and Tair 11A) the imrovement difference is drastic in terms of getting rid of colour bloating, CA and coma.
See here, it may be helpful:
http://www.iceinspace.com.au/forum/s...ht=canon+200mm

[janoskiss (Steve H)]

Thanks, Bojan.

There weren't any particularly bright stars in this image but on some of the brightest ones you can see a hint of diffraction from the rounded hexagonal aperture stop in individual frames, but for the most part coma and CA are the main issues with this lens at about f/5.6 and faster. Don't really get "spikes" till f/11 or slower, but get a "ceiling fan" kind of thing.

I was meaning to ask about using an external aperture stop, so thanks for the tip. I'll definitely give it a go. I read your comments and saw your impressive looking results in the other thread also about how it helps with CA and coma; would be fantastic if it worked for my lens also.

[janoskiss (Steve H)]

... and thank you for the encouraging comments everyone! I do enjoy the challenge of getting the most out of modest equipment. Can't wait to try Bojan's suggestion.

[bojan]

To cut precise aperture, use something like this:
http://www.ebay.com.au/itm/271904459...%3AMEBIDX%3AIT

I replaced the drill with pointed shaft to be able to cut thin material (black plastic folder).

[janoskiss (Steve H)]

I remember you Bojan and your amazing DIY setups - not sure of the details but I think you had a belt drive or two on your Dob. You're an engineer iirc, am I right? - bloomin engineers! they make the world go round (the good ones do anyway; the rest end up in management & sales either for lack of smarts or lure of the dollar).