Reccomend me a Refractor

Hi, I believe you have to narrow down a bit your question because by Barlow you have a full range between 1.5x to 5x, or even more, also you have the factor of the seeing. A decent f/7 ish refractor can do what you are asking but, the final result will depends if you match your pixel size of the camera will all the other parameters, so to achieve the sharp image at the resolution you want to. 
A number of ED refractors can do the job, all the way from 80mm to 110mm or 120mm of objective diameter, but the f number is relevant too. In some "recipes" it is suggested that the final combination should be around f/20 or f/21, so the f/7.5 with a 3x barlow is fine (for sun/moon/planetary).
But in my modest experience, the atmosphere stability is the more critical part when sharpness and resolution is what you want to achieve.

I apologize if I misunderstood your question, but this is what I can contrbute. I use an ED 80mm f/7.5 like the Vixen ED80Sf, a quite cheap and decent refractor, in my opinion.
Now if you want to keep the 400 mm of focal length, which I believe normally thay are around f/5, it could be possible with a 4x barlow, and many options are available. In this case, I believe that it will depend on what else you wish to do with that scope.
Cheers and CS

I plan to use it with 3x TeleVue barlow for lunar

and no barlow for DSO

Also, it would be very helpful if I didn't have to use a flattener

Are there any scopes that are already corrected to have flat FOV?

In this case I suscribe the FRA400
CS

FRA400 or 65PHQ

FRA400 is faster, but IMO gives slightly softer images than the next option

65PHQ is slower, but makes up for the slowness in sharpness; the stars taken with it are beautifully sharp and pinpoint.

pick your poison 

In your situation, I would choose the 65PHQ.

But that's just me; I like to choose maximum sharpness for my budget, over speed.

FRA400 or 65PHQ

FRA400 is faster, but IMO gives slightly softer images than the next option

65PHQ is slower, but makes up for the slowness in sharpness; the stars taken with it are beautifully sharp and pinpoint.

pick your poison 

In your situation, I would choose the 65PHQ.

But that's just me; I like to choose maximum sharpness for my budget, over speed.

I have been very happy with my 65phq (in my case the ZWO painted one!).  I too wanted sharpness over speed.  No complaints.  Even reduced with a full frame sensor the corner stars are not too bad.

Askar V all the way for me. Never turning back

I have a WO GT81 with the reducer I plate-solve at 384mm. Solid RP focuser, manual rotator is solid. Takes a ZWO EAF. Heavy, as most triplets are… does a solid job on the ASI2600's/571. 

CS Tim

Ferenc Szabo:

Samuel Fyfe:
I can only speak for my experience, but I have an Astro Tech AT72EDII --> https://www.astronomics.com/astro-tech-at72edii-refractor-ota-fpl-53-f-6.html

I absolutely love it, and even with some minor water damage in shipping (UPS's fault, not the seller on CN), it still gives great images. I use a 0.85x reducer/flattener, so I'm shooting at 344mm in my images, but stock, it's at 430mm. a 1x field field flattener should be perfect. It's got superior glass to most scopes in it's price range, shockingly low chromatic aberration for being a doublet (I don't correct for it in my images, and I think it speaks for itself), and the focuser is really smooth and easy to use.

Maybe I had a horrible luck or there was a bad batch present like a year ago, but I sent 2 of these back within just a few months.   The stars were bloating in one and unable to fix, while the other had pinched optics (stars looked like clover).  After that I gave up with buying Astrotech scopes.

@Ferenc Szabo 
Star bloat is definitely an issue with mine! No pinched optics though, which is good haha. Thankfully I’m mostly shooting narrowband so it keeps the stars a lot more in check, as well as BXT which gets me the rest of the way. It’s definitely in the budget category of scopes in this discussion, but it’s been a great introduction for me cutting my teeth in the hobby!

Alien_Enthusiast:
Upd: 

I got a pretty big camera that weights over half a kilogram

and the Star Adventurer Im using has a 2.5kg limit

So I need a telescope to be at least 2kg and better if its around 1.5kg

FRA weight almost 3kg

65PHQ weights 2.8kg



Does anyone know a scope within such limits?


WO Zenithstar 61 is around 1,45kg - but its only a doublet

Askar 135FMA looks nice, a tiny triplet. 



Any other options?

Great suggestions, but most of them are over 2,5kg

Takahashi FS-60CB seems to be the perfect match, but finding it on aftermarket can be easier said than done