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Initial Alingment, then Switching to CCD

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#1 astro-vert

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Posted 06 May 2013 - 11:47 AM

Hi Everyone,

Hope I am posting in the appropriate place.

Currently, I do my initial Go-To alignment (level/align tripod North, 2+4 star, then ASPA, then power cycle and 2+4 again) with a 12.5mm illuminated reticle eyepiece. After doing that, I need to remove the visual back/diagonal/eyepiece and thread on my reducer/spacer/CCD (I have this pre-assembled as one piece, so just threading the whole thing to the scope).

I use the Lepus .62X reducer that has a dovetail on one side and threads to the back of the scope on the other. I have the Optec correct length spacer with the mating dovetail for the reducer and then t-threads for my CCD.

My question is can I somehow do my go-to alignment with my CCD so I do not have to switch from eyepiece to camera? How do you folks handle your go-to alignment before imaging?

My setup is:
CGEM
EdgeHD800
Optec Lepus .62x telecompressor
Starshoot G3 CCD (color)
ST80 and Starshoot Autoguider
Nebulosity for image capture
PHD Guiding

Also, does anyone have success using something like Real VNC running on a computer at the scope to remotely control everything from a second computer? This looks really cool...

Thanks,
Andrew

#2 ghataa

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Posted 06 May 2013 - 11:52 AM

Yes. I defocus my stars to have a nice and round object. Then I center the defocused star in the cross-hairs of image acquisition program and that's it. Of course focus after alignment is complete.

George

#3 Raginar

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Posted 06 May 2013 - 11:53 AM

Hey Andrew,

Yes, you can do your alignment with your CCD. I take particular care to align my CCD on usually a bright object like the moon to start off. Then, I'll calibrate my telrad to that as well. Next, I go to a star and do the same process to really dial in that my CCD is aligned with my telrad. After that, I do my alignment with my finder. You could use your CCD to fine tune it from there if you wanted it to be very accurate.

Another option is to try something like Sequence Generator Pro with elbrus to get plate solving. Or, since you're using Nebulosity, you could try astrotortilla. What you do is take an image and pass that image to a software package that compares the stars to astrometric data. It figures out the 'real' location of where you're pointing. Then, you sync to that location and do a slew to your object of interest. It can take 1-2 iterations to hit your object, but it is spot on accurate. It'll prevent you from wasting time 'hunting' for your objects and it gives you a warm fuzzy that you didn't mess something up :).

I use Windows remote desktop connection to control my computer at my mount from inside. Basically I get outside, setup everything, then get the computer going and align the mount. Once i'm done and ready to take pictures, I go inside and use RDC to control it all. I have a webcam at the mount that lets me 'see' whats going on too. All of this is networked via a 150' section of ethernet (cat5) to my hub so I can control it via WIFI from anywhere in the house. Another option is long active repeater USB cables; they have some quirks and it's harder to focus if you don't have an electronic focuser.

If you have any questions, please PM me. Good luck!

#4 Madratter

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Posted 06 May 2013 - 01:36 PM

I pretty much always do my initial goto alignment with my Imaging Camera now days. The imaging camera is just as good as a reticle for this purpose. In fact, since you are using Nebulosity, frame and focus has a bulls eye pattern built. But what makes this work for me is that I use both a 60mm finder, AND a 50mm auto guider. A well aligned Telrad would also work. You need something with a wide enough field of view, but accurate enough to get those stars onto your imaging cameras field of view.

#5 astro-vert

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Posted 06 May 2013 - 02:38 PM

Thanks for the feedback, guys. I had kind of thought about the bullseye target in the frame and focus functionality, but when I am doing my initial focusing, I often get the image washed out and have to keep increasing my exposure time. Seems like somewhere between 5-10 second exposures takes care of it. Not a huge deal, but a little slowdown of the alignment process...

I also do have SG Pro, but haven't messed with it too much - especially the Elbrus part.

I also downloaded Astrotortilla and again, haven't played with it much. I understand what plate solving is, but trying to understand the functionality of the solving programs (and in particular w/ Elbrus, I was never successful solving and image) I just haven't spent the time.

Chris - thanks for the feedback on your remote setup and offer of sending you a message...my hunch is I'll have to take you up on it at somepoint!

Thanks again,
Andrew

#6 Madratter

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Posted 06 May 2013 - 09:02 PM

I also have been working with SGP and have the trial. It turns out they have a frame ability too and it also has a crosshair. So you could use either SGP or Nebulosity for doing the initial alignment.

As for the plate solving, hmm. That works pretty well for me. Actually, it works very well so far. You will need to know your imaging scale (approximately), and you will need to get the star within the initial 2 degrees FOV of the platesolver (which often does not happen for me when doing the initial alignment).

#7 Raginar

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Posted 06 May 2013 - 11:18 PM

Plate solving doesn't help with an initial alignment. It helps you get your target as close as possible to the coordinates you want.

Another option for a mo'better plates solving program is Pinpoint. It's not horribly expensive and it's more forgiving than Elbrus. The other option is installing the 'local failover' option of astrometry.net as detailed in the SGP Yahoo! Group.

Plate solving fixes a ton of things.

#8 Phil Sherman

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Posted 07 May 2013 - 01:05 PM

I use a combination of manual adjustment and imaging to get the sky alignment set up when I assemble by scope for use. I'm using an Atlas mount but the procedure will work with any GEM.

I do a polar alignment using the polarscope. If I'm not leaving the scope set up for a number of days and plan on taking only short exposures, I frequently skip drift alignment. My finder is also accurately aligned with the scope. I start with a goto to a bright star. Once the scope has stopped slewing, I loosen the clutches and center the target star in the finder. After the clutches have been locked, I use the imaging software's focus mode and its center crosshair to get the target centered in the frame. After the synch command, I slew to the next target, center it and synch again. After the first synch, targets are rarely outside the FOV of the camera.

If I'm doing a drift alignment, I perform that after the first synch operation. This gives me one accurate sky location to position the scope for drift alignment, which is also done using the camera. Camera drift alignment takes only 70 seconds for each alignment test and gives me results that are more accurate than the mount's adjustment capabilities. After drift alignment, I restart the sky alignment procedure.

Phil

#9 andysea

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Posted 07 May 2013 - 01:30 PM

I do my initial one star alignment with the CCD. I put a bright star in the center of the finder scope, turn on the reticle in SGP, put the star in the middle of it and then sync the mount. One star alignment usually gives me accurate gotos.
For plate solving I use pinpoint and so far it never failed to solve an image.
I really like the "center here" function in SGP.
The longest FL I image with is 1000mm which helps in having the star in the CCD field of view just from using the finderscope. I typically carry an eyepiece with me just in case I need to recalibrate the finderscope.

Andy






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