Finderscope webcam

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#584210
Steve Holmes
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Thanks for those comments. However, between them they do rather illustrate the problems with “standard” solutions which my friend Roger was trying to solve. In the case of the Evoguide 50ED plus ZWO camera bundle, the most obvious objection is cost! (£319, even as a “special offer”). While I’m sure there must be a market for such a device at this price point among “professional amateurs”, I rather doubt whether many casual backgarden skywatchers would be willing to invest this amount, possibly more than their entire setup has cost them so far, in order to obtain one. This is further compounded by the fact that this device does not seem to be able to make up its mind as to what it is. For example, a “webcam finderscope” does not need the ability to accept different cameras/eyepieces nor does it need to be able to alter the focus: once the selected webcam is in the correct position it should not need to be altered or adjusted thereafter. Also, does a finder for a “moderate” telescope really need a 50mm “Ohara ED doublet objective that includes an S-FPL53 ED glass element”? All these additions can only serve to increase the price. The fact that this item does not seem to be intended purely as a finder is to some extent borne out by the reviews, which refer to its use as a astrophotography camera in its own right. Irony of ironies, one review even mentions the need for a finder to be mounted on it! Which brings me to the next disadvantage of both the Evoguide setup and adapter rings – limited field-of-view.

The FirstLightOptics page for just the guider has an “applet” for determining the FoV of various setups, which shows that the Evo plus ZWO camera bundle can span from M32 to M110 – barely 1 degree. This again would tend to confirm that it is not really suitable purely as a finder for a moderate OTA. Adapter rings tend to have the same problem: Roger’s setup can achieve an FoV of over 6 degrees, which is much more usable for star hopping. Finally, although Robin’s setup is much nearer to Roger’s, he himself says that the webcam he used is not sufficiently sensitive, thus emphasising the need for careful selection of components.

In summary then, although there are products out there which address the same “operational space”, there does not seem to be anything currently on the market which combines high sensitivity, very wide fov, and modest cost – unless someone knows differently, that is!