First scope

[Catsick]

Ok, it's either a 2x extender for the camera or the SkyWatcher Startravel 120mm AZ3 Refractor Telescope.

Now correct me if I'm wrong but the telescope itself would provide a better deal as maintaining a low F number as compared to using the extender with a lens, as this would multiply the existing F number of the lens to a higher one than that of the telescope, so would any images obtained with the telescope be better than that with the lens?

[happy-kat]

Perhaps another difference might be that the telescope will have some CA on bright objects but does your lens?

[DaveS]

I would say put most of your money into a good enough EQ mount, you could do worse than the EQ 3-2 with RA drive, and image with your DSLR glass.

Yes you could "get away with" a tracking Alt-Az mount for short subs, and hope that DSS can cope with the field rotation.

BUT

Would you rather buy a mount that will do the job properly, or one that you'll have to fudge?

I think in "Making Every Photon Count" there's a section on imaging with a Canon DSLR / lens combination on an EQ 3-2, it can be done.

[Catsick]

I'll be honest and admit a lot of this baffles me.  The 75-300 will take a pic of Jupiter/Saturn with it's moons, but this will be limited to a bright white dot with smaller white dots, no sharpness in the image, but you know what you're seeing.  If I could get a scope that'd allow me to be a casual observer/imager that's all I'm after really. Alternatives to Sigmas 50-500 or 1.4/2.0x tele-extenders.

I forget the settings I used for this picture but usually keep the F number around 18+ with about 2-4 seconds exposure. manually focused using the 300mm.

[Alien 13]

If its just planets and lunar you are after then something like a C90 or bigger Mak would do, the 75-300 lens will be ok for some DSO work but you would still need a reasonable mount.

Alan

[DaveS]

Don't forget that with your particular camera you are actually at real focal lengths of 120 to 480mm with that lens.  Therefore you are not far off the FL of a decent wide field scope.  I began with using a 600D and a F4 300mm lens (so actual FL of 480mm).  Got some really nice DSO pics on an EQ mount.  You could use your budget to get a nice extension tube for example.

Sorry but this is wrong.

The FL of any optical system is independent of the sensor, all that changes is the field of view. I've seen the same misunderstanding on video / film forums too many time to let this go past.

The only thing that will change the focal length of an optical system is another optical element.

[happy-kat]

So it is an illusion of being closer but is really like cropping an existing image to make it look closer but you were not really closer.

[Owmuchonomy]

Here is a shot of M31 I did last Autumn using 600D and a 300mm lens on an HEQ5 mount.

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[Catsick]

Excellent picture. Maybe it's just me thinking I need a telescope to get such images. I've still yet to get my head around lights/darks etc although the chance of trying anything tonight is a joke!  I've seen the price of he mounts and is a bit offputting for a very casual imager/observer. Maybe just persevere with what I have and try and squeeze the max out of that before admitting defeat?

[Owmuchonomy]

M31 is more than 3 deg across so too big for most 'scopes'.

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[DaveS]

Yep, a 300mm lens is shorter than just about any 'scope, though the new Vixen VSD 100 runs to 380mm, or 300mm with the reducer, and the APS-C chip in a 600D is bigger than most mid-range CCDs, though you could use a full-frame CCD eg the Atik 11000

Vixen VSD 100 http://www.firstlightoptics.com/vixen/vixen-vsd-100-f38-flat-field-refractor.html 

Atik 11000 http://www.firstlightoptics.com/atik-cameras/atik-11000-mono.html

But at the price of a small car for the pair, before you've put them on a mount.....

A lot to be said for looking for an old manual 300mm f/4 lens, pretty much all of which could be adapted for Canon.

[Catsick]

The 300mm I use is an F4-5.6 AF, although using it on manual has proved a challenge.

[Owmuchonomy]

DaveS is on the money. You can get a load of experience with what you have got on a good mount.

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[DaveS]

For a 300mm f/4 manual, have a look at this.

http://www.ffordes.com/product/12052916021881 for £300

It's a Contax lens, so fairly up-market, but put an adaptor on to it and it will mount on Canon EF and will be:

A ) Faster, and

B ) Easier to focus at infinity

than your current lens, as well, dare I say it, as being better optically.

Ffordes is a good place to look for S/H lenses, I bought all my Leica "R" glass from them over the years.

[Catsick]

What sort of adapter could you use with the Contax?

Given the current equipment I have, would the advantages of a better mount outweigh that of the lens? Certainly not got the funds for the other 2 you mentioned Dave! lol

[DaveS]

Here you go

http://srb-photographic.co.uk/canon-eos-to-contaxyashica-adaptor-2451-p.asp

£25.

Given the choice either a better mount or a new lens I'd go with the mount and save up for the lens. Better to buy both though!

[Catsick]

Thanks Dave, think I might look into the EQ3-2....

Can you mount a camera on top of a Skywatcher Startravel 120 (EQ3-2), it looks like it has a mounting screw  but not sure about this?...

[Alien 13]

Thanks Dave, think I might look into the EQ3-2....

Can you mount a camera on top of a Skywatcher Startravel 120 (EQ3-2), it looks like it has a mounting screw  but not sure about this?...

Yes you can mount a camera on the scope rings but it will work better directly mounted to the EQ3-2, there are camera dovetails designed fot direct fitting or use the short skywatcher one and fit a camera ball head to it.

Alan

[Catsick]

Thanks Alan, the EQ3-2 with the telescope looks the best option, giving  the chance to either use camera & mount, scope & mount, camera & scope etc etc. Plus be a decent entry into observing. Getting used to how things work and progress from that. That's the thought anyways. Also it doesn't look too large a kit... or am I mistaken?

[DaveS]

The EQ3-2 is quite a portable option. I'm not sure how heavy it is in fact, but my HEQ5 is considerably bigger and that's an easy lift for me, and I'm not strongly built. The EQ3-2 was, in fact, what I was planning to get (Just to put my DSLR on) when I started back into astronomy a few years ago. Ended up buying the HEQ5 and Megrez 90 in my sig! So be careful, budget creep is insidious!

[Alien 13]

After using camera tripods for many years i found the EQ3-2 to be huge i certainly wouldnt want anything bigger, i can just manage it fully loaded with scope and camera but it takes two hands.

This might give you an idea of the size.

Alan

[happy-kat]

Nice scope :-)

Size and weight both so mislead in pictures as scale is deceptive, the camera helps give scale in this one.

[happy-kat]

This has been shared I see on a thread so a related read.

http://www.wwnorton.com/college/astronomy/astro21/sandt/startright.html

[DaveS]

No mount capable of AP is going to be a one-hand-lift, the requirements are much greater than a photo tripod, or even a video tripod.

I would say that the EQ3-2 is about the lightest mount that won't have you tearing your hair out in frustration.