f6.3 sc reducer can work well on an ed80 refractor

[Nikolas (Nik)]

With the purchase of the correct adapters for the celestron f6,3 reducer I attached it alltogether onto my ed80 Orion scope and rattled off some comparison photos from my backyard of the light towers 3 blocks away.
I purchased an asi 178mc cooled recently and am thinking the field of view is a little restrictive when I looked at the field of view calculator (awesome little link).
So I purchased an sct to 2 inch adapter and an sct to m42 adaper as well from Sirius optics and put it all together

The end result was, with this camera a great result with NO vignetting and a wider field of view. I have posted a comparo below as the heavens have not been kind to post any sky pictures but good enough for the backyard pictures. (I can't speak for dslr's as they have a much greater field of view and most likely don't need any reducer)

Thoughts and comments are welcome please

[Merlin66 (Ken)]

Yeah,
I recently tried a similar arrangement - x0.63 on the ED80 (thinking about spectroscopy) certainly appeared to work OK but I thought the reduction was more like x0.75 than x0.63.
(Interestingly, Measuring your images I get about x0.75 reduction!!)

[Nikolas (Nik)]

Thanks Merlin I wasn't 100% sure of the actual reduction but even 0.75 is very good.

Still have a few things planned so I'm gonna see if I can reduce the distance on the sct to 2 inch adapter and see if that will make a difference.
SCT to 2 inch attaches to the camera, the other adapter attaches to the scope.

[Merlin66 (Ken)]

According to my Reducers V2 spreadsheet, the reducer would need to be 120mm inside prime focus and the chip 80mm behind the reducer to get around x0.63.
(This is based on a reducer focal length of 240mm)

[Nikolas (Nik)]

So according to the spreadsheet the further from the reducer the greater the field area? Interesting, I have a few extenders as currently the lens is about 55 + 18mm from the reducer effectively 73mm reducer to chip
Gonna experiment further, thanks

[Merlin66 (Ken)]

Just a note of caution....
Look at the distance the reducer has to be placed in front of the prime focus - depending on your focuser this may be difficult to achieve.

[Nikolas (Nik)]

I have plenty of focal travel inwards and outwards when I took those photos still plenty of inward travel
Gonna play with this sometime next week
and post the results

[mental4astro (Alexander)]

Will be interesting to see the star testing results. May well be that things are really good with a small chip. But as these reducers also correct for the inherent coma in the SCT design, larger chips may show a soft outer edge. Also, this SCT reducer-corrector is designed for an f/10 light cone which is sharper in shape than that of f/7.5. This will introduce some aberrations too, but one that may be fine in smaller chips, but problematic with larger ones again.

Ultimately photographic testing is the proof of the pudding. Looking forward to your results!

Alex.

[ChrisV (Chris)]

When I've done live imaging I've used SCT reducers on a refractor to speed things up. And also to increase the FOV as I've used cameras with small sensors (ASI290/224) for this. Have use a celestron 0.63, a meade 0.33 and an Optec 0.33 on my refractor with a range a T-spacers to alter the reduction.

Here's some shots from 2016 on my 80mm F5.9 refractor with different focal reducers, no guiding. They were all live stacked & stretched in sharpcap with no post-processing:

- Sculptor with an ASI224MC & meade 0.33 with no spacer giving focal reduction of about 0.8 (so F4.7). A stack of 40x 10sec subs. Not much coma here.

- Barnard 72 with an ASI290MM & meade 0.33 and about 10mm spacer giving focal reduction of about 0.66 (so F3.9). A stack of 29x 6sec subs. You can see the coma around the edges, but that's pretty severe focal reduction with an SCT reducer.

[Nikolas (Nik)]

Awesome work, very little coma there in either picture, so glad it can be done, now for some clear Melbourne weather with no wind or sever dewing

[Nikolas (Nik)]

Originally Posted by mental4astro

Will be interesting to see the star testing results. May well be that things are really good with a small chip. But as these reducers also correct for the inherent coma in the SCT design, larger chips may show a soft outer edge. Also, this SCT reducer-corrector is designed for an f/10 light cone which is sharper in shape than that of f/7.5. This will introduce some aberrations too, but one that may be fine in smaller chips, but problematic with larger ones again.

Ultimately photographic testing is the proof of the pudding. Looking forward to your results!

Alex.

Luckily the 178 cooled is a small chip sensor though the proof will be in the pudding
cheers