HOW TO UTILIZE DSLR to TAKE PHOTOS (2)

[riogrande100]

I am new to the astro photography world, but have taken some pics. I have seen the vignette view of pics of the moon like looking down tunnel, and just assumed my lens wasn't close enough to the sensor but now i know better. My equipment i have is

Canon 1000D

Celestron Astromaster 130mm

Canon T-Ring

Celestron T-Adaptor

10mm Lens w/ scope

I can get some good pics, but not excellent pics as realtor has shown.

How should i go about getting a better shot of the moon as a whole, rather then either to much zoom (3/4 moon)????

rio

[SteveL]

I split the original thread and moved the above post into a new thread.

[riogrande100]

Thanks Steve

[arad85]

I can get some good pics, but not excellent pics as realtor has shown.

How should i go about getting a better shot of the moon as a whole, rather then either to much zoom (3/4 moon)????

rio

Hi,

There are a couple of things here. Firstly, as to image scale, the telescope is acting like a fixed length lens on the front of your camera. As you can't zoom it, the image size is fixed, so if you're seeing 3/4 of a moon, each pic will be 3/4 of a moon. To change this, you'll need to change the 'scope - just like changing a different camera lens - or change the camera to one that has a smaller sensor on it. Alternatively, you could go for eyepiece projection, but with a single eyepiece, you would be limited to what that would show you in area too.

As to how people take photos of the moon - generally with webcams and create a mosaic by stitching them together. As a webcam has a smaller chip than the Canon, you get a correspondingly smaller area of moon in each shot.

Webcams are used as you can take many hundreds of pictures as an image sequence and then "stack" them. This enables you to overcome some of the atmospheric effects you can see when looking at the moon (heat haze effects).

As to vignetting, at a guess it's because you're connecting a large sensor to a 'scope with a 1.25" adapter. Not sure whether your 'scope has a 2" eyepiece holder, but I (and others) use a MaxDSLR adapter that attaches to a 2" tube.

HTH

[riogrande100]

My scope has a 1.25" lens holder, so i doubt i can use the 2". I don't mind the vignetting to much as i can crop the image to remove the vignette.

I will see what a different lens gives me as the 10mm gives intense zoom on the moon, whereas the 20mm gives a nice wide view but the lens is not compatible with the t-adapter.

[arad85]

I'm assuming with the Canon on the t-ring adaptor, you're plugging that directly in the focuser with no eyepiece between you and the telescope. Is this correct, or are you trying to image through the 10mm lens?

[Cornelius Varley]

It appears that you are trying to take photographs afocally ie using the camera, with the camera lens attached and photographing the view down the eyepiece. With this combination it is difficult to avoid vignetting. A better method would be prime focus ie using the telescope as a large telephoto lens. Remove the camera's lens and attached the t ring and a 1.25" nosepiece adaptor. This can be placed into the focusser directly or with a barlow lens to increase magnification. To determine howlarge the moon will appear on the sensor or film plane divide the focal length of the telescope by 110 and the result will give you the apparent diameter of the moon on the sensor. 650/110 = 5.9mm, 1300 (650 + 2x barlow) /110 = 11.8mm.

You could also try eyepiece projection. An adaptor is placed around the eyepiece which attaches to the camera body via a t adaptor.

Peter

[riogrande100]

It appears that you are trying to take photographs afocally ie using the camera, with the camera lens attached and photographing the view down the eyepiece. With this combination it is difficult to avoid vignetting. A better method would be prime focus ie using the telescope as a large telephoto lens. Remove the camera's lens and attached the t ring and a 1.25" nosepiece adaptor. This can be placed into the focusser directly or with a barlow lens to increase magnification. To determine howlarge the moon will appear on the sensor or film plane divide the focal length of the telescope by 110 and the result will give you the apparent diameter of the moon on the sensor. 650/110 = 5.9mm, 1300 (650 + 2x barlow) /110 = 11.8mm.

You could also try eyepiece projection. An adaptor is placed around the eyepiece which attaches to the camera body via a t adaptor.

Peter

Thanks Peter

I am not using a lens, but had a t-ring attached to the body, and the tring then screw onto the T- Adapter. The T-Adapter has a 10mm eye piece in there. I am guessing the vignetting is the eye piece that is being picked up.

I am guessing from the comments that the best setup would be:

DSLR > T-Ring > Barlow lens > T-Adapter > Scope?

instead of my setup

DSLR > T-Ring > 10mm eyepiece > T-Adapter > Scope

[arad85]

Yes. With the eyepiece you are taking images afocally (eyepiece projection). Without you are taking it at prime focus.

[dark knight]

I think the more you try to magnify the image the more vignetting will be an issue.

For the moon try DSLR>T-Ring>T Adapter>Scope...

[riogrande100]

I think the more you try to magnify the image the more vignetting will be an issue.

For the moon try DSLR>T-Ring>T Adapter>Scope...

How would i go about focusing the image? would turning the nobs suffice???

sorry for all the noob questions!

[dark knight]

You set dslr to manual and use the telescopes focuser..

[dark knight]

Oh and no need to apologise, ask away...

[riogrande100]

thanks peter!!! When the sky is clear next i will try!!!

[pulsar]

And don't forget that focal reducers can help in lunar photography. As I need one to bring my LX90 down a wee bit in my 26mm eyepiece for when i want to do projection stuff as well as deep sky object like large nebulas or star clusters.

[riogrande100]

So how does the eyepiecome into play???? from the hostory of the thread i gather do not use the eyepiece but just adapter and camera attached to the scope

[pvaz]

It doesn't.

Pulsar was talking of the possible need for a focal reducer to reduce the magnification and gave an example of a case where he needed one for image projection. Image projection uses an EP, astro-photography is better without an EP, the idea is to use the scope as a camera lens. In between you can use focal reducers or barlows to either reduce or increase the effective focal length.

[arad85]

Eyepiece doesn't come into play. You plug the lensless camera directly into the focuser. You may find that you don't quite get enough in focus to get the image to focus though. I think the only thing you can do to change that is move the primary mirror (the big mirror at the bottom of the tube) up the tube a bit (you may be able to achieve this with the collimation screws or you may need to find a way of fitting/making your focuser lower profile to be able to get the camera closer to the secondary (the small diagonal lens you can see down the focuser).

[riogrande100]

Eyepiece doesn't come into play. You plug the lensless camera directly into the focuser. You may find that you don't quite get enough in focus to get the image to focus though. I think the only thing you can do to change that is move the primary mirror (the big mirror at the bottom of the tube) up the tube a bit (you may be able to achieve this with the collimation screws or you may need to find a way of fitting/making your focuser lower profile to be able to get the camera closer to the secondary (the small diagonal lens you can see down the focuser).

Thanks guys, i did realise when i first used the scope sans lens that the image never came into complete focus, and therefore threw the lens in there. but now that I know what to do i will try and adjust the mirrors at the bottom of the scope to try and bring my camera into focus.

Barlow lens and reducers will be purchased early next year, or when i can afford it.