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Is capturing Red Nebula with stock DSLR / no filter possible?

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#1 russellmm

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Posted 12 August 2020 - 10:44 PM

Is capturing Red Nebula with stock DSLR / no filter possible?

I have been reading across the web on this and think the Answer is no, but I wanted to be sure.

 

I have a Canon Mark IV. I understand that DSLRs have filters that block red unless they are made without them (Canon AP models) or have had the filter removed.

 

Everything I have seen shows people using HA filters and Light Pollution filters in their images with the exception of Clarkvision (I cant seem to find anywhere where he says he has modified his camera or is using filters). 

 

As far as I can tell there is no filter options for my camera as the clip on ones seem to support APC only. Does anyone know of ones that work with full frame DSLR?

 

Is there a trick to capturing the red if you don't have HA/LP filters?

 

Regards

Russell



#2 Alex McConahay

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Posted 12 August 2020 - 10:57 PM

It is not impossible, but it is more challenging in a standard DSLR. The filters in a standard DSLR do let in reds. They just do not let in quite the range of reds there are up there. The filters start trailing off (let less light through) as they head through red and into the infrared. This is where a lot of the bright red nebulae are shining. 

 

You have to change your processing and color balance a bit to get the red to shine through that. But, it certainly can be done. 

 

Alex



#3 bobzeq25

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Posted 12 August 2020 - 11:15 PM

Sure.  But you won't get much, and even getting something decent will require hours of subs.  These are just not good targets for an unmodded camera.

 

Filters don't help, the problem is that the internal filter blocks most of the Ha light.

 

There's no trick, no magic solution.  Good targets for an unmodded camera are broadband sources like clusters and galaxies.  Some reflection nebulae, like the Pleiades.


Edited by bobzeq25, 12 August 2020 - 11:18 PM.


#4 17.5Dob

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Posted 12 August 2020 - 11:21 PM

It's possible....you just have to realize a stock camera only allows 20-25% of Ha light past the manufactures cutoff filter...You just need to expose 4-5X longer.....



#5 russellmm

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Posted 12 August 2020 - 11:21 PM

ok, thank you for the responses. I'll just have to practice on other objects for now :)



#6 BQ Octantis

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Posted 12 August 2020 - 11:58 PM

Sure you can. Two to four hours at f/2.8 yields excellent results. You just need a good processing workflow to bring it out:

 

post-273658-0-36140600-1593838303.jpg

 

I documented a method for my Carina Nebula shot:

 

post-273658-0-52696700-1585966555.jpg

 

It's easy to go overboard…

 

med_gallery_273658_7587_12477.jpg

 

The biggest mistake you can make with an unmodded DSLR is to assume those Ha-only shots represent reality. The results from modded cameras tend to severely under-emphasize other colors. Case in point: the Tarantula Nebula is not red. Like at all—it is clearly aqua blue through binoculars, any telescope, and any happy-snap of the sky that includes the LMC.

 

med_gallery_273658_7587_855306.jpg

 

Yet what you find online is always something other than blue.

 

BQ


Edited by BQ Octantis, 12 August 2020 - 11:59 PM.

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#7 17.5Dob

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Posted 13 August 2020 - 12:19 AM

Sure you can. Two to four hours at f/2.8 yields excellent results. You just need a good processing workflow to bring it out:

 

4 hrs at f2.8= 8 hrs at f4= 16 hrs at 5.6...etc...

You made the case, that it's extremely difficult, no shoot Ha with a stock cam, better than anyone else...

Who shoots at f 2.8........for 4 hrs to get what a modded cam can do in a few minutes...

This is 9 minutes total, 180mm camera lens, f2.8, modded cam

50220276108_e3e66782e8_b.jpg
 


Edited by 17.5Dob, 13 August 2020 - 12:44 AM.

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#8 russellmm

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Posted 13 August 2020 - 12:54 AM

BQ, 

so there is hope :). I read your other thread and for the most part it went over my head with regards to how you editted the different channels. I'll need to find a video tutorial of something similar to wrap my head around it

 

What were the camera specifics? (I see you were using a 200mm F2.8) but how many subs and how long was each exposure? I would think pretty short at 2.8. I am using a 300mm F2.8 IS II. 

 

Best Regards

Russell

 

Sure you can. Two to four hours at f/2.8 yields excellent results. You just need a good processing workflow to bring it out:

 

Pictures Clipped to shorten quote:

 

 

I documented a method for my Carina Nebula shot:

 

 

The biggest mistake you can make with an unmodded DSLR is to assume those Ha-only shots represent reality. The results from modded cameras tend to severely under-emphasize other colors. Case in point: the Tarantula Nebula is not red. Like at all—it is clearly aqua blue through binoculars, any telescope, and any happy-snap of the sky that includes the LMC.

 

 

 

Yet what you find online is always something other than blue.

 

BQ



#9 BQ Octantis

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Posted 13 August 2020 - 01:42 AM

4 hrs at f2.8= 8 hrs at f4= 16 hrs at 5.6...etc...

You made the case, that it's extremely difficult, no shoot Ha with a stock cam, better than anyone else...

Who shoots at f 2.8........for 4 hrs to get what a modded cam can do in a few minutes...

This is 9 minutes total, 180mm camera lens, f2.8, modded cam

Sorry, Dave, I should have clarified what I meant by excellent results:

 

Excellent results ≡ usable results at 100-200% sensor scale.

 

It is not uncommon for any AP shooter to have long integrations (long ≡ dozens of hours). But I, too, can get good results (good ≡ passable results at 50-100% sensor scale) with 9 minutes at f/2.8—even with poorly-tracked data:

 

post-273658-0-13410000-1590029202.jpg

Capture details / Astrobin (.jpg, 100%) / Original post

 

Sorry for the confusion.

 

BQ


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#10 sharkmelley

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Posted 13 August 2020 - 02:09 AM

Yes, it is possible to capture H-alpha with a stock DSLR.

 

However the problem with a DSLR is that it is purposely designed to mimic the eye's response to colour and the eye is relatively insensitive to H-alpha.  So using a stock DSLR records the universe as the eye would see it if the universe were brighter.  The Clarkvision site is all about doing astrophotography in "natural colour" which is why the author does not use modified cameras.

 

Once you start using an H-alpha modified camera, you will record much more H-alpha and you'll be able to record fainter nebulae but regions of Hydrogen emissivity will appear a lot redder than the eye would see them.  

 

Mark


Edited by sharkmelley, 13 August 2020 - 02:48 AM.


#11 BQ Octantis

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Posted 13 August 2020 - 03:35 AM

The Clarkvision site is all about doing astrophotography in "natural colour" which is why the author does not use modified cameras.

Exactly. Roger also pushes his RNC stretch algorithm, which does an excellent job of boosting color.

 

What I appreciate most about Roger is that he shows you that in the pursuit of curiosity, much dogma should be ignored (or at least taken with a grain of salt). I'm taking a class on happiness in the workplace, and it gives a most fascinating set of factors that define curiousity: openness to new ideas, inquisitiveness, creativity in problem solving, and—most signficantly—distress tolerance. I've found that Roger induces much distress in AP purists! laugh.gif

 

BQ



#12 BQ Octantis

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Posted 13 August 2020 - 04:08 AM

BQ, 

so there is hope smile.gif. I read your other thread and for the most part it went over my head with regards to how you editted the different channels. I'll need to find a video tutorial of something similar to wrap my head around it

 

What were the camera specifics? (I see you were using a 200mm F2.8) but how many subs and how long was each exposure? I would think pretty short at 2.8. I am using a 300mm F2.8 IS II. 

 

Best Regards

Russell

Of course there's hope! smile.gif

 

The capture and processing details were

 

Canon 200mm f/2.8L II, Canon 600D/T3i (stock)
133×30sec@ISO1600 f/2.8, 58×darks, 1×flat
153×30sec@ISO800 ∅52mm (~f/3.85), 50×darks, 1×flat
Debayered & calibrated in RawTherapee 5.6
Aligned & stacked in Lynkeos 3.3, processed in PS CS5
w/Astronomy Tools 1.6 & Annie's Astro Actions 7.0

 

I would highly recommend reviewing Roger's page on RawTherapee—it has significantly improved my processing.

 

Sadly, no video…

 

Do you have a target in mind?

 

BQ


Edited by BQ Octantis, 13 August 2020 - 04:29 AM.


#13 sharkmelley

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Posted 13 August 2020 - 04:24 AM

I've found that Roger induces much distress in AP purists! laugh.gif

The main controversy is that the methodology documented on the ClarkVision site subtracts the light pollution from non-linear data.  This has been proven to cause bluing and colour saturation of faint signals in the data, which can be seen in many of the images on that site. 

 

Mark


Edited by sharkmelley, 13 August 2020 - 04:27 AM.


#14 BQ Octantis

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Posted 13 August 2020 - 04:31 AM

The main controversy is that the methodology documented on the ClarkVision site subtracts the light pollution from non-linear data.  This has been proven to cause bluing and colour saturation of faint signals in the data, which can be seen in many of the images on that site.

Very true. But inspiring results nonetheless. Had I not discovered his site, I might have thrown in the towel by now. A limitless budget and overnight deliveries aren't an option here in the middle of the outback. frown.gif

 

But between his clear instruction and good, instructive cajoling from you (and others) has pushed my results to what I think are the bounds of my unmodded 600D/T3i and the equipment I brought with me. smile.gif

 

BQ


Edited by BQ Octantis, 13 August 2020 - 04:39 AM.

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#15 BQ Octantis

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Posted 13 August 2020 - 06:29 AM

Here's one 2-minute sub at f/3.5:

 

(Click for 1440×900 @ 30%.)

carina_30%.jpg

Carina Nebula 2018-04-04

Canon 200mm f/2.8L II @ f/3.5

Canon 600D/T3i (stock) @ ISO400

1×120sec + 6×darks + 1×flat

Debayered & calibrated in RawTherapee 5.8

Processed in Photoshop CS5 & StarNet++

Scaled to 30%, cropped to 1440×900

Tropic of Capricorn, Red Centre, Oz

 

BQ


Edited by BQ Octantis, 13 August 2020 - 07:17 AM.

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#16 bobzeq25

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Posted 13 August 2020 - 09:45 AM

Sure you can. Two to four hours at f/2.8 yields excellent results. You just need a good processing workflow to bring it out:

 

post-273658-0-36140600-1593838303.jpg

 

I documented a method for my Carina Nebula shot:

 

post-273658-0-52696700-1585966555.jpg

 

It's easy to go overboard…

 

med_gallery_273658_7587_12477.jpg

 

The biggest mistake you can make with an unmodded DSLR is to assume those Ha-only shots represent reality. The results from modded cameras tend to severely under-emphasize other colors. Case in point: the Tarantula Nebula is not red. Like at all—it is clearly aqua blue through binoculars, any telescope, and any happy-snap of the sky that includes the LMC.

 

med_gallery_273658_7587_855306.jpg

 

Yet what you find online is always something other than blue.

 

BQ

This argument has two sides.  Our eyes are not very sensitive to H alpha, which is clearly the dominant emission from many of these nebulae.  Physics.  One can argue that the image should match that, one can argue that the actual structure is better shown as more red.

 

Exactly. Roger also pushes his RNC stretch algorithm, which does an excellent job of boosting color.

 

What I appreciate most about Roger is that he shows you that in the pursuit of curiosity, much dogma should be ignored (or at least taken with a grain of salt). I'm taking a class on happiness in the workplace, and it gives a most fascinating set of factors that define curiousity: openness to new ideas, inquisitiveness, creativity in problem solving, and—most signficantly—distress tolerance. I've found that Roger induces much distress in AP purists! laugh.gif

 

BQ

What any of us do is somewhat art.  Building on the above, our eyes don't see color in dim light, and some people's idea of reality is muted color.  Roger, on the other hand, takes things a bit far re color.  By _my_ taste.  And his processing methods seem to distort things.

 

So my images have color somewhere between the muted colors and Rogers.  Just my personal style, not "better".  

 

I'm not distressed, just don't care for his images or his somewhat idiosyncratic methods, which I would not recommend to beginners.  I think the majority of serious imagers have things right, PixInsight is the outcome.  A large number of very smart people, who have done this for a long time.
 



#17 Huangdi

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Posted 13 August 2020 - 10:06 AM

To get back to the topic, I want to highlight the possibility of simply purchasing a cheap camera and modifying it yourself. I did that to my Nikon D3300 which you can buy used for under 200€. Add a uv/ir cut filter for 50 € and you have a perfectly fine Astro camera.

However if you decided to go down that route, I'd recommend the D5300 since it has proper software support which is the only thing the D3300 lacks.

#18 russellmm

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Posted 13 August 2020 - 01:45 PM

My DSLR time in the sky is planned to be temporary as I first want to prove to myself it is something I can achieve and enjoy over time before dropping real money on a APO/monochrome camera. I am retired now, so the days of dropping $7K on a lens (like my canon 300mm F2.8 II) are much harder to come by. So I want practice

 

To get back to the topic, I want to highlight the possibility of simply purchasing a cheap camera and modifying it yourself. I did that to my Nikon D3300 which you can buy used for under 200€. Add a uv/ir cut filter for 50 € and you have a perfectly fine Astro camera.

However if you decided to go down that route, I'd recommend the D5300 since it has proper software support which is the only thing the D3300 lacks

 


 

BQ

 

I have a good view of the Eastern Sky, so was thinking the Soul or Heart Nebula if they are viable targets. I did try to shoot them a few days ago and literally nothing showed up in my frames.

 

I have been reading Clarkvision's site a lot over the past week. I spent quite a long time getting his rnc-stretch routine working (it wont work on a few of my images, like my poor little dumbell nebula picture with only blue no red). Davinci for the most part has been depreciated on windows so it lacks the ability to handle TIF's properly (so need to convert to PNG). I am in no position to try and recompile it my self or run linux. I even went so far as finding a program out there that did recompile it for their own use (fixing the TIF issues) called TMSB/Dshadow but I cant figure out how to make that work properly yet.

 

I really need to work hard on learning the processing and make sure I am using the right tool/workflow since it is so critical to whether I will enjoy this hobby long term. 

 

Lastly, I notice you have no Bias' in your work flow below. Only Darks and 1 flat?

 

 

 

Of course there's hope! smile.gif

 

 

The capture and processing details were

 

Canon 200mm f/2.8L II, Canon 600D/T3i (stock)
133×30sec@ISO1600 f/2.8, 58×darks, 1×flat
153×30sec@ISO800 ∅52mm (~f/3.85), 50×darks, 1×flat
Debayered & calibrated in RawTherapee 5.6
Aligned & stacked in Lynkeos 3.3, processed in PS CS5
w/Astronomy Tools 1.6 & Annie's Astro Actions 7.0

 

I would highly recommend reviewing Roger's page on RawTherapee—it has significantly improved my processing.

 

Sadly, no video…

 

Do you have a target in mind?

 

BQ

 

 

 

 

Best Regards

Russell


Edited by russellmm, 13 August 2020 - 04:40 PM.


#19 BQ Octantis

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Posted 13 August 2020 - 05:47 PM

This argument has two sides.  Our eyes are not very sensitive to H alpha, which is clearly the dominant emission from many of these nebulae.  Physics.  One can argue that the image should match that, one can argue that the actual structure is better shown as more red.

 

What any of us do is somewhat art.  Building on the above, our eyes don't see color in dim light, and some people's idea of reality is muted color.  Roger, on the other hand, takes things a bit far re color.  By _my_ taste.  And his processing methods seem to distort things.

No argument from me Bob. I fall on the art side of things—who is to say what something you can't see should look like? And I got beat a lot as a kid, so I learned to ignore my distress. My wife shattered a Pyrex in the oven yesterday, and she froze in front of the mess, completely unable to overcome her distress. I simply grabbed my heavy BBQ gloves and picked out the steaming glass shards. So a novel imaging technique is easy for me to explore. And Roger's images look pretty cool to me. Not my style either, but a ton of great knowledge and processing nuggets.

 

My big concern is that for a budding imager, Ha-boosted and mono images are totally unrealistic goals for unmodded cameras. I find it better to help them find the limit of their setup so they can focus on upgrading what they need to. As you well know, it will inevitably be the mount that is the limiter. Very occasionally it's the lens that's simply an unusable lemon. Most often, it's a combination of total imaging time and processing technique. Rarely is it the camera for DSOs. And better to understand their goals before sending them down just any rabbit hole—maybe Ha is their goal!

 

Planetary is a whole other story.

 

BQ


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#20 BQ Octantis

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Posted 13 August 2020 - 06:00 PM

My DSLR time in the sky is planned to be temporary as I first want to prove to myself it is something I can achieve and enjoy over time before dropping real money on a APO/monochrome camera. I am retired now, so the days of dropping $7K on a lens (like my canon 300mm F2.8 II) are much harder to come by. So I want practice

 

I have a good view of the Eastern Sky, so was thinking the Soul or Heart Nebula if they are viable targets. I did try to shoot them a few days ago and literally nothing showed up in my frames.

 

I have been reading Clarkvision's site a lot over the past week. I spent quite a long time getting his rnc-stretch routine working (it wont work on a few of my images, like my poor little dumbell nebula picture with only blue no red). Davinci for the most part has been depreciated on windows so it lacks the ability to handle TIF's properly (so need to convert to PNG). I am in no position to try and recompile it my self or run linux. I even went so far as finding a program out there that did recompile it for their own use (fixing the TIF issues) called TMSB/Dshadow but I cant figure out how to make that work properly yet.

 

I really need to work hard on learning the processing and make sure I am using the right tool/workflow since it is so critical to whether I will enjoy this hobby long term. 

 

Lastly, I notice you have no Bias' in your work flow below. Only Darks and 1 flat?

Those aren't exactly easy targets. The dimmer the target, the longer the integration time you'll need. And some relatively dark skies to extract them from the background. Fortunately, you have a reasonably fast optic—as I posted before, at f/2.8 you'll just need 2-4 hours in reasonably dark skies. And I assume by Canon Mark IV, you have the 5D—a full-frame sensor with big pixels that gather lots of light.

 

Questions through the chain:

 

  1. How did you achieve focus?
  2. What lens/camera settings did you use?
  3. How did you stack?
  4. How did you calibrate?
  5. How did you stretch?

 

While I implement several of Roger's ideas in my workflow, I am a disciple of Charles Bracken when it comes to calibration. RawTherapee only takes in 1 flat, so that's all I use—and it works fine. And bias is already in my (roughly) temperature-matched darks, so it's redundant.

 

Getting nothing in a stretch is unnatural—even a bias frame will have something in the image. Can you post a single sub and/or your initial stack? I prefer 16-bit TIFF for the stack.

 

BQ


Edited by BQ Octantis, 13 August 2020 - 06:02 PM.


#21 russellmm

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Posted 13 August 2020 - 07:44 PM

Those aren't exactly easy targets. The dimmer the target, the longer the integration time you'll need. And some relatively dark skies to extract them from the background. Fortunately, you have a reasonably fast optic—as I posted before, at f/2.8 you'll just need 2-4 hours in reasonably dark skies. And I assume by Canon Mark IV, you have the 5D—a full-frame sensor with big pixels that gather lots of light.

 

Questions through the chain:

 

  1. How did you achieve focus?
  2. What lens/camera settings did you use?
  3. How did you stack?
  4. How did you calibrate?
  5. How did you stretch?

 

While I implement several of Roger's ideas in my workflow, I am a disciple of Charles Bracken when it comes to calibration. RawTherapee only takes in 1 flat, so that's all I use—and it works fine. And bias is already in my (roughly) temperature-matched darks, so it's redundant.

 

Getting nothing in a stretch is unnatural—even a bias frame will have something in the image. Can you post a single sub and/or your initial stack? I prefer 16-bit TIFF for the stack.

 

BQ

BQ,

 

1. I used a Bahtinov Focusing Mask I purchased

2. Canon 5D Mark IV, 300MM F2.8 lens, ISO 1600, F3.2 (I stopped down hoping for additional clarity), 10 sec exposure (If i went higher the light polution seem to get pretty bad and the picture just looked over exposed). I do have a decent amount of light polution facing east but I am in a green zone on the Light pollution Map.

3. Used Deep Sky Stacker (using mostly the defaults). 70 images, + darks + Bias + Flats

4. Not sure what you mean by Calibrate

5. Used PS CS6 following a tutorial I found online. I.E. Adjusting levels (but nothing fancy like individual channels)

 

When I say "nothing" I simply mean no color. When I stretched the Andromeda Galaxy detail came out of the stretch.

 

Here is a link to a frame I captured (I posted a 5mp shrinked version and the full 20mp version)

https://www.amazon.c...5THtG1mMMOQ3WqO

 

I suspect what it comes down to is: I need to find an easier target, I need to take lots more exposures, and I need to learn how to stack/post process them correctly smile.gif

 

I attached screenshots of the histogram of the file I shared as well as the plate solve of the region the image captured

 

P.S. I bought a Orion Atlas Pro AZ/EQ-G as my mount since I thought it would be sufficient for anything I plan to put on it

 

Best Regards and thanks for the continued feedback

Russell

Attached Thumbnails

  • 2020-08-13 17_26_38-- APT -.jpg
  • 2020-08-13 17_20_31-Stellarium 0.20.2.jpg

Edited by russellmm, 13 August 2020 - 07:45 PM.


#22 BQ Octantis

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Posted 13 August 2020 - 09:33 PM

Sorry, Russel, I should have clarified: I prefer the RAW for an individual sub. Plus a single RAW flat. These are unstretched linear data, so I can do some color manipulation in linear space. It's the stack I prefer in 16-bit TIFF.

 

Regardless, the full-size TIFF you posted is telling:

 

1. Your focus is off. If you zoom into NGC 1027, you can see the coma around the stars:

 

ncg1027.jpg

 

The impact to the nebula is that it gets spread out into the noise.

 

2. That's a major light pollution gradient. Looking at the sky from Detroit, these nebula are pretty low in the sky (~29˚ elevation) at 11:30 p.m., so their light is being absorbed through two air masses of atmosphere. And from the gradient in the image, I assume you were shooting through a significant light dome. With just 10 seconds of exposure at f/3.2, under normal conditions the signal from this target may not even be above the noise floor of the camera; shooting it this low and through such pollution may very well require narrowband. For your unmodded camera, I'd recommend waiting for the target to rise above the light dome and closer to 1 air mass (use Stellarium for airmasses). For nebula, I don't recommend below 30 second exposures at f/2.8.

 

BQ



#23 russellmm

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Posted 13 August 2020 - 10:15 PM

yea, i kind of figured i needed something higher in the sky to reduce the light pollution or something in the higher up SW sky ( i have trees in the lower area)

 

i'll try harder on the focus, but thought i had it dialed in the the mask. I even tape the focus ring after focusing to try and keep it from moving

 

I wonder if the north american nebula is a more viable target since its so much higher up.


Edited by russellmm, 13 August 2020 - 10:19 PM.


#24 17.5Dob

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Posted 13 August 2020 - 10:26 PM

H & S from Bortle 8 skies with a modded cam 85mm f4.....45 min total, because that's the length they were only visible through the trees, from my old house

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#25 17.5Dob

17.5Dob

    Fly Me to the Moon

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Posted 13 August 2020 - 10:30 PM

Side by side shots using my stock D7100 and modded D5300, with all other factors being equal...

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  • rbish237 and 06AwzIyI like this


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