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Old 28-09-2013, 12:34 AM
Nathan76 (Nathan)
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Unhappy NOT enough INWARDS focus

Greetings all,

I have a United Optics 110mm F7 refractor which i am told is made by the same manufacturer as Williams Optics(Not the same optics though, I'm not even sure if it's an APO).

I have jumped straight in the deep end and tried to capture some images with my Nikon D7100 DSLR.

As the scope does not have a built in field flattener i have purchased a williams optics FFIV.

My PROBLEM is when coupling the DSLR with the FF to the scope it seems i don't have enough inwards focus travel to get even close to a nice pic, it is completely out of focus.

The FF is adjustable, i have tried all the distances, focus all the way in with no luck.

I was sold this scope with astrophotography in mind so would assume it is suitable given the reputation of the shop.

Now correct me if i am wrong please...

Could it be that the DSLR chip is just set too far back in the camera?

In future i will be looking at getting a dedicated CCD(I have taken a liking to the QHY9)- Would/could this be the solution simply because the chip is set much closer to the front of the unit, Its a pretty expensive scenario to test with out going out and buying one.

Could it be i got a bum deal and this scope is no good for AP?

I thought one way to test it would be to position a guide scope CCD(which i am yet to buy, prob go for a QHY5 II) in the same pos that the QHY9 would be and see if i can get focus then- Can anybody help with the distance from the front of the unit/T thread to the chip on a QHY9(I've checked the web/technical drawings and can't seem to find a number.

Anybody else had any joy APing with a United Optics scope? I can say that visually it is impressive both in how it looks(classy/well made) and and the views it gives(Planets/Star clusters etc very crisp/clear no CA that i can see not that I'm an expert!)

Hopefully someone can help, thanks in advance, and could everybody over east Aus send WA some clear skies, I think ever since i got my scope 6 out of 7 days have been cloudy

Cheers.

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  #2  
Old 28-09-2013, 08:50 AM
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naskies (Dave)
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I think the WO FF IV eats up a lot of back focus - I wasn't able to get it to work with a SW ED80 either. There will be other flatteners that use up less back focus.

Have you tried focusing without a flattener at all, i.e. DSLR attached straight to the refractor? This will give you an idea of how much back focus you have to work with.
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Old 28-09-2013, 10:44 AM
cfranks (Charles)
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I have a Williams FLT132 with a Williams FF but I don't know which one, there is no mark on the device. Attached are the specs which might be useful to give an idea (possibly) of back focus etc.

Charles
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Old 01-10-2013, 07:05 PM
Nathan76 (Nathan)
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Thanks for the replies.

I've tried attaching the camera directly minus the FF, but because i did not have a 2" adapter i went through a diagonal. Thinking back to that i set up i thought i would have plenty of focus travel.

Stupid question but...

Does a diagonal affect the focusing distance?

Cheers

NB
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Old 01-10-2013, 07:12 PM
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Astroman (Andrew Wall)
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you were using the diagonal with the flattener and DSLR?
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Old 08-10-2013, 01:15 AM
Nathan76 (Nathan)
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Nah, DSLR to diagonal to scope.

Because i did not have a 2" t mount adapter, only 1", just to test it i fitted it to the diag...put a bit of pressure on it but i got some mediocre test shots, suffered badly in the not fat out from centre and in the corners which is why i got the FF.
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Old 08-10-2013, 05:23 AM
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Astroman (Andrew Wall)
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if you can go get yourself a 2" T, and lose the diagonal, put the DSLR pointing straight through the telescope.
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Old 11-10-2013, 01:08 PM
Poita (Peter)
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Or just remove an inch or so off the tube and re-attach the focuser etc.
I did this with a Celestron 80mm scope, just got the local engineering shop to face it off in the lathe. It cost me a beer and a look through the scope
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