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Going to try OAG

Started by fblue, 11/21/2009 02:11AM
Posted 11/21/2009 02:11AM Opening Post
Well,\I got my new FLI ML8300 camera, 7 position filter wheel and RGBL fitlers and the Narrow Band set is on its ways.

For the last few days I have been researching OAG's (Off Axis Guiders) to find one that will fit my needs. I found the TS-2 from APM that looks like it will fill the bill. It is only 9mm thick, so I can set up the reducer and maintain the correct distance to the CCD Chip. Today I ordered it and it will ship tomorrow. Should see it Tuesday, about the same time I will get the Narrow Band filter set.

I have had some issues with apparent flexure or maybe my guiding software, not certain. But I do know that if I use my built in guide chip in the ST2000, it produces very nice round stars. So, I decided that I was going to just give up fighting the Guide Scope and Camera issues and just go with OAG. I have been told this was the right move so many times, but I kept figuring that I would find a solution to the flexure. But, inconsistant guiding has been driving me nuts for 9 months and though I keep thinking I have found the cause, I keep getting bad nights.

This last time out I got some good data one night, but most poor results on the other. I was having real problems and had wasted about 3 hours when I just said the heck with this, unplugged the guide camera and plugged in the ST2000 guide cable and started guiding with CCDSoft and the internal chip, after that I got nothing but good exposures. This was not the first time that I had resorted to this and I kind of kicked myself in the butt for waiting until the 2nd night to use the ST2000 for guiding as well as imaging. So, the new ML8300 does not have a guide chip and I realized that I was going to have to do something different and OAG was the obvious answer. Basically it is the same thing as the on board guide chip when you use the OAG, so I a pretty certain that the new setup will do as well as the ST2000 does.

So, I missed the New Moon this month with it, but am working hard at getting it ready for the next one. Hopefully the
weather will be good enough to allow me to give it a try.

When I get it all together and make sure it all fits and works, I will post some pics of the setup.

Here is one picture that I did manage to finish, NGC1396, the Elephant's Trunk. It came out pretty good for having all the hassles that I did.


Attached Image:

fblue's attachment for post 49131

[SIZE="Large"][/SIZE][COLOR="Blue"][/COLOR] Floyd Blue grin
Amateur Imager
Posted 11/21/2009 02:12AM #1
The I got luminance only on M81, but I will try to finish it later.


Attached Image:

fblue's attachment for post 134070

[SIZE="Large"][/SIZE][COLOR="Blue"][/COLOR] Floyd Blue grin
Amateur Imager
Posted 11/22/2009 07:23PM #2

Floyd,

Guide scope flexure was not an issue for me while imaging with a G11 at a scale of 2.5 arc-sec/px but results were poor while imaging at 1 arc-sec/px. Most of my exposures had stars that were elongated at an angle to the RA axis. After upgrading the front cover of my QSI 516ws to the integrated OAG version my guiding improved to the point where I can consistently get good results with 15 minute exposures at 1 arc-sec/px. Before getting the OAG I had spent a lot of time chasing "mount" problems that in the end turned out to be flexure problems. I wish I had moved to an OAG sooner!

One thing I did learn about OAGs is that it is much easier to find a guide star if the imaging scope has a wide flat field with little vignetting. Finding a guide star with my M703 at f/10 is easy as I can guide with a mag 10.5 star using 2 sec exposures. However, while using an Optec UWF 0.7X focal reducer the vignetting at the pick-off prism is too great to use. The Optec FR works well while using a guide scope but the vignetting is just too great to use with my OAG. It will be interesting to see if you have a similar experience while using a FR.

Have fun with the new toys!

-Eric