Tuning up the Celestron Travelscope 50

In the good old days, refractors are used to be worry free instruments. Even for those without adjustable lens cells, the scopes would be correctly collimated out of factory. However, this is not the case any more, especially for the entry-level models. This is hardly anyone's fault because we are now paying one-third or even … Continue reading Tuning up the Celestron Travelscope 50

DIY Old School Guiding Eyepiece

In the old days when doing astrophotography without digital auto-guiding, most guide-scopes were long focal length refractors, usually no larger than 4". On top of that, one would also need a high-power eyepiece (about 9~12mm) with an illuminated reticle for continuous monitoring on guiding errors. However, such guiding eyepieces are often quite expensive, about 2~3 … Continue reading DIY Old School Guiding Eyepiece

The Celestron Stock 10mm Eyepiece

Many entry-level telescopes (Celestron, Orion, Skywatcher) include a set of eyepieces like the above, economical 3-element of unknown designs. Most people simply called them "modified achromatic", "modified Kellner", or just "Kellner". So what actually are they? A "true" Kellner consists of a singlet bi-convex field lens and an achromatic doublet plano-convex eye lens, it has … Continue reading The Celestron Stock 10mm Eyepiece

The Celestron Travelscope 50 and Its Upgrades

I bought this Celestron Travelscope 50 used without the tripod, the 3x barlow, and its bag, for $20CAD several years ago. At that time, it was the cheapest way to get two 1.25" barrels for my DIY eyepiece projects. Since then, I have been doing numerous upgrades to the OTA in order to make it … Continue reading The Celestron Travelscope 50 and Its Upgrades