Focal reducer for C80-ED with 300d

rikyuu · (#1 (**permalink**))

hi,

I'm wondering if it's possible and how best to drop the focal ratio of my C80-ED from f/7.5 to f/5'ish. All my equipment is packed away at the moment (hence the endless clear nights) for moving house, so I have to think about using it instead!

.

Attached is a diagram of the adapters I use to attach the 300d to the C80. I realised there are limitations due to the 1.25" drawtube adapter restricting the tube diameter. I have a 0.5x 1.25" focal reducer which can fit into this adapter, but of course this creates an even smaller inner diameter and is quite far from the camera sensor.

It's probably a long shot, but I was wondering if there are any 0.6'ish x focal reducers that are either EOS clip (will attach directly to the 300d) or T-thread (will attach to either end of the extender tube or allow it to be ommited and attach to the drawtube T-thread adatper)?

Thanks

steve51450 · (#2 (**permalink**))

others may tell you better than me but if the c80ed has the same focuser as a skywatcher 80ed a lot of people have been using a sct 0.66 reducer on those to good effect

rikyuu · (#3 (**permalink**))

Steve,

I'm not sure, but I think the Skywatcher has a 2" focuser. Could the reducer be used with the C80 setup?

I couldn't edit my first post, but here's a more accurate and detailed diagram of the C80 setup

Can anyone comment on the "unknown" threads size and barrel size from the diagram? Are these Celestron "random" sizes or anything useful?!

jgs001 · (#4 (**permalink**))

My C80ED has a 2" focuser with an adapter in the read end. I take the adapter out and use a 2" extention and 2" MaxDSLR adatper without any problems. I'm surprised that you can't use 2" fittings in there.

rikyuu · (#5 (**permalink**))

Quote:

Originally Posted by jgs001

My C80ED has a 2" focuser with an adapter in the read end. I take the adapter out and use a 2" extention and 2" MaxDSLR adatper without any problems. I'm surprised that you can't use 2" fittings in there.

John, is that a standard C80-ED from the UK? Could my 'unknown' thread size be 2" perhaps? But I've seen people having to buy a hole new rear end assembly in order to have a 2" focuser

.

steve51450 · (#6 (**permalink**))

mmm

i am unsure but it may be worth pm'ing George as i am sure its him who uses an sct .66 reducer with an ed80

you could ask him if he will take a photograph of his imaging train

jgs001 · (#7 (**permalink**))

I got it just before Xmas from FLO as it was such a good price, shame it went down in price after

...

The same scope as is mounted here but sold as a spotter. I can check the internal thread size shortly, and see if my 2" filter will screw in directly.

rikyuu · (#8 (**permalink**))

hmm interesting, I also got mine from FLO, just after Xmas, I'm wondering if I'm missing something fundamental here that I should have checked/realised ages ago. I also noticed in your other post (below) that you use a 50mm extension tube with it and a MaxDSLR adapter. Which bit (in my picture) do you fit the 50mm tube to?

Mounting DSLR onto 80ED and C9.25

I think I'm going to have to quickly unpack it tonight to put my mind at rest!

arad85 · (#9 (**permalink**))

Quote:

Originally Posted by rikyuu

I also noticed in your other post (below) that you use a 50mm extension tube with it and a MaxDSLR adapter. Which bit (in my picture) do you fit the 50mm tube to?

The bit you have labelled "unknown holder size, not 2"". It IS a 2" holder (I know, I had my 2" diagonal in it last night

)

jgs001 · (#10 (**permalink**))

Remove the 1.25" fitting adapter with the T-thead on it, the fitting beneath is a 2" fit.

rikyuu · (#11 (**permalink**))

Really

! How daft of me never to have checked it. For some reason I was thinking it was some strange size

. That changes everything now!

Is there a possibility that the "unknow size of thread" bit is SCT size....no it couldn't be could it?!!!

Right, vernier calipers out tonight!

PS updated diagram below, incase anyone reads this in the future!

arad85 · (#12 (**permalink**))

Quote:

Originally Posted by rikyuu

Is there a possibility that the "unknow size of thread" bit is SCT size....no it couldn't be could it?!!!

Unfortunately not. I just tried it on my C80ED with the 9.25SCT back...

rikyuu · (#13 (**permalink**))

ah, never mind. It saved me unpacking the scope, so thank you for trying it.

My plan now is to perhaps try this EOS to 2" adapter
Adaptors - Max DSLR Camera Adaptor
with a 2" 0.5x or 0.7x focal reducer screwed in the end.

I wonder if this would work or if it would end up too vignetted etc?

Kai · (#14 (**permalink**))

At SGL4 i had a play with MikeP's ED80.

We used a 450d with a T ring , to this we screwed a William Optics FF III and then this went into the focusser in the scope.

Im sure you could do this as well.

kev 102 42 · (#15 (**permalink**))

William Optics FF III that what i use with my ED80 and 300D....kev

rikyuu · (#16 (**permalink**))

nb it's a C80-ED, but presumably it's effectively the same as the ED80.

I can't seem to find the William Optics FF III online, do you have a link please? What fraction of focal reduction does it do? Is it T-thread one end and 2" the other?

How about this one:
http://www.epinions.com/review/Willi...t_409038786180