Focal reducer for C90 Mak?

I’m not sure there are reducers for it? I can’t find much on the interwebs about it, at least not about dedicated ones for the C90.  I also can’t quickly find reducers for other branded Maks (skywatcher and Omegon), so i doubt it.

and even if there are, is it really worth it? 

at F14, how much can you reduce it? Maybe F10?, which is still very slow for a scope and limiting for a lot of targets. Maksutov just aren’t great for nebulae photography. 
They are beasts at visual, Lunar, planetary, solar (with a filter) and maybe some bright targets (orion, dumbbell nebula), so i’d keep it for sure for those targets! But not sure how much it’s worth to invest into it to use it for nebula photography. 

great to see you have a redcat though, i have one too on my second rig and it’s a great way (and very forgiving way) to capture a lot of good sized targets. I’d focus on that, and then maybe work on upgrades after. 


no idea what would be best after. Maybe a 550mm triplet. Or a 600-750mm Newtonian. Or upgrade somewhere else first, like the mount, and maybe a dedicated cooled camera if you don’t have that already.

Rod Van Meter:
Thanks, that's pretty much the conclusion I'm coming to, also.

I'm definitely focusing on the Redcat for now, and the next big purchase is definitely a stronger, lower-vibration mount. I don't yet have a guide scope or a cooled camera, so those are on down the road; my next 2-3 grand in purchases is pretty clear.

But if a few hundred bucks would turn the C90 Mak into something in the 600-800 range (and equivalent f/ gain) with reasonable quality, I'd jump at it. Otherwise, it's wait until those above purchases are done, then drop 2-4 grand on a bigger APO or maybe a Celestron 8" RASA.  (f/2! Holy cow! Sounds demanding on focus, though.)

Given that we are *always* an hour or three's drive from dark, portability is also a factor, which is one reason I love both the C90 and the Redcat.

Are you using any filters? Consider something like an Optolong L-Pro or L-Extreme. Cuts out on a lot of light pollution and it means you don't always have to drive the 1-3 hours to the dark.  More than enough people are enjoying this hobby from quite light polluted areas, or even the middle of cities, with the use of the right filters. Which might mean that portability could be less of an issue for your future purchase choices by throwing in a 200 dollar filter into your setup.

(that said, I understand how enjoyable the hobby is from a true dark site)

You might try this:
https://www.firstlightoptics.com/reducersflatteners/vixen-062xfocal-reducer-for-vmc200-and-vmc260.html

andrea tasselli:
You might try this:
https://www.firstlightoptics.com/reducersflatteners/vixen-062xfocal-reducer-for-vmc200-and-vmc260.html

Thanks, Andrea. I know the newer C90 Mak has different threading & structure on the back than earlier models, will have to figure out if that is compatible.

Rod Van Meter:
I have a Celestron C90 Maksutov-Cassagranian spotting scope that I use for looking at the moon and planets, and I have photographed the moon through it. For a couple of hundred bucks, it's a pretty nice little scope. I'm considering whether it's potentially useful as a photo instrument, but of course at f/14 it's slooow, and it's a little long for a lot of diffuse nebulae. So, I'm looking for reducers.
https://www.celestron.com/products/reducer-corrector
tells me that the Celestron focal reducers aren't compatible with the C90 Mak. So, a) does anybody know of a reducer for this, and b) would you recommend it?

FYI, I used to do visual astro and dabbled in astrophoto in high school, four decades ago, so I know my way around a scope, but am just getting back into the hobby after a long time away. Just acquired a Redcat 51, did first light on it last week, and am very happy with the results; it will be a while before I have exhausted its possibilities and my skill level has outgrown it. But a second lightweight option in the 500-700mm range would be nice. My next major purchase clearly needs to go to a better tripod & mount, but wondering if I can make use of the C90 for other than the above visual uses.

I have some experience with this. I am using a 127mm maksutov cassegrain, native FL of 1900mm, so F15. I am reducing it. It took a good deal of work to figure out. Almost all SCT focal reducers also correct/flatten, which is not needed with a mak-cas as the corrective lens already produces a fully flattened field. 

Here’s what I ended up doing. I bought the Antares 0.63 SCT reducer; which is the only one I could find that does not correct, only reduces. This model was already discontinued but OPT still stocks it. here is a link. This is the only place where I found it: 
https://optcorp.com/products/antares-f-6-3-sct-focal-reducer

But…attaching SCT threads to the 1.25” visual back of the mak-cas was the next challenge that you’ll also have to overcome. For this I found this baader adapter ring that works between a mak-cas to SCT threads. 
https://agenaastro.com/baader-sct-adapter-etx-nexstar4-c90.html

From there you can use an SCT T-adapter to the T-ring of your camera. BUT…you will then run into the final issue to overcome, finding proper backfocus. Why is this hard here? Because Antares doesn’t publish a backfocus spec for this reducer ANYWHERE. After much trial & error I finally came to understand that the actual backfocus of this Antares reducer is about 105mm. I found different numbers posted in threads on cloudy nights, etc., but those were all wrong in actual practice. 

I hope all this helps & saves you the time it took me to work all this out. I worked all this out in a month long project at the beginning of this year. After doing all this it brought my setup down to F9.

Do not listen to others on this thread who tell you that is “too hard” to image with a small scope at a higher focal ratio, etc. I BEGAN with this rig I mentioned above & am still using it with excellent results through a lot of light pollution. Keeping well under your mount’s weight limits (less than half) & having a well balanced setup & getting excellent polar alignment allow for this F9, 5” setup to be very good for me. I often hear that you “have to” begin AP with an ultra wide field, fast focal ratio rig. This is not a requirement & you can do plenty with that scope you have, believe me. 

here’s an example of what you can do with that mak-cas & the reducer I mentioned above. Keep in mind that I have only been doing AP since this past March. 
https://www.astrobin.com/02m98e/

The next issue of fitting filters into the imaging train in this is a different conversation, but I worked that out too & do use different sized filters at different times. If you want tips there based on my own trial & error just ask.

@astrodawg P.S. I know the back on the newer C90s is different than the older ones, so gotta figure out what threads to what, and whether there is enough travel to be able to focus that way.