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Favorite Light Pollution Filter for EAA?

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#126 StarCurious

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Posted 04 June 2016 - 01:48 AM

Hi Jim,

The culprit could have been focuser tube not square with OTA.

Thanks for noticing my focusing problem. I just inspected and noticed that the focuser was not installed squarely. At one time, I removed the focuser to allow a dovetail nut to fall out of the OTA. This was needed when I replaced the stock OTA mounted short dovetail with a longer one and tube rings to balance the OTA. I did not tighten enough one of the three screws for the focuser! I have now fixed this.

There is a lock screw for the focuser and I will use it in future. This however may not have been the problem as the DC motor for the Orion Accufocus could have supplied enough braking or stickiness in focuser position.

Thanks,
Joseph

#127 StarCurious

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Posted 07 July 2016 - 06:24 PM

I used Sharpcap 2.8.2378.0 with the FCUSB/Accufocus ASCOM driver and FWHM to achieve focus. This was probably the best focus I have achieved so far with the C102 Achromat, and with the Astronomik Proplanet 642 BP filter (band pass 642 - 842 nm).  The result, cropped to smaller file for uploading, is below:

 

M51 F2.3.642BP.4S_Stack_46.Cropped.png

 

M51 at F/2.3 stack of 46  x 4 seconds or 3 minutes 4 seconds.



#128 ChrisFC

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Posted 01 July 2017 - 09:34 PM

Rather than start a new thread ...

 

I currently have an optolong UHC filter for light pollution.

 

But I've been looking at a hutech IDAS LPS P2 filter. Would this be better ? It is similar to the UHC but has extra pass bands near 565 and 605nm.

http://www.sciencece...das/filtplt.htm

 

I don't know what these passbands are for. Are they just to avoid Hg etc from lights. So better than UHC for galaxies as they let in more light, but no better for emission nebulae as you only want the the HO bands ?


Edited by ChrisFC, 01 July 2017 - 09:42 PM.


#129 Ptarmigan

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Posted 01 July 2017 - 09:55 PM

I have used Lumicon Deep-Sky and UHC filter. UHC filter casts a bluish-green tint. The Deep-Sky is more natural. Of course with filters, you need longer exposures.



#130 Umasscrew39

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Posted 03 July 2017 - 02:25 PM

Rather than start a new thread ...

 

I currently have an optolong UHC filter for light pollution.

 

But I've been looking at a hutech IDAS LPS P2 filter. Would this be better ? It is similar to the UHC but has extra pass bands near 565 and 605nm.

http://www.sciencece...das/filtplt.htm

 

I don't know what these passbands are for. Are they just to avoid Hg etc from lights. So better than UHC for galaxies as they let in more light, but no better for emission nebulae as you only want the the HO bands ?

Chris

 

I am using the IDAS LPS-D1 which came highly recommended to me by Starizona and it works great.  They also sell the LPS P2 filter you mentioned but preferred the LPS-D1.  



#131 jimthompson

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Posted 04 July 2017 - 01:32 PM

Rather than start a new thread ...

 

I currently have an optolong UHC filter for light pollution.

 

But I've been looking at a hutech IDAS LPS P2 filter. Would this be better ? It is similar to the UHC but has extra pass bands near 565 and 605nm.

http://www.sciencece...das/filtplt.htm

 

I don't know what these passbands are for. Are they just to avoid Hg etc from lights. So better than UHC for galaxies as they let in more light, but no better for emission nebulae as you only want the the HO bands ?

Hi Chris,

 

The answer to your question depends on what you are looking for in terms of "better" performance.  The Astro Hutech IDAS LPS-P2 and its successor the LPS-D1 are both well liked filters because they provide a very nice colour balance.  This is primarily due to the filter allowing much more blue through than other nebula filters like your Optolong UHC.  If you want to observe objects with a lot of reflection nebula content, such as the Trifid or Running Man, then this filter does a nicer job of showing them.  If however you are looking for better light pollution rejection in general, the LPS-P2/-D1 are worse then what you already have.  This is especially true on galaxies since the LPS-P2/-D1 have an integrated UV/IR cut filter which really hurts the filter's performance on galaxies.  I have attached a series of charts I posted back in Feb 2016 that compare the performance of a number of filters.  The objective in the plots is to have the highest delta RGB value for the highest % luminous transmissivity, where delta RGB is the amount of greyscale difference there is between the background and the object of interest in your image.

 

Cheers,

 

Jim T.

Attached Files


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#132 ChrisFC

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Posted 04 July 2017 - 06:40 PM

Many thanks Jim - your well researched threads and charts are an invaluable source of information. I'd already downloaded all of them, including that one..

I might give one a go and see what the colour balance is like, as thats always an issue with my UHC



#133 Umasscrew39

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Posted 05 July 2017 - 08:50 AM

 

Rather than start a new thread ...

 

I currently have an optolong UHC filter for light pollution.

 

But I've been looking at a hutech IDAS LPS P2 filter. Would this be better ? It is similar to the UHC but has extra pass bands near 565 and 605nm.

http://www.sciencece...das/filtplt.htm

 

I don't know what these passbands are for. Are they just to avoid Hg etc from lights. So better than UHC for galaxies as they let in more light, but no better for emission nebulae as you only want the the HO bands ?

Hi Chris,

 

The answer to your question depends on what you are looking for in terms of "better" performance.  The Astro Hutech IDAS LPS-P2 and its successor the LPS-D1 are both well liked filters because they provide a very nice colour balance.  This is primarily due to the filter allowing much more blue through than other nebula filters like your Optolong UHC.  If you want to observe objects with a lot of reflection nebula content, such as the Trifid or Running Man, then this filter does a nicer job of showing them.  If however you are looking for better light pollution rejection in general, the LPS-P2/-D1 are worse then what you already have.  This is especially true on galaxies since the LPS-P2/-D1 have an integrated UV/IR cut filter which really hurts the filter's performance on galaxies.  I have attached a series of charts I posted back in Feb 2016 that compare the performance of a number of filters.  The objective in the plots is to have the highest delta RGB value for the highest % luminous transmissivity, where delta RGB is the amount of greyscale difference there is between the background and the object of interest in your image.

 

Cheers,

 

Jim T.

 

Hi Jim

 

After looking at your chart and some images with the various filters, I am trying to determine how significant these differences really are in practice.  It seems to me (given my not-so-great vision) that many of the differences your research eloquently demonstrates may not make a significant difference upon visual inspection of an image.  I realize there are numerous variables like sky conditions, scope set ups, user skill level, etc., but am I missing the point?  Are the differences subtle in most cases or am I way off base here?

 

Bruce 



#134 jimthompson

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Posted 05 July 2017 - 11:00 AM

 

 

Hi Jim

 

After looking at your chart and some images with the various filters, I am trying to determine how significant these differences really are in practice.  It seems to me (given my not-so-great vision) that many of the differences your research eloquently demonstrates may not make a significant difference upon visual inspection of an image.  I realize there are numerous variables like sky conditions, scope set ups, user skill level, etc., but am I missing the point?  Are the differences subtle in most cases or am I way off base here?

 

Bruce 

 

Hi Bruce,

 

You have a good question there.  Indeed numbers are not really that useful to us if we can't relate them to something tangible.  That is why I have also tested many of the filters I discuss, and made screen captures so people can compare visually for themselves.  You can find many of these tests documented on my website:

 

http://karmalimbo.co...rts/reports.htm

 

When looking at the predicted filter plots attached in my above post, you can use as a ruler the rough rule of thumb that the human eye+brain can detect a difference in brightness of approximately 1 in 50. This translates to a minimum delta RGB of 5 being required for a person to distinguish an object from the background...to be able to even detect that something is present in the image.  Thus if you were trying to observe a dim nebula like NGC7000 (N. American), with no filter you might not be able to see it at all (dRGB<2) but with an Astronomic UHC you would be able to see it (dRGB~6).  For the same example the LPS-P2 is not predicted to provide enough light pollution reduction to make the object visible against the skyglow (dRGB~3.3).

 

Regards,

 

Jim T.


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#135 jimthompson

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Posted 05 July 2017 - 11:07 AM

Just to be clear I am not bashing the LPS-P2/-D1.  I have a -P2 and use it from time-to-time, but under specific situations.  I don't use it from my backyard in a red zone for light pollution since it does not provide enough suppression of LP to make many objects I want to observe visible.  I do use it however when I am at the cottage with mag +5 skies in order to improve contrast on nebulae and reduce star bloat.  The LPS-P2 does a really smashing job on M20 Trifid Nebula when you are in semi dark skies.  Unfortunately I am not able to go to the cottage much, and thus have to deal with the high LP of the city.

 

Regards,

 

Jim T.


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#136 Umasscrew39

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Posted 05 July 2017 - 11:49 AM

Thanks much Jim....very useful and I will continue to review.  And no worries about the bashing....I have the LPS-D1 and have been using it in my red zone area on my hyperstar to take EAA images with my UltraStar C on a C11.  I noticed (in my gallery on CN) that I get very clear resolution on most of the large emission nebulae like the Lagoon and Eagle nebulae, M20 Trifid (as you noted), etc but struggle to get similar results with the N. America and both Veils as well as many bright galaxies (e.g., M81).  I have not tried the hyperstar with no filter and I have not purchased any other filters yet to help with the bright galaxies or other planetary nebulae like the Cat's Eye N. which essentially looks like a white dot with the LPS-D1.  Interestingly, I took the Ring planetary nebula M57 at prime focus on my C11 EdgeHD (f/10) with the UltraStar C with no filter and it came out really well (see below).  However, I just purchased the Baader 35nm H- alpha (which I noted on your charts) and will be trying it on both Veils and NGC 7000 (N America) to see if I can get an enhancement of them.    

 

It sounds like for the bright galaxies and some planetary nebulae (e.g, Cat's Eye N.) that maybe an Astronomic UHC might be more useful; however, it looks like this filter could be a problem when using it at f/2.  It seems it works best from f/4 and above.  

 

Bruce

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  • M57.png

Edited by Umasscrew39, 05 July 2017 - 12:11 PM.

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#137 Hsewalia

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Posted 13 March 2019 - 01:11 PM

Hi Guys

 

I’m a newbie at this and was hoping to get an understanding of some of the concepts related to astrophotography camera/filter pairings. 

So here’s what I’ve gathered thus far,

1. Typical DSLRs have an IR filter but CCDs and most modded DSLRs do not

2. Because of this it is recommended to use a filter with IR cut for CCD/modded DSLR but without IR cut for stock DSLRs

 

What I wanted to know is what is the downside of using an LP filter with IR cut on a stock DSLR? Would it significantly remove more reds than the camera’a built in IR filter already does?

Would it prevent me from photographing any objects that I could do the bare DSLR?

 

Reason I ask this is because it makes more sense to buy an LP filter with IR cut although I have a stock DSLR since I can still use it for AP when I decide to either mod the camera or upgrade to CCD....Of course this is iff there are no downsides :)

 

 



#138 jimthompson

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Posted 13 March 2019 - 01:25 PM

Hi Guys

 

I’m a newbie at this and was hoping to get an understanding of some of the concepts related to astrophotography camera/filter pairings. 

So here’s what I’ve gathered thus far,

1. Typical DSLRs have an IR filter but CCDs and most modded DSLRs do not

2. Because of this it is recommended to use a filter with IR cut for CCD/modded DSLR but without IR cut for stock DSLRs

 

What I wanted to know is what is the downside of using an LP filter with IR cut on a stock DSLR? Would it significantly remove more reds than the camera’a built in IR filter already does?

Would it prevent me from photographing any objects that I could do the bare DSLR?

 

Reason I ask this is because it makes more sense to buy an LP filter with IR cut although I have a stock DSLR since I can still use it for AP when I decide to either mod the camera or upgrade to CCD....Of course this is iff there are no downsides smile.gif

Personally I would go with the configuration that gives the most flexibility, which would be: an LP filter without integrated IR cut + a separate UV/IR cut filter.  Splitting the IR cut out into a separate filter gives you the flexibility to use it only when you need/want to.  To answer your question is there any drawback to using an IR cut filter on an unmodded DSLR I'd say the answer is "not really".  The IR cut will attenuate the signal a little bit, but probably not enough to be concerned.

 

Regards,

 

Jim T.



#139 Hsewalia

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Posted 13 March 2019 - 01:47 PM

Personally I would go with the configuration that gives the most flexibility, which would be: an LP filter without integrated IR cut + a separate UV/IR cut filter.  Splitting the IR cut out into a separate filter gives you the flexibility to use it only when you need/want to.  To answer your question is there any drawback to using an IR cut filter on an unmodded DSLR I'd say the answer is "not really".  The IR cut will attenuate the signal a little bit, but probably not enough to be concerned.

 

Regards,

 

Jim T.

 

Thanks for suggestion Jim...will certainly take that into consideration!



#140 Hsewalia

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Posted 18 March 2019 - 10:28 AM

Hi Jim,
I’m limited by the following things:
1. Heavy light pollution
2. Slow scope on Alt-Az GOTO mount (8se with reducer @ f/6.3)
3. Unmodified DSLR (Nikon D5000)
Which filter would you best recommend for EAA given my situation?

I know I cannot expect “stellar” (npi 😁) results with my setup but I’m just trying to get the best out of what I have!

Thanks!
Hsewalia

#141 DSO_Viewer

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Posted 18 March 2019 - 10:49 AM

Hi Jim,
I’m limited by the following things:
1. Heavy light pollution
2. Slow scope on Alt-Az GOTO mount (8se with reducer @ f/6.3)
3. Unmodified DSLR (Nikon D5000)
Which filter would you best recommend for EAA given my situation?

I know I cannot expect “stellar” (npi ) results with my setup but I’m just trying to get the best out of what I have!

Thanks!
Hsewalia

The more light pollution you have the stronger the light pollution filter must be. Unfortunately what will not allow for the strongly light pollution filter is all three points that you made like slow scope, unmodded and # 1 Alt-Az. Perhaps you can try an IR cut filter or milder LP filter.

 

Steve 


Edited by DSO_Viewer, 18 March 2019 - 10:50 AM.


#142 jimthompson

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Posted 18 March 2019 - 11:44 AM

Hi Jim,
I’m limited by the following things:
1. Heavy light pollution
2. Slow scope on Alt-Az GOTO mount (8se with reducer @ f/6.3)
3. Unmodified DSLR (Nikon D5000)
Which filter would you best recommend for EAA given my situation?

I know I cannot expect “stellar” (npi ) results with my setup but I’m just trying to get the best out of what I have!

Thanks!
Hsewalia

Hi Hsewalia,

 

To help in making a filter suggestion, it would be good to understand where you are at right now with your setup.  With no filters installed, how long of an exposure would you say you can achieve presently before the image is washed out by light pollution?  If light pollution was not an issue (eg. you are at a dark site), how long of an exposure time could you go to and still have reasonable tracking with your mount and scope combination?  These two numbers will give me a good idea where you are at and where we can get you to.

 

cheers,

 

Jim T.



#143 Hsewalia

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Posted 17 April 2019 - 10:50 AM

Hi Hsewalia,

 

To help in making a filter suggestion, it would be good to understand where you are at right now with your setup.  With no filters installed, how long of an exposure would you say you can achieve presently before the image is washed out by light pollution?  If light pollution was not an issue (eg. you are at a dark site), how long of an exposure time could you go to and still have reasonable tracking with your mount and scope combination?  These two numbers will give me a good idea where you are at and where we can get you to.

 

cheers,

 

Jim T.

Hi Jim,

 

In my light polluted area, a single exposure at ISO 400, gets washed out after about 10 seconds.

At a dark site I get about 30 seconds at most before the tracking of my Alt-Az mount breaks down. 



#144 jimthompson

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Posted 18 April 2019 - 08:55 AM

Hi Jim,

 

In my light polluted area, a single exposure at ISO 400, gets washed out after about 10 seconds.

At a dark site I get about 30 seconds at most before the tracking of my Alt-Az mount breaks down. 

Hi Hsewalia,

 

It sounds like your light pollution level is similar to mine.  The narrower a band-pass you can go the better, but ultimately you will be limited by your mount.  You should be okay with using something like an Astronomik UHC or the cheaper Optolong version.  I have been successful using a 10nm Halpha on nebulae with my Alt-Az mount but that was with a short focal length refractor (f.l. = 380mm).  On your 8" SCT I don't think you will be able to benefit from the Halpha filter with such short exposures.  My advice is to start with a medium band width filter like the two I mention above, and see how it goes.  Once you see how that performs you can decide if you want to try a narrow Halpha filter.  You can also in the interim construct a wide Halpha filter using a #29 dark red filter plus a UV/IR cut.

 

Best Regards,

 

Jim T.



#145 Hsewalia

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Posted 18 April 2019 - 10:27 AM

Hi Hsewalia,

 

It sounds like your light pollution level is similar to mine.  The narrower a band-pass you can go the better, but ultimately you will be limited by your mount.  You should be okay with using something like an Astronomik UHC or the cheaper Optolong version.  I have been successful using a 10nm Halpha on nebulae with my Alt-Az mount but that was with a short focal length refractor (f.l. = 380mm).  On your 8" SCT I don't think you will be able to benefit from the Halpha filter with such short exposures.  My advice is to start with a medium band width filter like the two I mention above, and see how it goes.  Once you see how that performs you can decide if you want to try a narrow Halpha filter.  You can also in the interim construct a wide Halpha filter using a #29 dark red filter plus a UV/IR cut.

 

Best Regards,

 

Jim T.

Thanks Jim for your recommendation.

I was actually considering the Astronomik UHC but at over CAD300 (taxes and shipping included) it was prohibitively expensive!

Then I found your post where you evaluated and compared Optolong products and revealed that the performance is pretty comparable...so I think I'll definitely be giving the Optolong a go!




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