Tag: Astronomy

Nexstar SE Wedge

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The final part of my Nexstar project was getting it on a wedge which would make auto-guided long exposure shots possible. Unfortunately, the Nexstar wedge has long since been discontinued and even if it hadn’t — $160 for a weenie little wedge for this scope was a bit much for me. So I decided to buy a cheap used wedge from an older Celestron system and make whatever modifications were needed to get it to work with the Nexstar.

What I didn’t expect was how little modification was needed to get an old 1980’s era Celestron C8 wedge to work with the Nexstar SE. All the holes, both on the tripod and drive base lined up perfectly and the only modification I really had to make to the wedge was to hammer out the center guide peg.

Mounting the Nexstar

In the first photo on the right, the wedge with the center peg removed has been mounted on the Nexstar SE tripod. The center peg on the tripod fits well as it is much smaller than the space left by the removed wedge peg. The tripod bolts hold everything in alignment and there is little to no lateral movement of the wedge in relation to the tripod. The bolts are 5/16" x 24 x 1.5" cap screw bolts from the local hardware store. The azimuth adjusters work perfectly with this setup as long as you don’t tighten down the cap screw bolts too much.

One rather major item of caution is the length of the bolts that attach the Nexstar drive base to the wedge. Inside the drive base is a gear (right under the fork arm) that rides very close to the opening for the mounting bolts and is completely unprotected. (Seen in the 2nd photo.) If a bolt is too long and protrudes very far inside the telescope, this gear will bind against the mounting bolt probably causing damage to the drive base. These bolts are 3/8 x 16 — I got lucky and had an extra set from my old Losmandy GM-8 that were the right size but much too long. I cut and sanded them with a Dremel and then added some thick washers just to be extra careful. The final image on the right shows underside of the wedge with the Nexstar mounted.

Another modification I made was to remove two of the rubber feet from the Nexstar base to allow for more latitude range before the Nexstar base impacts with the side of the wedge as the drive base is slightly wider than the wedge. With the rubber feet removed I can get the latitude all the way to the 14 degree mark before the base connects with the wedge — with the rubber feet on, this was more like 30 degrees. The rubber feet peel off without too much difficulty and if I ever what them back on, they’re easy to reattach with some rubber cement glue. (I left one of the rubber feet on to designate the ‘top’ of the mount.)

Adding a Latitude Adjuster

My very first telescope back in 1999 was a Meade LX50 on which one of the first modifications I made to it was upgrading the rather flimsy wedge latitude adjuster that came with that scope. Since then I’ve had the old adjuster kicking around from box to box mainly because I’m a pack-rat but now I’m glad I never threw it away! The length of the bar turned out to be too long for the Celestron wedge by only about 3mm. I cut and sanded the bar down to size with Dremel cutting and grinding disks (at one point I had to wear work gloves because of how hot the bar was getting!) until it was a snug fit and then ‘painted’ any visible scuffs with a black Sharpie. The end result almost looks like it was meant to be there. 😉

Once down to size, I fixed the bar in place to the lowest point on the latitude guide groove on the wedge with a couple of bolts and washers to hold it in place. The long latitude adjustment screw fits well to the underside of the wedge and since this setup is not going to take a bunch of weight (certainly much less than the LX50 it was originally designed for!) it works very nicely. This modification also added a great deal of stability to this wedge. I was lucky to have saved the LX50 latitude adjuster and I think that even if I didn’t have it, I would have eventually wound up trying to make something similar out of wood.

One thing I’d eventually like to add is a pair of knobbed bolts in place of the current cap-screw bolts I have for the latitude adjustment on each side of the wedge so I can loose the allen wrench I currently have to use to loosen them.


Nexstar SE Camera Platform

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I recently picked up a used Nexstar 6/8 SE mount and tripod with the idea of using it not only as a grab-and-go for my 72mm f/6 Orion EON (and hopefully a 5 or 6" SCT OTA down the line) but also in the hopes of using it for some lightweight wide-field long-exposure and time-lapse astrophotography.

I wanted to side-by-side mount a DSLR camera and wide-angle lens combo alongside my unused Celestron 9×50 finderscope from my CPC800 and use an Orion Starshoot autoguider attached to the finder to guide the whole contraption for long exposure photos. That this setup can run on batteries and is lightweight enough to chuck in the back of the car for camping trips made this a really interesting camera platform despite the Nexstar’s well known astrophotography limitations.


Celestron 9×50 Finderscope Autoguider

I found a few pages and forum posts (http://bit.ly/N5GJ7D, http://bit.ly/QoZl9f and http://bit.ly/MUgGDD) with instructions on making an adapter for Orion’s autoguider using PVC pipe fittings but unfortunately all of them required drilling a hole in the finder which I didn’t want to do. I wanted a solution which would require no modifications to the finder and would be easy to undo.

Luckily, while fooling around with the finderscope one afternoon I realized that the threads on the back of Celestron’s 9×50 Model # 51611 finderscope that the cross hair eyepiece attaches to are common 2" SCT threads! Given that the 1.25" adapter on the Starshoot autoguider attaches to a standard T-thread on the autoguider body all I needed to find was a male SCT to male T-thread adapter to fit everything together.

I had no clue if such a beast existed and after a little bit of googling I found what I needed at http://agenaastro.com — their Blue Fireball T / T2 Male Thread to SCT Male & M48 was exactly what was needed to make this work. (Seen in the first photo on the right.) This adapter is very low profile and easily allows the finderscope to achieve infinity focus with the Starshoot autoguider.

As shown in the middle and bottom photos on the right, the whole thing comes together in a nice, compact and sturdy assembly and it fits perfectly on the standard Celestron finderscope mount with no modifications needed.

Side-by-Side Camera/Autoguider Mount

Next up was finding a sturdy way to mount the finderscope and camera on the Nexstar.

From a previous project I had a mounting bar with a center hole tapped for a standard 1/4-20 tripod stud with 4 untapped holes on each side. A couple of bolts and washers from the local hardware store worked to mount the Celestron 9×50 finder mount securely to the bar.

To attach the whole thing to the Nexstar, I used the mounting block from the Orion EON 72mm f/6. (Which normally rides piggyback on my CPC800.)

The second photo shows the system all set up with the finderscope, Starshoot autoguider and an IR modified Canon 300D. One of the lenses I plan to use with this setup is a Zenitar 16mm fisheye but unfortunately, the finderscope is mounted so far forward that it projects into the Zenitar’s 180 degree field of view. So I’ll either need to crop the resulting images or figure out some way of mounting the camera further forward or the finderscope further back.

The last image shows everything attached to the Nexstar SE mount and ready to go. Note that I did have to remove the plastic altitude gear covering for the side-by-side mounting to fit which detracts a bit from the looks but everything still works fine.

I love how compact and multi-functional this setup is and can’t wait to get some time out in the field with it. Running with rechargeable batteries for the mount and with spare batteries for the camera and my netbook I think I can get a solid evening of imaging with this setup without ever needing a power plug.

The next step was to adapt a cheap, old wedge for the Nexstar


Cookbook Autoguider

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April 13 2003 update: Due to, among other things, time constraints and a brand-spanking-new MX7C, this autoguider is pretty much an abandoned project. Which isn’t to say that I won’t give folks a hand if they need it. I have some goodies that may be of help or at least a starting point for this project.

This is page will hopefully help some out there build the CCD Cookbook based autoguider circuit and provide some background on how to connect one to an LX50.

First of all I want to thank a good friend of mine, Michael McNeil over at http://www.caltel.com/~cno [on http://web.archive.org] for all the help and great advice.

This is really his baby as he put the board together for me leaving my limited knowledge of electronics to work out how to connect the thing to my LX50. Even then a good number of e-mails went back and forth reflecting on the pro’s and con’s of 74LS14’s… Sheesh!! :o)

This autoguider is an update of the version available in the CCD Cookbook which is based on the AY-3-1015D chip that is no longer in production and getting harder to find. The guider will work with the CB211 and CB245’s as well as with the old Connectix black and white parallel port quickcams thanks to Martin Niemi’s great autoguider software.

Here’s a link to Marty’s page [on http://web.archive.org]:

http://www.ameritech.net/users/mniemi000/auto.html

To the Cookbook autoguider page:

http://www.wvi.com/~rberry/cookbook/serial1.htm

Here are a couple of shots of Mike’s handy work. Component side and solder side. Everything was setup on a Radio Shack breadboard. Mike marked up the board with instructions even I can understand…

The box is just a regular plastic project box you can pick up at any electronic components shop. I chose plastic simply because I find it much easier to work with. All the holes in the box top were made first by melting away more or less the size I needed with a hot soldering iron and then just cutting and filing to a perfect fit.

I cut some foam for the top and bottom of the box. When the box is sealed it’s a snug fit and the foam holds everything in place. Here is the finished product hooked up and powered on! I really like the box I put together for this thing. Its solid, there are no bits falling off (thank goodness for glue guns!), and all the cables come off the thing to facilitate storage.

This is the pinout for the LX50 Autoguider port. The orientation is as if you were looking at the LX50 panel straight on. The best thing to do is just to get a ready made cable that is wired straight through.

You need a 6 pin RJ-12 plug. The pin numbering on these plugs is read from left to right (duh) with the plug held ‘upside down’. That means the little plastic flange that locks the plug is pointed at the ground, the embedded contacts are pointing up and the side the cable goes in is pointing towards you.

Here’s a screen shot from Marty’s program in action. One thing that had me confused the first night out is that if the guide star is too bright the program won’t lock on it. I was using a bright star just to make life easier but I eventually chose a dimmer star and threw my Hartmann mask on the scope for good measure and everything went great from there.

In my case, the calibration routine threw the guide star right off the frame in the Y-axis the first couple of times. Try, try again and start the calibration with the guide star as close to center as possible!

Click image for larger version


Centering the CB245 CCD chip

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The very fist thing I noticed after the first night imaging with my CB245 was how badly I had centered the CCD and the cold finger. Objects I wanted to image were not only completely out of the FOV of my illuminated 9mm reticle but also almost out of the FOV on my 26mm Plössl! Finding things was just a completely ludicrous waste of time. After asking around on the CCD list and realizing that nobody had any tips on and easy way to do this I decided to start rubbing my 2 remaining neurons together to see if I could maybe get a spark.

The idea I came up with was pretty simple. If I could get the CCD to see a perfectly centered crosshair I could then move it into the right spot.

Great! Easy! I pulled off the top of the camera head and traced a circle around it. Found and marked center with a compass and then drew a crosshair through it.

I placed the camera head cap on top of the crosshair drawn on paper and made sure the cap was centered in relation to the circle around it.

Now for the hard part: Going in to my mom’s sewing stuff. After a few mumbles and threats I managed to grab a spool of the thicker type white thread that I taped into place in line with the crosshairs.

In the first image you can see the cap with the threads and in the next one everything mounted and ready to go on the scope for testing. I made an aperature mask out of cardboard with about a dime sized hole in it. Fired up Win245 and played with find mode untill I could see something.

In the first image below you can see the best I could do to center the chip by eye. The next one is after only about 2 or 3 tweaks of the position of the cold finger. The last image is of the top of a lamp post about 15 meters away.

The little ball centered in the Meade 9mm illuminated reticule ep’s FOV and then switched for the CB245 and presto! Quick and dirty centering of your ccd in 15mins or your money back! Now if it would only stop raining! ;o)

Before

After

Test Image


CCD CookBook CB245

If you’ve enjoyed these tips and are in the market for electronics or photo gear, using these links to buy from TigerDirect or Amazon.com or alternatively using the PayPal Donate button to make a small contribution helps me keep this site going. Thanks!

First of all my electronics knowledge is little or none. Sure I’ve had to learn a bit in the process of putting this thing together but I still consider myself a complete newbie when it comes to reading a wiring diagram or even figuring out how to wire 2 transformers together. If you fit this description this is not exactly an easy project but if you are patient and are willing to learn, adapt, and implement modifications to suit your needs it is an immensely enjoyable and ‘doable’ project.

Berry, Kanto, and Munger have put together an incredibly simplified and unbelievably robust project. My list of boo-boo’s in building this have been long and severe but somehow its kept on ticking and is finally ready to take some pics. This thing surviving my building it is an achievement in itself! ;o)

Also keep in mind that it is not an elegant solution. There are wires running everywhere, water cooling is a pain, and every once in a while something will probably stop working, forcing you to drag out the Cookbook, multimeter, and the soldering iron and do some detective work. If you want something you can bang on the back of your scope to take pictures and not have to worry about anything else get an ST4 or a Starlight or something. But if you’re a tinkerer, and if you want to learn not only about how to take pictures but also about how a CCD works, and especially if you’re on a budget this project is a whole lot more fun…

Besides, the finished product is yours. By that I mean, (good or bad), there’s not another one out there exactly like it.

And never forget help is always available on the mailing list. The people on this list have been incredibly patient and completely indispensable in helping me put this thing together. (Thanks guys and gals!) You can subscribe to the mailing list on the AstroArchive web page and its called the “Homebuilt CCD” list.

Well now that I’ve gotten off of my soapbox let me tell you about how I’ve built this thing.

The power supply and interface are housed in an old external SCSI drive bay. There was plenty of space for everything and I decided to leave the SCSI power supply in (board at the top) to feed the Peltier off of the 5v it provides. I wired everything to the same AC input and switch and also used the SCSI power supply to power a fan, led’s, etc.

Next down you can see a couple of 12v/500ma transformers. I had to opt for this solution because I simply could not track down a 15v/500ma supply here in Portugal. Silly huh? Anyway this setup gives me about 17v which is within spec and so far has been working great.

The bridge and 4700uF capacitors have been glued with a glue gun to the back of the box.At the bottom you can see the interface board and the heat sinks which barely fit.

Here is the closed box. From the left is the connection for the Peltier from the SCSI supply, then the fuse, power led, the signal shield jack, and 2 female DB25 connectors for the camera head and computer… (have to label those!)

Surprisingly I’m getting a very clean image even with everything stuffed into the same box. From what I read on the CB list I was expecting to get of lot of interference from the power supplies sitting next to the interface board. On the first night out I did 2 min integration’s and got very clean images none the less. Lucky me?

For the camera head I didn’t deviate at all from what’s in the CookBook. I tried some wacky ideas that went very badly and quickly decided to stop trying to be a smart ass and follow the instructions provided. For the newbies: Boy are you going to have fun with this part! Little tip: look for 16 pin ribbon cable connectors like the ones used for connecting IDE drives. Long ago the 16 pin ones were used to connect joysticks but I’m sure they’re still pretty easy to find. The plastic connector can be easily trimmed down to fit in the opening on the camera head and epoxied into place. Worked for me!

“First light” was on the 3rd of October, 2000 at 00:56UT with the camera head on the table and a 50mm Canon lens on top of it. I taped a Kodak film box top to the ceiling and hoped for the best…

Check out my CB245 gallery for images taken with this camera:
http://astroturtle.com/imaging/

I’d like to end this by leaving some links for would be CB245’ers:

Richard Berry’s CookBook Home Page
http://www.wvi.com/~rberry/cookbook/cookbook.htm


Win245 CookBook control software by Tybee Evans
http://www.intricate-ms.com


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