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M31 with Optolong L-PRO - Better than I was expecting

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#1 sn2006gy

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Posted 25 October 2020 - 09:53 PM

Ever since trying to image with the LPRO I've had the curse of the clouds.  Finally got some time with it on Saturday night and I'm pretty happy with it - all things considered I got more M31 then I expected.

 

Relative Humidity was upwards of 90%

Bortle ~8 Skies

Moon ~60%

 

 

2600mc pro camera.

140x 90 seconds at gain 0

 

With so much moon/skyglow this initial test was at gain 0 and 90 second exposures.  I haven't had time to do a unity gain test - but that is next and i'll update my guide/review as I get more data.

 

You can read more and download my XISF (fits coming tomorrow probably) and mess around with processing an L-PRO data set.

 

https://rockchucksum...g-l-pro-review/

 

Yes, dark skies rule - but i'll be honest, i'd have no problems trying to milk more out of this filter and i certainly don't feel it was worse than no filter and working on removing gradients. Working with the output from this filter was extremely easy.  Download and see what you can do - data released to creative commons attribution license.

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  • m31-small-lpro.jpg

Edited by sn2006gy, 25 October 2020 - 10:02 PM.

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#2 bobzeq25

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Posted 25 October 2020 - 10:10 PM

Nice image.

 

For a different view of "light pollution" filters on galaxies (and other broadband targets), see these threads.  Some very experienced imagers there.

 

The L-Pro is not awful in this situation.  But many (including me) think it's not helpful, either.  Getting good color is one problem.

 

https://www.cloudyni...-the-answer-is/

 

https://www.cloudyni...-be-a-bad-idea/

 

Note that Madratter's initial post got 8 likes.

 

Bottom line.  Most every serious imager uses gradient reduction, it's pretty much a given in any serious workflow.  Some experienced imagers will add a "light pollution" filter, some won't.  Most of those who do add one, do so for emission nebulae only.


Edited by bobzeq25, 25 October 2020 - 10:19 PM.

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#3 sunnyday

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Posted 25 October 2020 - 10:37 PM

really superb capture , thanks .


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#4 celegroz

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Posted 25 October 2020 - 10:40 PM

What scope? You're inspiring me as I just ordered the 2600MC pro this week and shoot under Bortle 7/8 here at home. I have the L-Pro as well but have only been able to try it on my DSLRs (Canon 60D, Nikon 750D, Nikon 850D). There sure seems to be controversy surrounding the use of LP filters and if they're really worth the cost. But, still can't wait to try it out once I get the 2600. 

 

Edit: NVM, I just read your post above and see you used an Esprit 120. 


Edited by celegroz, 25 October 2020 - 10:42 PM.


#5 Jim Waters

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Posted 25 October 2020 - 11:27 PM

sn2006gy - nice image, processing and report-out.  I will be downloading your XISF image.


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#6 bobzeq25

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Posted 26 October 2020 - 12:19 AM

What scope? You're inspiring me as I just ordered the 2600MC pro this week and shoot under Bortle 7/8 here at home. I have the L-Pro as well but have only been able to try it on my DSLRs (Canon 60D, Nikon 750D, Nikon 850D). There sure seems to be controversy surrounding the use of LP filters and if they're really worth the cost. But, still can't wait to try it out once I get the 2600. 

 

Edit: NVM, I just read your post above and see you used an Esprit 120. 

LP filters can be very useful on emission nebula.  The combination of a duo or triband filter (like the L Enhance or L Extreme) and a one shot color camera (which is what they're designed for) is very popular for good reasons.

 

It's all about the target, a little about the nature of the light pollution.


Edited by bobzeq25, 26 October 2020 - 12:21 AM.


#7 sn2006gy

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Posted 26 October 2020 - 08:22 AM

What scope? You're inspiring me as I just ordered the 2600MC pro this week and shoot under Bortle 7/8 here at home. I have the L-Pro as well but have only been able to try it on my DSLRs (Canon 60D, Nikon 750D, Nikon 850D). There sure seems to be controversy surrounding the use of LP filters and if they're really worth the cost. But, still can't wait to try it out once I get the 2600. 

 

Edit: NVM, I just read your post above and see you used an Esprit 120. 

Yup, esprit 120 with Apex-L reducer and 2" L-PRO for this image.

 

2600mc is a nice camera and if you're in bortle 7/8 like me, the l-pro seems to work well. I think with some more time i could complete some of the larger rings and continue to get more color - someone with more processing skills can work on the data and i'm sure get even better image than I, so have at it :D


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#8 sn2006gy

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Posted 27 October 2020 - 09:26 AM

Posted up FITS and TIFF file if you're interested in exploring around with the M31 LPRO Data



#9 endlessky

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Posted 27 October 2020 - 01:04 PM

So far I have only managed to try my L-Pro filter for 1h and 18min on the Heart Nebula.

 

The results is definitely better than 2h without filter, on the same object.

 

See post here, if you are interested in checking the two images. No other post-processing was done on the images, beside automatic gradient removal and permanent stretch. Beside the more signal from the nebula being captured in 2/3 the time, I really love the added bonus of smaller and less stars that cloud the picture.

 

I haven't tried it on broadband targets, yet, because of lack of clear nights in this period. Results seem promising enough to warrant at least trying, though.


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#10 bobzeq25

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Posted 27 October 2020 - 02:10 PM

So far I have only managed to try my L-Pro filter for 1h and 18min on the Heart Nebula.

 

The results is definitely better than 2h without filter, on the same object.

 

See post here, if you are interested in checking the two images. No other post-processing was done on the images, beside automatic gradient removal and permanent stretch. Beside the more signal from the nebula being captured in 2/3 the time, I really love the added bonus of smaller and less stars that cloud the picture.

 

I haven't tried it on broadband targets, yet, because of lack of clear nights in this period. Results seem promising enough to warrant at least trying, though.

Worth trying, sure.  But the difference in effectiveness with an emission nebula and a broadband target is _big_.  So your results on an emission nebula don't provide much information about how it will work on a broadband target.



#11 endlessky

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Posted 27 October 2020 - 02:48 PM

Worth trying, sure. But the difference in effectiveness with an emission nebula and a broadband target is _big_. So your results on an emission nebula don't provide much information about how it will work on a broadband target.

I agree. And after reading the two threads you linked, I must say I have a better understanding on how these filters work and how they can benefit or hurt the images.

Fortunately I suspected this already, by reading a lot of stuff, before making my purchase. That's why I went with a very mild filter, the L-Pro, instead of the more aggressive IDAS on their various models. I am shooting from a Bortle 5/6 zone, so I didn't want to kill too much useful spectrum.

The way I understood these filters - and was hoping they would work this way - was that by killing the light pollution they would render the sky under which one images closer to a better Bortle zone (darker sky), therefore allowing for a longer sub-exposure for the same swamping factor, which results into fainter details being captured.

So far, from my experiments on the Heart Nebula, this seems to be true. Both in terms of seconds for a given mean ADU count, and in terms of resulting images.

As an example, for around 900-1000 ADU:

- no filter, with Moon at 70+%, but 50+° away from target, 90s
- L-Pro, no Moon, 240s
- L-Pro, tonight with Moon at 85+%, but about 70° away from target, 180s

So, there's definitely a gain, if I can expose from 2 to 2 and 2/3 times longer, for the same background mean ADU.

I was hoping, since the notches on the L-Pro are relatively small and confined, that this would also work on most subjects, including broadband ones.


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