I'm not looking to "cure" mediocre seeing. Just for something that will perform at least as well as my FC100DL in mediocre seeing. My C-8 does not. I have set it up on a variety of surfaces including asphalt, cement and yes grass. It performs poorly on any surface until it's cooled which typically takes three hours or more, even on grass, and in mediocre seeing it doesn't matter what surface it's on, the planetary performance has been less than mediocre. The one time it performed well on planets I had it set up on a second floor deck. And it was a mild evening in mid July with good seeing and a cloud layer moving in, so my viewing was unfortunately cut short. But the C-8 gave a brilliant view of Saturn before the clouds moved in. I don't think my FC100DL is "magic". I have seen my C-8 out perform it by a wide margin on occasion, but only rarely when the conditions were perfect which is rare where I live. My experience has been that the FC100DL out performs the C-8 on planets the vast majority of nights when set up on exactly the same surface. The FC100DL even performs well when it is set up on warm black asphalt. It's not "magic", it's just a non-folded unobstructed light path with a near perfect optical figure in a small tube that cools to ambient quickly and performs well in a variety of temperature and seeing conditions. I'm looking for something a little larger that maintains the performance of the FC100DL in less than ideal conditions.
It's unfortunate that real estate prices and massive fires from New Mexico up into Canada are convincing me not to retire to the west (where I grew up). I would love to see my c8 take 3 hours to cool down because I have never ever seen that here in the NE. But I hear it from west coast people with great regularity.
I have a good friend who has a Ph.D. in materials science with whom I used to observe regularly. Our discussions were about why the C14, which weighs 3x the c8, cooled down so *fast*, not why it cooled down so slow. It was his observation. As a practical matter most of my energies are put into heating the C8 and C14 up (to prevent dew); cooling down takes care of itself.
Nonetheless a 5 inch apo is a great thing. Get one. You can't go wrong with a TEC. And I sometimes have a hankerin' to get a CFF 135 or 140. That's when I think I would be wise to get out of this forum and cool down for a bit. I have my reasons for wanting two 92mm apos, but I'm not sure I would want a GT130 and a 140 anything (TEC or CFF).
For sure you leave the domain of the GT130 and get a 140mm you're leaving the domain of an airline portable optic. Well, maybe. Never say never. But it would take some thinking.
Spurred by the endless wisdom on the topic offered here, at the last NEAF I asked Roland whether there was any truth to significant difference in cooldown times for triplet oiled apos versus triplet air spaced. He offered the view that it was part of the weird stuff out on the internet and that he didn't have an opinion about it either way.
Edited by gnowellsct, 12 October 2020 - 10:03 PM.