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 Post subject: Guide camera/view finder
PostPosted: Thu Feb 14, 2013 4:42 pm 
Brian very kindly agreed to manufacture a bracket for my mount to accept the guide camera and lense, now I'm planning on using the guide setup as a viewfinder also using a 50 mm lense. Does anyone know the best way to apply crosshairs to a lense ?? Inside or outside the lense ?? I guess I may have focus issues trying this as in I will either focus on the sky with blurry crosshairs or focus on the crosshairs with no sky in the background .........
I may even do away with them on the lense altogether and use a crosshairs overlay on the old laptop screen to produce the desired effect, i guess trial and error may be the way forward here .........Any ideas ??


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 Post subject: Re: Guide camera/view finder
PostPosted: Thu Feb 14, 2013 5:37 pm 
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Dean,
Are you looking through the finder? If so crosshairs go at the focus of the eyepiece - there is usually a field stop there and any hairs/wires glued across it will be in focus. Not as easy as it sounds though!
If you are using it as an electronic finder then digital crosshairs in the PC software is the way to go. Most software does this.


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 Post subject: Re: Guide camera/view finder
PostPosted: Thu Feb 14, 2013 6:14 pm 
Thanks David, I'm not using the finder scope no, I'm just going to use the webcam/guiding setup as a viewfinder via a smaller lense, 50mm, find my object then switch back to the guiding lense and away it goes. So it sounds like crosshairs in the software is the way, will check if astrocapture has the option to start with then go from there, cheers


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 Post subject: Re: Guide camera/view finder
PostPosted: Thu Feb 14, 2013 6:57 pm 
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Quote:
So it sounds like crosshairs in the software is the way, will check if astrocapture has the option to start with then go from there, cheers


Astrocapture does have the option for cross hairs, its what I use. The camera at the back is the image from the viewfinder.
http://www.boltonastro.co.uk/gallery/displayimage.php?pid=517&fullsize=1

I have the guide camera hanging underneath but also digital view finder on top. Works a treat.
http://www.boltonastro.co.uk/gallery/displayimage.php?pid=518&fullsize=1

_________________
Celestron 11" Telescope
Eq6 Pro Mount
Eq5 Mount
EQ Mod
QHY5 Guide camera
Cannon 1000D SLR Camera

I choose to image with an 11" SCT Celestron in this decade and do the other things, not because they are easy, but because they are hard......


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 Post subject: Re: Guide camera/view finder
PostPosted: Thu Feb 14, 2013 8:08 pm 
Thanks Carl, that looks spot on, will give it a dance when I get my guiding stuff back from Brian and a clear night .... Although could line up the scope with viewfindercam during the day on a distant antenna or something I guess ;)
Cheers


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 Post subject: Re: Guide camera/view finder
PostPosted: Sat Feb 16, 2013 12:04 am 
Tried this out this evening but to be honest was good and bad really.... Managed to line the finder/guidance cam up with the main scope without much fuss using a bright star and seems to be as near as dammit spot on now. But, the problem I have is field of view from the finder, even with the 50 mm lense on this doesn't make a great deal of difference as the view through my 300 mm guide lense. Although this is not really a major problem, I'm struggling because my mount doesn't slew as fast as the modern ones and I have to get it close to target first by hand and the fine tune using the mount controls and could really do with a bigger field of view in the viewfinder to give me an idea where I am in the sky. Is there a lense with a wider fov than a 50 mm that I can use for this purpose ?


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 Post subject: Re: Guide camera/view finder
PostPosted: Sat Feb 16, 2013 6:47 am 
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dean_kos wrote:
Is there a lens with a wider fov than a 50 mm that I can use for this purpose ?

:idea: What about your original webcam lens (6 or 9mm focal length)?
I recall that you had this fitted at Kelling Heath to get a nice view of the Milky Way.

Or if you need an SLR fitting, proper "fish-eye" lenses are very expensive, but if you get a 28 or 24mm wide-angle and then fit a fish-eye converter on the front, that may do the trick.
This is exactly the combination which I used (with a Pentax DLSR) for my "whole-sky" image:
http://www.boltonastro.co.uk/gallery/displayimage.php?pid=3&fullsize=1

Meanwhile, I have an 18-28mm zoom with Pentax-K fitting which you may borrow to try.


Last edited by rwilkinson on Mon Feb 18, 2013 9:14 am, edited 2 times in total.

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 Post subject: Re: Guide camera/view finder
PostPosted: Mon Feb 18, 2013 9:12 am 
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Location: Bolton
I've prepared this graphic to illustrate your webcam's field of view when fitted with a 300mm telephoto, standard 50mm or 18mm fish-eye lens:
Attachment:
webcamfov.png
webcamfov.png [ 8.24 KiB | Viewed 7162 times ]


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 Post subject: Re: Guide camera/view finder
PostPosted: Mon Feb 18, 2013 9:34 am 
To be honest I'm really struggling with this, can't find a damn thing !!
I have ordered a bracket to attach the laser pointer to the scope so once it's aligned with scope at least I will know I'm in the general area of what I'm trying to find, the next step is the goto system for my vixen mount although this is expensive eventually it's going to be something ill invest in.
The problem I have is not having a view through the viewfinder wide enough to figure out where I am, using a 300 mm lense........ I have tried my 50 mm lense but that didn't help much as the view wasn't much different. The original webcam lense would do the trick but its to much fiddling to install it, get it focused, find object then take it off and reattach the guiding lense to guide.
I had a bash with the star wave last night, trying for m44 and failed miserably, just couldn't find it, although the guiding and imaging was working perfectly I just don't think I was on target.
I'm going to try going back to the c8 next clear night with the laser attached and see how I go.


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 Post subject: Re: Guide camera/view finder
PostPosted: Mon Feb 18, 2013 12:19 pm 
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Location: Adlington
Dean,
Anyway you can put the Canon on the finder lens? A 15 second exposure would give you something to on.
PS I could have said why don't you use setting circles just like us oldies used to do!


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