Hi Tungkian,
Here is my take and interpretation on things:
It is best to see out in the field how a 4-inch good refractor performs. I am not sure your meaning of "good" has to refer to APOchromatic or a semi-apo or even an achromat will do, such as the typical fast 4-inchers derived from Chinese manufacturers. A 4-inch good APO will cost an arm more. I might be second guessing on things, but your experience with "smudgy" images from your 6-inch may be interpreted as "soft", where even at focus or collimated, it still looks like that, then I would suspect you are suffering from a want for an unobstructed system, where you have a clean airy disk, then that is where you would yearn for a refractor, albeit smaller aperture. However, I would agree with KH that you must collimate your current scope well enough (OVER 200X......300-400X is best). 200X is just not enough.
Do attend one of the stargazing sessions where you have a few people coming with telescopes, and see your take on justifying for a bigger refractor purchase. That would be best. I have a 4-inch apo to sell currently, but it is an astrograph though.
WTB a 4 inch or larger refractor
oops..ok..i jus calculated..i collimate my scope at 333 x (1500 mm focal length/9mm TMB planetary with a 2x barlow).
yes, i do think that i'll need to take a look around before i decide. i think 'soft' would be the term to use.
had a conversation with weixing just now, and judging from his experience, he mentions that the difference between a 6inch SCT and a 4 inch apo is not really significant to justify the cost..so the best judge would be looking through one!:D when's the next stargazing session???
:D
yes, i do think that i'll need to take a look around before i decide. i think 'soft' would be the term to use.
had a conversation with weixing just now, and judging from his experience, he mentions that the difference between a 6inch SCT and a 4 inch apo is not really significant to justify the cost..so the best judge would be looking through one!:D when's the next stargazing session???
:D
It has been released. On the website now.ariefm71 wrote:If die die must have a portable refractor, wait for the new Orion 102 f/7 FPL-53 doublet (no, this is not a typo) which will be released later this year. Optically it should be better than the SV or AT or WO which is using FK-51.
I don't think it will be better optically than the SV. Don't know about the AT or WO. Having FPL-53 does not guarantee a better telescope. As Roland has pointed out many times, it is the mating element that determines how good the correction is. There are a few features that it lacks as compared to the SV at least.
The elements in the SV are hand matched.
Lenes are in a temperture compensating cell that is collimatable.
Each telescope is star tested before shipping to ensure performance.
Availablilty of the FT focuser direct from SV.
The Orion is in essence a mass produced scope. The SV is hand made with care and extremelyl high QC.
Vincent
Hehe, if you look through my ED 115S (4.5" apo) and feel like getting it, then Remus Pentax 100mm Astrograph is within my dreams already!
Photo Album:
http://www.flickr.com/photos/14113965@N03/
http://www.flickr.com/photos/14113965@N03/
Roland has also pointed out that making a doublet is much more easier than triplet. I have a confidence that the Chinese can pull this off, same as what they did with the ED80 and ED100. I guess only time will tell.I don't think it will be better optically than the SV. Don't know about the AT or WO. Having FPL-53 does not guarantee a better telescope. As Roland has pointed out many times, it is the mating element that determines how good the correction is. There are a few features that it lacks as compared to the SV at least.
True, a doublet is only 2 elements and much less complicated. But how good the second element matches the first still ultimately determines the color performance. TEC has made telescopes using FPL51 up to 200mm. I would hardly call their telescope inferior to ones using FPL53.
These scopes are made with the bottom line as the first priority.
So... what will be given up? You can't get a free lunch!! In the previous ED series, it was shown that they vignetted the aperture. This effectively increased the focal ratio and so allowed them to achieve the better then expected color correction.
But anything can happen. I might try and get one to test, Orion has a great return no questions asked policy. I'll try and get an SV102ED to compare side by side if I can.
Vincent
These scopes are made with the bottom line as the first priority.
So... what will be given up? You can't get a free lunch!! In the previous ED series, it was shown that they vignetted the aperture. This effectively increased the focal ratio and so allowed them to achieve the better then expected color correction.
But anything can happen. I might try and get one to test, Orion has a great return no questions asked policy. I'll try and get an SV102ED to compare side by side if I can.
Vincent
Photo Album:
http://www.flickr.com/photos/14113965@N03/
http://www.flickr.com/photos/14113965@N03/
