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Filters for Narrowband Imaging

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#1 shkong

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Posted 17 October 2013 - 04:25 AM

Hello gentlemen

I am going to try narrowband imaging with ST 8300M and AT8RC carbon tube( AP CDT 0.67 reducer).

I happened to get used Astrodon 3nm 36mm Ha filter and Astrodon 5nm OIII filtesr in good condition.

But i still need SI filter for Hubble Palette.



If I can not get used SI filter in good condition, then I may need to order new one.

Is there much difference in performance between Astrodon 5nm and 3nm Si filters?

I need advice on choice between 5nm and 3nm. :help:

thanks

Thomas

#2 vpcirc  Happy Birthday!

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Posted 17 October 2013 - 06:21 AM

Save your money and go with the 5. I don't know to many people using a 3 on SII

#3 dawziecat

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Posted 17 October 2013 - 06:23 AM

I have the 3nm versions on one camera and the 5nm Ha version on another.

I have no real experience with the 5nm yet though as it is "new-to-me."

One thing you might want to consider is your sky. Dark or light-polluted? Also, do you want to image in bright moonlight?

The narrower filter should be better at rejecting those "unwanted" wavelengths.

I don't think there is ever any reason NOT to go to 3nm on SII or OIII unless you habitually use uber-fast optics. Going that narrow on Ha can have some negative consequences on some objects, in some conditions as that narrow a window pushes the NII emission down.

Myself? I'd eat the $$$ and go for 3nm in all filters. I know the dollar hit hurts. :(

Lots of excellent info on these matters at this Astrodon site.

#4 DrDispatch

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Posted 17 October 2013 - 08:37 AM

not to hijack the thread, but I have similar question.
I am using Baader 2" filters in my QHY9.
was going to buy the 7nm HA filter.
I am interested in being able to image SOME while moon is up.
will this work, the 7nm? before I spend the $$

#5 orion69

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Posted 17 October 2013 - 08:54 AM

Imaging with Baader H-Alpha 7nm is OK, I do it all the time. But with SII and OIII there are noticeable problems, Moon should be as far as possible from imaging object.
I don't recommend using Baader SII and OIII filters in moonlight.

#6 DrDispatch

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Posted 17 October 2013 - 09:26 AM

orion69 thanks so much for taking time to reply, was just pressing the BUY button. done deal!

#7 shkong

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Posted 17 October 2013 - 05:31 PM

Thanks Mike, Terry, Knez.

I will wait until the end of this year for the used Astrodon SII filter in good condition.

If not, it is not going to be easy decision.

I will try to compare the performance of 3nm Ha and 5nm OII filters.

Thomas

#8 PGW Steve

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Posted 17 October 2013 - 07:38 PM

I've got 3nm Ha, SII, OIII and 5nm Ha in my STT. In my STF I have the Baaders, I don't remember the bandwidths. I shot some exposures the other night with the Baader Ha and I was pleased with the performance on the Crab with the Moon fairly close. I couldn't say how the SII and OIII would have performed.
The major issue I have heard is using a 3nm Ha on planetary nebulae tends to clip a lot of the signal and thus a 5nm is a better choice for PN's.

#9 Rick J

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Posted 17 October 2013 - 09:05 PM

The 3 nm Ha pretty much isolates Ha from NII so appears dimmer with planetaries that have NII which is a lot of them (M27 is a good example). It's not cutting out Ha however.

Rick

#10 shkong

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Posted 18 October 2013 - 01:02 AM

Thanks Steve and Rick for the comment.

I also found useful link to Astrodon site. to compare 6nm and 3nm OIII filters.

Here is the link-- http://www.astrodoni...owband/6v3.html

Some people may like 3nm better and other also 6nm.

You judge yourself.

Thomas

#11 Chris.Baron

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Posted 18 October 2013 - 09:00 AM

It probably depends on your imaging site. Anyone who is happy with wider bandpasses is likely in a less light polluted site. Mike for example is imaging from New Mexico. I have family in New Mexico and have been down there several times. I can tell you with 100% certainty that even Albuquerque or Santa Fe are no match for the light pollution I suffer from in a Toronto suburb, let alone the city proper.

I went progressively went from the Baader filters to the 5nm Astrodons and the difference was not insignificant. When I moved to 2" filters, I went 3nm for SII and OIII and recently moved from a 6nm HA to a 5nm HA. I'd probably move to the 3nm HA if one turns up used.

My light pollution is that bad. If you can use wider filters, I'm truly envious.

#12 shkong

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Posted 20 October 2013 - 01:00 AM

Chris

You may be right. The choice of bandpass will depend on seeing condition.

It is going to be tough to do AP in Toronto. :foreheadslap:

One of my daughter graduated from Univ of Toronto this June with Chemical engineering major and I was there for the ceremony.

My youngest is still sophomore in UT majoring in Mineral Engineering.

#13 neptun2

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Posted 20 October 2013 - 01:39 AM

Interesting topic guys. I also plan to get narrowband filters and wonder which to get. I thought to buy the baader set which includes 7nm H-alpha and 8.5nm SII and OIII. My site is relatively dark but i want to be able to image during full moon so will these filters be too wide for that? My system is relatively slow (f 7.5) so going narrower is not a problem. Looking at Astrodon i don't see any 2" filters from them (only unmounted). This is problem because i plan to use filter drawer for the narrowband and manually change filters between exposures. I also looked at astronomik but their filters are even wider than baader (12nm for S2 and O3). Is there any other manufacturer that have 2" mounted narrow filters?

#14 SL63 AMG

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Posted 20 October 2013 - 01:50 AM

Even in non light polluted skies, such as I have here in Arizona, using 3nm filters is the best choice if you plan to take your images during bright moonlight. If you have light polluted skies, there's even more reason to use 3nm filters.

You should read this.

The image below is comprised of a stack of 18 thirty minute 3nm SII exposures of NGC 1491 taken at 2857mm FL F/9 during a full moon. The pixel scales 0.39"/px and the image has only been stretched.

As you can see, there's plenty of signal and contrast using a 3nm SII filter during a full moon.

Posted Image


You might read this recent discussion.

#15 neptun2

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Posted 20 October 2013 - 06:12 AM

Thank you for these links Dave. I definitely got some new information and will have food for thoughts. It seems like 5nm or even 3nm O-III filter is especially useful when imaging during full moon. Unfortunately i do not see how to get such. In europe i can get astrodon, astronomik and baader filters but only astrodon produce 5nm and 3nm filters from these 3 manufacturers. Too bad that they don't have 2" mounted filters.

#16 Chris.Baron

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Posted 20 October 2013 - 07:17 AM

Neptun2,

Your QHY filterwheel will allow you to use the 50mm round unmounted Astrodons. I know this because I've used the QHY filterwheel myself.

The nylon screws and washers are what you use to hold the filters in place. It's a pain to get set up, but once done, works flawlessly. One word of advice; when you have the filters mounted in there and screwed in, you will likely need to cut a bit off the thread end of the screws else they'll prevent the carousel from turning.

BTW, just as an aside, right after I mentioned that if a 3nm HA went on the used market I'd probably get it, guess what happened? I'm now the proud new owner (awaiting delivery) of a 3nm HA filter.

Let's try this again. If a used AP3600/DDM85/Paramount ME comes on the market for $5000, I'd likely buy it ;)

#17 neptun2

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Posted 20 October 2013 - 07:51 AM

Congratulations Chris for the 3nm Ha and good luck with the mount :)

About the QHY filter wheel - i have already installed there baader LRGB 2" filter set and i don't want to disassemble it and change filters every time when i need to go between narrowband and lrgb. It has only 5 positions for 2" filters so my idea is to use the fifth blank position together with manual filter drawer for narrowband. I will see if it is possible to use 50mm unmounted filters with the filter wheel. Should be possible.

#18 Chris.Baron

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Posted 20 October 2013 - 08:43 AM

Heh, thanks neptun2

Alas, I don't have the too many filters problem. I've bought and sold LRGB filters a few times and found imaging with them very unrewarding. It might have been my lack of knowledge at the time, it might be that light pollution truly makes wideband imaging impossible, it could be a number of things. I might take a stab at it again at some point, but for now I've gone narrowband only. It makes even the cheapest filterwheel viable.

I've gone with the QHY22 for increased sensitivity and long ago went 2" filters for versatility, but part of me would like to get one of the SBIG STT-8300 or QSI683 rigs all decked out. If I sell off all my imaging accessories I could wind up just about $2,000 short :) :(

#19 neptun2

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Posted 20 October 2013 - 09:07 AM

Chris i am really new to the LRGB but at least from the first few objects that i tried i see substantial difference with the DSLR that i used before that. I definitely see very big potential in LRGB if the skies are relatively dark (i have such at around 80km from my city). Of course for imaging during full moon or under heavy light pollution narrowband is definitely the way to go. I personally would like to have both possibilities with LRGB as main and narrowband as backup during full moon or for specific objects that are suitable. About qhy22 - a friend of mine have one with badder 2" narrowband filter set and is very happy with that combo. He uses it together with takahashi 130 APO :) I also had hard time to decide between qhy9 and qhy22 but the FOV with my scope put me towards qhy9 in the end.

#20 JWalk

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Posted 20 October 2013 - 09:12 AM

With a 3 I sometimes miss on the S2 that is present. But, sometimes it gives you that little extra. I think if you like Planetaries the 3 may be the winner every time. If you like shooting a lot of Nebulas then the 5 may be more fun and you can get less with more. I know some guys use both if you can. I have the 3.

#21 microstar

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Posted 20 October 2013 - 10:46 AM

There was a thread on this a while back:

http://www.cloudynig...Board=ccd&Nu...,,,,,f27,,,,,&Words=&Searchpage=5&Limit=25&Main=5640617&Search=true&where=bodysub&Name=37180&daterange=1&newerval=2&newertype=y&olderval=&oldertype=&bodyprev=#Post5641707

I posted a image comparing 3nm and 5nm SII (post #5641707) and as you can see in that post there isn't a lot of difference - stars are a little bigger in the 5nm, but that might be good as they will match the OIII better.
...Keith

#22 vpcirc  Happy Birthday!

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Posted 20 October 2013 - 11:41 AM

In my discussion with Don at AIC, it really depends on your goals. As Jimmy stated there are some planetary nebulas that will separate and show greater detail with a 3 verse 5. In the case of nebulas the detail difference would be minimal. In an ideal world you like to have both, but most of us don't want to spend that much or have the open slot. I am most intrigued with a process Ken Crawford is using and I am trying to understand, a red containment filter. Most of man made light and moonlight fall into the blue green spectrum so Don encouraged me and I listened to go with a 3 nm on OIII. As I dive deeper into NB the more I learn. I still personally believe a 5 nm is a good multi purpose choice for SII and HA but of course I base that advice from Ken from when I bought my first set 2 years ago. Don showed me examples of PN's where a 3 nm HA brought out far more structure, but I don't currently have enough aperture or any open filter slots. I like to tease Don that as I've changed to larger filters 3 times, I'm funding his vacations. In my opinion nothing beats his quality but many people especially in Europe produce some outstanding images with Badder.

#23 shkong

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Posted 20 October 2013 - 03:27 PM

Fine

The conclusion is if you want to shoot in full moon, 3nm is a better choice and in other case 5nm may work.

It makes my decision on SII more complicated since I already got 5nm OIII.

I will experiment it myself to see what happens in my condition.

#24 vpcirc  Happy Birthday!

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Posted 20 October 2013 - 04:15 PM

Take the time to send Don an email, he'll answer any question you have.






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