As I mentioned on the Photo Basics page, normally you must mount your scope on an equatorial wedge to do any type of astrophotography (other than very short exposures with a camera mounted piggy-back on your scope.) This is because the stars rotate around the celestial pole, so if you track them with an alt-azimuth mount the stars will rotate during your exposures, causing them to become streaks. There are a number of wedge options for SCTs, described below.
Note however that new software now available, allows you to stack a series of short exposures with CCD cameras and combine them to yield a good image, and this software is
allowing astrophotographers to take good images with Alt-Az-mounted scopes, thereby obviating the need for a wedge (see the Using a Webcam for Planetary Photography
page for more information). This is a good trend because a 10” or 11” fork-mounted SCT is heavy and thus difficult for one person to mount on a wedge, and a
fork-mounted SCT larger than 11” is near impossible for a person to mount on a wedge without help from a second person. Such scopes, when mounted on a wedge, are usually mounted on a pier in a permanent
Regardless of which wedge you use, here’s a tip for
mounting your scope on it. Most wedges have a slot at the top of the tilt plate, so that you can readily screw one of the mounting bolts into the base of the scope and then
slide it onto the wedge. (This is done because holding the scope at an angle while screwing in one of the mounting bolts from underneath, would be very difficult with a 30-pound U2K and even worse with a 40-pound
LX200 or NexStar.) Now, the optimum configuration for the U2K on a wedge is for the Azimuth Downstop Indicator on the fixed (non-rotating) base of the scope to
be at the lowest point when the scope is on the wedge. I.e. when the scope is on the wedge the Azimuth Downstop Indicator should be closest to the top of the
tripod. To do this you need to screw the first mounting bolt into the hole located opposite to the Azimuth Downstop Indicator. To make this easier I recommend
you take some red fingernail polish (all do-it-yourselfers have a bottle of red fingernail polish handy for marking things) and color the side of the base where the first mounting bolt should be screwed in. In the photo to the right the red dot is indicated by the red arrow. (The scope is shown mounted on Jim Mettler’s wedge, described below.)
Celestron “Standard C8 Wedge”
This wedge is useful for visual observing with an 8” Celestron scope, relatively light and
inexpensive. For some very odd reason, Celestron does not include the “Deluxe Latitude Adjuster” with the wedge, which is a screw system to accurately set the latitude setting
of the wedge. There really isn’t a good way to set the latitude of this wedge accurately without the Latitude Adjuster so you need to purchase it along with the Standard C8
Wedge. The Standard C8 Wedge is Celestron part #93656 and sells for about $90, and the Deluxe Latitude Adjuster is Celestron part #93528 and sells for about $40, for a total of $130. I use
this wedge when I’m transporting my scope for visual observing (such as a star party) because it is fairly light, but it is not sufficient for astrophotography - for that application see the options below.
Celestron “Heavy-Duty Wedge”
This wedge is beefier than the Celestron Standard Wedge, and is the one
used by many of those astro-photographers using Celestron scopes who are listed on the Links page of this site. (It was actually designed for the
Celestron 9.25” and 11” scopes, which are of course heavier than the 8” scopes.) As is the case for the Standard C8 wedge described above, this
one doesn’t include a “deluxe latitude adjuster” either, and you certainly need it for this wedge as well. The Heavy-Duty Wedge is Celestron part #93655
and sells for about $230, and the Deluxe Latitude Adjuster for this wedge is Celestron part #93662 and sells for about $120, for a total of $350.
Similarly to Celestron, Meade sells a “standard” 8” equatorial wedge for about $130 ($195 for the version for a 10” scope) and a more heavy-duty Superwedge for a 10” or 12” LX, for about $390.
There are several other very heavy-duty wedges worth considering, especially if you are looking at the Celestron Heavy-Duty Wedge or the Meade Superwedge. These wedges are heavy and thus reduce the
portability of an SCT - they are designed to be rock-solid and are often used by astrophotographers to mount a scope to a permanent pier. If you do enough astrophotography you will become convinced of
how nice a permanent pier is - once you polar-align the scope on a permanent pier with a sturdy wedge you can remove the scope for storage and replace it on the wedge without redoing the polar alignment.
(All you need is for your significant other to not object to the pier in your yard...)
The Mettler Wedge is built by Jim Mettler and is made from thick aluminum - one of the best
wedges I’ve ever seen. The price is $500 plus S&H (in the US), and Jim makes makes a version of this wedge to fit either the Meade or Celestron bolt patterns. This is the wedge I
purchased for my permanent pier. It is solid as a rock and although it’s about as heavy as one (at about 30 pounds), the design is exemplary. The latitude adjustment is convenient and much more
substantial than the “friction-clamping” system used by most other wedges, and the wedge design places the combined weight of the scope and wedge more directly over the tripod head or
pier so the whole system is balanced well. This design thus ends up creating a front tray, which I really like since it provides space for the scope’s keypad as well as an electric focus motor controller. Also,
the space at the back behind the inclined plate will hold a beverage cup without danger of being knocked over at night...
The Milburn Wedge is made by Ken Milburn and sells for $390 + S&H. It is also a very heavy-duty wedge. Since it
is lower-priced than the Mettler wedge I might have bought this one instead, but at the time I was shopping for one (December, 2000) Ken Milburn indicated at least a 6
-month backlog before he would get to a new order and I didn’t want to wait that long (plus I really liked the design of the Mettler Wedge). But it is worth looking at since it
costs about the same as the Celestron or Meade heavy-duty wedges and does seem to be more robust. Note that Ken Milburn also sells a deluxe version of this wedge
for $490, but at that price I’d recommend taking a good look at the Mettler Wedge instead.
One of the most finely-adjustable wedges is the
Ulti-Wedge. This is a massive wedge with ball
bearings at the adjustment axles; it sells for $685 plus shipping and insurance. Although it is designed for Meade SCTs, it appears that the vendor can also make one for Celestron SCTs.
APT Astro has introduced a wedge that is receiving extremely good reviews by astrophotographers. It is
heavy and very solid, and the folks who have one are very happy with it (except, perhaps, the color). It sells for around $550 plus shipping, and accepts both Celestron and Meade SCTs.
Most wedges, whether from Meade, Celestron, or from one of the custom vendors described above, aren’t designed to readily line up the screw holes in the fork base with the bolt holes in the wedge as
you place the scope on the wedge. (At least this is true for the wedges designed for Celestron scopes. I don’t have experience with the Meade LX scopes but from what I can tell
this is also true for them.) In the case of my Mettler wedge, I’ve added a pair of stops to line up those bolt holes for my U2K’s fork base. They are
the two black objects in the photo on the right, and are 1/8” thick aluminum shims positioned so that when the scope is lowered onto the wedge they
index the fork base in the correct position. This required drilling and tapping holes in the wedge, but if you have these skills you might consider
adding shims like these to your wedge. You can’t believe how convenient it is, especially at night, to have the scope simply slide into place so that the lower mounting screw holes are positioned properly.
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