Custom made webcam adaptor?

[Gweedo]

Is this the sort of thing that you're after? I've turned this out of aluminium using my camera adapter as the base. As you've said in your earlier posts this would be an adapter to glue onto your existing 1.25" adapter. You'd need to remove the ridge on the existing adapter.

[AstroTux]

Is this the sort of thing that you're after?

That looks like a way forward - like the 'collar' I mentioned in an earlier post but maybe a tad longer. I think I could probably get my man with a lathe to turn something like this more easily than making a complete new adaptor. Are you going to keep the images up on the net for long?

Thanks,

Alan

[Gweedo]

PM me your address and I'll stick it in the post for you.

[simonmc]

Unfortunately I don't, but I know a man with a lathe and he has said he will try. Unfortunately he is unsure as to whether he can cut the 1.125" x 42 tpi thread to attach the filter/focal reducer....

Are you sure thats the correct thread size? Just had a look at one of my 1 1/4" filters and the thread looks more like 28.5 x 0.6 metric. It is quite hard to measure though with only 2 threads on my filter i was looking at. It seem an odd size but that works out to be about 1 1/8" x 42 tpi. As only 2 threads are involved i guess that you could pretty much call them interchangeable.

Simon

[Gweedo]

I've got to agree with SimonMC, I've just measured the thread with a thread gauge and 28.5 x 0.6 looks good. On the nose piece end I reckon its a 112 x 0.5.

[AstroTux]

Are you sure thats the correct thread size? Just had a look at one of my 1 1/4" filters and the thread looks more like 28.5 x 0.6 metric.

I have to say I'm not sure, but 1.125" x 42 tpi is the 'standard' size given by Lumicon here: http://www.lumicon.c...pg/10-FAQs.aspx

They say:

"Q: What are the thread sizes on Lumicon filters?

A:The 1.25" filters employ industry-standard 1.125" x 42 tpi threads (except for Questar/Brandon, which use a thread pattern unique to Questar). The 48mm filters employ industry-standard 48 x 0.75 mm threading, which thread into 2" eyepieces. All larger filters use the given size with 0.75 mm pitch (e.g. a 72mm Minus Violet filter has 72 x 0.75 mm threads). "

This is the only info I've found so far when trawling the In'erWeb, so it could well be wrong.............. :undecided:

[AstroTux]

I wonder if it would achieve focus if you could just make the nosepiece longer? If you, say, put a UHC or LP filter into the nosepiece, and the reducer into that? Or even two filters?

Sorry to take so long responding, SWMBO had many tasks for me yesterday :sad: , but I eventually got around to trying your suggestion and the results are 'mixed'.

It turns out that increasing the distance between the CCD and the reducer made the problem worse but got me thinking along new lines. When the reducer is 4cm from the CCD ( as is the case if the reducer is the only thing screwed into the adaptor ) then I can focus on relatively near objects, but further objects become impossible. If I move the reducer further from the CCD then even relatively near objects cannot be brought into focus.

What if I were to bring the reducer closer to the CCD?

I have to say that I'm not sure how I would achieve this yet, and I really do not understand the optics behind it. I still have no idea of how a Barlow actually works ( despite searching the In'erWeb ) and how by adding an extension you can increase the magnification, but I'm fairly sure that this reducer acts like a 'reverse Barlow'.

I'm also rather confused by the 'bumff' that came with it. It quotes:

"Approximate Reduction Ratio for various distances between Reducer and CCD:

2cm ~ .75x, 4cm ~ .50x, 5cm ~ .40x"

I can see from this that a 4cm distance would give me approximately twice the field of view ( 4 times if you work on area rather than width ) but don't understand whether 2cm would give 1.333 or 3 times the field of view.

Anyone got any ideas?

Alan

[JamesF]

I read it as 2cm giving you 1.333 times the linear field of view, 4cm giving you 2 times the field of view and 5cm 2.5 times the field of view. That is, the reduction ratio quoted is the factor by which the effective focal length of the optical train is changed.

James

[AstroTux]

I read it as 2cm giving you 1.333 times the linear field of view, 4cm giving you 2 times the field of view and 5cm 2.5 times the field of view. That is, the reduction ratio quoted is the factor by which the effective focal length of the optical train is changed.

James

Cheers James,

that makes more sense. I hadn't thought about the ratio being a multiplier of focal length. I really do need to go and learn a bit more about optics........

Alan

[AstroTux]

Just thought I'd let you see what looks like the way to go with this one, but first of all a great many thanks to Gweedo who has very generously donated this piece to the project without wishing anything in return. In the words on Brian Cox "I'll buy him a pint..." or maybe even three!!

As can be seen, I've had to remove the microphone from the webcam ( such a great loss - I don't think ) and the flange will have to be turned down on the existing adaptor, but once this is done testing can commence.

If testing is a success ( which I think it will be ) then all that will need to be done is to remount the webcam in a suitably small box and possibly glue the piece to the rear of the adaptor. The collar is quite a tight fit, so it may be possible to leave it unglued so that the adaptor can still be used with a normal webcam.

Many thanks to you all for your help, especially James, Jim and Gweedo and I will keep you posted as to the results of testing.

BTW I've located a .pdf about optics so hopefully I will have more knowledge of them in future... :grin:

Cheers,

Alan

[AstroTux]

Just to let everyone know that I've had the flange on the original adaptor turned down and have mounted the camera in a small plastic case. It got its first light tonight on a bridge over a river in deepest darkest Argyll :grin: .

Here is the first image captured with it using the focal reducer:

This was taken using just 8 16 second subs.

As you can see this will not set the world of astro-photography ablaze - the focus is not right but that's not the fault of the collar or the web-cam, more the fault of the old codger trying to focus while standing in a biting wind and having his proverbials frozen off :icon_shaking: !! As a first shot it leaves a lot to be desired but at least we have solved the problem of not being able to achieve focus.

Many thanks to you all for your help, and I still owe Gweedo a pint..........

Alan

[Gweedo]

Excellent stuff all round! Getting to see that it works is reward enough!