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Images of Moon not sharp enough

astrophotography collimation reflector equipment accessories
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#1 Seralyn

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Posted 05 June 2020 - 03:55 AM

Been a lurker for a while, but this is my first post to CN. Hi :)

 

So, I've long been interested in viewing celestial objects with my own eyes and also astrophotography but only recently been able to start acquiring the gear needed to do this. This includes my first telescope. I'm on a 114mm Newtonian Reflector (National Geographic-branded, but produced by Kenko). I know, I know. But it's what I could afford at the time. I got a lingering payment I've been waiting on and after doing some research have just ordered the Sky Watcher 127mm 1500mmFL Maksutov-Cassegrain and am beyond excited to receive it in a few days, but that's neither here nor there. I live smack dab in the middle of Tokyo, so the only objects visible to me are the moon, planets, and maybe 3 stars. So, a Cassegrain it is, for the time being.

 

Here's the deal. I understand photography very well. I earned my living from it for years. I have a good camera and I know how to use it. Well, terrestrially, anyway. I understand that photography and astrophotography are quite different beasts, just as DSO and SSO astrophotography are different beasts still. I also understand that most people choose to use webcams or webcam-like devices and stack their images using programs like AS2/3! and Registax and form their images that way. I will acquire that gear soon enough, but in the meantime, this is my setup:

-Camera-
Sony A7RII

 

-Telescope-

Type: Newtonian Reflector

Aperture: 114mm

Focal Length: 500mm

State of collimation: possibly in need, but I don't fully know how to tell (I've owned it for a month, but I have to carry it around frequently to be able to use it and as I live in Tokyo and have a tiny room, I have to shift it constantly to reach my clothing)

 

-Optics-

9.7mm included-in-the-kit eyepiece

26mm included-in-the-kit eyepiece

18 dollar cheap off-brand 2X barlow lens

 

When I photograph the moon, I have my A7RII connected to the 2X barlow, along with its little extender tube slid into the eyepiece slot and I focus using the focus wheels of the telescope. My issue is that no matter how minutely I focus, I cannot get a clear focus on the thing. Don't get me wrong, I'm getting as clear of a focus as is possible, it just isn't enough. I have standards, y'know? When shrunk, the images look fine enough, but when expanded, it is blatantly obvious that they are blurry. I do understand that atmoshperic disturbance is one of the culprits, but I assumed that was just the oddly blurry and somewhat darker aspects along the edges. (though that could be the scope in need of collimation?) I guess my main question is: could this be due to the cheap barlow I'm using? I'm not unwilling to invest in a more expensive one, but I don't want to spend that money unless that is the actual issue. The price of everything in Japan is like 2-5 times higher, depending on the product. Scopes that cost 200 dollars in the West cost 800 here. It's insane, so it's usually cheaper for me to purchase things from the US and ship them here and pay international shipping and import tax and still get out better. I have some hope that my new MCT will be able to get a better focus, if for no other reason than being honed in closer on the objects (500mm vs 1500mm focal length). 

 

Full resolution images of some of my photos for you to better judge the issue:

https://www.dropbox....sro1X2bLPa?dl=0

 

Bear in mind these images have been edited(feel free to criticize, but I've only been doing astrophotography for 3 weeks and I'll find my rhythm on the editing) all to hell and sharpened as much as can be without it being blatantly evident to the untrained eye. And yet, if you zoom in, you'll see what I'm talking about.

 

mmm...It's my barlow, isn't it?

 

 

 

 



#2 ris242

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Posted 05 June 2020 - 04:20 AM

Been a lurker for a while, but this is my first post to CN. Hi smile.gif

 

 

mmm...It's my barlow, isn't it?

Hello.

 

Is it your barlow?

Are you actually getting to focus or do you think you have to go in more?
Or are you using the barlow to get there cause you can't go in far enough?

 

ISO? low?

 

Can you go into a live view and magnify the back of the camera to check focus?

 

edit - I should add - do you have say ..... - a 2 sec timer or are you clicking while still touching everything?


Edited by ris242, 05 June 2020 - 04:24 AM.


#3 pyrasanth

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Posted 05 June 2020 - 04:23 AM

Looking at the images you can see as viewed that the left hand side is sharper than the right hand side. This might be tilt in the optical system but also could be down to the quality of the optics- hard to determine which without changing all the couplings between camera & telescope.

 

I would try a star test- pick a sprinkling of stars like the double cluster and focus the stars on the left of the field & check if they are equally sharp on the right side of the field- this will give a clue as to whether tilt is involved. It is difficult to tell with the moon so far easier with stars as you can judge what is happening across the field. Take 30 frames of the star field & zip up the files & drop box them. I can run them through CCD inspector & evaluate the field for you.

 

Good luck with your testing.



#4 BQ Octantis

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Posted 05 June 2020 - 04:41 AM

G'day Seralyn,

 

Welcome to the forums!

 

Your focusing issue is most likely just the Newtonian design. Many telescope designs have some sort of edge distortion; Newtonians and SCTs have edge coma. This is because their focal plane (i.e., where the image comes into focus) is actually spherical. Since your camera's sensor is planar, the part that is most in focus is the part that's closest to the center of collimation. Your Luna 06 image is the most telling—the center of collimation is off to to the middle left, where the moon is the sharpest.

 

If you shoot a rich star field, only the stars at the center of collimation will be round. The stars around its periphery will look like little comets that all face the collimation point.

 

The only way to deal with this is either settle for the sharp center (and crop your images to the sharp part of the image) or correct it with an expensive coma corrector. Correctors are made for the specific telescope design and focal ratio.

 

The good news is, your 127 Mak will be practically coma-free.

 

Cheers,

 

BQ



#5 Greyhaven

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Posted 05 June 2020 - 06:11 AM

Focusing on the Moon involves the atmosphere and its messing with the image you are trying to capture. That is why the AVI and web cam combination works so well. Instead of attempting to capture the fleeting moment of steady seeing you can stack your images and after sorting out the worst examples and tweak the rest in Registax. Welcome to the Good Ship Cloudy Nights!

Grey



#6 Seralyn

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Posted 05 June 2020 - 06:32 AM

Hello.

 

Is it your barlow?

Are you actually getting to focus or do you think you have to go in more?
Or are you using the barlow to get there cause you can't go in far enough?

 

ISO? low?

 

Can you go into a live view and magnify the back of the camera to check focus?

 

edit - I should add - do you have say ..... - a 2 sec timer or are you clicking while still touching everything?

Thanks for your response ;)

I'm getting to focus because I can focus in and hit a point that it's more or less "clear" and continuing on in that same direction pulls it back out of focus. It's just that...what is considered "focus" in this case is not nearly clear enough for my tastes. If I take the barlow out, the closer the camera moves to the body of the telescope, the more clear it becomes, but it then hits the body and cannot get any closer, so the barlow is the only way for me to achieve focus. I've read that this is why using DSLR/Mirrorless cameras with a Newtonian doesn't really work without a barlow and have been able to confirm that on my own.

ISO - I've tried it two different ways. I've tried my ISO at 50 (lowest setting my camera offers) and accounted for exposure via shutter speed, hoping to eliminate noise. I then had the thought that...maybe, just maybe, I was shooting at too slow of a shutter speed and was experiencing motion blur, so I kicked the ISO up and made the shutter speed 1/200 and there was more noise present, but not less blurriness, so I then concluded it was likely due to poor collimation or the lack of quality on the part of the barlow. That's where I'm stuck now.

Focus - When I focus, I alternate between using the EVF and the live view on the back of the camera. When I do the live view, I magnify the screen a few hundred percent so I can get as crisp focus as is possible, like I do when I'm shooting portraiture on manual focus. It certainly aids the endeavor, but the clearest it gets just isn't clear enough.

I'm using a remote shutter in order to eliminate vibrations. Sorry, I should have mentioned that!



#7 Seralyn

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Posted 05 June 2020 - 06:34 AM

Focusing on the Moon involves the atmosphere and its messing with the image you are trying to capture. That is why the AVI and web cam combination works so well. Instead of attempting to capture the fleeting moment of steady seeing you can stack your images and after sorting out the worst examples and tweak the rest in Registax. Welcome to the Good Ship Cloudy Nights!

Grey

Thanks for the warm welcome! Perhaps I'll just try to stack the images. I do have a PC and a Mac. I tend to do my creative endeavors on the Mac and have been trying to use Lynkeos, the only software I can find for astrophotographical image stacking. It keeps giving me strange results, so maybe I'll just use my gaming PC for this. I'll give it a spin, thanks~!



#8 Seralyn

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Posted 05 June 2020 - 06:53 AM

G'day Seralyn,

 

Welcome to the forums!

 

Your focusing issue is most likely just the Newtonian design. Many telescope designs have some sort of edge distortion; Newtonians and SCTs have edge coma. This is because their focal plane (i.e., where the image comes into focus) is actually spherical. Since your camera's sensor is planar, the part that is most in focus is the part that's closest to the center of collimation. Your Luna 06 image is the most telling—the center of collimation is off to to the middle left, where the moon is the sharpest.

 

If you shoot a rich star field, only the stars at the center of collimation will be round. The stars around its periphery will look like little comets that all face the collimation point.

 

The only way to deal with this is either settle for the sharp center (and crop your images to the sharp part of the image) or correct it with an expensive coma corrector. Correctors are made for the specific telescope design and focal ratio.

 

The good news is, your 127 Mak will be practically coma-free.

 

Cheers,

 

BQ

BQ, the thoughtful response is much appreciated! I see what you mean, on Luna 06, now that you've pointed it out. I feel like such a dork for ordering a Newtonian while living in the middle of Tokyo. From what I understand, it would have been a nice little starter scope for DSO in a dark sky environment, but that is quite the opposite of what I have access to. I cannot contain my excitement over the Mak...! Looking forward to sharing some Lunar photos I can be proud of :) Thanks for your advice!



#9 BQ Octantis

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Posted 05 June 2020 - 07:05 AM

BQ, the thoughtful response is much appreciated! I see what you mean, on Luna 06, now that you've pointed it out. I feel like such a dork for ordering a Newtonian while living in the middle of Tokyo. From what I understand, it would have been a nice little starter scope for DSO in a dark sky environment, but that is quite the opposite of what I have access to. I cannot contain my excitement over the Mak...! Looking forward to sharing some Lunar photos I can be proud of smile.gif Thanks for your advice!

No worries at all! Here in the middle of the Outback, I often wish I had a Newt! But yes, for DSOs in particular. Ironically, I have a Mak 180, which has been great for planetary.

 

Note that Lynkeos is a PITA for lunar alignment. It likes small, high-contrast points. It does great for planets and stars (just set the alignment box(es) to about 200-300% the size of the target). But if your points drift more than 10-20x the object size, it'll give up. For my most recent shot of the moon, I had to first align in Photoshop, crop, and then align & stack in Lynkeos.

 

BQ



#10 guidoforrier

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Posted 05 June 2020 - 08:12 AM

dear Seralyn ,

i

I had myself better photo's of the moon , also with the same camera , but different optics ( skywatcher Mak 127 + Lacerta Barlow on Sky adventurer )

Your pics are grainy and not quite sharp .

Possible reasons :

1. your scope is not one of the bests . with 500 mm , even with a Barlow 2X , you need a lot to crop .

2. a cheap Barlow lens will do no good , you need a one with very good optics

3. the focuser is a very cheap and unreliable , did you use a Bahinov mask ? The camera has good life view but focussing has to be very accurate  .

4. was the combination camera + scope stable enough ?

5. the focuser is only 1,25" , this means vignetting on a ff camera .

6. wat was the visibility ? air temperature ?

Do you have a long tele on the Sony ? Try one .

I stopped astrophotography because the virus left me home and here in town the sky is murky . In the following weeks ( I hope the weather will be better) I wil travel a 300 km to a very dark place , 690 m above sea level . I will also use my new Ioptron cem 25 . And then is will start again to photograph the stars ...

50 iso : NO the Sony sensor is very noise free up to 1600 /3200 iso .

Use the silent mode (no mechanical shutter ) + remote control .

for stacking : I use SIRIL ( free , for Mac) for the moon  (or planets ) .

Guido


Edited by guidoforrier, 05 June 2020 - 10:40 AM.


#11 Seralyn

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Posted 05 June 2020 - 09:46 AM

dear Seralyn ,

i

I had myself better photo's of the moon , also with the same camera , but different optics ( skywatcher Mak 127 + Lacerta Barlow on Sky adventurer )

Your pics are grainy and not quite sharp .

Possible reasons :

1. your scope is not one of the bests . with 500 mm , even with a Barlow 2X , you need a lot to crop .

2. a cheap Barlow lens will do no good , you need a one with very good optics

3. the focuser is a very cheap and unreliable , did you use a Bahinov mask ? The camera has good life view but focussing has to be very accurate  .

4. was the combination camera + scope stable enough ?

5. the focuser is only 1,25" , this means vignetting on a ff camera .

6. wat was the visibility ? air temperature ?

Do you have a long tele on the Sony ? Try one .

I stopped astrophotography because the virus left me home and here in town the sky is murky . In the following weeks ( I hope the weather will be better) I wil travel a 300 km to a very dark place , 690 m above sea level . I will also use my new Ioptron cem 25 . And then is will start again to photograph the stars ...

Guido

Guido, thanks for the follow up. 
1. You're absolutely right. I cannot wait for the 127mm Mak to arrive on Monday. The first day without clouds in almost one month is the same day I get the new scope. Such providence!
2. I see! I'll bite the bullet and invest in a better Barlow.

3. I do not have a Bahinov yet and wasn't sure if I truly needed one. You think I do? The focusing isn't a problem, I've become very familiar with the manual focusing of this camera, I think my optics are just sub-par.

4. It's highly unstable while I'm adjusting focus and shutter speed, etc, but once I stop touching it, it settles after a moment and then I use a remote shutter.
5. There is a bit of vignetting, for sure. I usually just crop it out.

6. Visibility is never good in Tokyo, but I chose the best nights I could. Air temps are low to mid twenties. (I am American, but I use Celsius because Farenheit is kind of stupid)

I usually shot portraiture and events so all of my lenses are 100mm and shorter, unfortunately.

I'm sorry to hear the virus left you stuck in a murky sky spot. Here in Tokyo, if I get 3 days a month without clouds, I'm so happy, so I really understand. I hope you get to travel to the Dark Skies soon!! I look forward to seeing you post what you get from that journey :)




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