Backyard Voyager
Top Six Necessary (and nearly necessary) Accessories for Your New SCT
It would be unfortunate if you believed that the spending was nearly over. Truthfully, it's only begun, but, if it's any consolation, this first year will be the worst-- well, at least the worst for this telescope.
But if you bought an SCT, then you already spent a healthy sum and own a decent telescope. A couple of the accessories on this list are pricey, but you can always think of it this way: you wouldn't replace the tires on a relatively new Mercedes with twenty-five dollar recaps. Why treat your telescope any differently?
Anyway, here's a list of items that I consider to be either necessary, or so close to necessary that,once you've seen or tried them, you will soon feel a need for them.
1. Bob's Knobs
Number one on this list, without any shred of doubt, has to be a set of Bob's Knobs for Schmidt-Cassegrain telescopes. The images above are probably enough information for anyopne who has used an Allen wrench or screwdriver to align a telescope's optical components. For those who haven't, Bob's Knobs are thumbscrews that replace the factory collimation screws on the secondary mirror's housing.
These are made for reflectors, as well, but they're even more advantageous to SCT owners, since they make the collimation process safer,as well as easier. They eliminate the need to point sharp steel instruments at your corrector plate in the middle of the night, while looking through the eyepiece and adjusting the focus knob with your other hand. They sell for $19.95 U.S. If I could only have one accessory, this would probably be it.
2. William Optics 2" Diagonal
Without a 2" diagonal you will never use your SCT to the extent of its abilities. The SCT's long focal length gives it a distinct advantage, as well as a disadvantage. The advantage is that the high magnification needed for some photography and for lunar and planetary observation is easily achieved through a broad selection of eyepieces. The disadvantage is the other side of the same coin. Low magnification, wide-field perspectives are harder to come by.
This is not an insurmountable problem, and can be corrected, for the most part, by using 2" eyepieces, which give a wider field of view. And, an advantage of the SCT's f/10 focal ratio is that it is less susceptible to the sort of image degradation at the edge of field, a flaw that seems to be inherent to the less expensive 2" eyepieces.
It might be a good idea to replace the diagonal anyway. As good a job as Celestron and Meade do with mass produced SCT optics, both companies apparently find it necessary to bring costs down by shipping diagonals and finder scopes that are only adaquate at best. These are not the diagonals or finders you would select if you set out to buy them, if, in fact, these factory models are even offered for retail sale from any other source.
William Optics offers two types of diagonals. One is made specifically for SCTs and screws directly into the rear port of the optical tube assembly (OTA). The other, refractor type, has a drawtube made to fit into a 2" focuser. If you're not using a third party Crayford style focuser, such as the Feathertouch, then you would need a 2" adapter known as a visual back. This may sound inconvenient, and in fact, adding to the length of the optical train means that certain eyepieces may not come to focus at that distance. But the advantage is significant. It means that to reposition the diagonal/eyepiece combination to a more comfortable position would only require you to loosten one or two set screws. This is a lot simpler than changing positions with the SCT type diagonal, which would involve loostening the entire visual back adjustment ring. If you win the lottery, buy both. Otherwise, its an apples/oranges situation. Which is more important to you?
3. JMI Wheelie Bars
Have you ever wanted a quick view with your SCT, but lacked the time or energy to go through the setup and breakdown processes? This could be the solution. Wheelie Bars and similar setups are not for everyone. It just depends on the layout of your house, garage, shed, yard, etc. If you have a storage area, such as a garage, that is level with your observation area, then Wheelie Bars will solve the problem.
The picture above should be self-explanatory. The tripod ends fit into the holes at the end of each bar. This should enable you to keep the scope, mount and tripod ready to go at all times. Whenever you need to move it, just place one hand on the mount and the other on a tripod leg, then roll it carefully to your location. By eliminating the scope/mount/tripod part of the process means that getting setup, including a star alignment for the go-to, takes me no more than five minutes.This is particularly handy on nights when I spend the entire session imaging.
In my case, Wheelie Bars just about doubled my number of opportunities for observation each month. Moreover, it enabled me to view for much longer periods of time, and it allowed me to view at times when I had less than an hour to spare.
4. Dew Shields, Guns and Heaters
One of the drawbacks to any telescope that uses a lens or corrector plate is that once the glass cools beyond the air's dewpoint condensation will form. There are three ways of fighting dew. A dew shield is a thin hollow tube that extends beyond the edge of your optical tube and protects the glass from the outside air, prolonging the dew formation process. It might slow down the formation by an hour or more, but it is not going to stop the process. They are available in either aluminum or flexible material versions. The aluminum versions are usually painted to match telescope company colors-- gray for Celestron, Blue for Meade, etc. They give the combination a seamless look. The flexible versions can be rolled up or folded for easier storage.
A dew gun is simply a small hair dryer adapted for use by amateur astronomers. They run on batteries and are really a necessity. They provide insurance against dew. Once the dew shield has done all it can do, the dew zapper will get rid of anything that accumulates.
The most expensive but best way to fight dew is with a system of heaters and controllers. Kendrick probably makes the best. They eliminate dew by keeping the optics slightly warmer than the ambient air temperature via flexible heating strips that wrap around lenses, mirrors or corrector plates. Programmable Kendrick controllers distribute heat evenly and prevent the optics from becoming over heated. Controllers are available in models with up to ten outputs.
5. Orion Ultrablock (narrowband light-pollution filter)
If you haven't thrown it away, then get out that list of things to buy that you made while making the decision to get an SCT. Now, scratch the filter set from the list. There are exceptions, but for the most part those colored filters will get about as much use as the excercise bikes that provide habitats for so many spiders in American garages.
With the possible esception of an 0xygen ||| filter, you'll probably get more use from a narrowband light-polluton filter than any other. The broadband filters seldom work, or at least they don't work quite as advertised. Supposedly they are helpful for galaxy viewing. I bought Lumicon's broadband and it helped slightly--almost imperceptibly-- with two objects on an unusually dark night. And that was it. I had heard bad reports about them, but had to try it for myself.
Next I tried Orion's Ultrablock, which is a narrowband light-pollutionfilter. Televue makes a similar one, but Orion's is a little cheaper and I had read a few reports by authors who couldn't see a lot of difference between the two. It worked out exactly as I had hoped. As advertised, it really enhanced the contrast on emission and planetary nebulas. I couldn't believe the difference on M42. it looked like a CCD image.
6. Feathertouch focuser
Finally, the crayford focuser-- in this case, the Feathertouch by Starlight Instruments. If you are reading this, you have probably heard of them. For several years this has been regarded by many as the Ferrari of third party focusers, and with good reason. They now have competition from companies like Moonlite and William Optics. In fact, the Moonlite dual-speed focuser may be as good, but nothing surpasses the quality of Starlight Instruments' Feathertouch.
In reviews you often hear like phrases "buttery smooth," or "silky" to describe the drawtube movement. They weren't exaggerations and there's really no other way to adequately describe these focusers. As soon as you pick one up you know that a lot of thought and work went into their design and production. Machined from hardened stainless steel, brass and aluminum, they are built to last. These things are so beautiful, they're almost too nice to use; you're tempted to just put it on the mantle.
There are a couple of versions of each model, some including internal brake systems. The adjustable tension will allow it to hold up to 5 lbs., which may be the only thing about this product resembling a drawback; five pounds might be considered a little light in the world of CCD imaging. All models have both coarse and fine focus knobs, with 10:1 reduction on the fine focus.
You sometimes hear people complain about the stock focusers that come with their SCTs. I never had a real problem with my C9.25's focuser. I mean, it had no real faults and never failed to function in the way that it was meant to. But I was just never entirely comfortable with it. Most of the time it would "snap" into what was I'm sure the best focus point, but there were times when I would get this feeling that better focus could have been achieved, but that I lacked the sensitivity to get it right, particularly when imaging highly magnified planetary images via a laptop screen. That was why I bought mine-- as an aid to planetary and lunar imaging. The process is much easier now, and the quality of my pictures improved noticeably, right from the beginning.
There are accessories that provide a more practical upgrade in terms of everyday use, but nothing will ease the processes of observation and astrophotography any more than a focusing system of this quality. It's well worth the money.