45 replies to this topic

[Dpasqa]

I have a Canon T3i and the adapter with T ring. Last night I gave it my first try, what a disappointment. I used my AT72EDll and didn’t have it mounted on a goto, that will be my next move. I connected the camera directly to the scope with the t ring and adapter. 
 

I have only one question for now. The pictures I took, everything looked small. Is there a way to zoom in without an eyepiece. If not what’s the point of using a telescope if you don’t get higher magnification. Since the telescope isn’t magnifying anything why use it?

[gstrumol]

The telescope doesn't magnify anything; it just gathers light. All magnification is achieved through the EP. I too just got a Canon Rebel T7 and did my first pic with it. Target: the sun in white light. I used my AT80EDL with a Baader solar film over the front. I added the lens portion from a 2x Barlow to the end of the adapter. Just a single shot; I have to learn how to add a delay after pressing the button! 

 

Anyway here is the result:

 

(screenshot from a 7MB file)

 

I clearly have much to learn, but you should be able to do this as well. I also have a zoom eyepiece that can attach to the T-adapter (make sure it has threads on top!). You can also use a Barlow.

 

Good luck and don't get discouraged!

 

 

[kgb]

You can digitally magnify in post processing or introduce a Barlow. Given the large size of that sensor, you are looking at an approximate magnification of about 16x. The scope's primary purpose is to collect the light. The magnification, in the case of visual observing, is for the eyepiece to magnify the image. The magnification is calculated by dividing the focal length of the telescope by the focal length of the eyepiece . Since you are using a sensor instead of an eyepiece, you would instead divide the focal length by the size of your sensor. Therefore, adding a 2x Barlow would double the magnification, 3x Barlow would triple, etc....

[Dpasqa]

The telescope doesn't magnify anything; it just gathers light. All magnification is achieved through the EP. I too just got a Canon Rebel T7 and did my first pic with it. Target: the sun in white light. I used my AT80EDL with a Baader solar film over the front. I added the lens portion from a 2x Barlow to the end of the adapter. Just a single shot; I have to learn how to add a delay after pressing the button! 

 

Anyway here is the result:

 

FirstSunS.jpg

(screenshot from a 7MB file)

 

I clearly have much to learn, but you should be able to do this as well. I also have a zoom eyepiece that can attach to the T-adapter (make sure it has threads on top!). You can also use a Barlow.

 

Good luck and don't get discouraged!

I’m glad it isn’t just me.

[Dpasqa]

You can digitally magnify in post processing or introduce a Barlow. Given the large size of that sensor, you are looking at an approximate magnification of about 16x. The scope's primary purpose is to collect the light. The magnification, in the case of visual observing, is for the eyepiece to magnify the image. The magnification is calculated by dividing the focal length of the telescope by the focal length of the eyepiece . Since you are using a sensor instead of an eyepiece, you would instead divide the focal length by the size of your sensor. Therefore, adding a 2x Barlow would double the magnification, 3x Barlow would triple, etc....

I’ll have to buy a Barlow. I don’t need it for visual, I have eyepieces for just about everything I need. 

[Jim Davis]

What object are you trying to image? Most objects you will just crop the outer edge of the image off so you can resize the image post processing. Very few things will fill the image frame. Using a barlow will just dim the image by spreading the light out over a wider area. Normally only barlow imaging when doing planetary or lunar imaging, which are bright enough.

[DeepSky Di]

In DSO astrophotography, high magnification is not necessary. Many popular targets don't fit in the field of view of a high magnification OTA or lens. What you gain from a telescope rather than a lens is 1) a decent focuser that is accurate enough for astronomy and 2) none of the unwanted features that are necessary for daytime photography but are not just unnecessary but may be detrimental to astro picture quality - zoom, variable aperture, stabilization, autofocus.

 

Get the free Stellarium app for your computer, go to the wrench in the top right corner, add the specs for the OTA and camera and then take a tour of the skies - start with Andromeda Galaxy, Orion Nebula, Pleiades - to see how they fit into the field of view.

 

Instructions from Mike Shaw on YouTube here: https://youtu.be/tKyja_iSuNM at approx 17:24

[michael8554]

"what’s the point of using a telescope if you don’t get higher magnification. Since the telescope isn’t magnifying anything why use it?"

 

The "magnification" (image scale really) is proportional to the focal length of the scope.

 

The AT72EDll has the same focal length as a 430mm camera lens.

 

Those big images of galaxies you've seen are taken with much longer focal lengths, often 1400mm to 2000mm.

 

So for a start you could use your Astro-Tech AT115EDT, which has 803mm focal length

[bobzeq25]

Some basics.

 

Imaging solar system objects and imaging deep space are completely different activities, require completely different setups and techniques.  So there are different forums here for each.

 

I'll talk DSOs.  This forum is mostly about DSOs.

 

Nebulae and some other targets are really big.  So, you do not want to magnify them because they wouldn't fit on the chip in the camera.  Here are the Pleadies, an excellent starter target, would work well with your 72 and a DSLR.  Click on this thumbnail for a better version, and details about how it was done.

 

 

 

 

Most galaxies are small (Andromeda though, is _four_ full Moons wide, another good starter target).

 

What makes this work is not magnification, it's two other things.  You gather a lot of data including many long subexposures of your subject.  20 3 minute subs combined is a good starter level, one hour of "total imaging time".  You process the data intensively on a computer.  You need good software for that, a good starter program is Astro Pixel Processor.

 

The most important part of the setup is NOT the scope.  Or the camera.  It's an excellent mount, your eyes compensate for motion when looking through the telescope, the camera doesn't.  A good one for the 72 would be an HEQ5 or iEQ30.  About $1500.

 

The telescope that did the image above was a 100mm.  A bit large to start with, far better would be your 72.  This is _really_ unintuitive.  The mount was a $2500 CEM60, needed for the larger scope.

 

If that's too much money, the solution is to shorten the focal length, a lot, by using a camera lens instead of a telescope.  That reduces the effect of tracking errors (which are always an issue).  Then you can use a $300-500 "camera tracker".  The setup looks like this.

 

 

It's a lot of fun.  It takes time to learn to do it well, the pretty pictures do not come easy.  It's both complicated and unintuitive, you need to study how to do it.  Here's a good place to start, quite beloved on this site.

 

https://www.amazon.c...d/dp/0999470949

 

That's enough for now.  There's way more to this than fits on a short post.  Get the book.  Spend some time reading the Beginning and Intermediate Imaging forum.

 

Yes, it's complicated (very).  The good news, a charm of the hobby for many of us, is that you will never run out of new things to learn.

Edited by bobzeq25, 26 March 2023 - 10:37 AM.

[Dpasqa]

Thanks for your comments. I now understand that the telescope gathers more light and uses the three lenses on a triplet but doesn’t zoom. I’m good with that, the triplet eliminates CA. 
 

Here are my first tries. The moon needed a filter, Venus was ok and Orion had streaky stars because I set it to 4 seconds without goto. Next time I’ll use the AT115EDT with my Ioptron goto mount and try different exposure settings. Maybe 30 seconds or less and also try bulb setting. 

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[Dpasqa]

Some basics.

 

Imaging solar system objects and imaging deep space are completely different activities, require completely different setups and techniques.  So there are different forums here for each.

 

I'll talk DSOs.  This forum is mostly about DSOs.

 

Nebulae and some other targets are really big.  So, you do not want to magnify them because they wouldn't fit on the chip in the camera.  Here are the Pleadies, an excellent starter target, would work well with your 72 and a DSLR.  Click on this thumbnail for a better version, and details about how it was done.

 

 

 

 

Most galaxies are small (Andromeda though, is _four_ full Moons wide, another good starter target).

 

What makes this work is not magnification, it's two other things.  You gather a lot of data including many long subexposures of your subject.  20 3 minute subs combined is a good starter level, one hour of "total imaging time".  You process the data intensively on a computer.  You need good software for that, a good starter program is Astro Pixel Processor.

 

The most important part of the setup is NOT the scope.  Or the camera.  It's an excellent mount, your eyes compensate for motion when looking through the telescope, the camera doesn't.  A good one for the 72 would be an HEQ5 or iEQ30.  About $1500.

 

The telescope that did the image above was a 100mm.  A bit large to start with, far better would be your 72.  This is _really_ unintuitive.  The mount was a $2500 CEM60, needed for the larger scope.

 

If that's too much money, the solution is to shorten the focal length, a lot, by using a camera lens instead of a telescope.  That reduces the effect of tracking errors (which are always an issue).  Then you can use a $300-500 "camera tracker".  The setup looks like this.

 

skytracker-with-camera-and-lens-444x545.jpg

 

It's a lot of fun.  It takes time to learn to do it well, the pretty pictures do not come easy.  It's both complicated and unintuitive, you need to study how to do it.  Here's a good place to start, quite beloved on this site.

 

https://www.amazon.c...d/dp/0999470949

 

That's enough for now.  There's way more to this than fits on a short post.  Get the book.  Spend some time reading the Beginning and Intermediate Imaging forum.

 

Yes, it's complicated (very).  The good news, a charm of the hobby for many of us, is that you will never run out of new things to learn.

Thanks for this info. You got one great shot of Pleiades, I’ll try that one next. I do have an Ioptron AZ Mount Pro. It will suffice for what I am doing. I will most likely keep it simple, I don’t want to get too deep, I only want some reference shots for fun. From what I’m learning this can be as simple or complicated as I wish. I’d I can slightly improve on the three photos I’ll be happy. 

[bobzeq25]

I’ll have to buy a Barlow. I don’t need it for visual, I have eyepieces for just about everything I need. 

The Barlow is used only for Solar System imaging.  It dims the light too much for DSOs, and you don't need the magnification.

 

There's an expert technique for using eyepieces for Solar System imaging, but few use it, they use a Barlow instead.

 

Did I mention this was complicated?  <smile>

Edited by bobzeq25, 26 March 2023 - 10:49 AM.

[Dpasqa]

What object are you trying to image? Most objects you will just crop the outer edge of the image off so you can resize the image post processing. Very few things will fill the image frame. Using a barlow will just dim the image by spreading the light out over a wider area. Normally only barlow imaging when doing planetary or lunar imaging, which are bright enough.

I’m not trying to image anything in particular. I’m just learning how to use the camera in a telescope. Eventually I’ll try some nebulae.  

[bobzeq25]

Thanks for this info. You got one great shot of Pleiades, I’ll try that one next. I do have an Ioptron AZ Mount Pro. It will suffice for what I am doing. I will most likely keep it simple, I don’t want to get too deep, I only want some reference shots for fun. From what I’m learning this can be as simple or complicated as I wish. I’d I can slightly improve on the three photos I’ll be happy. 

With those goals, you probably want to check out the Electronically Assisted Astronomy forum.  EAA attracts people who want to keep things simple.  The mount is far less important for EAA, the exposures are shorter, and the data is simply stacked, not intensively processed.

[gstrumol]

Thanks for your comments. I now understand that the telescope gathers more light and uses the three lenses on a triplet but doesn’t zoom. I’m good with that, the triplet eliminates CA. 
 

Here are my first tries. The moon needed a filter, Venus was ok and Orion had streaky stars because I set it to 4 seconds without goto. Next time I’ll use the AT115EDT with my Ioptron goto mount and try different exposure settings. Maybe 30 seconds or less and also try bulb setting. 

The exposure settings are too high. This causes the earthshine to appear on the moon and Venus to appear full when it it's not (it's about 80% illuminated).

[Dpasqa]

The exposure settings are too high. This causes the earthshine to appear on the moon and Venus to appear full when it it's not (it's about 80% illuminated).

Do you mean the ISO setting or is the shutter speed too long. I had it set for 4 seconds. 

Edited by Dpasqa, 26 March 2023 - 11:33 AM.

[bobzeq25]

Do you mean the ISO setting or is the shutter speed too long. I had it set for 4 seconds. 

Typical Solar System exposures are a small fraction of a second.  They're _much_ brighter than even so-called "bright" DSOs, which are only bright compared to other DSOs.

 

Again, the difference between your eyes and a camera can lead you far astray.  Did I mention this was unintuitive?  <smile>

Edited by bobzeq25, 26 March 2023 - 11:56 AM.

[Dpasqa]

Typical Solar System exposures are a small fraction of a second.  They're _much_ brighter than even so-called "bright" DSOs, which are only bright compared to other DSOs.

 

Again, the difference between your eyes and a camera can lead you far astray.  Did I mention this was unintuitive?  <smile>

There is so much to learn but I’m in no hurry. I plan on keeping it as simple as I can, photography is not my passion. If I can take a few decent shots of things I’ll be happy. 

[bobzeq25]

There is so much to learn but I’m in no hurry. I plan on keeping it as simple as I can, photography is not my passion. If I can take a few decent shots of things I’ll be happy. 

Understand.  (Much) better book recommendation.

 

https://www.astropix...bgda_index.html

Edited by bobzeq25, 26 March 2023 - 12:17 PM.

[gstrumol]

This was taken 3 days ago on the moon. I made a 20sec movie with the Canon T7 DSLR and postprocessed (usual SW and GIMP)  the results for this picture:

 

(click to enlarge)

[jmerran]

Hi everyone:

Started planets viewing with an Explore Scientific 102 mm f/7 FCD100. Trying to experiment in astrophotography. Was quite successfull with pictures of the moon, jupiter, satuen. Trying to move to deep sky object  usibg my current gear with a picture of the Whirlpool galaxy. Seeing condition are poor to average in the Washington DC area suburbs.  I used the following configuration:

 

Ioptron Alt-Az Pro mount

ES 102mm f/7 telescope

DLSR Nikon D7500 camera

120 exposures of 15s

ISO 800

25 Bias frames, 25 dark frames, 25 flat frames

Stacking with Deepskystacker

 

Result was Pretty bad, although I could distinguish a very  very pale shape of the spirals  ! Any tip, advice to improve using this same equipment will be much appreciated.

[17.5Dob]

#1: you have the wrong mount for deep space astrophotography. You need an EQ mount....or wedge but a quick search shows no provisions to use the alt/az in EQ mode. At f7, you are seriously underexposed shooting 15" exposures and are read noise dominated . At f7, Bortle 5 skies, I need to shoot 150" subs to swamp my read noise. 120 x 15" is only 30 minutes. At f7 you need at least 8-10 hours of exposure. You might try a reducer to speed your system up, but your alt/az mount is still a serious problem and will always limit your su exposure time.

[jmerran]

Thank you Cosmos for your input. Not ready for an EQ mount yet. I will first try with a focal reducer. I also have a Celestron EdgeHD 8", should this larger aperture be a better choice at f/10 with a focal reducer ?

[17.5Dob]

Thank you Cosmos for your input. Not ready for an EQ mount yet. I will first try with a focal reducer. I also have a Celestron EdgeHD 8", should this larger aperture be a better choice at f/10 with a focal reducer ?

Is it on an EQ mount ?

[bobzeq25]

Hi everyone:

Started planets viewing with an Explore Scientific 102 mm f/7 FCD100. Trying to experiment in astrophotography. Was quite successfull with pictures of the moon, jupiter, satuen. Trying to move to deep sky object  usibg my current gear with a picture of the Whirlpool galaxy. Seeing condition are poor to average in the Washington DC area suburbs.  I used the following configuration:

 

Ioptron Alt-Az Pro mount

ES 102mm f/7 telescope

DLSR Nikon D7500 camera

120 exposures of 15s

ISO 800

25 Bias frames, 25 dark frames, 25 flat frames

Stacking with Deepskystacker

 

Result was Pretty bad, although I could distinguish a very  very pale shape of the spirals  ! Any tip, advice to improve using this same equipment will be much appreciated.

What's your processing software?  DSS is not processing software.  It has a few sliders so you can see what you've got.  That's not processing.

 

I recommend Astro Pixel Processor.  It calibrates/stacks/processes in just one software, a major advantage.

 

Suggestion.  Upload the (it's important) UNSTRETCHED stack to something like Dropbox, create a public link, and post a thread asking people here to take a run at processing it.  That can tell you whether your problem is data acquisition or data processing.  Beginners who do this are frequently amazed by the result.

 

There are some different ways to create the unstreched stack in DSS.  I like this simple reliable method.  Stack.  On the lefthand edge click "save image to file".  In the save box click "embed settings but do not apply".  That stops DSS from stretching the stack.  Creating a descriptive name for the file is good.

Edited by bobzeq25, 03 April 2023 - 06:24 PM.