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Need Simple, Cheap Elemental Imaging Equipment For Star Testing

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13 replies to this topic

#1 Tom Duncan

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Posted 20 January 2021 - 01:37 PM

As a vendor I would like to be able to take quick and easy images of star tests, mainly to be able to show what I'm talking about when discussing scope issues here in the forums. This will make my postings easier to understand and take any 70-year old eye issues out of the equation.

 

I have zero experience with astroimaging and have no desire to learn any more than the bare minimum to achieve my ends and also to spend as little as possible. 

 

Can anyone recommend a cheap, easy solution? I've done the 'hold the cell phone to the eyepiece' but it doesn't work very well, the image is usually over-exposed and it's cumbersome. I've also tried a few clamp-on camera holders but again, awkward and cumbersome. Ideally what I'm looking for is an eyepiece substitute with a small screen for composing and adjusting exposure and a button to press to record to an SD card...does such a device exist? 

 

Thanks

 

Tom Duncan 

 

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#2 mikefulb

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Posted 20 January 2021 - 01:47 PM

You might be able to do this with a DSLR and appropriate barlow/powermate depending on the telescope you are testing.  I know people are able to record video of planets for post-processing using DSLRs so it seems it would work.



#3 bobzeq25

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Posted 20 January 2021 - 01:50 PM

Have a DSLR?  That's the simplest, easiest solution.

 

You connect to the telescope with this, or something very much like that.

 

https://www.amazon.c.../dp/B013DN90EM/

 

Another one.

 

https://www.amazon.c.../dp/B0114CGRP4/

 

You may need t thread spacers to achieve focus.

 

https://www.amazon.c.../dp/B071ZSB7HC/

 

Most imagers have a bunch of those.

 

This setup is simple, reliable, easy to use.   It's what I used when I started imaging.

 

If you have no DSLR, you'll need something like this, and a laptop.

 

https://astronomy-im...120mm-mini-mono

 

A mirrorless could maybe substitute for the DSLR, depending on the LCD screen.


Edited by bobzeq25, 20 January 2021 - 02:24 PM.


#4 Alex McConahay

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Posted 20 January 2021 - 08:27 PM

What is the target of your images? Are you planning to image actual stars or artificial stars?

 

Will Monochrome images do, or do you need color?

 

Alex



#5 Tom Duncan

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Posted 20 January 2021 - 08:46 PM

What is the target of your images? Are you planning to image actual stars or artificial stars?

 

Will Monochrome images do, or do you need color?

 

Alex

Target is star tests on actual stars, though I do have a good artificial star, to show problems so fellow CN'rs can see what the situation is. Either monochrome or color, doesn't matter, mainly showing the shape and details of the test. 

 

Tom 



#6 Tom Duncan

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Posted 20 January 2021 - 08:50 PM

Have a DSLR?  That's the simplest, easiest solution.

 

You connect to the telescope with this, or something very much like that.

 

https://www.amazon.c.../dp/B013DN90EM/

 

Another one.

 

https://www.amazon.c.../dp/B0114CGRP4/

 

You may need t thread spacers to achieve focus.

 

https://www.amazon.c.../dp/B071ZSB7HC/

 

Most imagers have a bunch of those.

 

This setup is simple, reliable, easy to use.   It's what I used when I started imaging.

 

If you have no DSLR, you'll need something like this, and a laptop.

 

https://astronomy-im...120mm-mini-mono

 

A mirrorless could maybe substitute for the DSLR, depending on the LCD screen.

I do have a couple of mirrorless D-SLR's, I like that approach. They are light, have a built-in real time LCD so I can see what I'm getting. I'll give that a try. 

 

I also like the ZWO Mini, the implication is it can be connected directly to a phone. Would you need a special app to see the image?

 

Tom 



#7 Alex McConahay

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Posted 20 January 2021 - 10:35 PM

>>>>>>Target is star tests on actual stars,

 

Well, DSLR is certainly a workhorse----but, you do not have to spend that much. A good monochrome imager, like a simple monochrome Orion Starshooter autoguider from ten years ago can do the job. 

 

If you are shooting actual stars, though, you may have a problem. You are illustrating defects in optics, I gather. How will you mount the optics to the camera? You want something very flexible. Most DSLR are not all that flexible in how you mount them to the optics. An old Orion guider can be positioned in a stand on an optical bench. Or at one end of a tube with the other end holding the optics you are demonstrating. You can swap things around pretty easily depending on what you are testing. 

 

Well, you say, you want to use this on actual stars. Then, I imagine you need to think of a lot more than just the camera. You have to follow the stars long enough to see the error show up. Otherwise, all your tests will show eccentricity (the stars will move). This may not be all that long, of course. but anything more than a fraction of a second can start showing this eccentricity at enough magnification--just the place you will be if you are talking about demonstrating optical defects. 

 

I wish you well, but please let these ideas bounce around in your head a bit before you spend some bucks.

 

Alex


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#8 Der_Pit

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Posted 21 January 2021 - 01:49 PM

I assume with 'star test' you refer to looking at defocused star images, is it?  Else the problem is that the typical pixel size of the cameras is not sufficient to resolve diffraction patterns when in focus.  For that you'd need additional magnification via either some barlow lens, or (again), eyepiece projection.  For the latter you can find special adapters to firmly connect your camera, usually also via T2 threading.



#9 Tom Duncan

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Posted 21 January 2021 - 03:58 PM

Yes, by 'star test' I do mean de-focused images either side of focus to judge glass/mirror quality.

 

Interesting "...the problem is that the typical pixel size of the cameras is not sufficient to resolve diffraction patterns when in focus". I think I have an eyepiece projection tube adapter somewhere in boxes of astro stuff. 

 

I'll have to consider that when I try my mirrorless D-SLR setup, thanks for the tip.  

 

Tom 


Edited by Tom Duncan, 21 January 2021 - 03:59 PM.


#10 bobzeq25

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Posted 21 January 2021 - 06:52 PM

I do have a couple of mirrorless D-SLR's, I like that approach. They are light, have a built-in real time LCD so I can see what I'm getting. I'll give that a try. 

 

I also like the ZWO Mini, the implication is it can be connected directly to a phone. Would you need a special app to see the image?

 

Tom 

An app is absolutely necessary because the camera is just a sensor and an interface, it has no intelligence whatsoever.  You have to tell it everything, including how to take exposures.  NO intelligence, much less anything resembling a terrestrial camera.

 

I recommended a laptop with it, to provide the intelligence.  Sharpcap is reasonably simple high level software.  A smartphone won't work, the ZWO 120 uses a USB interface.  No intelligence of its own.


Edited by bobzeq25, 21 January 2021 - 06:55 PM.


#11 Tom Duncan

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Posted 21 January 2021 - 08:21 PM

An app is absolutely necessary because the camera is just a sensor and an interface, it has no intelligence whatsoever.  You have to tell it everything, including how to take exposures.  NO intelligence, much less anything resembling a terrestrial camera.

 

I recommended a laptop with it, to provide the intelligence.  Sharpcap is reasonably simple high level software.  A smartphone won't work, the ZWO 120 uses a USB interface.  No intelligence of its own.

The above linked website states: "USB 2.0 Port: Mini camera has one USB2.0 type C port. Type C port is very popular in mobile phones, it will not care about positive side and negative side of the adapter."

 

Tom 



#12 bobzeq25

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Posted 21 January 2021 - 09:36 PM

The above linked website states: "USB 2.0 Port: Mini camera has one USB2.0 type C port. Type C port is very popular in mobile phones, it will not care about positive side and negative side of the adapter."

 

Tom 

New one on me.  But note that the cable supplied with the camera has the type C on the camera side, and a conventional USB on the other end for plugging into a computer.  I suppose you could get a type C cable with Type C on both ends, but don't know if there's a smartphone app that would make that setup work.

 

The manual shows the camera connecting to a laptop.

 

https://astronomy-im...a Manual EN.pdf


Edited by bobzeq25, 21 January 2021 - 09:43 PM.


#13 jonnybravo0311

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Posted 21 January 2021 - 11:14 PM

The above linked website states: "USB 2.0 Port: Mini camera has one USB2.0 type C port. Type C port is very popular in mobile phones, it will not care about positive side and negative side of the adapter."

 

Tom 

That's what happens when marketing gets ahold of something. Hey, USB-C is popular with mobile phones and it doesn't matter which way it's plugged in! Also, English is very much a second language with the folks writing these materials.

 

What that link is really trying to tell you is the camera has a USB-C type port, which is convenient because you don't have to worry about which is the "right side up" when you are trying to plug the cable into it under dark skies.

 

The other end of that cable most certainly goes into something like a USB hub connected to a laptop, a raspberry pi, a ZWO ASIAir Pro, etc. What that other end does NOT go into is a smart phone.


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#14 Tom Duncan

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Posted 22 January 2021 - 07:44 AM

That's what happens when marketing gets ahold of something. Hey, USB-C is popular with mobile phones and it doesn't matter which way it's plugged in! Also, English is very much a second language with the folks writing these materials.

 

What that link is really trying to tell you is the camera has a USB-C type port, which is convenient because you don't have to worry about which is the "right side up" when you are trying to plug the cable into it under dark skies.

 

The other end of that cable most certainly goes into something like a USB hub connected to a laptop, a raspberry pi, a ZWO ASIAir Pro, etc. What that other end does NOT go into is a smart phone.

That all makes sense. 

 

Tom 




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