Tips for constructing camera support bar sought
I am considering adding a camera support bar to my 10" EQ 1120mm fl Newt for long focal length projection magnification. Although I have a simple design figured out, I was wondering what if one had done something similar and had any experience based tips or other suggestions. Basically, the a right-angle is inserted in the focuser, sending the optical path back to the rear of the scope. Then a barlow is used for negative projection, up to 300mm to 400mm long. This is intended to be used for projecting longer focal lenghts during astrophotography than what can be had by simply projecting "up" the axis of the focuser. - Canopus56 (Kurt) __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com
Kurt: The focal plane of the newt is right near the top of the fully racked in focuser. In order for the barlow to work properly, it needs to be upstream of the primary focal plane or down in the focuser. My 1 1/4 inch diagonal has standard filter threads on the front input opening. My barlow is just a small lense assembly tied to an extension tube with standard filter threads. So I often take the lense assembly and screw it on to the front of the diagonal and let the light path through the diagonal act as the extention tube. The spacing and thus the magnification at the eyepiece are the same as through the extention tube. DT --- Canopus56 <canopus56@yahoo.com> wrote:
I am considering adding a camera support bar to my 10" EQ 1120mm fl Newt for long focal length projection magnification. Although I have a simple design figured out, I was wondering what if one had done something similar and had any experience based tips or other suggestions. Basically, the a right-angle is inserted in the focuser, sending the optical path back to the rear of the scope. Then a barlow is used for negative projection, up to 300mm to 400mm long. This is intended to be used for projecting longer focal lenghts during astrophotography than what can be had by simply projecting "up" the axis of the focuser. - Canopus56 (Kurt)
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--- daniel turner <outwest112@yahoo.com> wrote:
Kurt: The focal plane of the newt is right near the top of the fully racked in focuser. In order for the barlow to work properly, it needs to be upstream of the primary focal plane or down in the focuser. . . . So I often take the lense assembly and screw it on to the front of the diagonal and let the light path through the diagonal act as the extention tube.
Daniel, Thanks, that's a good trick that I hadn't considered. This week, I installed a Cray 2" low-profile focuser in order to get enough flexibility to be able to conveniently set the "A" distance between the negative barlow and the prime focal plane. I am projecting through a filter wheel and a flip-mirror onto either a Meade DSI or film camera. In some configurations, the optical train is a little long. It looks like it would be safer for the scope body, the focuser and the projection/astrophoto components to have an extra point of support other than just the focuser itself. - Canopus56(Kurt) __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com
--- Canopus56 <canopus56@yahoo.com> wrote:
I am projecting through a filter wheel and a flip-mirror onto either a Meade DSI or film camera. In some configurations, the optical train is a little long. It looks like it would be safer for the scope body, the focuser and the projection/astrophoto components to have an extra point of support other than just the focuser itself.
- Canopus56(Kurt)
Kurt: I love the newt but it just isn't a worthy vessel for an optical train that includes flip mirrors and filter wheels. The length of the tube and the heavy mirror at the end gives it a large moment arm which will vibrate forever. The strength of the newt is a fast focal ratio. If you find yourself using a barlow to photograph on a newt, it's time to look at the Schmidt Cassegrain. It's already F/10 and the focal plane moves around to where you need it. With the fixed focal plane of the newt, the mountain has to go to Mohomed. Besides used SC tube assemblies are easy to come by and there is a vast after market of adapters to fit them. Not to mention kindred souls who know how to make them work right. So I suggest you save the newt for fast,widefield primefocus only work, with the filters screwed to the nose of the camera one at a time. Then use the SC for zoomed in long focal length narrow field work. You wouldn't be the first man to own more than one OTA for his GEM. Oh and then you could go for a third OTA consisting of a 80 ED APO for really wide field work. DT __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com
--- daniel turner <outwest112@yahoo.com> wrote: <snip>
If you find yourself using a barlow to photograph on a newt, it's time to look at the Schmidt Cassegrain. Thanks Daniel.
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Canopus56 -
daniel turner