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View Full Version : Ep 33 Choosing and Using a Telescope



haloflightleader
2008-May-02, 04:46 AM
Hi Everyone,

I finished listening to Ep 7 and 33 and enjoyed them very much. I just earned A's in Astronomy and its corresponding lab in the Spring Semester 2008 at a local city college here in Los Angeles and it awakened a long-dormant astronomer in me. I've always been into astronomy and physics, but astronomy was expensive so until I started making a little more money it has been a hobby waiting for when I could afford a decent telescope.

As a first telescope, I picked the Celestron Astromaster 130EQ. It arrived last week. It's a 5" newtonian on an equatorial mount. It cost less than $200 and was excited when it came. The Meade LX200 in my class spoiled me so much that the mickey mouse equatorial mount that came with it compelled me to return it. If the mount is going to be wobbly, why torture yourself with an equatorial? So I'm returning it.

As soon as gee-dubbya's money comes, I'm getting the Celestron Omni 127 XLT. I've joined the Los Angeles Astronomical Society and am booked for weekend star parties back to back for the next couple of weeks. The good thing with the Astromaster, though, I saw Saturn and Mars very clearly.

AstronomyCast is a fantastic show! Thank you. And Dr Pamela Gay sounds hotter than the sun on the radio -- G-r-r-o-o-w-l.

As a final thing, the suggestion on binoculars was great. In fact, I'm using little 10x20 binoculars and can see the beehive, orion nebula, Pleiades, and the open cluster at the foot of the Gemini Twins. I don't remember their Messier designations, but you know what I'm talking about. And I got to see the Andromeda Galaxy through our 8" LX200 over light-polluted Hollywood skies and it was still a spectacular thing to see.

p

dcl
2008-May-03, 12:19 AM
haloflightleader: I'll guess that it won't take you long to run out of things to look through with your telescope unless you become involved in an organized program. I will recommend an excellente one in which I have had many years of experience: The program of variable star observing administered by the American Association of Variable Star Observers (AAVSO), located at Harvard College Observatory in Cambridge, Massachusetts. The AAVSO supplies charts for each star at or very close to cost, stores data suuplied by members, and makes the data available to professional astronomers. I have described observing procedures in my 22 April 2008 contribution to "variable star observing - episode 66" in the Astronomy Cast forum.

For variable star observing, I would recommend an 8-inch reflector on an equatorial mounting. You'll want to devise a way to attach an AAVSO chart to a viewing position close to the eyepiece and to devise means for looking at the chart with a light that will not degrade your night vision.

haloflightleader
2008-May-03, 04:10 AM
That was the one thing in class we never got a chance to see, cepheid variables. We had Meade LX200 GPSes all around, and unfortunately the labs called only to see Messier objects. I was a bit disappointed I didn't get to see variables, but the Messier objects were still fantastic. I look forward to looking at variable stars in the future.

Although, an 8" is still quite a bit of time away from me. After having spent $629+ on the Celestron Omni 127, I'd need to let several months pass before I suggest getting another telescope without the risk of being killed on the spot by my wife.

I'll check out your contrib. Thanks for the advice.

dcl
2008-May-03, 09:28 PM
Observing Cepheid variables isn't a big deal unless you're doing it as part of a program such as that of the AAVSO. Unless you're in the AAVSO program, all you see when you take a casual look at a variable star is just another not particularly interesting star. You need to look at the same star periodically, each time noting how its brightness compares with those of comparison stars in the same field.

A particularly interesting type of variable star to observe is the eclipsing variable, wherein two stars are in orbit about each other with the earth in or nearly in their orbital plane so that one star passes in front of the other periodically. You can record an eclipse in the coarse of a single evening, observing it at, say, 10 or 15 intervals as the eclipse approaches, then speeding up the observations to every two or three minutes until the eclipse ends. To know when to catch an eclipse, you need an ephemeris for that star, telling at times and on what dates eclipses are expected. Conditions in eclipsing binary systems occasionally suddenly change, causing their periods to change. The AAVSO seeks to record these changes to provide data that they might use to figure out what caused these changes. The AAVSO provides ephemerides for this purpose. For ten years, I provided the AAVSO with these charts. Their now being provided by someone else who still has access to a large-scale computer. Now retired, I no longer have such access. In fact, I'm no longer a membger of the AAVSO even though I still have the 8" reflecting telescope that I made around 1978. I now use it only occasionally to enable people at the senior retirement facility where I live to see the first-quarter moom, Venus, Mars, Jupiter, and Saturn. The skies here in St. Louis aren't any good for anything else.

If you have dark night skies where you live, there are 104 Messier (pronounced "mess-e-aye", it's French) objects to look at. They include galactic and globular star clusters, gaseous nebulae, planetary nebulae, and galaxies. Thery're something else.

I don't recommend gettting yourself killed by your wife for buying a bigger telescope too soon. That sort of thing tends to put a real crimp into stargazing.

Vanamonde
2008-May-05, 06:01 AM
I know you cannot beat a good German equatorial mount for astrophotography and that catadioptric will fit in the back seat easier but why complete with Hubble, Keck, and all those? For the same money, you can find a 10" Dobsonian that give your eye some Great Views!

If you can find the room for this light bucket.

dcl
2008-May-05, 01:19 PM
The big advantage of an equatorial mounting for variable star observing is its automatic alignment of the chart showing the variable star and comparison stars. The Dobsonian offers no clue to how to orient the chart, and it can be amazingly difficult to find that alignment if you have no idea what direction in the field is east-west. All you need to do with an equatorial mounting to find this alignment is to rotate the telescope slightly about its polar axis. Of course, it helps to have the polar axis aligned with the earth axis! But aligning it with the north star is sufficient for that purpose with a portable equatorial.