The Questar^® Maximum-Resolution Solar Spectrometer may be used on a telescope other than a Questar^® provided, however, that the other telescope, according to its manufacturer, is compatible with solar observation and provided also that the telescope has a 1.25"drawtube.

In addition to these basic requirements, the focal length of the other telescope must be close to the Camera close focal length of either the Questar^® 3.5"or the Questar^® 7". These focal lengths are:

Questar^® 3.5" 1400mm

Questar^® 7" 2800mm

If the focal length of the other telescope is too short, then its focal length must be extended with an appropriate negative, or "Barlow", lens until the focal length of the other telescope is close to the focal length of either the Questar^® 3.5"or the Questar^® 7" telescope.

If the focal length of the other telescope is too long, then its focal length must be shortened with an appropriate positive lens, or focal reducer, until the focal length of the other telescope is close to the focal length of either the Questar^® 3.5"or the Questar^® 7" telescope.

In addition, the other telescope must be outfitted with an appropriate Infrared Blocking Filter. Questar^® must be told 1) the outside diameter of the front end of the other telescope, that is, the diameter of the end directed toward the sky, and 2) the focal length the other telescope is going to use. For telescopes using focal lengths in the vicinity of 1400mm, the Infrared Blocking Filter will have a clear aperture of 73mm. For telescopes using focal lengths in the vicinity of 2800mm, the Infrared Blocking Filter will have a clear aperture of 147mm.

For telescopes having focal lengths greater than 3400mm, the required Infrared Blocking Filter must be specially ordered.

Note: Questar^® does not sell "Barlow lenses" or focal reducers that fit telescopes other than Questar^®’s.