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ED80 - achieving focus DSLR and accessories


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Hi all

I am keen to progress from my ST102 refractor to something a bit nicer for imaging.

I have in mind the Equinox 80 APO Pro at £520 which seems very reasonably priced and is the perfect focal length, aperture and weight with some really good reviews and comments. Focuser looks decent enough.

The problem I have is that I want to use it for imaging with a Canon 1000D DSLR employing an OAG, filter wheel and flattener. Now on the cheapo ST102 I happily cut a length off the tube thereby gaining some inward movement to make room for the additional bits in the imaging train which worked really well, but I would not be particularly keen on cutting an Equinox 80!!! so I just wondered how people got round these problems.

I would have thought a similar issue would arise with any scope and these additional accessories but removing any of them would not let me guide, or filter, or flatten! I could use a guidescope I guess but I find the OAG super easy to use and lightweight. Not sure how I would get round filter wheel or flattening problems...

Any ideas greatly appreciated.

cheers

Chris

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Ok, I shall try a different approach - would anyone with an Equinox 80 and a Canon EOS 1000D be kind enough to tell me the following measurement when in-focus on a star or similar?

post-31053-0-76225500-1386413377_thumb.p

thanks

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Ok, I shall try a different approach - would anyone with an Equinox 80 and a Canon EOS 1000D be kind enough to tell me the following measurement when in-focus on a star or similar?

thanks

I've got about 4cm (to the mouth of your focusing tube, not to the spot which you've marked furthest to the right.) with an Evostar 80ED Pro and Nikon D3100 ....

What you need is to get yourself some T2 extension tubes. I bought a set of Baader T2 Extension Tubes from First Light Optics for this very reason. Couldnt get focus with camera, OR guiding camera.. ;)

Hope this helps... Alveprinsen.

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Hi M37,

I have the Evostar ED80 Pro and use the SW field flattener/focal reducer (0.8x) with it, which brings the focal length down to approx the same as the equinox.

Without a flattener you would need to use a 2" extension tube plus the Canon t ring camera adaptor to achieve focus with the DLSR... on my scope this would be achieved with approx 1" of draw tube extended.

When using the FF/FR + t ring adaptor the flattener replaces the 2" extension tube and focus is achieved at pretty much the same extension of the draw tube.

I would think much the same distances would also apply to the Equinox.

The problem I can see you having is that the flattener back focus distance is fixed at approx 55-56mm and with the Canons' EOS fixed focus distance being 44mm this would only leave you 11-12 mm to accomodate the t-ring, filter wheel and OAG... altering the tube length would do nothing to help, other than to increase the amount of draw tube extension.

I my case I use a Nikon Camera which makes things even tighter since the cameras' FFR is 46.5mm.

I use a 2" adaptor with my FF/FR which fits directly into the focuser draw tube and this has an internal thread for filters.

There would be no way to use an OAG that I can see... let alone a filter wheel in addition.

Hope this helps a bit.

Best regards.

Sandy. :grin:

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It occurs to me that it will be fine with the DSLR onto Field Flattener, no filters will be required as I currently only use my Fringe Killer on the DSLR which hopefully won't be as necessary with one of these scopes.

I will have to guide with a separate scope rather than OAG but that's fine. My HEQ5 should take the weight. For LRGB and narrowband I will use my mono cam which has less distance to the chip so the filter wheel might well fit in.

Excellent, FLO here we come...

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Hi M37,

That combo should work out quite nicely for you and the fringe killer should not be needed since the EQ scopes are much better corrected in the BLUE... If you do need a filter (possibly an LP filter) then the S.W flattener , as far as i am aware, does have a threaded focuser end (for 2" filters).

When you come to LRGB with the mono CCD then you may need to make a very small focus adjustment when taking the B frames... ED doublets are better, but not perfect in correcting the B channel.

Depending upon the thickness of your filter wheel assembly you may even find that can use the OAG with it since you will probably have around 40 - 42 mm of space available after taking the CCD backfocus distance into account... it may still be tight, but, by carefull selection of low profile adaptors/connectors you may be lucky.

Either way, the HEQ5 will be more than capable of handling the rig even with the added Guide scope.

I wish you every success with the new setup.

Best Regards.

Sandy. :grin:

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M37 if it is any help i have an Equinox 80 and i use an ST80 as a guide scope and a canon 1100d and i have had no issue at all with the weight on my HEQ5.  The only thing i did find is that the only FF/FR that actually works is the televue TRF 2008  and thats what really hurts the pocket,but that aside i would not change my setup, it is a well balanced rig and you would not regret it.

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M37,

Just to avoid any confussion, the field flattener I refered to was this one: -

http://www.firstlightoptics.com/reducersflatteners/skywatcher-field-flattener.html

This works just fine with the Equinox... however, it is not a focal reducer.

If you need the combined FF/FR then 'Thunderchild' is correct... the televue TRF is the one you will need... but you better have deep pockets :eek:

Best regards.

Sandy. :grin:

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