One of the persistent problems people new to astronomy have with getting a new astronomical telescope is manufacturers will only include one or two eyepieces with them. So, getting a few eyepieces to get rolling turns out to be a fairly major expense compared to the scope, though they will be useful later on in follow on scopes if you stick with the hobby. Colored filters and barlow lenses are only rarely included. The Celestron Accessory kits are designed to get around this, and the most useful kit for a 1 1/4 inch eyepiece compatible telescope is #94303, which comes with five Plossl eyepieces and a full set of colored filters in a case, and throws in a barlow magnification doubler to boot. It's a great value, and just flat-out useful. I have more general information on choosing telescopes in my article on
picking a telescope.
Background
The modern astronomical telescope is very different from spotting scopes, binoculars, and camera lenses. In the case of the usual spotting scope or binocular, the light gathering optics and the eyepiece are matched to each other for a single operating case, or in the case of ones with a zoom, a small barlow lens is built in to change magnification by moving it forward and back. This produces a very predictable range of focus points and operating conditions. In camera lenses, they are optimized to support only one operating mode: projecting an image on a plane at a single distance, so not only are their operating modes predictable, they are so uniform the focus can be dialed in from a scale on the barrel.
In contrast, astronomical instruments are designed for complete flexibility in producing their images. They can reach focus with anything from a camera to a high power eyepiece to a low power wide field eyepiece, or even a
binocular viewer. As a result, the superior performance of a dedicated
wide field eyepiece used with a large
mirror diagonal is availble without the penalties the telescope would pay in usefulness if this were permanently mounted.
But large sets of eyepieces aren't included with a telescope when it is good enough to be a serious instrument. The reason is all of the accessories for these telescopes are interchangable; if you are using a small Refractor such as the superb
AT66ED or a larger Schmidt Cassegrain like the powerful
CPC 800, you will be able to use the same set of eyepieces with either. And I use these as an example because they are each useful for types of observing the other is not good at, so it is likely for someone to have two scopes like these, and perhaps even
piggyback the smaller one on the larger scope, but share one set of eyepieces. So, high quality scopes like these don't each come with a full set of eyepieces since it would run up the cost for no good reason.
And yet, one has to start somewhere, and the absolute bottom of the line eyepieces many department store telescopes have come with over the years excel at hobbling even the limited performance of the 60mm refractors fraudulently labeled as "575X Telescope." There has been a need for a kit of eyepieces a bit nicer than the cheapo ones, but also reasonable for starting out. A secondary need has been for eyepiece filters, but to be honest, I find training the eye has been more useful than masking with a filter, but most people like to at least try them out.
Description and Usage
The Celestron Accessory Kit #94303 is their most thoroughly equipped and generally useful astronomical kit. The other two kits they sell consist of #94304, a stripped version of this kit with only two eyepieces, a barlow lens, and a flashlight, and #94305, a specialized 2" size wide field viewing kit with three large 2" format eyepieces, a 2" diagonal, and 2" sized filters.
This kit comes in an aluminum case with a locking lid and a custom foam insert for the eyepieces, filters, and barlow lens to fit into. All of the eyepieces are equipped with small rubber eye cups, which are unusual on astronomical eyepieces because the one thing you do not want to do is touch the telescope, because that will make the image shake. The good news is they are easy to fold down out of the way, and the eypieces larger than 15mm have enough eye relief (stand-off distance for your eye) to keep this from being a problem unless you wear glasses. The good news is, the eyepieces all come with caps for both ends. I am not sure why, but this has become a problem in recent years. The bottom caps have a small hole in them to let air through when going on and coming off, and the top caps fold the eyepiece cups down automatically.
The eyepieces have performance similar to any other Plossls, which have become the general multi-purpose eyepiece design. Like most others, their apparent fields are all around 50° wide, and the eye relief is directly proportional to the focal length. I have only been able to use the 15mm and longer ones with glasses. The fields are fairly flat, and there is no glaring color. Most people can get a focus with the shorter ones without glasses, and I suggest going ahead and giving that a try. For the money, it isn't reasonable to expect eyepieces with the 70° fields of the Tele-Vues or their unequaled image sharpness. Then again, I gave one of these kits to a 13 year old, while that just isn't going to happen with the Tele-Vue eyepieces.
The largest eyepiece is the 32mm Plossl, which is about the largest size Plossl anyone offers with the full 50° field. Normally at longer lengths, such as 40mm, the field shrinks to 46°, and more so for the rare longer eyepiece. The 32mm has the largest eye relief in this kit, and is the one most likely for an eyeglass wearer to be able to use. Note: Use this one with the Barlow to be able to produce a long eye relief 16mm or 24mm equivalent.
The filters are packaged in a case for each, and have a complete spectrum in 1.25" thread. The good thing about these is they are threaded on both ends, so if you like, you can stack them with another optical element, or another filter. So, for example, you could stack the red filter with a
Light Pollution Reduction Filter(not part of this kit) and produce an ersatz hydrogen alpha filter (kind of).
The included barlow lens is the basic Celestron Barlow produced for general use. The higher end Barlow is the Ultima Barlow, which is truly apochromatic. For general use, the one used here actually works quite well, and even has a neat trick included apparently by accident: you can take it apart. The 2X barlow element is mounted at the front of the barrel, which is the same type as the eyepieces. You can unscrew the barlow element the same way the filters do and thread it to the bottom of an eyepiece to make, in effect, a modest ~1.5X Barlow (this is the configuration which turns the 32mm into a 24mm eyepiece, but with great eye relief). You can also thread it to the front of a diagonal to get to a ~2.5X barlow, but this configuration may only come to focus in a Schmidt Cassegrain.
Conclusion
The Celestron #94303 Accessory Kit really has the best set of tools for someone just starting out in the hobby, and enough of the basic equipment to really feel-out what a telescope can do and experiment with different techniques. This is the difference between seeing an object and saying, "Huh," and being able to try a couple magnifications and find where it suddenly jumps out from the background and looks amazing. And if you get another telescope later, the kit will work with it, and if you upgrade various eyepieces, the new ones can fit into the same holes in the foam.
