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Eyepiece or Barlow for photography


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Just a couple of Questions.

1, I have a Mak 127, FL 1500, and was wondering what would be the best to use for planet photography with a DSLR, A Barlow or an Eyepiece?

2. Is it right a combination of both does not work?

If these are stupid questions, just asking for a friend!! 😀

 

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40 minutes ago, Cosmic Geoff said:

Don't use an eyepiece. Remove the eyepiece and connect the camera directly.  (will require an adaptor.)  Do not add a Barlow until you have tried it without.

 A dedicated planetary camera will probably give better results.

Thanks a lot for that, I have an adaptor already for my camera, I was just wondering what would give me the best results with what i have. I want a dedicated astro camera, but that will wait until I can get a good one, I dont want to waste money on a half hearted camera, only to have to replace it down the line. 👍

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I don't think planetary cameras vary too much, it's your scope optics which will influence the quality more as well as seeing at the time of capture. My 224 was my first astro cam, I still use it for planetary even though I've got other options.

As recommended above, try without any Barlow, you don't really want to image via an eyepiece. My celestron zoom eyepiece however has a t thread on it which I can screw cameras onto though I've never used it because of the reason you don't really want to shoot through an eyepiece.

Because the FPS of a DSLR is slower in comparison it may be an idea to record video instead so at least you're getting 25/30 frames per second, but I understand exposure controls can be limited in video mode.

Edited by Elp
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15 minutes ago, Elp said:

I don't think planetary cameras vary too much, it's your scope optics which will influence the quality more as well as seeing at the time of capture. My 224 was my first astro cam, I still use it for planetary even though I've got other options.

As recommended above, try without any Barlow, you don't really want to image via an eyepiece. My celestron zoom eyepiece however has a t thread on it which I can screw cameras onto though I've never used it because of the reason you don't really want to shoot through an eyepiece.

Because the FPS of a DSLR is slower in comparison it may be an idea to record video instead so at least you're getting 25/30 frames per second, but I understand exposure controls can be limited in video mode.

Thanks, I've already had a go at videoing with the DSLR, it was rushed, I never set up the tripod or aligned the scope, so it wasn't tracking, it wasn't bad for a 1st attempt, hopefully next time when I'm not trying to beat the clouds it will be better. Is the 224 the ZWO ASI224MC? because thats one of the ones I've been looking at.

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21 minutes ago, Elp said:

I don't think planetary cameras vary too much, it's your scope optics which will influence the quality more as well as seeing at the time of capture. My 224 was my first astro cam, I still use it for planetary even though I've got other options.

As recommended above, try without any Barlow, you don't really want to image via an eyepiece. My celestron zoom eyepiece however has a t thread on it which I can screw cameras onto though I've never used it because of the reason you don't really want to shoot through an eyepiece.

Because the FPS of a DSLR is slower in comparison it may be an idea to record video instead so at least you're getting 25/30 frames per second, but I understand exposure controls can be limited in video mode.

Be careful using video mode on a DSLR for planetary imaging, as the camera may be using downsampling, so although your image may cover a large number of pixels on the sensor, what the camera records to it's card is downsampled.

The Nikon D800 uses a 32 x 18 mm section of it's 36 x 24 mm sensor for 1080p video. It's full resolution is 7360 x 4912, so this section of the sensor has 6542 x 3684 pixels and is downsampled to 1920 x 1080, a factor of 3.4. So, a Jupiter that sits across 200 pixels when shooting stills is going to be recorded at just 65 pixels. Is that what you want?

It might be possible to Barlow much further in this mode, since it looks like you have bigger pixels (is that like binning? Not sure). I've found that with the D800 just shooting a lot of still frames works, but there is all the extra wear on the shutter mechanism, even in MUPpet (Mirror UP) mode.

Regarding Barlows and focal extenders, I prefer the latter as the image is less distorted. OK, so you cannot manipulate the magnification with an FE like you can a Barlow, but you cannot have everything.

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59 minutes ago, Joef said:

Thanks a lot for that, I have an adaptor already for my camera, I was just wondering what would give me the best results with what i have. I want a dedicated astro camera, but that will wait until I can get a good one, I dont want to waste money on a half hearted camera, only to have to replace it down the line. 👍

What are your future astronomy plans? Do you plan on doing long exposure astrophotography with DSLR (or dedicated astronomy camera) at some point?

If so - any planetary camera is sound investment at the moment - as you'll be always able to use it as planetary camera and it will double as your guide camera at some point.

For planetary imaging you want several things:

- high frame rate, a lot of short exposures taken. This is why we talk about video rather than still images. We are in fact taking large amount of short exposures (you can think of them as stills) - 20-30 thousand subs per run is not uncommon for targets like Jupiter or Saturn. In order to do this - camera runs on very high FPS - like 150-200fps is typical.

You can't do this with DSLR - you'll be limited to say 30fps to 60fps depending on model and this means that in same time - you'll capture x5-6 less data.

- You want your data to be "intact" - or what we call raw data. You don't want any manipulation done to it - especially compression that looses information (so called lossy compression).

DSLR can shoot video - but in order to do so and still be able to write it to SD cards (which are not know for great speeds) - it will be compressed. Check if your DSLR is capable of shooting in RAW video mode.

- You want to match pixel size to F/ratio of your scope - or rather other way around, given pixel size you want to be between x4-x5 that in F/ratio. Say your pixel size is 4um - then you want to be between F/16 and F/20 (x4-x5). You use barlow lens to achieve this.

In any case - seriously consider getting dedicated planetary / guider camera like this one:

https://www.firstlightoptics.com/zwo-cameras/zwo-asi224mc-usb-3-colour-camera.html

(it is fairly cheap at the moment - but still one of the best models for planetary imaging).

Just do note that you'll need laptop or other computer with USB3.0 port to capture and process the data.

By the way - you can use eyepiece as well as barlow to achieve magnification. You can even use both of them at the same time (although without any benefits and with some drawbacks).

Eyepiece will work a bit differently then barlow lens - and it will allow you to either magnify or even reduce image size, depending on distances involved (between eyepiece, focal plane and camera sensor).

General rule is that less optical elements equals better the image, so while you can use eyepiece  - barlow is both simpler to mount and use and has less optical elements and will produce better image - so it is preferred choice for this and other uses.

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9 minutes ago, vlaiv said:

- You want your data to be "intact" - or what we call raw data. You don't want any manipulation done to it - especially compression that looses information (so called lossy compression).

DSLR can shoot video - but in order to do so and still be able to write it to SD cards (which are not know for great speeds) - it will be compressed. Check if your DSLR is capable of shooting in RAW video mode.

It's not always straightforward to get uncompressed video from DSLRs (as you correctly indicate), but some professional cameras can do it another way. The Nikon D800 saves video files to CF or SD cards in MPEG 4 H.264 compressed format, but will output broadcast quality uncompressed video via it's integral HDMI port which can be recorded by commercial video recording equipment, but only when the cards are not present in the camera.

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23 minutes ago, Elp said:

I suspected it did something to the quality, it's why I always take images as the images are in raw none jpg format whereas video is usually compressed.

It was really just an opportunity to take the video between clouds, I really didn’t do anything right, scope right out of the warm house, not setting anything up, so I’m surprised I got anything at all, I even got two of its moons in, but they got lost in processing. But it was a chance to try my hand with PIPP, AutoStakker and Registax. Next time I’ll take my time, and try and get it right. I still enjoyed it though. 

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As long as you attempted it that's progress, sometimes that can be difficult to start if one spends too long ooing and ahhing over specs, workflows etc without going out there and doing it and getting practice in.

Edited by Elp
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1 hour ago, Mandy D said:
1 hour ago, vlaiv said:

What are your future astronomy plans? Do you plan on doing long exposure astrophotography with DSLR (or dedicated astronomy camera) at some point?

If so - any planetary camera is sound investment at the moment - as you'll be always able to use it as planetary camera and it will double as your guide camera at some point.

For planetary imaging you want several things:

- high frame rate, a lot of short exposures taken. This is why we talk about video rather than still images. We are in fact taking large amount of short exposures (you can think of them as stills) - 20-30 thousand subs per run is not uncommon for targets like Jupiter or Saturn. In order to do this - camera runs on very high FPS - like 150-200fps is typical.

You can't do this with DSLR - you'll be limited to say 30fps to 60fps depending on model and this means that in same time - you'll capture x5-6 less data.

- You want your data to be "intact" - or what we call raw data. You don't want any manipulation done to it - especially compression that looses information (so called lossy compression).

DSLR can shoot video - but in order to do so and still be able to write it to SD cards (which are not know for great speeds) - it will be compressed. Check if your DSLR is capable of shooting in RAW video mode.

- You want to match pixel size to F/ratio of your scope - or rather other way around, given pixel size you want to be between x4-x5 that in F/ratio. Say your pixel size is 4um - then you want to be between F/16 and F/20 (x4-x5). You use barlow lens to achieve this.

In any case - seriously consider getting dedicated planetary / guider camera like this one:

https://www.firstlightoptics.com/zwo-cameras/zwo-asi224mc-usb-3-colour-camera.html

(it is fairly cheap at the moment - but still one of the best models for planetary imaging).

Just do note that you'll need laptop or other computer with USB3.0 port to capture and process the data.

By the way - you can use eyepiece as well as barlow to achieve magnification. You can even use both of them at the same time (although without any benefits and with some drawbacks).

Eyepiece will work a bit differently then barlow lens - and it will allow you to either magnify or even reduce image size, depending on distances involved (between eyepiece, focal plane and camera sensor).

General rule is that less optical elements equals better the image, so while you can use eyepiece  - barlow is both simpler to mount and use and has less optical elements and will produce better image - so it is preferred choice for this and other uses.

I will be getting a dedicated Astro camera down the line, how deep I want to go, I really don’t know, in the short term I’ll be happy with the Moon and Jupiter with my DSLR until I get to know what I’m doing and how the scope and mount work. I’m pretty sure the DSLR that I have (Canon 70D) is not the ideal camera to be using, but I can use it in my learning curve, which right now, is more off a learning vertical. About the USB3 connection, I don’t have a USB3 on my laptop, I believe it will only work at the speed of a USB2, what effect that may have, I don’t know yet, apart from slowing down the data transfer somewhat, I’m sure there’s other things, but that’s something I will have to look into nearer the time. I thank you for your help. Whilst confusing and raising questions, it does help. 

Edited by Joef
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