Does the Celestron F6.3 reducer for SCTs correct any optical aberations?

[Ags]

Thinking of getting a Celestron 6.3 reducer for photography, but wondering if it might improve visual performance too?

Edited May 5, 2020 by Ags

[GazOC]

Seeing as no one else has had a stab at this 😉. Yep, the FR does correct for aberrations (field curvature IIRC) in the SCT but I'm not sure if they are detectable at the eyepiece or it's just for the pixel peepers

[Greymouser]

I got the Reducer when I bought my C9.25, so have used it quite a lot for visual use only. I would say it very much improves the view, it's almost like a different, better telescope. I do not think I would use the C9.25 without it now, the correction just so much improves thing. I am told it fits my C5 too, but have not yet tried that yet, but will, eventually. My C5 is excellent anyway, so I am not sure I could take much improvement! 

Without a doubt improves visual, no idea about photography, but a very good buy on my part I think, wouldn't want to be without.

[JG777]

I think if your imaging you might notice more, its been a while since I used mine on the 9.25 but I think I recall slight improvements around the edges. If I can find mine I will sell it as I prefer the native view, darker background and objects to me stand out a little more. 

[Ags]

@JG777 especially regarding sky background brightness, were you comparing at the same exit pupil?

[michael.h.f.wilkinson]

I think it also reduces coma

[JG777]

7 hours ago, Ags said:

@JG777 especially regarding sky background brightness, were you comparing at the same exit pupil?

I remember comparing a number of my EPs with and without the FR and although you get a wider field it was a brighter one as well, and some objects just didn't seem to stand out as well for me. Also on my cat I wanted to use a 2 inch  diagonal, which if you use with a focal reducer can introduce vignetting with some EPs, so if you go down the FR route then depending on your EPs you might need to stay with a 1.25 diagonal. 

If your imaging then the FR is a must have I would have thought, but for visual my personal thoughts are the scope operates better as it was intended. For widefield I have an F5 newt!

No right or wrong way here, maybe if you could borrow one to try before you purchase if your just visual. 

[michael.h.f.wilkinson]

I used to work with the focal reducer for visual, but have since switched to a 2" visual back and diagonal. I only use the reducer for imaging. The moon is captured nicely in a crop sensor camera with the reducer in place

[JeremyS]

2 hours ago, michael.h.f.wilkinson said:

I used to work with the focal reducer for visual, but have since switched to a 2" visual back and diagonal.

Me too: 2-inch eyepieces on my C9.25 were a revelation. I stopped using the reducer at that point as I don't mage with with that scope (I have a reducer on my C11 which is exclusively used for imaging, mainly to get a wider field)

[Ags]

@JeremyS and @michael.h.f.wilkinson Can I ask why 2-inch EPs are preferrable for you to 1.25" EPs with reducer? As I don't own any 2" accessories and don't plan to, the reducer seems logical - and will be much lighter (got to be kind to my AZ-GTi). And apparently the view with reducer will be more corrected...

Edited May 6, 2020 by Ags

[Ags]

I picked up a second hand 6.3 reducer/corrector for a very reasonable price and just came in from my first night out with it. Seeing was exceptional (in some directions, not in the direction of Tower Block C that looms to my south). I started out visual using my ES 24/68 and ES 6.7 eyepieces, with an achro Revelation barlow making a guest appearance. 

I had a shock when aligning on Arcturus - the star was massively distorted! But I soon realized it was just the 24/68 was misaligned in my cheap diagonal. Second alignment star and first target was Polaris. I have been having some trouble with doubles with my C6 - the star images have been looking a bit untidy making doubles unsatisfying. Polaris A looked a lot cleaner in the 24/68 but I could not split it at that magnification - it normally splits with this eyepiece when there is no reducer in the image train. I switched to the 6.7 mm EP and the view was delightful - a clean and round Airey disc with clear diffraction rings and the faint companion nicely resolved. The view was very similar to the clean and satisfying images I usually see in my Maksutovs. I added the barlow for 280x magnification, and the view held up nicely except for the chromatism of the barlow. 

Next stop was Izar. This has always been a difficult split with the C6. Once again the view with the 6.3 reducer was cleaner and more pleasing at 140x and 280x and the split was easy and the fainter companion much more prominent. Izar was in the vapor trail of Tower Block C so conditions were not favorable, but the scope, reducer and eyepiece performed well.

Next on to M3 - goto was slightly off but now my C6 is a widefield scope so the globular was easily located and centered! The view was OK, a tie with similar views without reducer. By the way I am comparing (by memory of course) the view on no-reducer with a 10 mm eyepiece and with-reducer and 6.7 mm eyepiece - so very similar magnifications and the same 82 degree fields.

M13 was next and I felt I got a particularly good view tonight, with stars resolved right across the cluster at 140x. Not sure if the improved and tighter star images the reducer/corrector is providing just helps me tease out those faint stars at the limit of my scope's light gathering abilities?

Switch to my camera and started shooting M13 - so much easier with a wider field. I don't have to keep correcting for drift every 30 seconds, the stars are more point-like, so much brighter on the pixels they do hit - and with less focal length the AZ GTi doesn't micro-wander nearly as much. Unlike imaging at F10, I could now image without binning. I kept shooting until my laptop ran out of space (which doesn't take a lot of shooting). Currently AS3! is refusing to process the gigantic video files, but I will sort that out in the morning.

On 05/05/2020 at 21:33, Greymouser said:

I would say it [6.3 reducer/corrector] very much improves the view, it's almost like a different, better telescope.

I absolutely agree!

On 05/05/2020 at 22:31, JG777 said:

I recall slight improvements around the edges

It's funny how two people can look through the same equipment and see polar opposites. I feel the difference with my scope is like night and day 😀

Edited May 21, 2020 by Ags

[JG777]

Great report Ags, a good advert for the reducer especially in a C6. Pleased its found a good home!

[Ags]

Processing my data from last night - normally AS!3 gives a quality graph with barely a quarter of the data over the 50% line, but last night's data is 90% over the 80% level! I think quality only dropped at the times when I recentered M13.

[ollypenrice]

I can only comment on the 6.3 reducer in a number of Meade SCTs I've used. Like Jeremy, I much prefer a good wide angle 2 inch EP over the reducer-and-1.25 option. There is no point in using the reducer with 2 inch widefields because the baffle tube limits the FOV anyway.

Olly

[gorann]

TS sells an Astrophoto Edition of the C9.25 and C11 where they add their own 0.63x reducer, so that one should at least correct the field. I assume the Celestron reducer does the same. No idea which one is the best but I assume there will be reviews to be found by googling.

https://www.teleskop-express.de/shop/product_info.php/info/p3657_Celestron-C9-Astrophotography-Edition---Crayford--Corrector-and-Off-Axis-Guider.html

Edited May 23, 2020 by gorann

[Ags]

3 hours ago, ollypenrice said:

I can only comment on the 6.3 reducer in a number of Meade SCTs I've used. Like Jeremy, I much prefer a good wide angle 2 inch EP over the reducer-and-1.25 option. There is no point in using the reducer with 2 inch widefields because the baffle tube limits the FOV anyway.

Olly

The wider fields  and ability to reach larger exit pupils are useful of course, but I want to emphasize I am seeing significant benefit at high mags too. Performance on doubles has been transformed by the reducer. 

Another consideration is weight - I don't want to be using enormous eyepieces or mixing barrel sizes.

[Ags]

Just come in from another night of looking at doubles with the C6 with reducer. Again struck by the Mak-like star images I see, notwithstanding a very teeny bit of miscollimation that I must sort out sometime.

I used my Explore Scientific 24/68 and 6.7/82 for all observations. Polaris was a lovely sight with perfect diffraction rings and a faint but clear companion. The Double Double was split into all four components despite still being a bit low. Albireo was colorful and best in the 24/68 with a slight touch of artistic defocus to bring out the colors. Sadly 61 Cygni was hiding behind my grape vine.

Paid another visit to M13 and it does seem better resolved at 140 magnification with the corrector than it did at 150x without corrector.

All in all, I would have given the C6 six out of ten for visual use before corrector, but now I would award it eight or nine.

Edited May 25, 2020 by Ags