Here is the place to talk about all those equipment(Telescope, Mounts, Eyepieces, etc...) you have. Not sure which scope/eyepiece is best for you? Trash it out here!
"Many first-time telescope buyers get seduced by slick multi-page ads in magazines that sell small aperture Schmidt-Cassegrain Telescopes (SCT). These mass produced telescopes utilize a folded optical design to save space and money. They all have a large 33%+ central obstruction, small primary mirror and a corrector plate that eats up and distorts light. The result is dim, dull images and a disappointed customer. (Most of our customers are former SCT owners that have seen the light, so to speak!).
We offer an alternative. The 15"Obsession has 4 times the light gathering power of the popular 8" SCT yet costs about the same. What's more, the Obsession 15" is a pure Newtonian telescope. It doesn't have any of the SCT's optical disadvantages. The Obsession 15" is a dedicated visual telescope. The result is bright, exciting images and an enthusiastic astronomer. Easy to set up, the eyepiece height is always less than 5 feet off the ground. It features the same award winning design and quality that has made Obsession the standard by which other Dobsonians are compared. If you and your family want to be turned on to visual astronomy, get an Obsession 15" and really see the Universe! "
That is "good" advertising! Makes me start to think that maybe my 8" SCT is not offering the best views ...
Any of the more experienced guys here wanna comment on this? Is the 8" SCT really as bad as they make it out to be? I know it is one of the more popular scopes around, but is it really so much better going for a 15" Truss dob? (Biggest selling point is the 4x light gathering power ... )
With the truss design, portability isn't such an issue anymore if one drives. With my 8" SCT, I've gotta consider the weight of the GEM and counterweights as well when transporting.
Also looking for comments in local context - light pollution, environment etc.
Any thoughts?
Jeremy Ng
C8, CR-150HD, TMB 80 f/6
Orion SVP Intelliscope, AstroSlew I
Minolta Activa 12x50WA
For visual use, I have always find that newtonians (even the mass-produced ones) consistently give better views than SCTs of the same aperture. There is truth to the conventional wisdom that the large central obstruction of the SCTs place them at a disadvantage when it comes to contrast. My 10" Orion dobs gave brighter, sharper and more contrasty images compared to a 11" SCT. And it achieves higher FOVs too.
In Singapore, the fact that you can't easily send your whiz-bang SCTs back to the factory for repair is a big disadvantage IMO.
We do it in the dark...
Portaball 12.5"
Takahashi Mewlon 210
William Optics 110ED
...and all night long!
As a dob owner. I feel that the dob will out peform the SCT as the central obstruction is much less and there are less mirrors (2 only) compared to SCT with 1 corrector and 2 mirrors, hence brigher images. Central obstruction will affect the Modulation Transfer Function (in plain english means contrast). The worse part of the SCT I feel is that the collimation using a star is real troublesome if you don't have a mount that tracts; I am waiting for my obsession 12.5 inch.. hehe. The 15 inch I feel is just too big for my car and too costly (in usd that's why) although about the same price as those GPS SCT; obsession scopes are very low profile (the height of the mirror box) compared to other dobs. The 12.5 inch on the other hand can fit into all car boots, has curved spider so no obvious diffraction spikes and you don't need a hatchback car or MPV whatever type that has 3 or 5 doors. Perhaps when I get the scope I will give a review on it.
Yup! I heard bout it too, but not sure who's doing it.
That would be too large a responsibility considering the price of the mirror and setup. I wouldn't mind helping with misc. stuff but I don't think taking over the project would be appropriate as the rest of the guys have spent lots of time and money on it already.
Jeremy Ng
C8, CR-150HD, TMB 80 f/6
Orion SVP Intelliscope, AstroSlew I
Minolta Activa 12x50WA
Can the owners of the 16" truss dob project please identify yourselves?
From what I understand, there were some mechanical issues with it such that it was not worth continuing e.g. counterweights of >30kg.
I think we have enough collective knowledge in Singastro to make it work. I don't mind taking a look at the progress and offering some input in terms of $ and time to see how we can resolve it.
Umm...how come nobody points out this : I don't think that 15" Obsession cost the same as that 8" SCT.
>>The 15"Obsession has 4 times the light gathering power of the popular 8" SCT yet costs about the same.
If it cost about the same, I would have bought one long ago.
But it is true that the newtonian always perform better than a similar aperture SCT. Lack of lens, lack of big central obstruction is a big plus. Go take your 8" SCT and put next to the 8" Portaball and compare. You will see a big difference in terms of contrast and sharpness.
