Neximage Reducer Pen or f6.3 focal reducer?

[ashworthacca]

Hi guys, I'm a little confused.

When I do actually get around to using my Celestron Neximage on my Celestron Nexstar 5SE I believe that some sort of focal reducer would be needed to increase the FOV.

Can anyone tell me the difference between using the Neximage Reducer Pen against the Antares f6.3 focal reducer.

Many thanks

[dark knight]

Hi Martin, I have a Neximage and the only reasonable use for the focal reducer is so more of the moon fits in the FOV. That is the only time I use one. For the planets using Barlows are the norm. Not exactly answered your question I know but hope it helps.

PS the Neximage Reducer lens is threaded and replaces the standard nose piece, it is also threaded to accept 1.25" filters.

[ashworthacca]

Thanks dark night, I'm getting the neximage modded for long exposure so may try and use it eventually for dso work so I thought a wider fov would be beneficial.

Thanks for the tip about the nose piece.......it appears mine is cross threaded as I can't get it off:mad:

Still curious as to the difference between the reducer lens and f6.3 focal reducer though..........do they do basically the same thing??

[dark knight]

The Antares attaches to the visual back of SCT's and changes the focal length of the telescope ie, an F/10 telescope becomes a F/6.3. The Neximage reducer lens only alters the ccd's fov, at least that's how I understand it...

[brianb]

Still curious as to the difference between the reducer lens and f6.3 focal reducer though..........do they do basically the same thing??

The Neximage reducer is 0.5x and will image a field only wide enough to cover the small sensor in the Neximage camera. The 0.63x reducer is much more flexible, it will cover a much wider field (almost out to APS-C size), and can even be used visually. The reduction can be increased by adding extension tubes (or a diagonal) though this makes the useful field smaller. However it also includes field of curvature reduction to match an f/10 SCT, it may be much less useful when used with other types of telescope - even the ACF optics in newer Meade LX90s and LX200s do not require field flattening and the focal reducers designed for SCTs will not work well with them.

[dark knight]

I think the reducer would only aid in taking wide field images and not DSO, of course I could be completely wrong, I'm sure one the imaging guys will be along to better explain and answer your question though.

[ashworthacca]

ahhh, so an f6.3 focal reducer can be used with the neximage without any particular problems with my f/10 Nexstar 5SE?

[dark knight]

Yes you can use it, but you will then need an adapter to reduce the 2" Antares reducer to 1.25" in order to connect the Neximage camera.

[ashworthacca]

Sorry, I'm confused again.

THIS is the focal reducer I have. I don't understand what adapter I need. I thought I would be able to fit the focal reducer to the scope before I put the diagonal on and just put the Nexiamge where the eyepieces go??? Am I totally on the wrong track?

[red dwalf]

i was as confussed about all of this as you but as i understand it for imaging planets you need to boost the f ratio using barlows so your scope being f10 a 2x barlow will increase it to f20 and 3x barlow to f30 and so on, but the more you increase the f number the smaller the field of view as it increases the mag of the object, but doing this on planets increases the contrast and detail weather permitting, on the other hand imaging DSO`s you need a fast focal ratio so adding a 6.3 focal reducer lowers the f ratio by a fair bit ( not to good understanding the maths) allowing you to gather the light faster onto the chip ( don`t forget imaging DSO`s reqiures long exposures )

[ashworthacca]

I think I understand red dwalf.....I'm just concerned that an f6.3 focal reducer won't work as well as the dedicated Neximage reducer lens, but why shouldn't it?

[dark knight]

Martin, so long as the reducer is between the telescope and camera it should work. How and where do you connect your diagonal, on the 1.25" eyepiece holder at the top, or the 2" visual back to the rear(there is a screw off cap that you unscrew to gain access)??

The Antares is 2" in diameter.

[ashworthacca]

Martin, so long as the reducer is between the telescope and camera it should work. How and where do you connect your diagonal, on the 1.25" eyepiece holder at the top, or the 2" visual back to the rear(there is a screw off cap that you unscrew to gain access)??

The Antares is 2" in diameter.

on the 2" visual back to the rear before you attach the diagonal.

[dark knight]

That sounds fine, SCT 2" visual back, reducer, diagonal, then Neximage.

If using the Neximage reducer, this attaches to camera and fits any 1.25" eye piece holder, and therefore can slot straight in the top eye piece holder of your SCT. This means the imaging train length is reduced therefore reducing the chances of vignetting.

[ashworthacca]

Brilliant, many thanks for your help.

[brianb]

That sounds fine, SCT 2" visual back, reducer, diagonal, then Neximage.

Hugely overcomplex - the 0.63x screws directly onto the SCT port, screw your stock 1.25" visual back into that, add a 1.25" fitting extension tube to suit (you'll need about 3" of extension to get the reducer working at its design backfocus) and pop the Neximage straight in. You can substitute a diagonal for the extension tube but it's never a good idea to use a diagonal when imaging, they alter the orientation confusingly, they can affect the definition and, unlike humans, cameras don't get neck strain.

[ashworthacca]

Thanks Brian......I'm new to all this and struggling with the terms (visual back/SCT port etc) so I'll read up a little more.

I think I understand what you are saying, just can't picture what goes where yet.

EDIT: Just read the telescope manual again and now get what you mean. The only thing I need for me to get it to work like you say is an Extension Tube. Would a 55mm one be ok?

[brianb]

Would a 55mm one be ok?

Yes ... you'll just get a bit less reduction, maybe x0.75 rather than x0.63.

[ashworthacca]

Yes ... you'll just get a bit less reduction, maybe x0.75 rather than x0.63.

Thanks Brain...I mentioned 55mm as that's the one I found after doing a quick search. I'll have another look for a 3" one now.

Thanks to everyone else who has contributed to this thread, I'm learning................albeit in a very slow way.

Regards