What are my prospects?

[Tom33]

I'm hoping to get a bit of advice here. I have re-kindled my interest in astronomy after a 42 year break, when I use to own a 4" relector. Things have moved on by leaps and bounds since then and I am currently reading / browsing everything before buying a thing. I would really like to get into imaging and am reading " making every photon count", which is a great book, but here's the problem.

I live in the suburbs, hence light pollution and before I get out my cheque book i need to know if reasonable results are possible. I wouldn't say my sky is really bright ( the council have just changed our steet lights for the ones where all the light goes down, which has made a difference) but the sky is definately not really dark. I was thinking of the Altair Astro 8" f4 imaging newtonian on the best mount I can afford but don't want to do this if I'm wasting my time.

Any comments would be appreciated

Tom

[themos]

I think you need to find a way of quantifying your light pollution levels. Can you see the 7 Ursa Minor stars?

[Tom33]

I'm not sure how many of them I can see. I have read this is a way of checking my limiting magnitude but haven't had a clear night since!

[pete_l]

One annoying thing about living in England is that a lot of the interesting stuff around Sagittarius is always quite low in the sky, which gives a double whammy of lots of turbulent air and the L/P is worse at low angles. What I've done is to use narrowband filters of Ha, O3 and S2 instead of the usual RGB set. This cuts through almost all of the light pollution and you can assign "false colours" to each channel to produce some spectacular (if unrealistic) images of deep sky stuff.

Since you're using these filters to remove unwanted LP, you don't need the extremely expensive very narrow ones - the merely very expensive 10+ um ones will do nicely.

[dph1nm]

I live in the suburbs, hence light pollution and before I get out my cheque book i need to know if reasonable results are possible

I think you will be (pleasantly) surprised at what is possible.

You can always overcome light pollution (in theory) by exposing for longer - so what takes 1 hour at a dark site might take 10 hours under polluted skies. Just depends how dedicated you are!

I am quite happy working under my light polluted skies (which can be pretty bad). Just don't expect as good results as you would get from a mountain top in Chile!

NigelM

[lukebl]

You'd be amazed what's possible, even in suburbia.

I live here (not saying exactly where in the picture!), surrounded by buildings and street lights:

and can manage to image the Helix Nebula over the street lights and rooftops:

Not bragging or anything, and I would prefer to be elsewhere, but it shows what you can manage even in suburbia.

[ollypenrice]

You'd be amazed what's possible, even in suburbia.

I live here (not saying exactly where in the picture!), surrounded by buildings and street lights:

and can manage to image the Helix Nebula over the street lights and rooftops:

Not bragging or anything, and I would prefer to be elsewhere, but it shows what you can manage even in suburbia.

Boy, you have every right to brag!! Astounding result.

I would say go for a mono CCD camera and do narrowband. This is the route of many suburban or urban astro-imagers. However the image above maybe urges otherwise.

Olly.

(No personal experience since I have a mag 7 zenith, I'm glad to say. Long way from a good theatre though!)

[lukebl]

I would also add that that image of the Helix was done with an unmodded Canon 450d.

[step_hen]

LP and narrowband filters can get around a lot of your problems if imaging i'd guess. Do you have access to dark sites nearby that you could use? if so, a portable imaging rig might be a possibility

Nice one Luke. I guess your house is the one with a pool?!

Stephen

[lukebl]

Nice one Luke. I guess your house is the one with a pool?!

Sadly, no.

[TheThing]

Reminds me of the beginning of that 80's soap which was a spin off from Dallas (forget the name now).

I think Luke has shown that you can achieve some good (nay, great, excellent, woderful) results in light polluted areas. Always worth giving it a go. Start small and work you way up from there.

[mark7331]

Reminds me of the beginning of that 80's soap which was a spin off from Dallas (forget the name now).

Knot's Landing. (so i've been told ).

Anyway: With suitable use of filters and if you select targets that are as near straight up as possible (so you're looking through less atmosphere), you should be able to get some good results as has been shown by Luke.

I've imaged M16 through a really yellowed out sky - I couldn't see it through the EP but the CCD picked it up without any problems through a 7nm Ha filter.

Mark

[Whippy]

I think most people live under light-polluted skies (including myself, my limiting mag is about 3.5 on average), that's why light pollution filters are so popular! It's perfectly possible to observe and image under skies that suffer from it. For example, I know the light pollution from my back garden is considerably worse on the western horizon because that's where the centre of the town I live in is so I normally image on the eastern side of the meridian. There's also several tricks during the image processing that enable you to eliminate it's effects too so don't be too worried by it.

HTH

Tony..

[Tom33]

Thanks for all the feedback Guys and Luke, that is a stunning image! I live in a village between the orange glows of Barnsley and Rotherham in South Yorkshire, so don't know how bad the light pollution really is. Over the next few clear nights I will try and establish what the limiting mag is at zenith. I mentioned going for an imaging newtonian. Is this considered worthwhils as I notice others are using ordinary reflectors and is bigger (maybe 10" skywatcher) going to give an edge over the 8" imaging newtonian?

Again thanks to all for the feedback

Tom

[Whippy]

I mentioned going for an imaging newtonian. Is this considered worthwhils as I notice others are using ordinary reflectors and is bigger (maybe 10" skywatcher) going to give an edge over the 8" imaging newtonian?

Unlike observing where the phrase 'aperture is king' is apt, the size of the scope isn't important in imaging. What matters is focal ratio, which determines how 'fast' the scope is and the focal length, that gives you how big or small your field of view is.

Newtonians are fast (especially the Altair f4) but they are big so they need a substancial mount, need collimating (optical alignment) frequently and you will almost certainly need a coma corrector to correct the erm, coma (it's an optical fault inherent in the newtonian design).

A lot of people find refractors much easier to use. Small scopes like the ED80 are a lot more easier to use and will cause you a lot less stress at first.

If you've been out of the hobby for 42 years then I'd looking into buying your kit with the initial idea of observing first, just to get yourself back into the swing of things but also thinking long term with your imaging ambitions. Once you've had a few sessions getting used to things like polar alignment and focusing, you'll find attaching the camera one more step rather than taking several steps at once.

Tony..

[Tom33]

Thanks for that Tony. WhenI was last stargazing calculaters were new and computers, what were they? I think you are probably right. I have now got some of the freeware that came with sky at night and managed to find M31, with my binoculars, whilst on holiday in Norfolk, but thats cheating! I'm happy to re-learn the sky for a while and save my pennies, so maybe a refractor would be a good starting point. I must say the amount of choice is mind blowing !

Tom

[lukebl]

Thanks for all the feedback Guys and Luke, that is a stunning image! I live in a village between the orange glows of Barnsley and Rotherham in South Yorkshire, so don't know how bad the light pollution really is. Over the next few clear nights I will try and establish what the limiting mag is at zenith. I mentioned going for an imaging newtonian. Is this considered worthwhils as I notice others are using ordinary reflectors and is bigger (maybe 10" skywatcher) going to give an edge over the 8" imaging newtonian?

Again thanks to all for the feedback

Tom

I've never actually checked what my limiting magnitude is! I must think about that when it's next clear. I can see M31 easily, so I guess it's not as bad as some areas.

Anyway, I use a 10" Newtonian for imaging and it suits me fine. Whatever anyone says about f/ratios, aperture is still king, even in light-polluted areas.

[Whippy]

Whatever anyone says about f/ratios, aperture is still king, even in light-polluted areas.

As I've previously mentioned, aperture isn't important for imaging. Otherwise, scopes like my ZS66 would be useless which I can assure you it isn't.

Tony..

[lukebl]

As I've previously mentioned, aperture isn't important for imaging. Otherwise, scopes like my ZS66 would be useless which I can assure you it isn't.

Tony..

Oh, I'm not denying that one bit. I just like my 10" for both observing and imaging, and I'm not in a position to change/upgrade in the near future.

[MikeD]

I image from Light polluted skies (swindon).

I don't use an LP filter as such with my RGB imaging but I do shoot some Ha filtered data ( I use a mono CCD) to mix with the red data to knock back the LP and at the same time bring out any Ha regions.

Mike.

[Tom33]

Taking everything inro account I am going to look at a SW 80ED on the best mount I can get and work up from revising my sky viewing onto imaging in the future. This seems the safest bet but I live near Rother Valley optics, so I am going to have a chat with them.

Thanks again

Tom

[dph1nm]

As I've previously mentioned, aperture isn't important for imaging.

It most certainly is - that is not to say you cannot do well with smaller apertures, you can, but you SHOULD always be able to do better with a larger aperture.

If you can't get the same image with an 8" in one quarter of the time you can with a 4" then you are doing something non-optimal with the 8"!

NigelM

[adamsp123]

I am with whippy on this, for imaging speed F ratio rules not aperture.

[dph1nm]

I am with whippy on this, for imaging speed F ratio rules not aperture.

Even if you believe the f-ratio myth, it is the pixel size in arcsecs that matters. This is partly determined by focal length and partly by the physical pixel size. If you insist on imaging at long focal lengths then you should choose a camera with large pixels, or one which enables you to bin-up smaller pixels. If you do this then aperture will always win.

We have some 10" f/10 Meades here for the students. With off the shelf amateur CCDs on the back, binned 3x3, to give about 1" per pixel, I assure you that images taken with these will blow anything taken with small scopes at any f-ratio out of the water.

NigelM

[adamsp123]

Isn't the f-ratio myth to do with the S/N ratio not how quickly you get an image?