Focal Reducer & Nebula Filter Advice

[alandee]

Hi folks,
Great forum, I'm a long time lurker. I'm currently using my D70 DSLR to image, with a view to getting a DSI II or better in the near future. I've decided that I need a focal reducer, unsure of .63 or .33, I think it is suggested only a f/.63 so I think that's going to be the answer, and I'd like a nebula filter. There are seemingly a billion options and I've not used either before ! Any suggestions ? I love eta carina and orion if that has any impact on the neb filter choice.

Also, I currently have a meade clear filter to 'seal' my OTA, If I get a Neb filter or a focal reducer, can you keep screwing them onto each other at the rear of the OTA ? or do you just use one, in which case an EP filter would be more sensible ? and easier to change or do you mix and match OTA filters with EP filters ?

Thanks for any assistance.
Al.

[Hitchhiker]

Hi alandee, welcome to IIS! I think an F3.3 FR would vignette very badly when using your D70. I have also read comments on the Yahoo Meade DSI group that suggest you might get vignetting with a F3.3 FR on the DSI II - I have a DSI-C which has a smaller chip, so I don't experience vignetting. Anyway, I think the F3.3 might be line ball with a DSI-II.

I think the F6.3 would be a better choice for a DSLR - not to say you won't get some vignetting, but very much less than the F3.3.

The Meade focal reducers will screw on to the back of the clear filter. My F3.3 FR came with a T-adapter that screws straight in to the front plate of the DSI.

Hope this helps.

[alandee]

Thanks for that, you've confirmed my suspicions !
And by the sounds of it, it doesn't matter where in the optical path the focal reducer lives .. interesting ..

Thanks again,
al.

[Hitchhiker]

And by the sounds of it, it doesn't matter where in the optical path the focal reducer lives

It does matter where the focal reducer is and how it is set up. The F6.3 FR is a lot more forgiving than the F3.3 but positioning is still important.

Does the LX200R come with a microfocusser? I have read that you can fit the F6.3 FR in front of the microfocusser and use your normal optical train, but you may have to experiment a bit - note that the distance between the FR and the plane of the imaging chip determines the focal reduction.

With my F3.3 reducer I mount it microfocusser<<FR<<T-adapter<<DSI (if I want to use my microfocusser!)

The biggest surprise I had with my F3.3 reducer is how much experimentation I've had to do with regard to positioning and setup. Consider the instruction sheet that comes with the FR as a guide only and be prepared to experiment!

[alandee]

Cheers, yep the R has a microfocuser, my understanding is that I can put the FR first, then the nebfilter then the optical train, but hey, i bought a Meade, so I'm used to 'slightly ambiguous' instruction sheets !

Thanks for the advice, I look forward to the new challenge !

al.

[Hitchhiker]

alandee, here is a quote from Chuck Reese over on the Yahoo Meade DSI group when asked about the set up of Focal Reducers.

The 6.3 reducer is designed to be used with a lot more distance
between RF and camera...we usually mount it to the rear cell of the
SCT, then the microfocuser, then the camera.

The 3.3 goes behind the MF, with either 15 or 30mm extensions for F5
or F3.3, respectively. Using both extensions (45mm total) gives you
F3.0. All that said, when using the pro, you need to factor the 15mm
height of the filter bar holder into the mix.

I'm now not so sure about your 'clear' filter. What sort of threads does it have on the back? (I've had a look at the BinTel site and the Meade clear filter there does not have the SCT rear cell threads on it)

[alandee]

Thanks for the heads up, I checked my filter, it's threaded female / male so it should be cool, but I'll keep the above arrangement in mind during reassembly thanks!

Cheers,
al.