LP filter for Bortle 4?

[DaveS]

According to the LP maps I have Bortle 4 skies with a SQI of 21.66 though I can see the sky isn't pitch black.

The LP is coming from Bridport in the west and Dorchester / Weymouth in the east, in both cases it looks to be a mixture of LED and HPS.

I was thinking of getting an IDAS D2 filter to go in the wheel of an Atik 16200 as Luminance when I get one, but was wondering if anyone else in similar skies uses a LP filter for L? My Luminance stacks so far don't show any obvious gradients, though I've limited them to 5 mins with an ASI1600 in Max DR setting. I'm also wondering if there're any 1.25" LP filters available that don't block too much light. I have an Astronomik CLS-CCD but that has very narrow pass bands.

[DaveS]

No replies?

Does that mean that nobody needs one in Bottle 4? Or nobody is imaging from Bortle 4?

I will say that the L subs I took of Markarian's Chain showed little or no gradients.

[tooth_dr]

Hi Dave

I image from Bortle 4 - when I used my DSLR I found a LPF really helped.  I'm using a mono CCD now and the EOS clip filter does not fit.  I havent bothered to replace it, and am just using a lum filter.   It might be too early to say as I'm still getting the ropes, but I've not noticed a requirement for it.

[DaveS]

Many thanks.

Up to now I've been mostly imaging around the meridian as the subjects I've been looking at have been low enough to get blocked by a neighbour's tree, but come autumn I have M33 and the Deer Lick / Stephan's Quintet on my hit list and they're high enough to be imagable right into the west / north west where the Bridport LP is starting to bite, reducing the sky to Bortle 5-6, though M31 is easy naked eye even when quite low.

An Idas D2 could go in a filter wheel with 2" filters, but I really do wish they'd make it in more normal filter sizes. The place for a LP reducing L filter is in a wheel, not in front of the camera train.

[vlaiv]

I suspect that at such low levels of LP - LPS is going to hurt your image more than help.

[DaveS]

Yes, that's part of the debate I'm having with myself, and why I've rejected the Astronomik CLS-CCD filter as it's too extreme. However the D2 has broader pass-bands, so might be less harmful. In either case I think I may wait and see how I get on later in the year, if I find gradients or degradation in unfiltered L subs then I'll get one.

[Gina]

I too have Bortle 4 skies and don't use a light pollution filter.  Just IR/UV for Luminance otherwise standard RGB Baader filters and Astrodon NB.

[DaveS]

Thanks Gina, that confirms what I was thinking, and saved me the cost of a filter.

[Jkulin]

I have Bortl4/5 skies with an SQM of 19.51 and I found my IDAS 2 totally wrecked my images, I now shoot without and much prefer the quality of the images. I do have an Astronomik CLS LP filter and that was not kind to the images either.

I got additional gradients when using them and the images appeared noisier.