The brightness, at least for a scope with newer Broadband coatings should be the same.
Clear skies, Erik
Visual astronomer since 1978.
Matthias Wirth 16" f/5
Takahashi FS-102 NSV on EM-10
Celestron 1983 C5
Zeiss, TeleVue and Celestron eyepieces
Nikon 18x70 IF-WP Zeiss Victory FL 7x42 Zeiss Victory FL 10x32
Les Canon 10x42L IS Swift 8x44ED Ultralite Questar 50th Anniversary Model, Astro Trac wedge on Manfrotto 475 tripod Stellarvue SV90T 90mm Fluorite refractor, Porta mount head on Bogen 3068 tripod Vixen GP-DX on Baader Surveyor Tripod
Quote:The forte of the Q is not ultimate performance per mm of aperture, but the superbly integrated and ergonomic package in a very compact and light form. And dare I say, beautiful colors and materials used? A timeless beauty:
Quote:I have read an interesting post on the Astromart site where Malcom Bird (also a contributor to this forum…thanks Malcom), was able to make a direct comparison between his 30 year old Questar and the Televue 85 refractor, on the same mount. He commented, as others have on this forum that the Questar image looked darker when compared to a similar sized refractor. This implied that the optics of the Questar disproportionally lost more light. http://www.astromart.com/articles/article.asp?article_id=909There was another post on this forum, where a member contacted Questar and asked what the loss of light was through a Questar 3.5 with Broadband coatings. They discussed this at the shop, and the answer was 1% loss through the reflective surface of the main mirror 1% from the corrector plate. There is another 2% loss through the control box if you do not use the axial port. The central obstruction adds another 10%. In total there is 14 % loss. Checking on the Company 7 website on the Televue 85, the transmission is 94%, so there is a 6% loss.Now some basic math to compare the surface area of 89 mm vs 85 mm, and factor out light loss of each scope. (8.9/2)^2 x pi = 62.21 x .86 = 53.5 for the Questar(8.5/2)^2 x pi = 56 x .94 = 53.3 for the Televue 85The brightness, at least for a scope with newer Broadband coatings should be the same.