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Message: <blockquote data-quote="DRodrigues" data-source="post: 1102753" data-attributes="member: 55152">I came back to this issue since still searching for a good image erector... First I have to correct what I told in my previous message about the information sent by Baader: - they told me that mirror diagonals preserve better image quality than prisms. They produce one of the best, if not the best, erecting prism but didn't knew if I would be satisfied. I didn't considered it since is a 90º prism so not usable for birding, at least to me...I bought the Siebert prism (the version with wide field - ICP125W) and for the first time I could focus correctly at >70x with my old C5. However it has some not so good things:- to use it with a zoom I had to to make some bricolage with some Celestron material in order to use it - I will post photos latter - zooms usually don't have space so receive the image erector;- it vignettes with a Celestron ultima 30mm but it only slightly vignette a Optolyth zoom 31.5-10.5mm;- last and main problem - it strongly decreases the light availability, resulting the C5 with less light then the Optolyth 100 with the 30-90x. The earlier mentioned zoom in the C5 should result in about 40-120x, but after some testing with the prism in the C5, I think it increases about more 20-30% - probably due to changing in focus range of the telescope - this is known to happens when using binoviewers in Schmidt-cassegrain telescopes as the C5 (this kind of telescope have focus range enough for binoviewers but as the main mirror move so much it increases the focal length... At least was what I understood from  <a href="http://www.weatherman.com/nagler3.htm" target="_blank">http://www.weatherman.com/nagler3.htm</a>). This decrease in light is not noticeable in the normal 45º erecting prisms even with the same magnifications range, but as I told before is not possible to correcty focus at >70x.Meanwhile I discover that  birding scopes adapters for use reflex cameras are lens erectors and I will try to use the one from Optolyth - it increases also the magnification but let to pass more light then the Siebert. Will post more info if will manage to put it to work in a practical way...Also discovered that Vixen as a lens image erector and I tempted to purchase it since shouldn't reduce light and, being lens, should not have the problems of 45º prisms. However still didn't found a review of it. Did any one tested or use it? David</blockquote>

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