topic

DE nerfed the Secura Lecta but it still isn't the worst method. Form a credit farm group.. Chroma + Secura Lecta on Akkad (Eris). You can find more details about this in any of the thousand YT vids on the subject.
http://warframe.wikia.com/wiki/Secura_Lecta

Then there is the Index. Which in my opinion in terms of time is the best method. Form a experienced quality group to do High Risk which nets you 200k credits.
http://warframe.wikia.com/wiki/The_Index

There are also Dark Sector missions which are guaranteed credits on victory. I recommend Seimeni on Ceres (20k), easy 5 wave defense against infested. I've seen other people suggest Hieracon on Pluto which is an excavation mission. They say to start one extractor and evac after it.
http://warframe.wikia.com/wiki/Dark_Sectors

For icing on the cake, a credit booster will cut your farming time in half.

Edit: Another way to scrape up some credits is to sell stuff from your inventory that you have duplicates of. For example plain Oberon Blueprints like Oberon Neuroptics Blueprint sells for 3,500 each, same for chassis and systems.

This post was edited by Mondain on May 2 2017 05:31am

thxbro

best for me is ARMANA on last planet(cant remember name lol)

survival against infested, 22k after 5min

chance for 400endo as 5min reward

Best for me is Index, u go with Medium Investment, u do it without any issues (unless u got team of noobs) and u get after 5 minutes, 135k credits (270k with booster)