Pricing for a magazine article

This is my first foray in professional nature photography.
Currently I'm negotiating with several Romanian photography magazines about collaboration and publishing articles.

This would be my 3rd article published, but the first one on a professional basis. Didn't ask money before.

OK, the material is about wide-field astrophotography,
It will be 2 page (minimum) 'how-to' article, based around an image I've posted here last month -->> Milky way before sunrise
The image will probably be printed full-page (or close to it) and the text will have screen captions to explain the post-processing workflow.

I have no idea what to charge. I know that photography magazines, in general, have low rates and generally prefer "donations", sort of speak, rather than paying for images and labor. In Romania that applies even more extensively.
On the other hand the image is unique, and the product of many many nights of hard work. The article itself will be very comprehensive and informative (probably a premiere in Romanian media). So I have to charge something.

I've also started organizing workshops and small photo-tours. Advertising them in the magazines I'll be publishing would be a BIG plus.
Should I settle for a small fee (for articles) + advertising space?
Or should I insist on a fair price and push it with the advertising? What should that fair price be (at minimum)?

Thanks for looking. Look forward to your replies.
I appreciate any advice.