12" Truss Newtonian f/4 or 14" Truss RC f/5.3 for astrophotography

I would think A lot would be down to your conditions. If it's just average I would think that you'll get more production at 1200 as compared to almost 2000. I just talking deep sky here. If you photograph the moon and planets regularly then I would change my answer!

Anderl:
I doubt that you will get more detail by going from 1200 to 2000mm of focal length.
1200mm paired with an imx571 chip will be fine even in good seeing conditions.

if your 250pds works for you why don’t you just stay with it? Another option would be an ts ontc 12 inch f5 scope, but same as before, i am not sure you will gain any additional detail. 

cs
andi

I cannot speak for the difference between a 12" mirror and a 10" mirror but I have compared results of 8" with my current 10" and the difference is sometimes astonishing. Those 2" of mirror diameter will add sufficient area to the mirror to be able to resolve more detail, which is why I am looking for something bigger.

Just keep in mind, CCDT67 is a pure tele compressor. Depends on the backfocus distance, it changes reducing factors.    It works best around 0.73x - 0.75. So, technically, it is not 0.67 reducer for RCs. 

In addition,   I had issue with elongated corner stars when I paired it with my 8" and 10" RCs with APS-C sensors.  Considering that, CCDT67 is not good choice unless you are small sensors.

Radu Marinescu:
Hello, everyone. 



Context: I am currently working on my backyard observatory which will be a completely homemade automated dome and will be ready sometimes next year, hopefully before summer. I have started documenting myself to pick a new telescope which will be installed in the observatory and of course that I want something more powerful than my current 10" Newtonian 1200mm f/5 astrograph, which was used for over 100 hours of exposure in the last two years.



Two of my choices so far are:


• TS-Optics GSO 14 inch f/8 Ritchey-Chretien Astrograph - carbon truss tube



- Native 2854mm | f/8 with dedicated 0.67x reducer to 1912mm | f/5.3


- Advantages: Larger focal length and larger mirror compared to the Newt which will resolve even more detail; good weight distribution; M117 focuser connector that allows easy upgrade to a heavy duty automated 3" focuser such as PrimaLuce ESATTO 3. 


- Disadvantages: Heavier; More expensive telescope and thus, accessories; harder to collimate, will depend on good seeing conditions to shoot the finest detail but Bin2 can be used as alternative for normal nights.

- PS, there is also a second generation model of this scope available with lighter and better primary mirror, but it's almost double the cost (9k euro), way out of budget.



https://www.teleskop-express.de/en/telescopes-4/newtonian-telescopes-315/newtonians-other-313/ts-optics-gso-12-f-4-newtonian-telescope-with-quartz-mirror-carbon-truss-tube-8972



• TS-Optics GSO 12" F/4 Newtonian Telescope with quartz mirror - Carbon Truss Tube

- Native 1200mm | f/4 with dedicated coma corrector for perfect flat field


- Advantages: Cheaper; sampling at 1200mm more forgiving in bad seeing; lighter; primary mirror with one connection point to the frame basically nullifying the concept of mirror pinching; easier to collimate; stronger body integrity compared to any other Newtonian tube due to the carbon truss build, ensuring collimation stability and temperature stability.


- Disadvantages: Smaller focal distance and mirror, will gather less detail on small galaxies which are my favourites; off axis weight for the standard Newt architecture focuser position, making the telescope more difficult to balance; less stability and structural integrity on the focuser since it's installed on the circular aluminium board (compared to the RC which has a strong focuser directly installed on the main frame), making it variable to flexure and tilt on complete heavy image trains (focuser motor, rotator, OAG, 7 slot 36mm filterwheel).



https://www.teleskop-express.de/en/telescopes-4/rc-ritchey-chretien-telescopes-75/ts-optics-gso-14-inch-f-8-ritchey-chretien-astrograph-carbon-truss-tube-7011


I hope I remembered all the pros and cons I see to both choices. The final telescope will be guided by an equatorial mount that has 75kg of photographic payload, so both choices will sit bellow half of the available payload of the mount. You can also recommend other telescopes if you know, that could be better choices but I am looking only for reflectors and an aperture larger than 10" (so it can be an upgrade over the current scope) and it must be within 6,000 euro. 



What do you all think? Thanks!

* Salut Radu, what mount are you using ?these are big scopes

I will get the JTW Astronomy Trident GTR

The step between 10" and 14' ist bigger. I would definitely go with 14". You can also think about a DOC telescope Truss 14" and buy separately a Astro Reflect mirror. 

CS,
Raul

I’m personally shooting with my DBA Certified 12” f/5 Newt as my main rig in my observatory. At some point I’d like a 14” myself. In my conditions here in Mid-Michigan the seeing just doesn’t get that great to image with anything much over 2000mm. Thus the reasoning for something 14” and a FR. Only telling you this for reference. BTW I’ve imaged with my 8” & 10” newts and resolution was very noticeable at each increase of aperture. See my gallery for the comparisons. Personally my 12” is a wonderful setup with upgraded optics all the way around and many modifications 

If you can afford the 14” then go for it. That said I think a 12” f5 newts is a great happy medium to your question in that your getting  1500mm FL along with 2” more of aperture to get more resolution in your images. 

FYI, again this is for reference, my mount is an AP1200GTO so a 12” newt is a fairly large scope. Not so much in weight but in mass so you’ll need to make sure you have a mount capable of handling the OTA.

Just my 2 cents.