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I've been at playing around with  astrophotography  for about  a year and a half now and  decided, a while back that a guide setup  is what I needed to  get very long exposures.

Without guiding, I was limited to  a maximum of about 60 second exposures. This was ok, but it took a lot of careful and tedious processing of the images to  bring out the subtle detail that  were hidden in the dark background.

As usual I didn't want to  spend a lot of money on guiding equipment so I perused the web classifieds and swapped e-mail with members of the various yahoo tech  groups ( LXD75 group, Meade DSI group for example) about what  the best choice would be for a guide scope.

As I found out the Orion 80mm f11 refractor  telescope was a good choice. As luck would have it, I found one on at a good price and bought it.  The other thing I wanted was another DSI-I as a guide camera. I have a Philips SPC900NC web cam that  I used as a guide camera for a while but I had problems with it's sensitivity, making it difficult to  find guide stars in the are that  I was imaging.  The other issue was that I was using two different programs in the process , PHD for guiding and MEADE envisage ( which came with the DSI camera) as the imaging software. Since Envisage can also guide using Meade cameras I figured that a DSI would allow me to  use envisage exclusively for both functions.

The gods were shining on me, one of the members of the DSI  group read my post and contacted me with  the information that  he had a DSI-PRO for sale. What luck! The price was right so I bought it.

Now I was set. I had everything that  I needed to  start guiding and take long exposure pictures. After making an adapter that  allowed me to mount the 80mm on top of my SN8 reflector I was set.

As I quickly found out, autoguiding is an art in itself. It seems like everything I attempt in this hobby come with a steep learning curve. However, what  makes it all worth while is the satisfaction when you  finally  reach  the top and things start working the way  you  expect.

The first thing I struggled with was aligning the guide scope with the main scope. The Guide scope sits on three screws in the mounting ring that  you  adjust  to  move the scope up down left or right. It's not absolutely necessary to  have to two aligned but it helps. The main thing is that  you  are able to  see a star which  to use for guiding once the object  you  want to  image is framed the way you  want. Once that  was accomplished came the next hurdle, actually doing some guiding. I used Envisage  to control the scope for guiding.

As I quickly found out, you  still must have a decent polar alignment for things to  start working. So I spent the better part of two hours doing a drift alignment of the mount ( the LINKS page for info on polar alignment). Good balance is also a must. I usually weight the scope a bit heavy toward the east and North to keep the worm gear loaded on one side. This is the recommended procedure. Click HERE for info on balancing an equatorial

The next time I went out and tried the guiding again. During this session I found that  I was unable to  keep the scope on target. It would start to drift off and the guider would not keep up or it would finally yank it back.

 When Guiding with envisage you  can alter the guiding gain which  changes the aggressiveness of the guide pulse. The program defaults the gain to  50% (.50) . Not knowing any better I played around with  the gain in that region but nothing that  I did seem to help the problem.  Since the target didn't move as much  when I turned the guiding off I decided to try  changing the gain to a low setting. First I tried 30%. Hmm, that  seemed a bit better so I went even lower. I ended up  using a guide rate of between 25% and 27%. That seem to have been the answer. Using this setting I'm able to  take exposures for 5 to  8 minutes and probably longer (haven't tried that  yet).

If you have a DSI and want to  get some more info on autoguiding with that and Envisage, Chuck Reese wrote and excellent document on how to  set up  Autostar and Envisage for autoguiding.

So far so good!! Off to  take some pictures tonight.!!!


Well I thought I had it made using Envisage to  auto guide, alas things didn't work out the way I had hoped. The guiding started to  drift off target. Since auto guiding was the only  way that  I was going to  be able to  get long exposures, I decided to  give PHD a try. PHD is a free guiding program form Stark-Labs. After loading the ASCOM 4 and the  4.1.1 driver for the LXD75,  I gave it a shot the next time out. To my delight the program locked onto the guide star and we were off and running.

The guiding still wasn't 100%, though. The stars in some of the longer exposures were oblong. After discussing the problem with  one of the guys on the Yahoo groups it was recommended that  I try to get  the focal ratio closer between the imaging scope and the guide scope.

The SN8 I'm using has a f4 ratio and the guide scope has a f 11 ratio. This makes the guide scope more sensitive to  change and thereby issuing guide commands when the really weren't needed. Luckily I had an f 0.6 reducer which  I was able to  screw onto the nose of the DSI-Pro on the guide scope. This changed the focal ratio to  f6.6. Still a bit long but as it turned out the guiding improved enormously.

That  is my current Guide setup and I'm real happy  with  it.


It's a few years later and I have changed my guiding setup a bit. I'm now using  an Orion 50mm mini guide scope and a DSI pro camera  guiding with PHD2. 

For those that  are having problems setting up  PHD here is an excellent adjunct document to the PHD manual  . Well written ,easy to understand and fills in the gaps in the original PHD manual.



 Since I'm now using a TPO10RC scope for imaging I have found that  the arc second  difference between  the 50mm mini Guider  and the main scope is too great ( .5 for the main and 11 for the mini guider) if gone back to using the ED80 as a guide scope and put a .67 focal reducer on the main scope.  That  combination get's me a bit closer in arc seconds ratio (.82 vs. 3.67 arc seconds per pix)

As mentioned above I use PHD2 as my guide program and found some excellent YouTube Videos on how to use PHD2  ( ).


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