Last updated: 25 April 2002
Subject: ETX-70AT Globular Clusters Sent: Thursday, April 25, 2002 13:11:51 From: firstname.lastname@example.org (Michael) I just read Thomas Henry's response to me the ETX 70 site; thanks. You are obviously a bit more knowledgeable than I, and I appreciate your tips. I have always been interested in astronomy, and took a couple of college astronomy courses (as electives while working toward my business degree), but have never owned a telescope of my own until I bought the ETX 70 last October. Living in Southern California, my viewing nights at home are few, and there is always way too much light pollution. But I drag it out whenever the skies are clear and it's amazing to me what I can actually see from my backyard - even with such a bright sky. We are avid campers, and make several trips each year up to the local mountains. Some of the most fun I've had with this thing was camping at Big Bear Lake in January. This little scope performed great for several hours, until it reached about 12 degrees (F) outside and we both had to give up and go sit by the heater in the RV. Anyway, Albireo was great the other night - I was finally able to see it at about 1:30, after it came up over the trees. Thanks also for the tips on the other doubles, you're right that the Autostar's catalog leaves a bit to be desired. Have you or anyone else had any luck seeing any globular clusters through this scope? I have seen a few Globular Clusters, such as M13 and M92, through much larger scopes, and was dazzled. I'm not sure what to expect with this little scope, but when I choose most of the ones listed in the Autostar catalog, I don't see a thing! I'll double-checked my alignment by slewing to another known object. But when I come back to where the cluster is supposed to be, and nothing! I would expect to see something at least as bright as Andromeda, but usually can only make out a faint smudge, if anything at all. Can anyone tell me which globular clusters I should be able to see with the ETX-70AT? Thanks again, MichaelMike here: Most Globular Clusters are small. To get a feel for what each looks like, see the SEDS Messier web site (on the Astronomy Links page). They have photos (taken with larger telescopes), magnitudes, and angular sizes.
From: email@example.com (Thomas Henry) What might be good globulars to go after with the ETX-70AT? This is a timely question, since the season of globulars is upon us! (The distribution of them is such that most are only well placed in the heavens for us in North America during summer and fall). The ETX-70AT is really a richfield instrument and excels on this type of object. You should be able to see most of the Messier ones. Several will be faint and may offer quite a challenge, while many will be quite bright. In no cases will you be able to resolve the globular to individual stars (the aperature of the ETX-70AT is just too small). However, on a number of them you will be able to see a "form" or gradations in the light across the extended object. To add to your fun, make sketches and keep a log book. And don't ignore the dim ones; I enjoy the challenge of just finding them. I pulled out my astro log book and checked which ones I've seen this month. Here are a few to get you started, with comments straight from my log: M13: spectacular with 9mm, even with bad skyglow M92: bright, still one of my favorites, averted vision doubles the size, good with 6mm M5: amazingly good given skyglow; a rival to M13 M3: fabulous with 6mm; can see gradations M53: nice; variations in brightness clearly visible M68: very faint; near horizon; had to fight tree limbs, too M10: faint, but obvious; near horizon so somewhat washed out M12: faint, but obvious And get ready for M22 in Sagittarius! I've haven't seen it through my ETX-70AT yet, but can hardly wait! One final tip: the Autostar menu tree can be unwieldly at times. I take the following approach to minimize keystrokes. From the OBJECT menu press [enter], then [down] twice to DEEP SKY, then [up] once to MESSIER. Then simply enter the Messier number. I'm so used to this pattern that my fingers remember exactly what to do and do it rapidly. Best wishes, Thomas HenryAnd this:
From: firstname.lastname@example.org (Thomas Henry) At 09:18 PM 4/25/02 EDT, Mike wrote: >Thanks. Most Globular Clusters are small. To get a feel for what each But if you restrict yourself to the Messier globulars, I have to respectfully disagree. They are in fact quite large compared to Jupiter and Saturn which most people seem to enjoy in their ETX-70AT's. For example, Jupiter currently has an angular size of 36 arcseconds. But M92, not one of the largest globulars by any means, is at a healthy 11 arcminutes---that's some 18 times larger in diameter. And M13 is a whopping 38 times larger than Jupiter. If we're ranking apparent size of deep sky objects within reach of the ETX-70AT, then I would say that most galaxies (ignore M31 and M33!) are the troublemakers, not the globulars. In any event, the Messier globulars are general pretty bright and usually put on a good show. Please consider this a courteous and respectful difference of opinion; I just want to put in a good word for the globular clusters who have given me hours of entertainment over the years! Best wishes, Thomas HenryMike here: Good point! That's what I get for a fast reply (trying to get a Site update done).
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