Agonising over LP filters - help appreciated

[rubecula]

I'm confused about which light polution filter to buy.  I'm very new to AP and at this stage want to photograph pretty much everything that's within reach of my scope (galaxies and all types of nebulae).

I live in a semi-urban area and most of the local street lights have been changed to the new white type.  Although there is distant polution from other areas that have not been converted so far.

It seems that the IDAS filters are highly regarded and I found this discussion on them: http://www.cloudynights.com/topic/458137-understanding-idas-d1-p2-v4-heuibii-filters/

I found some of that confusing but think from that it comes down to a choice between the V4 and the HEUIBII.  Confusingly the FLO site says both the P2 and D1 are the BEST!!

The images on the FLO site make the HEUIBII rather tempting. 

I understand that a single filter might not be appropriate for my broad imaging desires at present but am finding it difficult to determine which I would get most use out of.

It's a pity I can't have 2 or 3 of them here to try out.

 

[red dwalf]

flo do a 30 day money back policy

[carastro]

If your new lighting is LED I have read that normal LP filters such as CLS are now rendered useless.

Carole 

 

[Astroboffin]

Surely it's not just about the close by street lighting that you need to consider, but on a much wider scale, if you have LED street lamps around your house, but on a much wider scale they are sodium, then the CLS and suchlike will work fine.

i live in the middle of three major cities, around 25miles from each of them, so that's where my LP comes from, not the three or four street lamps down the road....it's the cities that give my images the orange glow...especially if imaging low down towards any horizon.

or maybe I have it wrong

[Oddsocks]

Hi Robin,

The information on the FLO website regarding the different Hutech filters seems to have been lifted off the European distributors page as the text is identical and has in parts translation errors.

There is better information available by looking at the wavelength versus transmission characteristic charts to be found at various astro supplier websites.

The choice of Hutech LPS filters depends not only on the sources of your local LP but also on whether your DSLR camera has been modified by removal of the standard sensor IR/UV block filter and replaced by either a wide-band IR/UV block filter or no filter at all.

To summarise the differences between D1 and P2:

The LPS-D1 is primarily for use with unmodified DSLR cameras using the standard manufacturers IR/UV blocking filter or OSC CMOS and CCD cameras that have a built in IR/UV blocking filter that can not be removed.

The LPS-P2 is for modified DSLR cameras with either the standard IR blocking filter completely removed or replaced by a modified wide-band IR/UV block filter and OSC CMOS or CCD cameras with no IR/UV filter fitted.

The reason for the difference is that the P2 passes more light in the deep red end of the spectrum to allow the SII emission line to pass, this line is only very weakly detected in DSLR, CMOS and CCD cameras that have a standard manufacturers IR filter fitted, if you use the P2 filter in this case the SII line just appears as very random "noise" in the red channel. If you have either no IR/UV filter fitted or a modified filter then the SII line is detected more strongly and is worth capturing.

The HEUIB-II filter has no LP reduction capability, it is an enhanced IR/UV blocking filter specifically for a DSLR that has had the stock IR/UV filter removed and allows the Ha emission line to pass cleanly while blocking IR either side of the Ha line.

I can confirm from my own experience that LPS or even narrow band filters are not effective against white LED lighting which produces an even background "fog" across the entire visible spectrum. On the plus side the new LED lights are usually better directed down to the ground where used for street lighting and are not so obtrusive unless it has rained recently and the ground is wet in which case the white light is reflected back up into the air, the use of LED lighting in commercial sites is more of an issue since it is largely unregulated and I have a local commercial source of super bright white LED lighting that's all but destroyed my ability to do any sort of conventional imaging from home and I have to be content with just spectroscopy and astrometry.

If you still have a large local source of sodium (yellow) or mercury (green-blue) lighting, within about ten miles or so, then either the D1 or P2 chosen to suit your camera will help improve your images, as long as those sources remain, there is nothing you can do about LED sources apart from shielding if possible, or imaging from a dark site.

Comparison chart attached below showing different wavelength pass bands for the D1 and P2

 

[rubecula]

Oddsocks (feels odd calling you oddsocks) thank you for that very full reply.  Not wishing to put you to any more trouble, but.....

Do you have any thoughts on the V4?  and,

are any of these any use in combating moon light?

Thanks,

BTW my camera has had the colour-correcting filter removed but not the front IR/UV one.

[Oddsocks]

13 minutes ago, rubecula said:

Oddsocks (feels odd calling you oddsocks) 

Do you have any thoughts on the V4?  and,

are any of these any use in combating moon light?

Thanks,

BTW my camera has had the colour-correcting filter removed but not the front IR/UV one.

Hi Robin,

You can call me William if you prefer but oddsocks does accurately describe my inability to match footwear style and colour when rushing to get out somewhere 

The V4 filter is tailored for emission line objects, so gaseous and planetary nebulae mainly, there are big chunks of the visible spectrum blocked so it wouldn't be useful for galaxy, star clusters or dark clouds and it would not show star colours accurately. The D1 or P2 would cover a wider range of objects you might choose to image with a better colour balance.

The moon pretty much re-radiates all the Suns wavelengths in various amounts, changing slightly with the phase and proportion of Earth shine that comes back...You really need to be looking at narrow band 5nm or 3nm Ha/SII/OIII/Hb filters if you want to image under moonlight but I feel these are only of limited use with a colour DSLR since only a small proportion of the available pixels actually record anything, the rest just record noise and again these are emission line pass filters so are mainly used for nebulae. If you plan to invest in 3nm or 5nm narrow band filters I would be looking to leave the DSLR behind and go straight to a cooled mono CCD, the performance gain using narrow band with a DSLR is so small it hardly justifies the expense....thats my opinion for what it is worth... 

It is the camera's front, manufacturers IR/UV blocker that limits the bandpass, the widest wavelength response will be obtained if the filter is removed and a wider (front) bandwidth filter fitted (if you want to keep using the camera for daytime shots as well as astro) or removed completely and then rely on an external filter for the IR/UV blocking such as the P2.

William.

[rubecula]

Hi William (great name that, it's my middle name )

Thanks for all the info, it's been a great help.  I realise that a CCD is probably the way to go, but I've only recently bought the 550D and had it modified so I'd like to get some use from it before I spend a lot more money.

 

[wxsatuser]

7 hours ago, rubecula said:

I'm confused about which light polution filter to buy.  I'm very new to AP and at this stage want to photograph pretty much everything that's within reach of my scope (galaxies and all types of nebulae).

I live in a semi-urban area and most of the local street lights have been changed to the new white type.  Although there is distant polution from other areas that have not been converted so far.

It seems that the IDAS filters are highly regarded and I found this discussion on them: http://www.cloudynights.com/topic/458137-understanding-idas-d1-p2-v4-heuibii-filters/

I found some of that confusing but think from that it comes down to a choice between the V4 and the HEUIBII.  Confusingly the FLO site says both the P2 and D1 are the BEST!!

The images on the FLO site make the HEUIBII rather tempting. 

I understand that a single filter might not be appropriate for my broad imaging desires at present but am finding it difficult to determine which I would get most use out of.

It's a pity I can't have 2 or 3 of them here to try out.

 

How about an Astronomik CLS clip filter, just as good as the Hutechs but a bit cheaper.