In March, college basketball fans love to talk about brackets for the NCAA national championship tournament. I thought this would be a good time to talk about some astronomy brackets I've just installed.
I have two of Celestron's goto telescopes: a NexStar 5 and a NexStar 80GT. These scopes provide good pointing for each of the two telescopes on the mount. But I also have a few other optical systems that I wanted to put onto the mounts.
For example, I picked up a use LOMO Astele 95 MAK. This is a sharp little OTA that fits in between the optical capabilities of Meade's ETX-90 and Celestron's NexStar 4. But the LOMO 95 didn't come with a mount. So I looked at the bracket system from Baader Planetarium in Germany. This system is for the "baby" NexStars: the 60GT, 80GT, and 114GT.
With the Baader brackets, you remove part of the NexStar mount and insert a nicely made metal dovetail holder. Then you attach the original telescope ring to a supplied dovetail bracket and put the OTA in the telescope ring. The dovetail bracket is held securely by screwing the clamp knob. With the dovetail system installed, it's easy to replace OTAs on the mount using a second dovetail plate. For example, I have my original NexStar 80 telescope ring mounted on one dovetail plate and my LOMO 95 mounted on a second dovetail plate. To switch OTAs, all I need to do is loosen the clamp knob, remove the NexStar 80 plate, slide the LOMO's plate into the dovetail and tighten.
A side effect of the dovetail system is that you can rebalance the system as you add accessories front and rear. For example, if I decide to use heavy 2" eyepiece on the NexStar 80, the telescope could easy be too back heavy. To adjust, I just loosen the clamp and slide the OTA forward in the dovetail.
Some people buy new or used baby NexStars only for the drive mount, intending to mount a favorite system onto the inexpensive goto mount. You can see examples the Alpine Astronomical site or by googling "baader bracket".
The second bracket I'm having fun with is "Ray's bracket". Ray's bracket is designed for use on the NexStar 5 and NexStar 8 mounts. The brackets work with the older models or the newer "i" models. This system uses two long metal plates - one on the mount and one on the telescope - to keep the system rigid and balanced. The plates are held together with two knobs that you tighten. Using the instructions, it was easy to remove my NexStar 5 OTA from its mount. (Unlike the baby NexStars, it's not designed for user removal.) Adding the mount bracket is easy and the kit comes with a bracket to attach to the NexStar OTA. Once the two plates (one on the mount and one on the OTA) are mated and the knobs tightened, the telescope is ready to go.
As with the Baader brackets, you can use the bracket system to adjust the balance of the optics forward or backward as you add accessories front and rear. This was one of my main objectives with Ray's bracket because I like to use my 2" eyepieces (and a 2" diagonal) on the NexStar 5. Without the bracket, the system is too tail-heavy and the drive motors struggle. With the bracket, I can just loosen the two knobs, slide the OTA forward to align the new center of gravity with the altitude axis and retighten.
The other reason I got a Ray's bracket was to allow easy switching of optics on the NexStar 5 mount. It's my intention to use the NexStar 5 mount in equatorial mode for some wide field astroimaging via film and CCD. In fact, I expect the system to operate without any telescope on it.
To attach the imaging systems, I bought an extra blank Ray's bracket. I could just attach the cameras to the blank plate, but I wanted more versatility. So, with engineering help from Leon Fasano, I was able to attach still another bracket system - Losmandy's dovetail system - onto my blank Ray's bracket. I have several Losmandy adapter items that I use on my LX-200 telescope: some adjustable rings, and a blank bracket. Losmandy makes a generic utility plate, but it's very long and heavy. Fortunately, I found someone selling 1/2 of a utility plate on Astromart. I was able to attach the semi-plate to my blank Ray's bracket add the other Losmandy mounting items to the system and adjust the balance of the brackets and optics.
So with the three mounting systems: Losmandy, Baader and Ray's, I have an amazing assortment of potential configurations. For example, I can have the super lightweight NexStar 80 mount driving the powerful, compact LOMO 95 for the ultimate in grab-and-go or I can use the heavier duty NexStar 5 mount to drive my digital or film cameras.
Now all I need is some clear skies!
For more information on...
... Ray's brackets: www.buyastrostuff.com
... Baader brackets: www.alpineastro.com/mounting_accessories/nexstar_bracket/nexstar_bracket.htm
... Losmandy dovetail system: www.losmandy.com/secondary.htmlPublished in the March 2004 issue of the NightTimes