Geoptik CCD to Camera lens adapter.

[ollypenrice]

This is a great looking gadget from Altair Astro. A while back I posted a question about how one would deal with UV/IR filtration but having contacted Ian at Altair I now have the delightfully simple answer; the adapter has an internal thread for a 1.25 inch filter. You could even do RGB with it, presumably by removing the camera or lens each time. My own thinking is to use our Atik 4000 OSC with the device, maybe switching to the mono for a dedicated luminance layer.

Playing with SkyMap the possibilities of CCD-camera lens imaging are ravishing to any widefield junkie like me. The Rosette up to and around the Cone in HaLRGB... Oh yesssss.

Any thoughts on the gravity of undersampling?

Olly

[Merlin66]

Olly,

I was thinking along the same lines....

What about a Gerd Neumann slide filter holder with a modified front thread/ section??

You could fit the lens mounting bayonet onto a T2 adaptor (??!); this would allow you to easily change filters???

( Now I think of it - what we really only need is that "reverse" lens to T2 adaptor... we could then screw it onto a filter wheel and still have enough back focus???)

Ken

[ollypenrice]

Cor, all these adapters (some almost but not identical for no reason known to man) drive me nuts. I'm lucky. Being 'in the business' means I can indulge in having a mono and colour version of the same camera so the colour will get the colour - there's rocket science for you!

I've just ordered the adapter and can't wait to get started.

Anyone know where to find camera lens CCD images on the net?

Also what are likely to be the best lenses for using with a CCD camera? (Canon EOS fit.)

Olly

[Whippy]

I was looking into this a while back Olly as I was planning on having a play with my Atik. I did come across the Mogg adapters and did email the guy but he never got back to me. The Geoptik thing looks interesting though..

I believe the 'plastic fantastic' 50mm lens is supposed to be superb for the money but other than that I haven't got a clue as to what lenses are good. SteveL did something similar with his QHY8 a while back, I think he was inspired by this guy: Astro Anarchy .

Tony..

[skye at night]

You have to be careful what lenses to use, not just the optical compatibility.. but the electronics.. because some are full time focus via the camera electronics....The guy in Finland 'butchered' a 3 grand eos 200m f1.8 lens to mate to his qhy9, I couldnt do that to mine!!! but older fd lenses can be picked up...

Steve

[FLO]

When choosing a camera lens for astrophotography consider the number of iris blades it has. Together they create the aperture. If it has, for example, only five then the further you stop the aperture down (make it smaller) the more the circular aperture starts to adopt the shape of a hexagon with straight edges which can cause diffraction artefacts. A lens with more aperture blades can more easily produce a circular aperture, producing tighter stars. You might think that you won't be stopping the lens down so no need to worry but reducing a lenses aperture by just one or two stops can noticeably improve its performance.

(The regular Canon 50mm f1.8 EF has five aperture blades, the faster 50mm f1.4 has eight blades).

HTH

[ollypenrice]

Good info there guys. Thanks. Steve, hadn't thought of that though I would always stop down a bit. More thanks!

Olly

[Merlin66]

As mentioned previously, there should be a price available in the next few days for a Gerd Neumann EOS to T thread filter adaptor which will allow you to fit an Canon lens ( or any other with a suitable adaptor ie Oly Zuiko) to any CCD camera AND have the opportunity of dropping in 1.25" or 2" filters...

PM me.

ken

[skye at night]

This is a device that I got from a guy in Italy....

It allows connection of Nikon lenses to 1.25 ep holder or ccd via the helical adjust 1.25 clamp on the right (made by Baader). With a male- male T 2 type adaptor I can add a filter wheel also...

A great item, thing is i am mainly Canon now so eos fit would suit better..

but might be nice to try a ccd (if I ever take the plunge) and a wide/fisheye lens.

Trying to find the mans card as I would like to know if he can do a canon one.

Steve

[Merlin66]

Looks very neat! but it doesn't include provision for a filter??

( I have something similar made from a x2 camera adaptor and a 1.25" sleeve)

[NickH]

Great thread this, very interested in these options too..for the 383+ camera

[brianb]

If this: Teleskop-Express: Astro-Shop + Fotografie + Naturbeobachtung

is the adapter you're talking about, it has no internal threads. If it did have an insert threaded for 1.25" filters, it wouldn't clear the rear element on EF lenses (though EF-S lenses might work).

OTOH you very likely need a spacer of some sort between the T thread of the adapter and your CCD camera. For the Atik 314L you need about 7mm; other cameras probably vary. Anyhow the point is that you can obtain filters - including colour seperation filters - threaded 42mm x 0.75mm (T2) male at one end, female at the other, and by a strange coincidence these are almost exactly 7mm long, this providing the necessary extension as well as filtration.

I have one of these & intended to use it for "bright object" photometry but got sidetracked into DSLR. When I get round to trying the setup I will be using a T threaded IR blocking filter and a Wratten #58 on the camera lens to give an approximation to V band response. This setup also gives the capability for trichromatic imaging without disturbing the bottom end of the stack, when imaging at full aperture I think you'd "get away with" just one set of flats as dust on the front filter would have little if any effect on the flat frame.

[skye at night]

Looks very neat! but it doesn't include provision for a filter??

( I have something similar made from a x2 camera adaptor and a 1.25" sleeve)

filter wheel can go at ep holder end using nosepiece then camera or after the lens adaptor using a male-male t threading...

Steve

[Merlin66]

Steve,

I think I'd quickly run out of back focus space....

The adaptors and the width of the filter wheel would be greater than the 55mm camera lens focal length?? Yes - No????

Brian,

Can you supply a weblink for the T threaded filters? On a previous thread there was a need to fit filters (cheaply!!) behind a SCT thread - with a suitable adaptor (SCT> T) these could be used??

Ken

[skye at night]

Steve,

I think I'd quickly run out of back focus space....

The adaptors and the width of the filter wheel would be greater than the 55mm camera lens focal length?? Yes - No????

Ken

Yes.. definitely a possible issue, but maybe more flexibility with a small chip camera? and depending on lenses.

perhaps filter wheel tight against camera front and one with a 'well forward' positioned sensor???

all a bit trial and error for me I think.

Steve

[brianb]

Can you supply a weblink for the T threaded filters?

Google "Modern Astronomy", go to the filters page - you can select T2 fitting in the Astronomik range. (And Bernard knows what he's doing!)

[brianb]

I think I'd quickly run out of back focus space....

Indeed. The Geoptik itself uses quite a chunk. As I said above, with the Atik 314L you have about 7mm left to play with. That's an impossible engineering problem using conventional threaded filters in a sliding or rotating mount. Other cameras may have their sensor mounted a further forward with respect to the mount threads, OTOH some may not even have the 7mm leeway.

[Merlin66]

Brian,

Thanks for the T2 thread filter link.

Very handy to know they are readily available.

[skye at night]

Adapter: Durchgehendes T2 Außengewinde / 1,25" Filtergewinde - Teleskop-Express: Astro-Shop + Fotografie + Naturbeobachtung

filter option with zero effect on backfocus

Steve

[brianb]

filter option with zero effect on backfocus

My German is very rusty but I get the impression this is a device which fits inside a (Baader) T2 extension tube, allowing a 1.25" filter to be threaded into it. In which case it is a reasonable alternative to a T2 threaded filter when you need an extension tube anyway - assuming your camera chip is small enough that vignetting isn't an issue, naturally.

[skye at night]

click on the uk flag and you get a translation in full.....

looks to me like it IS a male-male thread so will 'hide' a filter within and go into a ccd camera or any female t-thread.

Steve

[petevasey]

An old topic this, but I thought I'd resurrect it - Paul J is considering getting a Geoptic unit, and I came across this page when browsing around:

http://www.dangl.at/ausruest/geoptik/geoptik_e.htm

It's clear that there IS provision for a 1 1/4" filter. And because it is fitted on the camera side of the adapter, it will not interfere with the lens.  Worth checking with the supplier that the 1 1/4" insert comes with the unit.  The Geoptik version is available from Teleskop Service and Altair Astro and probably others.  An apparently identical unit from 356 Astronomy definitely has the 1 1/4" insert'

I'm sure Olly bought lenses years ago, but for the record I use a Canon 400L f5.6, Canon 70 -200 L f4 zoom (almost as good as the 200L f2.8 prime and more versatile) and a Tamron 17-50 f2.8.  All lenses have given good results,  the Tamron  has slight distortion round the edges with an AF size sensor, the 70 -200 zoom very slight, the 400L almost perfect    Smaller sensors in dedicated CCD cameras (the SX 694 is the one Paul J will be using) should be even better.  To avoid 'starburst' diffraction spikes when stopped down I use an external mask made from a lens cap with the centre turned out on my little lathe - might be difficult to do accurately any other way.   See:

http://www.madpc.co.uk/~peterv/astroplover/Bits.htm#Lenscope

This works ok on both the Canon lenses, but vignettes horribly on the Tamron.  Not so important on the Tamron anyway because at the short focal lengths the stars are very small.  Only extremely bright objects such as bright planets or mag 1 stars show any noticeable starburst.

The only problem I can see other than the requirement for sufficient back focus is the way the camera is fitted.  Screwed on to an adapter, even with an extension, the framing cannot be adjusted,  BUT if a slim rotating ring can be fitted within the back focus constraints, that would do the job.  Again these are available from Teleskop Service, and possibly others.  This one looks a likely candidate provided the camera is not too heavy:

http://www.teleskop-express.de/shop/product_info.php/language/en/info/p7356_TS-T2-360--rotator---only-5-5mm-back-focus.html

Looking at the design of the rotater, it might be possible to slacken the clamp and recessed adjustment screws to remove the camera and change the filter without unscrewing the whole assembly.

Fun!

Cheers,

Peter 

[petevasey]

Oops, sorry I mean APS sensor - must pay attention!

Peter.