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Sizing DSO Objects?

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#1 Blackbelt76

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Posted 22 January 2020 - 09:38 AM

This is the unprocessed image of M-81 stacked with DSS.

 

I shot this with a Nikon D300s w/ 200mm lens at f/4 unmoded.

 

20 lights x 75s iso 640

20 darks

20 bias

No flats

 

Question: Is 200mm simply not enough reach? Seems really small?

 

I understand the angular size is small, so perhaps I need to choose larger objects such as M31, M-42 etc.

 

My first attempt using the same setup of M-1 seemed better success, it too is small angular size?

https://www.cloudyni...st-m-1-attempt/

 

I can "scale" in Adobe PS, but only to a point.

 

Any advice appreciated.

 

Attached Thumbnails

  • M82-3.jpg


#2 happylimpet

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Posted 22 January 2020 - 09:46 AM

I dont think thats M81 - I think you'd have it more clearly ,particularly having seen your M1 image. I think its a much fainter galaxy.

 

Also the star field looks wrong.

 

Can you plate solve the full image?

 

https://nova.astrometry.net/upload



#3 happylimpet

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Posted 22 January 2020 - 09:55 AM

https://nova.astrome...37908#annotated

 

Yeah, you're waaaaaay off. Note i had to crop the full image to just the left side to eliminate the inset - but you get the idea!

 

http://www.worldwide...51307&wtml=true

 

On the other hand, lets accentuate th epositives and note the youve imaged NGC3877, a much fainter galaxy....

 

https://en.wikipedia.org/wiki/NGC_3877


Edited by happylimpet, 22 January 2020 - 09:57 AM.


#4 Blackbelt76

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Posted 22 January 2020 - 09:57 AM

I dont think thats M81 - I think you'd have it more clearly ,particularly having seen your M1 image. I think its a much fainter galaxy.

 

Also the star field looks wrong.

 

Can you plate solve the full image?

 

https://nova.astrometry.net/upload

You may be right.

I don’t have software yet to plate solve. Just using the DSLR and skywatcher EQ6R unguided.

I was using the setting circles to star hop to it from MIzar.

Been checking my Redshift program trying to ID nearby stars close to the object.

 

Great link. I was unaware of it. Seems useful.


Edited by Blackbelt76, 22 January 2020 - 10:03 AM.


#5 Ishtim

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Posted 22 January 2020 - 09:58 AM

Here's a handy tool to "size up" your equipment with various targets.  Choose the imaging tab and enter values for your equipment and desired target.

 

https://astronomy.to.../field_of_view/


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#6 Blackbelt76

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Posted 22 January 2020 - 10:42 AM

You may be right.

I don’t have software yet to plate solve. Just using the DSLR and skywatcher EQ6R unguided.

I was using the setting circles to star hop to it from MIzar.

Been checking my Redshift program trying to ID nearby stars close to the object.

 

Great link. I was unaware of it. Seems useful.

Seems to be NGC 3877?

Thanks for that link.

I've been away from astronomy for years; we did not have such a tool then.

Attached Thumbnails

  • M82-3.jpg


#7 Blackbelt76

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Posted 22 January 2020 - 10:55 AM

@Happylimpet.

 

Yep.

I sure did miss it.

Freezing my butt off this morning (20F), I think my setting circle slipped.

Was just using the Camera on the EQ6R.

OTOH..I guess I'm thrilled to have captured a 12 mag galaxy with a unmoded camera.


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#8 bobzeq25

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Posted 22 January 2020 - 11:04 AM

This is the unprocessed image of M-81 stacked with DSS.

 

I shot this with a Nikon D300s w/ 200mm lens at f/4 unmoded.

 

20 lights x 75s iso 640

20 darks

20 bias

No flats

 

Question: Is 200mm simply not enough reach? Seems really small?

 

I understand the angular size is small, so perhaps I need to choose larger objects such as M31, M-42 etc.

 

My first attempt using the same setup of M-1 seemed better success, it too is small angular size?

https://www.cloudyni...st-m-1-attempt/

 

I can "scale" in Adobe PS, but only to a point.

 

Any advice appreciated.

In addition to being off the target...

 

I don't think galaxies are a good target for 200mm.  Here's M31, which is gigantic.

 

https://www.astrobin.com/209498/

 

Nebulae and constellation images work better.  Orion (below) is spectacular, as is Deneb.

 

https://www.astrobin.com/227049/C/



#9 happylimpet

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Posted 22 January 2020 - 11:48 AM

@Happylimpet.

 

Yep.

I sure did miss it.

Freezing my butt off this morning (20F), I think my setting circle slipped.

Was just using the Camera on the EQ6R.

OTOH..I guess I'm thrilled to have captured a 12 mag galaxy with a unmoded camera.

Quite right to be thrilled! Dont let perfection be the enemy of good enough, or whatever the phrase is. Im sure you'll get a great (little) image of M81 when you get it framed!

 

I take huge pleasure in tiny little smudges in my image which are vast distances away or extreme objects in some way or other.



#10 JDShoots

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Posted 22 January 2020 - 12:18 PM

I am going to have to look into  affiliate links, because I seem to be recommending the same site a lot these days:)  

I use Telescopius ALL the time to get an idea of size and framing.   

I keep a list of targets I want to hit, and inside the page for each is a Telescope simulator.   In there you can enter your equipment and see what it frames up like.   As with daylight photography, I am always attempting to fill the frame with my subject, so it is nice to see what size a target is, and what field of view a particular lens has on my camera.  

 

For my DX camera, my 135mm lens has a similar FOV as your 200 on the FX which is roughly 10° by 6.5°.  Then knowing Bodes is less then a 1/2° that doesn't fill much of the frame.  I plan on shooting Bodes soon, and will add a TC to my 500 for a 700mm lens, even that is a little short, thankfully there is more then one subject in the frame.  

 

m81 fov 135.JPG

 

Here is a framing with a 700mm lens on a DX body.   Still small, but assuming the TC doesn't kill my image quality, it should be decent.  

 

m81 fov 700.JPG

 

 


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#11 Blackbelt76

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Posted 22 January 2020 - 02:03 PM

@bobzeq25: Great M31 with a 200mm! Question: Did you scale the final image? It appears large from a 200mm w/o some scaling..

 

I generally do all my pre-post work in Capture NX at a pixel level,Then Adobe PS for bicubic enlargement with resample off. Last I do is "scale" where I seem to max out at about 250%.

---------------------------------------------------------------

 

@happylimpet: Appreciate the encouragement.

 

I've been away from this hobby a long time. I didn't have the tools I see today. Back then I used a 8" f/6 Newt (ground the mirror myself), cold cameras and gas hypered 35mm film; hand guiding for sometimes 2hrs while peering thru a 80mm APO (talk about tube flexure!)..ahh the good 'Ol days. smile.gif

 

When I re-entered this hobby, I was awe struck by the new technolgy available to the amateur. "Auto-Guiding" in particular when coupled to a computer is amazing; as are the new crop of CCD dedicated astro-cams. I can see how AP could get addictive, not to mention expensive from what I've seen. $$$

 

As I've only recently re-entered this hobby; I'm content trying to use my DSLR and simple visual only thru my newly acquired Celestron Edge 9.25".

I've considered mating the DSLR to the prime focus, but at f/10 I doubt it's a good choice for DSO. The focal reducers sure are not cheap nor is Fastar, which is pretty cool.

 

I will confess, as cold as it here at the moment in the midwest, with few consecutive clear nights in Jan or Feb, I am a bit lazy about polar aligning and I tend to rush my setup.

So far I must be getting lucky just doing the PA with the polar scope as my stars seem to exhibit little trailing if any up to 4 mins unguided. (No PEC)

 

I'm just outside a city of 200,000, LP is a big problem. The sky fog is quite noticeable and disappointing; especially to the east.

 

I'm finding focusing the DSLR quite a challenge, even using "Live-View" magnified. So far all I've done is focus the best I can and VERY gently place a piece of tape across the focus ring. My 80-200 f/2.8 is not image stabilized so I've ruled that out, but am starting to wonder as I slew to new positions if the lens may have some optical train components that may be shifting ever so slightly? Not a issue for normal terrestrial use, but AP is obviously a different set of rules.

 

Clear skies to all!


Edited by Blackbelt76, 22 January 2020 - 02:05 PM.

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#12 bobzeq25

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Posted 22 January 2020 - 05:14 PM

@bobzeq25: Great M31 with a 200mm! Question: Did you scale the final image? It appears large from a 200mm w/o some scaling..

No.  M31 is _gigantic_.  Over 3 degrees from end to end.  6+ full Moons.  If you could see it all with your eyes, it would look like something out of a science fiction movie.  <smile>

 

The next biggest is M33, about one degree.


Edited by bobzeq25, 22 January 2020 - 05:45 PM.

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#13 Ranger Tim

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Posted 22 January 2020 - 07:29 PM

M31 is a great object for a 200-300mm lens, especially for a beginner. It takes a lot more work to get it looking awesome though.

 

The dead of winter is a challenge for me. The seeing is usually terrible, there's a lot of clouds, and the temperatures are harder to tolerate than when I had more body fat. Can't wait for spring!! 


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#14 Blackbelt76

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Posted 23 January 2020 - 07:13 AM

M31 is a great object for a 200-300mm lens, especially for a beginner. It takes a lot more work to get it looking awesome though.

 

The dead of winter is a challenge for me. The seeing is usually terrible, there's a lot of clouds, and the temperatures are harder to tolerate than when I had more body fat. Can't wait for spring!! 

I know what you mean.

Here in the midwest, we get lousy weather in Jan..not much better in Feb.

I don't mind the cold; I can dress for it; the issue here is wind..30 degrees and a 10 MPH wind and I'm done.




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