Catanonia

If the focal length is (more or less) the same you can just directly compare the areas of the objectives, Pi R squared. That is your light grasp and it is concentrated onto the same area because the f length is the same. OK, central obstruction, but in round terms you are indeed twice as fast.

Olly

Sweeter than a sweet thing that has been molested by the big sister of all things sweet

So my MN190 is gathering twice as much light in the same time on the same object as my ED120 ?

They are roughly the same FL 1000mm compared to 900mm the only difference is 190xF5.3 compared to 120xF7.5

Well, your Mak gathers (190/120)^2 = 2.5x more light (ignoring the central obstruction). However, it also spreads it out over ((190*5.3)/(120*7.5))^2 = 1.25x more area. So, if you haven't changed you camera, it is putting 2.5/1.25 = 2x more light into each pixel than before.

(though it's 4am, so I absolve myself of stupid maths errors )

Wow : Nice work mate and makes sense.

So a 5min sub now on the MN190 is almost the equivalent of a 10min sub on my old ED120....

Simple questions really, or maybe not.

120mm F7.5 scope 900mm My old ED120

compared to a

190mm F5.3 1000mm scope My new MN190 Mak Newt

What is the percentage difference in light gathered between the two over a nomimal period say 5 minutes ???

Fantastic work Olly, never seen this before. Wonder what this would look like full mosiac in Ha.

nice. I use Microsoft ICE for the final image. See this section of the forum for some file scripts I shared to help will all the files and even batch processing in Registax to save you processing each avi. Believe me it does help especially if you have 120 of the blighters

Come up north. I am in Sandbach, Junction 17 of M6 and nice skies. Further enough away from Manchester and Stoke on Trent with nice skies. Not quite countryside, but close.

I personally hate London. Too big, busy, noisey and polluted and 'most' people couldn't care less for you.

Move north, much cheaper and friendly