Table of apertures and comparative light gathering amounts

[mhc]

Quick and approximate table I knocked up to show the %increase (or decrease) as one changes aperture. Thought it might help fellow newbies when deciding on OTAs.

Read across to find OTA diameter (mm) that your moving from, then

Read down that column to the OTA you're considering moving to see %change.

	80	127	130	150	200	250
80	100%	40%	38%	28%	16%	10%
127	252%	100%	95%	72%	40%	26%
130	264%	105%	100%	75%	42%	27%
150	352%	140%	133%	100%	56%	36%
200	625%	248%	237%	178%	100%	64%
250	977%	388%	370%	278%	156%	100%

So, going from 80mm to 150mm = 352% increase, whereas going from 150mm down to 127 provides only 72% of the light you had.

Note that it doesn't work exactly across different types of scopes, as their is no accounting for secondary obstructions, etc.

HTH,

Mark

[geppetto]

Nicely done Mark

Very usefull

[Kaptain Klevtsov]

So if I use the 200mm Newt. with a focal reducer to get the same image scale as the ED80, I'll get 625% more light down it. Cool.

Captain Chaos

[Whippy]

Bit bulky for a light sabre though isn't it?

[Kaptain Klevtsov]

I have it on good authority that a green laser pointer, a Barlow lens and a 200mm Newt. will do a great lightsabre impression.

Captain Chaos