Minimum eyepiece for deep space objects?

[sophh6699]

I’m just wanting to start out taking photos of objects further than the moon, ie nebulas and was wondering if there is a certain magnification needed to achieve this or whether just using a long exposure on a camera can do this? Thank you!

[Elp]

Nebulae generally ask for your optics to track the object (counteract the rotation of earth) so you can do long exposure per image with your camera connected to the scope, then stack the images to average the signal and noise, and post process to bring out and enhance all the detail.

You might be able to image globular clusters through an eyepiece with eyepiece projection or the camera screwed onto the eyepiece, but the tracking requirement remains.

Most serious deep sky images use auto guided setups which is more accurate than relying on a mounts sidereal tracking (unless the mount is a substantial (costly) one or has encoders).

Edited August 23, 2023 by Elp

[RT65CB-SWL]

Hi @sophh6699 and welcome to SGL. 

Question: What equipment do you have at the time writing/posting?

To help with getting the answer for your needs. I would first suggest obtaining a copy of the books ‘Make Every Photon Count’ or ‘Digital SLR Astrophotography’. I have the first and second editions of the last book.

There are two types of astrophotography...

• Prime focus. You use the OTA/‘scope as the camera lens and a 1.25” or 2” nosepiece adapter with a T-thread.
• Afocal. You use an eyepiece in an eyepiece projection unit or eyepiece projection adapter... abbreviated to EPU or EPA with a T-thread. Mostly used with a DSLR or digital compact camera and appropriate adapter. [image below].

 

 

 

 

This section is targeted for SGL’ers and visitors that own Olympus ’Camedia’ series digital compact cameras...

[image below]. The tube next to the left of camera is a CLA-1 adapter and screws onto the camera body. The wider end is the T-thread and this screws into your EPU / EPA. This is what I use when attaching my Olympus C2040 digital compact camera to my ‘scopes. When the camera is not in use or powered off, the lens is retracted. 

note: For those that own and use Olympus ‘Camedia’ series digital compact camera, make sure you have the correct or purchase the CLA adapter for your camera. They are not universal and cannot be used with another model. BTW the image is the same as the setup I use... minus the conversion lens.

Edited August 23, 2023 by RT65CB-SWL

[sophh6699]

8 minutes ago, RT65CB-SWL said:

Hi @sophh6699 and welcome to SGL. 

Question: What equipment do you have at the time writing/posting?

To help with getting the answer for your needs. I would first suggest obtaining a copy of the books ‘Make Every Photon Count’ or ‘Digital SLR Astrophotography’. I have the first and second editions of the last book.

There are two types of astrophotography...

• Prime focus. You use the OTA/‘scope as the camera lens and a 1.25” or 2” nosepiece adapter with a T-thread.
• Afocal. You use an eyepiece in an eyepiece projection unit or eyepiece projection adapter... abbreviated to EPU or EPA with a T-thread. Mostly used with a DSLR or digital compact camera and appropriate adapter. [image below].

 

 

 

 

This section is targeted for SGL’ers and visitors that own Olympus ’Camedia’ series digital compact cameras...

[image below]. The tube next to the left of camera is a CLA-1 adapter and screws onto the camera body. The wider end is the T-thread and this screws into your EPU / EPA. This is what I use when attaching my Olympus C2040 digital compact camera to my ‘scopes. When the camera is not in use or powered off, the lens is retracted. 

note: for those that do use and own Olympus digital compact camera, make sure you have the correct CLA adapter for your camera. They are not universal and cannot be used with another model.

Thank you so much! I’ll look into those books. At the moment i have the Nikon d300 and the Sky-Watcher Explorer 200p. :))

[Louis D]

1 hour ago, RT65CB-SWL said:

There are two types of astrophotography...

• Prime focus. You use the OTA/‘scope as the camera lens and a 1.25” or 2” nosepiece adapter with a T-thread.
• Afocal. You use an eyepiece in an eyepiece projection unit or eyepiece projection adapter... abbreviated to EPU or EPA with a T-thread. Mostly used with a DSLR or digital compact camera and appropriate adapter. [image below].

You left out telenegative projection which adds a Barlow lens to regular prime focus photography for greater magnification and eyepiece projection where the eyepiece directly projects its image onto the imaging chip (or film for old schoolers).  Neither of these use a taking lens on the camera/imager.

Afocal projection is what most beginners do first when they hold their phone's camera up to the eyepiece.  It is the only technique requiring a taking lens on the camera/imager to form the final image.

[sophh6699]

18 minutes ago, Louis D said:

You left out telenegative projection which adds a Barlow lens to regular prime focus photography for greater magnification and eyepiece projection where the eyepiece directly projects its image onto the imaging chip (or film for old schoolers).  Neither of these use a taking lens on the camera/imager.

Afocal projection is what most beginners do first when they hold their phone's camera up to the eyepiece.  It is the only technique requiring a taking lens on the camera/imager to form the final image.

I have a Barlow lens with my telescope, would you be able to expand any more on what you mean - do you mean that if you add the Barlow lens while using a camera then the photos will come out more magnified? 

[Bivanus]

Easy there tiger, first thing first: on what mount is your telescope? The old adagio "location, location, location" translates in "mount, mount, mount" in astro-world and even double so for anything involving imaging.

[sophh6699]

48 minutes ago, Bivanus said:

Easy there tiger, first thing first: on what mount is your telescope? The old adagio "location, location, location" translates in "mount, mount, mount" in astro-world and even double so for anything involving imaging.

It’s on a Skywatcher EQ5 equatorial tripod mount I believe, however we’re going to try making a 3D printed tracker for it. 

[Astronomist]

a eq5 is marginal with a 8" for DSO imaging, you would be better off with a beefier mount

7 minutes ago, sophh6699 said:

3D printed tracker for it

elaborate please...

[sophh6699]

7 minutes ago, Astronomist said:

a eq5 is marginal with a 8" for DSO imaging, you would be better off with a beefier mount

elaborate please...

We are looking to 3D print the components to add an extension to the mount so that we can use software to follow objects so we can take exposure photos with our camera

[Astronomist]

see this thread over on Cloudy nights for some inspiration.

To take long exposures with the scope you will most likely need autoguiding too, which can be achieved using OnStep to control the mount with stepper motors

[Elp]

Doesn't the EQ5 have male brass pins to connect an EQ drive motor to? I'm sure it does as my EQ3-2 did. This way you can sidereal track in RA and DEC, though only RA tracking is required once your target is framed.

You can also likely use your camera as is to capture wide field once your tracking is setup and running.

Note an unmodded dslr/camera won't be as sensitive as an astro camera, but you can still capture deep sky with it. It will be more forgiving than trying through your telescope. I've used compact cameras in the past fine, only major issue was edge of lens distortion and associated coma. If you've got good lenses not so much of an issue.

Edited August 23, 2023 by Elp

[RT65CB-SWL]

2 hours ago, Louis D said:

You left out telenegative projection which adds a Barlow lens to regular prime focus photography for greater magnification and eyepiece projection where the eyepiece directly projects its image onto the imaging chip (or film for old schoolers).  Neither of these use a taking lens on the camera/imager.

Afocal projection is what most beginners do first when they hold their phone's camera up to the eyepiece.  It is the only technique requiring a taking lens on the camera/imager to form the final image.

Never heard of telenegative projection until now. Thank you @Louis D for the explanation too! 

[Bivanus]

Me and 3D printing have a... lets say questionable...history. Also , I am notoriously lazy - in the best engineers way possible I mean 😂

Say hello to Flo: https://www.firstlightoptics.com/astronomy-mount-upgrade-kits/synscan-pro-goto-version-3-upgrade-kit-for-eq5.html 

[bosun21]

The EQ5 has the means to accept motors on the RA and DEC. They are secured by allen screws in a fixed location necessitating the motors to be a standard fitting. If you are serious about AP then you should buy the full upgrade kit mentioned above as this will allow you to guide. If not so serious then a single motor on the RA axis will give you tracking after polar alignment.

[Bivanus]

Oh , right , about that little crazy thing called "polar alignment" , how do you do it ? Do you do it ? 

There is also the other HUGE crazy thing called collimation , but that lovely chore explanation I'll let to somebody with a reflector to explain , I'm in the refractor gang  😊

[Louis D]

5 hours ago, sophh6699 said:

I have a Barlow lens with my telescope, would you be able to expand any more on what you mean - do you mean that if you add the Barlow lens while using a camera then the photos will come out more magnified? 

The Barlow lens is inserted in the focuser and then the bare camera (no taking lens) is inserted in the Barlow.  The magnifying effect is dependent on the focal length of the Barlow and the separation distance between it and the imaging plane.  Since Barlows never list their focal length, just know that a 2x Barlow is roughly 2x in magnification if the focal plane is at the top of the Barlow's eyepiece holder.  Since the imaging chip will be somewhat to a lot farther back from that plane, the magnification will be higher than 2x.

As others are alluding to here, increasing magnification demands increased tracking performance.  On bright solar objects like the moon and Jupiter, you can get away with poorer tracking by letting stacking software handle the details of stacking thousands of short exposure images.

[sophh6699]

1 hour ago, Louis D said:

The Barlow lens is inserted in the focuser and then the bare camera (no taking lens) is inserted in the Barlow.  The magnifying effect is dependent on the focal length of the Barlow and the separation distance between it and the imaging plane.  Since Barlows never list their focal length, just know that a 2x Barlow is roughly 2x in magnification if the focal plane is at the top of the Barlow's eyepiece holder.  Since the imaging chip will be somewhat to a lot farther back from that plane, the magnification will be higher than 2x.

As others are alluding to here, increasing magnification demands increased tracking performance.  On bright solar objects like the moon and Jupiter, you can get away with poorer tracking by letting stacking software handle the details of stacking thousands of short exposure images.

Thank you so much I’m starting to understand a little bit better now haha, so also if I was to image a DSO, would a tracking software connected to my mount and if I were to take long exposure photos (maybe 90 seconds) and edit them myself work? I know it will take a lot of practice but I will obviously build up to further objects etc. 

[Louis D]

I'll leave your last question to the imaging experts on here.  I only dabble in afocal projection imaging on solar system objects.

[Bivanus]

As many have told me , in usually hushed tones so the significant others could not hear, astrophotography is a deep deep hole from here to evermore. However, in my own experience and others , there is a question one must answer for  itself - do you want to take pictures for your enjoyment or to spite NASA/ESA into hiring you ?

If a career in space imaging it's not in the books , there is a thing called EAA ( electronically assisted astronomy) aka not so fancy AP ( don't shoot brothers !) so my opinion remains to first buy that T2:adapter & T2-1.25"  tube and simply enjoy the moon , Jupiter and Saturn first followed by some 'standard' targets. https://www.galactic-hunter.com/post/summer-the-15-best-astrophotography-targets

[Elp]

15 hours ago, sophh6699 said:

if I was to image a DSO, would a tracking software connected to my mount and if I were to take long exposure photos (maybe 90 seconds) and edit them myself work?

You have two options, maybe three.

1. Once polar aligned you set the mount to sidereal track at a specific rate, you'd have to adjust the sidereal rate depending on the focal length you're imaging at, the roundness of your stars and the target you're imaging.

2. Connect the mount to computer software be it an on board computer or PC and use the software to control point 1, note the basic Ra and Dec drive won't allow this connection as it's a simple handset controller, you'd need the advanced version though I've never used this one.

3. Get your setup autoguided, this will provide the most accurate guiding. You'll need an additional guidescope and guide camera and the computer connection and software to control it all.

The length of time you can do a single exposure will heavily depend on your tracking/guiding accuracy and your local light pollution levels. With good to excellent guiding it's pretty normal to do 3-10 minute exposures. I typically do 60-120s, if it's windy down to 30s. If you're imaging something faint or using a narrowband filter your exposure time goes up because after stacking the signal is averaged as is the noise. With targets like M42 Orion Nebula and M31 Andromeda galaxy you can capture them without guiding with a camera lens if you keep your exposures to within 5-10s, because they're so bright and relatively large. All other targets other than stars require tracking/guiding.

As an example here are two of the same target, the first one when I first got a tracking mount which transformed my AP and I used my astro modified Canon connected to my scope, imaging in alt az configuration so exposure times were limited, and the second a fully autoguided setup with a fast lens and astro camera. Post processing was very similar as there's limited processing involved with galaxies:

Edited August 24, 2023 by Elp

[Bivanus]

Love them both ! The first image I find more familiar tho 😀

[sophh6699]

On 24/08/2023 at 14:23, Elp said:

You have two options, maybe three.

1. Once polar aligned you set the mount to sidereal track at a specific rate, you'd have to adjust the sidereal rate depending on the focal length you're imaging at, the roundness of your stars and the target you're imaging.

2. Connect the mount to computer software be it an on board computer or PC and use the software to control point 1, note the basic Ra and Dec drive won't allow this connection as it's a simple handset controller, you'd need the advanced version though I've never used this one.

3. Get your setup autoguided, this will provide the most accurate guiding. You'll need an additional guidescope and guide camera and the computer connection and software to control it all.

The length of time you can do a single exposure will heavily depend on your tracking/guiding accuracy and your local light pollution levels. With good to excellent guiding it's pretty normal to do 3-10 minute exposures. I typically do 60-120s, if it's windy down to 30s. If you're imaging something faint or using a narrowband filter your exposure time goes up because after stacking the signal is averaged as is the noise. With targets like M42 Orion Nebula and M31 Andromeda galaxy you can capture them without guiding with a camera lens if you keep your exposures to within 5-10s, because they're so bright and relatively large. All other targets other than stars require tracking/guiding.

As an example here are two of the same target, the first one when I first got a tracking mount which transformed my AP and I used my astro modified Canon connected to my scope, imaging in alt az configuration so exposure times were limited, and the second a fully autoguided setup with a fast lens and astro camera. Post processing was very similar as there's limited processing involved with galaxies:

wow i love those photos !! What telescope did you use? i’m thinking about selling the scope i have right now and possibly just getting one that’s already got the tracking and everything included. Is there any specific software you could recommend for this? Also if I get a fully automatic scope will i need the guide camera still? Thank you

Edited August 25, 2023 by sophh6699

[Bivanus]

@sophh6699If you look at the lower left corner of @Elp pictures you can find out :

* the mount : SkyWaycher AZ GTI 

* the telescope : William Optics Z61 used with a flattener so the stars look pinpoint to the limits of the view field  in one picture OR a Samyang 135mm T2.8  in the other - that is a photographic lens adapted for AP.

* the cameras : ZWO ASI 485MC - that's a color camera OR a Canon 600D DSLR in the other

Yes , selling what you have and ADDING some £££ to get a smaller , more manageable scope on a equatorial Go-To or even an Alt Az Go-To mount like the AZ GTI would make sense. Until then , I still encourage you to play with what you have , it's a bit funny for me to say this since I am a refractor guy , but still , that Newt it's not the worst thing you can start with .

Here are two clips I thing it would give you more info:  

And this :

 

And this - "back in the day" AltAz mounts were not really hot for AP , however , times achangins , especially if you DO NOT want to get hired buy NASA 😁 tho you've seen what Elp can do with it !

 

[Louis D]

2 hours ago, sophh6699 said:

wow i love those photos !! What telescope did you use? i’m thinking about selling the scope i have right now and possibly just getting one that’s already got the tracking and everything included. Is there any specific software you could recommend for this? Also if I get a fully automatic scope will i need the guide camera still? Thank you

You could pick up a ZWO Seestar 50 and have an integrated solution.  They are not yet generally available, though.