One for the DSLR imagers please

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skyhawk
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One for the DSLR imagers please

Post by skyhawk »

I am NOT an imager, unfortunately being Autistic I never will be as I don't have the necessary patience, but I am connecting my DSLR to my scopes.

Therefore I have the most basic problem you will all have overcome.

72mm ED Skywatcher and 120mm Triplet ED Esprit.

Can not focus on infinity, assuming not enough inward travel.

See images

I have tried attaching the camera directly to the scope (72mm) NO luck, attaching the camera via 2" diags to the larger scope, NO luck, the only way is to use a reducer? screwed into the front of the camera nosepiece

So, is that it :(

Thanks
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Celestron 8" Edge HD Evolution, Esprit 120mm triplet, 72mm APO, Sky Tee 2, 6" reflecting scope, William Optics Binoviewer, Quark Daystar Ha Chromosphere on 72mm ED, LVW8mm eyepiece and Celestron 19mm Axiom, matched W.O 10 and 20mm, and a few others, D4s, D810,

For info, I am Autistic, Aspergers, ADHD, therefore if I come over as a little "short" on occasions it is not intended, thank you
skyhawk
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Re: One for the DSLR imagers please

Post by skyhawk »

reducer ?
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Celestron 8" Edge HD Evolution, Esprit 120mm triplet, 72mm APO, Sky Tee 2, 6" reflecting scope, William Optics Binoviewer, Quark Daystar Ha Chromosphere on 72mm ED, LVW8mm eyepiece and Celestron 19mm Axiom, matched W.O 10 and 20mm, and a few others, D4s, D810,

For info, I am Autistic, Aspergers, ADHD, therefore if I come over as a little "short" on occasions it is not intended, thank you
skyhawk
Posts: 559
Joined: Tue Dec 05, 2017 11:53 am
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Re: One for the DSLR imagers please

Post by skyhawk »

The SCT is fine though
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Celestron 8" Edge HD Evolution, Esprit 120mm triplet, 72mm APO, Sky Tee 2, 6" reflecting scope, William Optics Binoviewer, Quark Daystar Ha Chromosphere on 72mm ED, LVW8mm eyepiece and Celestron 19mm Axiom, matched W.O 10 and 20mm, and a few others, D4s, D810,

For info, I am Autistic, Aspergers, ADHD, therefore if I come over as a little "short" on occasions it is not intended, thank you
Brian
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Re: One for the DSLR imagers please

Post by Brian »

From what I read you probably need a 50mm extension tube between the focuser and the DSLR.

I find a useful trick is to locate the focus point by pointing at a bright object (Moon) and then move a sheet of translucent paper (tracing paper) back and forth behind the focuser until some details are seen in decent focus on the paper. That is a good indication of where you need to get your camera sensor in order to have the image in focus,
regards
Brian
52.3N 0.6W
Wellingborough UK.

254mm LX90 on Superwedge, WO ZS66SD, Helios 102mm f5 on EQ1, Hunter 11x80, Pentax 10x50
ASI120MC Toucam Pros 740k/840k/900nc mono, Pentax K110D
Ro-Ro roof shed
skyhawk
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Re: One for the DSLR imagers please

Post by skyhawk »

Brian wrote:From what I read you probably need a 50mm extension tube between the focuser and the DSLR.

I find a useful trick is to locate the focus point by pointing at a bright object (Moon) and then move a sheet of translucent paper (tracing paper) back and forth behind the focuser until some details are seen in decent focus on the paper. That is a good indication of where you need to get your camera sensor in order to have the image in focus,
regards

So are you saying that the camera needs to be FURTHER away from the scope, rather than needing "inward" travel ?
Celestron 8" Edge HD Evolution, Esprit 120mm triplet, 72mm APO, Sky Tee 2, 6" reflecting scope, William Optics Binoviewer, Quark Daystar Ha Chromosphere on 72mm ED, LVW8mm eyepiece and Celestron 19mm Axiom, matched W.O 10 and 20mm, and a few others, D4s, D810,

For info, I am Autistic, Aspergers, ADHD, therefore if I come over as a little "short" on occasions it is not intended, thank you
Brian
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Joined: Fri Dec 03, 2004 9:58 pm
Location: Wellingborough
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Re: One for the DSLR imagers please

Post by Brian »

Just got that info from the web, so cannot guarantee it.

If you locate the focal plane of the telescope with a piece of tracing paper then you will know exactly where you need to place your camera on your system,

regards,
Brian
52.3N 0.6W
Wellingborough UK.

254mm LX90 on Superwedge, WO ZS66SD, Helios 102mm f5 on EQ1, Hunter 11x80, Pentax 10x50
ASI120MC Toucam Pros 740k/840k/900nc mono, Pentax K110D
Ro-Ro roof shed
JohnM
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Re: One for the DSLR imagers please

Post by JohnM »

skyhawk wrote:
Brian wrote:From what I read you probably need a 50mm extension tube between the focuser and the DSLR.

So are you saying that the camera needs to be FURTHER away from the scope, rather than needing "inward" travel ?
If you try to focus on an extended object such as the moon the image should get smaller and less fuzzy as you approach the focus point. If it gets bigger and more fuzzy you are going the wrong way !

If you reach maximum in and the image is getting smaller but not in focus you need to shorten the path by removing some component. If you get to maximum out and it is not in focus you need to add an extension.

I suspect your path is too long looking at the images.

I added a scale to the drawtube of my Skywatcher 80ED - it is really useful in providing a recoord of the focus position with a particular camera and set of extension tubes. I keep a record of the settings and images of the setup in a word document so it is easy to edit. I still got caught out on Monday morning - I used a different camera adaptor which is shorter than the one I had in my telescope book and was not able to reach focus. At the time (03:30) I did not remember I had purchased a new adaptor to reduce the vignetting :) .

If you have a setup that focuses with an eyepiece you can get a good idea of where the focal point is - the focal point for an eyepiece is normally between the lower lens and the end of the barrel. You can mesure the exact point by (very carefully !) inserting something into the lower part of the barrel and moving it upwards till it focuses. The position this happens is the focal plane - don't blame me if you scratch your eyepiece though.

Your camera will have it's focal position marked on it with a symbol of a circle with a line through it. I can't remember how far it is from the front flange on a Canon Camera but an internet search should find that - if not post a message here and i will measure mine. A (platic) vernier caliper is very useful to measure the lengths of various extension pieces as well as the apparent position of the focal point.

With an SCT you can reach focus with almost any length of path - howver it does not mean you should do this - the optical performance falls off quite fast away from it's designed position even a few millimeters has an effect. Little is published on the designed position for SCTs - there is a paper on the Celestron Edge with a dimension - the other thing is to measure the path length of the supplied diagonal and eyepiece and 'hope' that is the sweet spot. If not you are into measuring the performance at different focal positions which is a bigger challenge.

John
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Image shows the focal plane symbol on a Canon 40D
Image shows the focal plane symbol on a Canon 40D
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Last edited by JohnM on Wed Jan 23, 2019 11:50 am, edited 1 time in total.
Engineer @ Work - Astronomer @ Play
skyhawk
Posts: 559
Joined: Tue Dec 05, 2017 11:53 am
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Re: One for the DSLR imagers please

Post by skyhawk »

Thanks all, appreciated
Celestron 8" Edge HD Evolution, Esprit 120mm triplet, 72mm APO, Sky Tee 2, 6" reflecting scope, William Optics Binoviewer, Quark Daystar Ha Chromosphere on 72mm ED, LVW8mm eyepiece and Celestron 19mm Axiom, matched W.O 10 and 20mm, and a few others, D4s, D810,

For info, I am Autistic, Aspergers, ADHD, therefore if I come over as a little "short" on occasions it is not intended, thank you
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