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Chucknorris1975

I need help to achieve focus

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Hi all.

I'm pretty new to all this, so need some advice as google didn't answer my questions (possibly asked wrong questions)

I have a Saxon 1309 EQMS http://www.saxon.com.au/products/product-details.php?productid=10222 and also bought a Micsrosoft Lifecam HD-3000 http://www.microsoft.com/hardware/en-au/p/lifecam-hd-3000 which i modified with a webcam lens to telescope adapter, in order to try photograph the planets and moon.

The problem i'm having is that i can not achieve a sharp focus. The object will come into focus as i wind in the focuser, but is by no means a sharp focus, and if i keep winding in it will go completely out of focus.

So i am achieving a kind of focus before the focuser bottoms out, its just that the object is blurry still, maybe 70% focused.

Any tips or advice would be appreciated as my images are coming out blurry.

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Sounds like you might not have enough travel in the focus tube. Some Newts like yours are not really made for prime focus imaging and you may have to move the primary mirror forward. You can find your exact prime focus point by removing the focuser and holding the camera over the hole while moving it back and forth. It's really a good idea to use the moon when doing this. When you find focus you will see where it does and if it is within the travel of your focus tube or not. Another thing to keep in mind is that most primary mirrors on these types of scopes are usually parabolic and curved. The middle of the mirror will be sharper than the edges. Thats why when using a Newt type scope taking pictures one must use a coma corrector with them to get the most usable sharp coma free area in your pictures.

Edited by Leveye

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Sounds like you might not have enough travel in the focus tube. 

I get the best focus about 5-10 mm from the bottom of the focus tube. If I keep winding in past this point the image goes way out of focus again until I get to the end of the focusers travel.

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I found it quite difficult to focus when I first used a webcam as the slightest touch of the focuser made the image jump all over the place and this gets worse when you add a Barlow to get a decent size image. I eventually added an auto focuser which made things much easier. I can get focus manually but it really is a matter of keeping at it and  making very small adjustments  then waiting for the image to stabilise each time. Good luck and keep at it!

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It quite likely that the seeing has not been good when you have been trying to focus. Often when the seeing is not great, no matter what you try you won't ever get it to appear perfectly in focus because of the turbulence in the atmosphere. The turbulent seeing is combatted during the stacking process. Nearly all my planetary images never appear to be fully in focus on the capture screen whilst filming them.

So before you go doing large tasks like moving your primary maybe wait and get out again an check if the problem you're having is consistently the same or if it appears to improve it get worse (as in gets easier or harder to get close to sharp focus) on different nights. Bearing in mind that with planets especially you will rarely see them as truly sharp in live view. The moon is an easier target to judge whether it's the seeing that is the problem.

Sent from my iPhone using Tapatalk

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If you are achieving a sharpish image within the range of the focuser then this is probably the sharpest image you will achieve. Atmospheric disturbances will make the image look blurred and distorted even when you are in focus, the live image will never look as sharp as the final processed still. Processing the avi through registax or one of the other stacking programs will help to reduce the distortions and blurryness.

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I agree with the above and would add that it may also be to do with the seeing conditions. Sometimes the sky looks clear but actually it has ice crystals or thin cloud which can make focusing almost impossible. I suggest that you try to focus during the day if you can find an object far enough away. If you can get focus during the day it could well be the seeing.

Peter

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Are you sure that the sensor of the camera is 100% clean?

I know I've never touched it with my fingers or anything else, but i did have bits of plastic swarf from modifying it show up on screen once i tested it. I used compressed air to blow it off, and that disappeared immediately. Other than compressed air, I don't think you're meant to clean it with any type of solvent or physically touch the sensor so i haven't.

I found it quite difficult to focus when I first used a webcam as the slightest touch of the focuser made the image jump all over the place and this gets worse when you add a Barlow to get a decent size image. I eventually added an auto focuser which made things much easier. I can get focus manually but it really is a matter of keeping at it and  making very small adjustments  then waiting for the image to stabilise each time. Good luck and keep at it!

I have tried during the day to focus on a tree about 250 meters away, and I slowly turned the knob, let it stabilize and re tried, but could not get a sharp focus. It would focus to a certain point, then go out of focus as i kept turning the knob.

Maybe i need more practise. I'll try to upload an image when i can.

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Maybe 250M is not far enough. Can you see anything about 1/2 mile away, that would be a better test.

Peter

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post-34861-0-11045400-1396190114.jpgThis is a stacked image of Saturn from the other night. Second time i used Registax and Sharp cap 2. Am i expecting too much with the equipment i have?

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I think that you probably are. That image of Saturn is pretty good and I don't think that you can expect much more with your equipment. You probably need to adjust the colour a bit but I doubt if you could get it much sharper. Did you use the wavelets in Registax? There is also a histogram adjustment tool in Registax. How many frames did you take - should be 2000 or so I would suggest.

Keep at it. Good luck.

Peter

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I have tried during the day to focus on a tree about 250 meters away, and I slowly turned the knob, let it stabilize and re tried, but could not get a sharp focus. It would focus to a certain point, then go out of focus as i kept turning the knob.

Maybe i need more practise. I'll try to upload an image when i can.

Have you checked that the scope is collimated. Planetary imaging requires spot-on collimation to resolve fine detail.

Allow a good cooling down to ambient temperature time.

If the planet imaged is wobbling about going in and out of focus then the seeing conditions are poor or you need more cooling down time.

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Have you tried to check your focus with a Bahtinov mask? If you get focus with the mask, and it still looks a bit fuzzy, then either, you have poor seeing, or you are asking too much from your optics. 

If I try to focus my Astromaster 114 I can wander all the way from out of focus on one side to out of focus on the other, without really achieving focus. I can get what looks like a nice Bahtinov pattern, but it still looks like a big white disc when I take a photo. Turns out that the optics on the telescope are just not up to imaging.

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Have you tried to check your focus with a Bahtinov mask? If you get focus with the mask, and it still looks a bit fuzzy, then either, you have poor seeing, or you are asking too much from your optics.

If I try to focus my Astromaster 114 I can wander all the way from out of focus on one side to out of focus on the other, without really achieving focus. I can get what looks like a nice Bahtinov pattern, but it still looks like a big white disc when I take a photo. Turns out that the optics on the telescope are just not up to imaging.

I dare say you're right. It is a beginners scope after all.

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I think that Saturn shot is great. Your asking a bit to much out of you optics but all said fine work. Keep at it well done!

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I've gone out during the day and retested the focus on an object roughly 700m away, and I must admit, I could get a pretty sharp picture. Not the greatest quality image but edges were reasonably sharp. I tweaked the focuser a little by loosening the 2 screws under the pinion slightly and that made for smoother less jerky focusing. I'll look into a Bahtinov mask to try get the best focus at night, and see how my images stack up then.

Thanks for all the input guys, I've got a better grasp on focusing I think. Just have to practice more. Especially processing.

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I've gone out during the day and retested the focus on an object roughly 700m away, and I must admit, I could get a pretty sharp picture. Not the greatest quality image but edges were reasonably sharp. I tweaked the focuser a little by loosening the 2 screws under the pinion slightly and that made for smoother less jerky focusing. I'll look into a Bahtinov mask to try get the best focus at night, and see how my images stack up then.

Thanks for all the input guys, I've got a better grasp on focusing I think. Just have to practice more. Especially processing.

One trick I have seen that I like, is to take a steel ruler and place it a distance away. Because the lines are etched onto the ruler, they are fairly sharp. Then try to focus on that. 

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skywatcher 114 @ 1000mm 

i reach focus using a microsoft lifecam Hd5000, with the drawtube 24mm away from the focuser holder top.

i hard modded my camera, i totaly pulled it apart made a small balsa wooden box ( hand carved)

and mounted the whole camera pcb inside it. it moved my sensor 10mm closer to the top of the focuser tube to.

the moon, on a clear night ( NOT a full moon )

add a 2x barlow and pop camera in.

find the craters where the crescant is, now focus hard 

when scope wobbles, stop... let it settle then adjust again.

when i say adjust your not going to turn the focuser but just tap it a touch

theres a very fine line between nailed and just off.

MARK this point with a little bit of sticky tape or something.

when you go to use setup again back out focuser to the mark, pop camera in and use this 

as the base focus point. 

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