<p><a href="https://i.sstatic.net/ttW20.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/ttW20.jpg" alt="Moon" /></a>When using DSLR with Newtonian (130mm/1000mm), I am not able to get perfect focus.</p>
<p>However, when I use an eyepiece, I am able to get crystal clear views. So, I think collimation is okay.</p>
<p>The focusing tube is <strong>not</strong> short. I am able to focus upto a certain point using the DSLR. But the best focus that I am able to get is not crystal clear.</p>
<p>Any suggestions?
Thanks!</p>

CC BY-SA 4.0
2021-05-24T09:17:14.240Z
How are you connecting the camera to the scope?  Are you using a T ring or are you attaching the camera to the eyepiece?
Dr Chuck
CC BY-SA 4.0
2021-05-24T12:47:12.030Z
Also, if possible please send a photo of your setup showing how the camera is connected. Also please upload an image of the best focus that you can get; there may be things in the image that help to debug the problem. Also mention which kind of DLSR you are using and how you are doing the focus; are you looking at an LCD screen on the camera, or through the viewfinder? (for example this one has both). You need to add a lot more detail if you 'd like a good answer. *Thanks!*
uhoh
CC BY-SA 4.0
2021-05-24T16:16:24.657Z
Just putting the DSLR on the focuser works for me, as it is stable. But I was getting severe coma aberration. Then I got to know about backfocus. Then after some adjustment (increasing the distance between CMOS sensor and the corrective lens in the focuser tube) the comas weren't that severe. I am posting a moon picture (which I could focus the best).
Mathematicie
CC BY-SA 4.0
2021-05-24T22:35:08.310Z
*Thanks for the edit, information and image!* The Moon's terminator is pretty sharp near the bottom and very fuzzy near the top, I'll bet that the focal plane of the telescope is not parallel to the plane of the camera's image sensor, and you'll have to figure out what more to tilt. If you have great focus over the full FOV of an eyepiece with a large entrance pupil (as big as the camera's sensor) then maybe the tilt of your diagonal is not a problem, but if it's got adjustments on it it might be something to visit as a last resort.
uhoh
CC BY-SA 4.0
2021-05-24T22:38:24.813Z
Instead, I'd take a good hard look at the way the camera is mounted; is there any looseness in the focusing mechanism or the tubes that the extra weight of the camera body might cause to bend under gravity? Also, once you get any mechanical issues resolved and your camera's imager plane parallel to the telescopes focal plane, remember to **take many images** and look for the best one (e.g. [lucky imaging](https://en.wikipedia.org/wiki/Lucky_imaging)) since [astronomical seeing](https://en.wikipedia.org/wiki/Astronomical_seeing) can make any one image more blurry in some areas than others.
uhoh
CC BY-SA 4.0
2021-05-24T22:40:25.620Z
Also, does your SLR camera have a moving mirror that goes "thwack" when you take the photo? It could set up vibrations. It's better to electronically delay the image after any vibrations have died down, and so that you are not using a shutter release cable or your finger to trigger the image.
uhoh
<photography><newtonian-telescope>
Not able to get Perfect Focus with DSLR and Newtonian
Mathematicie
# Not able to get Perfect Focus with DSLR and Newtonian

(Asked by: username_0 on 2021-05-24)

[![Moon](https://i.sstatic.net/ttW20.jpg)](https://i.sstatic.net/ttW20.jpg)When using DSLR with Newtonian (130mm/1000mm), I am not able to get perfect focus.

However, when I use an eyepiece, I am able to get crystal clear views. So, I think collimation is okay.

The focusing tube is **not** short. I am able to focus upto a certain point using the DSLR. But the best focus that I am able to get is not crystal clear.

Any suggestions?
Thanks!

**Tags:** photography, newtonian-telescope

> **Comments:**
> **username_1**: How are you connecting the camera to the scope?  Are you using a T ring or are you attaching the camera to the eyepiece?  
> **username_2**: Also, if possible please send a photo of your setup showing how the camera is connected. Also please upload an image of the best focus that you can get; there may be things in the image that help to debug the problem. Also mention which kind of DLSR you are using and how you are doing the focus; are you looking at an LCD screen on the camera, or through the viewfinder? (for example this one has both). You need to add a lot more detail if you 'd like a good answer. *Thanks!*  
> **username_0**: Just putting the DSLR on the focuser works for me, as it is stable. But I was getting severe coma aberration. Then I got to know about backfocus. Then after some adjustment (increasing the distance between CMOS sensor and the corrective lens in the focuser tube) the comas weren't that severe. I am posting a moon picture (which I could focus the best).  
> **username_2**: *Thanks for the edit, information and image!* The Moon's terminator is pretty sharp near the bottom and very fuzzy near the top, I'll bet that the focal plane of the telescope is not parallel to the plane of the camera's image sensor, and you'll have to figure out what more to tilt. If you have great focus over the full FOV of an eyepiece with a large entrance pupil (as big as the camera's sensor) then maybe the tilt of your diagonal is not a problem, but if it's got adjustments on it it might be something to visit as a last resort.  
> **username_2**: Instead, I'd take a good hard look at the way the camera is mounted; is there any looseness in the focusing mechanism or the tubes that the extra weight of the camera body might cause to bend under gravity? Also, once you get any mechanical issues resolved and your camera's imager plane parallel to the telescopes focal plane, remember to **take many images** and look for the best one (e.g. [lucky imaging](https://en.wikipedia.org/wiki/Lucky_imaging)) since [astronomical seeing](https://en.wikipedia.org/wiki/Astronomical_seeing) can make any one image more blurry in some areas than others.  
> **username_2**: Also, does your SLR camera have a moving mirror that goes "thwack" when you take the photo? It could set up vibrations. It's better to electronically delay the image after any vibrations have died down, and so that you are not using a shutter release cable or your finger to trigger the image.  

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## 0 answers

