I've been an astronomy nut for decades. More than I care to count. Much of that time has been spent searching for the best bang-for-your-buck telescope. As a youth, I figured out that I couldn't put a 200" (5m) telescope (At the time, it was far and away the largest telescope out there) in my backyard. Never mind that its lowest usable visual power is around 700x. Compromises would have to be made.
I wound up building a 6" (15cm for the metric mavens) f/10 reflector, and even made its mirror, and in the clear Colorado skies in which I lived, it was lovely. Alt azimuth mounted, I could find most objects of interest with the Skalnate-Pleso atlas and a nearby bright star.
I considered most other telescope types, but, as far as image sharpness and light gathering power was concerned, nothing but nothing beat the Newtonian reflector. Refractors, despite their rock solid durability, unsurpassed sharpness, and field flatness, just didn't gather enough light and were awesomely expensive. A well made and aligned 6" (15cm) reflector easily outperformed the 4" refractors that cost triple or quadruple the price of the reflector, and gave better images for most objects.
Then along came the Celestron, the first of the widely available Schmidt-Cassegrainians, and, while expensive, it had reasonable light gathering power and excellent portability. However, careful research revealed that:
For me, this eliminated the Schmidt-Cass as a viable telescope. This theoretical impression was confirmed by looking through a couple of Celestrons (or were they Meades?) at Stellafane a while ago. Bad images. I started referring to Celestrons as "OGTs" [Orange Garbage Tubes]. I built 6 other Newtonian telescopes, and my current 10" (25cm) f/6 is a delightful example of the Dobsonain design. John agreed, and graciously consented to autograph my telescope. "Inspected and passed, John Dobson". I was immensely proud.
This optically exquisite telescope now gathers dust.
You see, I was looking for a telescope that would fit into my Saturn SL-2, and my 10" (25cm) f/6 Dobsonain in a rigid tube cannot do this. On Craig's List, I found an 8" (20cm) Celestron Ultima for a very reasonable price. It fit into the back seat and trunk of the Saturn, with room to spare. A pre-purchase look through the telesecope at Venus revealed no serious problems, so I bought it.
The delights of an accurate clock drive were soon apparent. Tracking at 500 power, which, on a good night, the Dob was optically capable of, was possible on objects other than Polaris.
The drive is one of the joys of this telescope. At my dark sky site, where it is very quiet, I have at times wondered if the drive was still on, as I couldn't hear it. It will run all night, indeed, for several nights, on a single 9v alkaline battery. It has done this at temperatures well below freezing.
Accurate setting circles, on a carefully aligned mount, allowed objects far from bright stars to be located in very little time at all, without star hopping. Wow. The Celestron came with a driven RA circle. <I can hear you guys with go-to mounts sniggering, but this was a big deal for me.>
Much to my amazement, and I do mean amazement, the optics the Celestron were superb. I could drop in a 4mm Orthoscopic and, by golly, find myself looking at the diffraction patterns of whatever double star I was trying to resolve (provided, of course, that the air above me was steady!). Despite the very real theoretical complaints of an oversized secondary and non-optimized tube length and corrector, the optics would hold, on those rare, steady nights, 500 power. There is very little difference between the out of focus star patterns inside and outside of the focus, once I had realigned the secondary. I think the telescopes I had looked through previously were poorly aligned, or perhaps the optics were not well made. The design flaws, listed above, were real, and, on an optical bench, you'd be able to detect them but they are not significant when looking at stars through the eyepiece. Air turbulence pretty much swamped the deleterious effects mentioned above. The atmosphere was, and is, the worst optical problem any telescope has to deal with.
Schmidt Cassegrainians are often excoriated by their owners for focus shift and backlash. As you focus one of these telescopes the primary mirror rotates about a helix which doubles as the light baffle that extends through the hole in the center of the mirror. If the primary mirror is not exactly perpendicular to this helix/baffle, the object you're looking at moves a bit as you focus the telescope. This can be very annoying.
If the gears in the focusing train are even a little loose, there will be "backlash" in the focusing train, that is, you turn the focusing knob and nothing happens until all the gears touch. Also annoying, but not as bad as the focus shift. Now that I've described these problems, I'm pleased to report that my sample Ultima has no discernible focus shift and only a tiny amount of backlash. It's a very well made telescope.
This mount is the heaviest mount Celestron made for an 8 (20cm) inch telescope. It is far from perfect, however. The slightest bump will cause it to vibrate in declination for around 5-10 seconds, and at high power especially, this is annoying. That said, once you lock it on an object it stays on that object. Change eyepieces, and the object is unmoved, if jiggly. The Byers drive tracks with unerring accuracy, provided your polar axis is within a few arc-minutes of the north celestial pole
The setting circles are accurate, albeit a bit small. It's easy to be off by up to a quarter degree, especially if the mount is not precisely aligned to the pole. This can be important when finding faint objects.
The mount's drive can run all night and then some on a single 9v battery. Not bad at all.
The telescope is adjustable. You can adjust the setting circles, the secondary, and the mount. All of these must be accurately set for the telescope to perform well. It's worth the effort.
On a windy night, a pillow, stuffed under the telescope between the fork arms helps damp out the declination jiggle mentioned above.
I've found the 8x50 "Polaris" finder on my telescope to be only marginally useful. The optics in it are poor. The rear objective surface is not coated, and the images lack sharpness. Given the light pollution mentioned above, almost all of the objects I observe are invisible in the finder. I keep it on the telescope only because it is fairly useful in beginning an alignment on its namesake, thereby allowing the setting circles to do the real finding. It is very easy to knock this finder out of allignment. A recently acquired telrad finder is more accurate, as it stays in allignment.
Celestron, I'm told, no longer supplies the electronics for this telescope. This could be a problem, as the drive requires them. (I suspect that someone more compentent in EE than I could easily cobble together a replacement board from components bought at radio shack)
Rod Mollise, who has written extensively on the Schmidt Cassegrainian telescope, points out that the current crop of Schmidt Casses are not quite as well built as the earlier models. Click here for the article.
I had acquired a few Meade ultrawide eyepieces. They were the proverbial "Porthole into the Universe" and I delighted in showing the Moon and Pleiades to the public through them. A more critical evaluation, however, found them lacking. They did indeed have an enormous field, but the outer third of it was unsharp curved; a star that was sharp at the center was much less so that the edges. This was disconcerting when looking for faint doubles, as most stars looked double at the field edges of these eyepieces.
For my f/6 Dobsonain, this is not so much of a problem as the edge of my field is coma limited, and this is true irregardless of the eyepiece used. The Ultrawides, with their build in Barlow lenses, actually help the coma problem a bit. Using them with the C-8, with it's more uniform field, (well, more uniform that an f/6 newtonian, a refractor can't be beat for this) the edge aberrations were more painful when observing stars. It's much less of a problem with nebulae and galaxies.
The humble Orthoscopic, and a single Meade super plossl I have did not have this problem. They soon became my eyepieces of choice. I replaced my 40MM super wide with a 56mm Plossl (again, a Meade), and the 40mm gathers dust. The flat field of the cheaper, but optically superb Orthoscopics and Plossl are much more satisfying to use, although at focal lengths lower than around 10mm, their eye relief leaves much to be desired.
Update. For a superb image, nothing beats an orthoscopic. That is, at focal legnths greater than 12.5mm. Below that, and the eyepiece becomes an easily dirtied, hard to clean, contact lens. They have very short eye relief. I recently acquired a 5mm Pentax 70 degree eyepiece, (a 4X barlow + a 20mm erfle, with a lot of multi coatings and tweaking). It has a 20mm eye relief, and nice, sharp images. It's also a heavy fistful of glass, and a slight dimunition of light transmission. The reduced light is worth it. Eye relief is important, as is a clean eye lens. The more comfortable you are, the more you see.
Even more recent update. I just won a 30mm Burgess Optical/TMB "Paragon Orthoscopic" eyepiece at a star party! It's a 68° field eyepiece that is significantly sharper at the field edges than the 15+ year old first generation Meade 4000 super wide described above. An eyepiece does not have to be narrow field to deliver sharp images.
The really low power 56mm plossl can be a tricky eyepiece to use. One needs to center the eye over the eyepiece to get it's maximum sharpness, but even then, don't expect too much. This is not a problem with the eyepiece. It's your eye. The 56mm, on the f/10 Celestron, gives an exit pupil of 5.6mm. This includes quite a bit of the edge of your eye lens, which is not as well corrected as its center. Your images will be as much as function of your eye's acuity as the eyepiece itself.
A good observing chair is around the price of a good eyepiece. It's well worth the investment. Regular chairs don't cut it when trying to be comfortable in front of an eyepiece that has a wide variety of possible positions. The more comfortable you are, the more you see. It took me decades to figure this out, hopefully you'll be a bit quicker.
Comfort in summer usually means mosquito repellent. I put it on my clothes, and try to minimize the amount on my skin, as DEET might not be as benign as the labels sometimes suggest.
Eye-patch. My C-8 came with an eye-patch. This is one of those things that was never a blip on my radarscope until I got one, and now I can't live without it. You can observe with both eyes open. This makes observing more comfortable and again, the more comfortable you are, the more you see. Click here to find out more.
Observations. I always have an observing list written out before I go observing. Perhaps it's just my scientific training, but it really focuses what I'm trying to accomplish during a given observing run. I take along an old stool, which functions as a desk, and clipboard containing my observing list. My notes are made in pencil, as a pencil writes at any temperature, whereas a ball point pen runs into trouble at temperatures below freezing.
Update. A tape recorder, for some, is better than a pencil. The tapeless, solid state recorders are a big improvement on the older tape recorders.
Lights. I use an "Astronomers" red led light. It has a rheostat, and as the night progresses, and I become more dark adapted, I dim my light.
In my backyard, on a moist summer night, I find that a hair dryer will clear the dew off of the corrector plate in around 15 seconds. That I have to do this every 10 minutes is a bother. I have recently invested in a heated dew strip with a temperature sensor and a rather heavy 12V gel-cell battery (~ $375!! Yikes) I'll report how well they work at the end of next summer. I've noticed that a dew cap is only useful if you're observing objects at an altitude of less than 45 degrees. I tend to look at things while they are on the meridian, as this lessens my rather severe light pollution, so I've not found dew caps to be very useful.
The easier it is to use your telescope, the more you'll use it.
This rule took me a very long time to figure out. For around 15 years, I almost gave up on visual astronomy, as the nearest good dark sky site is around 100 miles away. Going there was a huge disruption to my fairly busy schedule, so it was rather rarely done. I was reduced to taking out the telescope every Halloween to show the trick-or-treaters the moon.
On acquiring the C-8, I did a few calibration runs in the backyard to align the optics, calibrate the setting circles, and see what the telescope could do. I realized that while all but the brightest galaxies (M31 or M68) were invisible, there was a host of doubles, red stars, planetaries, and clusters to be seen. Not to mention the planets and moons whose brightness made them impervious to the bright skies above my house.
I had discovered Urban Astronomy. Here are a few things I've learned about observing from a back yard, well lit by the "Aurora Commercialis".
I have done more observing and had more astronomical fun in the past year than in the 15 preceding it by learning to live with my very accessible, overly bright, skies.
I cannot, despite valiant attempts, see objects like M51, NGC 4565, NGC 891, NGC 2419, or Hubble's variable nebula (NGC 2261) from my severely light polluted back yard. On a good night, I can see Albireo (beta cyg) from my backyard, naked eye. At the zenith! We're talking serious light pollution here. I have found that you can penetrate space despite these limitations. I have actually seen magnitude 13.0 stars in M15. The trick is to use enough power to beat the sky brightness back, but not enough power to make the diffraction patterns stand out, so that the star's light is concentrated in the smallest area on your retina, while the sky brightness is spread out as much as possible. This works out to around 20x/inch (8x/cm), so a 12.5mm on the Celestron at f/10 works admirably. Could you explain that in more detail?
The moon and planets are pretty much unaffected by urban light pollution, so I have no trouble viewing them. It was fun to find Saturn's moon Enceladus, which comes in at around magnitude 11.5, in the glare of Saturn and it's stunning ring system. Hard to do, however! Our own moon has so many interesting features that my books on it's surface don't begin to chart what can be seen.
The Celestron came with a couple of Orion "Ultrablock" light pollution rejection filters. For my eyes, all they do is make the view much dimmer, and all stars in the field look rather blue. With the exception of a couple of planetary nebulae, they have not helped my visual observing.
An eye-patch, which is helpful when observing from a rural, dark sky site, is almost essential when viewing from a brightly lit backyard.
It allows you to see fainter stars than otherwise possible. Click here to find out more.
Rising at 2:30AM is a difficult thing to do. If you do, you'll notice that the skies are a bit darker, as any early evening lights that get turned off have been turned off. The neighborhood is quieter, and there's less traffic. In the summer, the mosquitoes are at their quietest. This is something worth missing the late show for. (Actually, I dumped my TV six years ago and have reveled in the time it gave me for things like astronomy.)
I have found that the clearest skies occur (at least on the east coast of the US) after a cold front has blown through. The best time is between 6 and 18 hours after the front has passed.
In skies where the limiting magnitude at zenith is 3.5 and above, it's hard to star hop to find objects. You'll need to use setting circles, electronic or otherwise. The goto telescopes are the obvious choice, but as most telescopes made in the 20th century and many made in the 21st lack this feature, you need to carefully align your telescope's optical axis to the north celestial pole. Instructions are to be found in the next section.
Clear skies are almost always cold skies.
Layer your clothes. Start with long underwear, flannel shirts, insulated pants. I follow this up with a "Snowmobile" suit, a one piece insulated set of coveralls. Then my oversized winter parka. My head is covered with a watch hat and one or two hoods. So what if you look like the abominable snowman. "Micky Mouse" cold weather boots. Hard to find, as they are not great for an extended hike, but they excell. You'll be comfortable, and (it bears repeating) the more comfortable you are, the more you see.
This goes for more than just urban astronomy. When it's really cold, and you're sitting before the telescope, observing away, the tops of you legs get really cold, Never mind you've got long underwear, pants, and perhaps insulated pants on. Cold.
I've found that a pillow, an old squashed pillow, so flattened by years of use as to be replaced by a new fluffy one, is just the thing for your lap. Warms it up quit nicely.