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Originally Posted by floyd_2
What an excellent article Joe. Thanks for sharing it with us all mate. The final practical example in Appendix 3 is sort of scary for the oldies with big scopes. A lot of us dream of having a retirement scope of 18"+ for visual, but it sort of doesn't make sense to move in that direction in later life as alluring as it is.
Like others here, I've already moved on to EAA and traded eyepiece time for screen time. Certainly I've seen more with EAA than I ever did visually, but it has been at the expense of the enjoyment of relaxing under the stars in my observing chair enjoying the views through my (now sold) Naglers.
I guess we all have to make allowances for being fortunate enough to get old and EAA for me has been a minor one that's opened my eyes to so much more viewing in recent years. This is especially so given the endless march of light pollution into my area.
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Thanks Floyd. The aim of the article is not to make you give up visual observing but to make you aware of how you can lose light and use strategies to make sure you don't. I have an 18" f5.5 and I live in a location that has no light pollution but varies from Bortle 1-3 depending on sky transparency. Visual observing is still a highly rewarding activity. An example is the Dumbbell Nebula. I don't just see the dumbbell lobes but also the fainter nebulosity in the full shell. So it looks roughly circular with the Dumbbells superimposed on the roughly circular shell.
I don't use 40mm eyepieces in the scope any longer unless I am hosting a much younger observer. A few years ago, I bought a second hand Tak LE50 eyepiece for a friend of mine. He had been looking for one for a long time but was in surgery having a pacemaker fitted. Just for giggles I tried it out using an 8" f9 Cass for comparison.
The brightness of a view of Eta Carina through the 18" with the LE50 closely matched the view through my 8" f9 Cassegrain because of light loss due to the nearly 9mm exit pupil. I am just on the verge of aging out of my 31mm Nagler in this scope. It currently gives me the light of a 15.5" scope so still an impressive wide field. In future, I might consider moving to a 21mm Ethos
for my wide field goto eyepiece which will give me a similarly wide field to the 31mm and transmit 100% well into my 70's and perhaps 80's by which time, the scope will be far too big and heavy for me to set up.
As you get older, consider moving to ultra-wide shorter focal length eyepieces. Sell off the long focal length models.
Cheers
Joe