Big camera lenses VS small aperture scopes for imaging?

[rocketandroll]

Ok... so having just got (and being massively happy with) my f2.8 200mm Eos prime lens for widefield stuff... I am now thinking about the options of longer focal length fast lenses for DSO imaging...

Specifically, when I sell my 80ED I'll have a gap between the 200mm lens and the 900mm or so focal length of my Meade.

I've seen a second hand 50 - 500mm Sigma zoom that'll run at f4 up for sale for about £500... depending on what the optics are like in comparison with a similar stronomical refractor, that sounds quite reasonable.

Obviously one of the Canon USM f4 500mm prime lenses would be better, but at £5K they're a bit outside my price range :-)

Anyone have any thoughts on whether this should work and what I could expect optically out of a large zoom lens?

Ben

[ollypenrice]

I doubt that any would match your ED80. Don't you like this scope? I have never had one but they seem to get great results. Zooms have a sweet FL, usually, so primes seem to be better. A Tak FSQ 85 (450 or 328mm FL) is cheaper than the Canon lens you mention and better for astronomy. Borg astrographs are a cheaper option for fast f ratio short FL imaging, too.

Olly

[Psychobilly]

There are 20 pieces of glass in the 50-500 as opposed to 3 in a decent triplet or 2 in a semi apo scope...

If you can get it for a good price give it a go.. if it doesnt work out for astro its a very capable general photography lens and should be able to move it on for little or no loss....

Peter...

[steppenwolf]

I'd be very tempted to keep the ED 80 over your proposed Zoom, I can't see you getting any improvement, in fact, quite the reverse.

[Psychobilly]

Agreed the ED80 should produce much better results... (says the man whose been buying short FL Canon L series zooms for the flexibility they will provide for widefield shooting...)

Peter...

[roundycat]

crazy to sell the ED80 and replace it with a zoom of any make or fl range. I have a Nikon 500/f4P that is superb on birds, aircraft, motor racing and so on and universally bad at astro. Zooms are worse.

Dennis

[Viv]

Have to agree with the other guys here.

I have a 500mm (few years old) Sigma, attached it to a doubler & tried to take Saturn pics - not a chance - just an orange blob.

[rocketandroll]

Cheers for the thoughts all

Just to clarify, i wasn't selling the 80ED to buy a lens, I had agreed to sell the 80ED anyway simply because I wasn't using it... it was too slow and covered an awquard field of view... way too big (not enough magnification) for galaxies and most small DSO's and not wide enough for nebulae etc.

I bought it because everyone recomended I buy it but I think I've used it once in the two months since I got it.

It was the draw of getting something at f4 or so with similar magnification for not much more money that really appealed. I just don't get the time to spend 4hrs imaging a target at f7.5 when I could get it in 1hr at f4 :-)

Ben

[Psychobilly]

The ED80 with a 0.8X reducer flattner is one of the "staples" pretty much ideal for NGC7000, IC5050,IC 1396 , M31, M33 , M42, M45..... not much use during galaxy season but come the autumn and winter it should get plenty of use...

Shooting bright point sources against a dark background is a pretty severe test of any optics...

I think Bigwings picked up the OS version of the lens quite recently for Everyday use...

Peter...

[ollypenrice]

If you have only had it a couple of months you are bang slap in the season that cries out for 2 metres of FL! I'd get the reducer, sure, and hang on for the three quarters of the year when the FL is a dream.

Olly

[rocketandroll]

...I already have the 0.8X reducer :-)

Ok, well, if I can I'll hold on to the 80ED for now then.

I guess f6 is better than nothing :-)

Ben

[Gina]

Lots of people seem to do very well with the ED 80 which is which is why I'm thinking of buying one when my finances recover enough from the EQ6 mount.

[Rossco72]

Zoom camera lenses as has been said are not going to compete optically with a dedicated scope. As has already been indicated, there is simply too much glass and too many imperfections.

A prime camera lens will have fewer glass surfaces and is a better proposition but still not a telescope...

[Psychobilly]

The SuperWASP uses Canon 200mm f1.8 L's - quite a few of them...

SuperWASP Homepage

There was a Mint second hand one on Ebay a Snip at £4,999.00

[ollypenrice]

An ED 80 is not not better than nothing, it is nearly as good as a Tak FSQ. Reality check!!!

Olly

[rocketandroll]

An ED 80 is not not better than nothing, it is nearly as good as a Tak FSQ. Reality check!!!

Olly

Cheers Olly :-)

Reality check accepted and absorbed.

Ben