Library Telescope!

 Our library (The Darby Community Public Library) has a small telescope available to check out. It is part of an outreach program by the Western Montana Astronomical Society. They supply small telescopes to several libraries in western Montana. The one in our library is an Edmunds Astroscan. 

 

Telescope kit. Astroscan, 28mm and 12mm eyepieces, Rigel Quickfinder, Nightwatch  and Night Sky references and star charts. Red duffel bag to carry it all.

 They are an older reflector telescope, with a design that originated back in 1976. The Edmund Scientific company used to be a ubiquitous supplier to technical and scientific hobbyists of all kinds, The Astroscan was designed as an entry level, easy to use telescope. The base is a ball and rests in a cradle with pads that allow it to be aimed easily, but it is balance so that it will stay put where it is aimed. There have been larger amateur built telescopes that use essentially this same type mount. It is a form of altitude-azimuth (alt-az) mount. The telescope itself is a Newtonian reflector with a 4.125" mirror (105mm) and a focal length of 445mm. This yields an f number just over 4, making it a very "fast" telescope. It was designed as a wide field telescope, and is great for that. 

The two eyepieces that are with it yield magnifications of 16x and 37x. This is plenty for general wide field views, and even works well on the Moon. The entire Moon just fits in the field of view (FOV) of the 12mm eyepiece. One of the librarians told me that one of the last people who checked it out said you would be better off using binoculars. While a good pair of binoculars are great for wide field views and learning the sky, the Astroscan does have an advantage. A pair of 7x50 binoculars has a total light gathering area, or aperture, of about 3295 sq mm. The Astroscan mirror has an area of  about 8655.625 sq mm. This means it has over twice the light grasp of the binoculars, and will normally see fainter objects. Binocular magnifications typically come in 7x, 10x or 12x, with 7 being the most common. Again, this is less than the Astroscan. I also had occasion to talk with the person who had trouble with the Astroscan. He hadn't realized there was a screw locking it in place in the base, and was trying to use it balanced on one ore two feet of the cradle!

I checked the Astroscan kit out on 12 July so I could try it for myself. I took it out at about 21:45 MDT on 13 July. It was still daylight, but  the Moon was just past zenith and close to 50% illuminated. That made it an ideal target to try this 'scope out on. I set it up on a makeshift table I've been using, and sat on a bar height stool. I didn't bother with the Quickfinder and just started scanning with the 28mm eyepiece. It was initially way out of focus, but I was pleasantly surprised at how well the friction wheel focuser worked. It moved easily, but held position no matter the orientation. The entire moon fit inside the FOV, and there was a star visible just to the left of the Moon ( remember that images are inverted in a Newtonian reflector) . That star focused down to a pinpoint and the lunar features were very sharp. Given the heat (100F earlier, still about 80F), the smoke and haze in the atmosphere, I was amazed that  the seeing was so good. There was almost no wavering in the image. I changed over to the 12mm eyepiece, and the Moon filled most of the eyepiece. The view was still sharp, and details along the terminator easily made out. I tried unsuccessfully to use my cell phone camera to take a picture through the eyepiece. I did make a very rough quick sketch, but the scale is messed up so I won't post it!

I tried to mount the Quickfinder so I could try it out and use it to locate some other targets. Unfortunately, there appears to be a loose connection between the added on AA battery box and the  finder, so I couldn't get it to work. I just started scanning areas of the Milky Way And had some nice views of different star fields. I used the Skyview app on my phone to locate M13 and was able to scan and find it. Changed over to the 12mm eyepiece. The globular cluster was visible as a small fuzzy gray ball, denser towards the center. Surrounding stars were visible. 

My own opinion is that this is a great little 'scope for learning the sky. We need to see about getting the finder fixed, but it is still very usable without it. There are large numbers of experienced observers on the astronomy fora that  talk about how sometimes it is just enjoyable to use a manual wide field telescope to just wander the night sky, and others that highly recommend it as a way to explore and learn the sky.

I should note that one reason that I picked the Moon as my initial target is that it isn't getting really dark until almost 23:00. Astronomical dark was actually only from about 02:00 until 04:00.

Clear skies!