Skywatcher OIII filter

[rikyuu]

hi,

I've just ordered a 2" Skywatcher OIII filter from FLO as some of my favourite targets are nebula. I have a couple of queries;

I believe the OIII filter is good for the Ring, Dumbell, Owl and Veil nebula. Are there any others in the autumn/winter sky that are good in OIII?

I would like to stretch to a Ha filter, but they are significantly more expensive, particularly for the 2" version. I don't think Skywatcher do one do they?

I have a modified 300d with an EOS clip CLS filter, which lets through OIII, Ha, etc and blocks IR. I would prefer to leave this in place, apart from some light loss, would I generallly be ok putting the 2" OIII filter in front of the CLS filter?

Thanks.

[Doc]

Almost all of the planetary nebulas need a O111 filter and also all of the Abell Planataries need one.

[rikyuu]

Thanks Mick, I haven't heard of Abell Planetaries before, but found some useful info here The Abell Planetaries

[Doc]

Thanks Mick, I haven't heard of Abell Planetaries before, but found some useful info here The Abell Planetaries

Interesting site. Abells are very dim so you need large aperture, dark skies and a O111 filter.

[Whippy]

Not quite sure what you're wanting to achieve but it's worth noting that there's two types of filters. One for visual and one for imaging. The visual versions tend to have wider bandpasses whilst the imaging ones are narrower.

AFAIK, the SW OIII model is a visual filter and whilst I'm sure you could use it in front of a camera I'm certain you wouldn't get the same results as if you would using a specific imaging one.

Certainly double stacking it in front of a CLS filter would be a waste of time, use one or the other depending on what target your scope is pointing at.

Personally if I had to choose one filter for each, I'd go for a UHC for visual and a Ha for imaging.

Tony..

[rikyuu]

Not quite sure what you're wanting to achieve but it's worth noting that there's two types of filters. One for visual and one for imaging. The visual versions tend to have wider bandpasses whilst the imaging ones are narrower.

AFAIK, the SW OIII model is a visual filter and whilst I'm sure you could use it in front of a camera I'm certain you wouldn't get the same results as if you would using a specific imaging one.

Certainly double stacking it in front of a CLS filter would be a waste of time, use one or the other depending on what target your scope is pointing at.

Personally if I had to choose one filter for each, I'd go for a UHC for visual and a Ha for imaging.

Tony..

My understanding was that if the CLS CCD filter lets through 95% O3, Hb and Ha and blocks IR for example, then adding another filter which passes 95% of O3 only would result in about 90% of O3 only.

Additionally, as the bandpass of the CLS filter is relatively wide around O3 (70nm), then the bandwidth of the O3 passed through both filters, would be limited by the Skywatcher O3 filter as it is more narrow.

I realise there's no actual gain in keeping the CLS filter in place other than negating the risk of removing it, dropping it and dust getting on the sensor, but if the only loss is a few % of O3 then I thought it would be worth leaving it fitted.

[Whippy]

I realise there's no actual gain in keeping the CLS filter in place other than negating the risk of removing it, dropping it and dust getting on the sensor, but if the only loss is a few % of O3 then I thought it would be worth leaving it fitted.

Makes sense to me, I think an Ha filter would offer you more choice of targets though.

Tony..

[Andrew*]

Does anyone know how good the SW OIII is?

[rikyuu]

Does anyone know how good the SW OIII is?

I couldn't find its characteristics on the net, but I received it yesterday from FLO (very quick as usual) and it has a photocopy of its characteristics stuck on the back of the box. It's in Chinese, but easy to understand the graph. I'll scan it and post it here for information. From memory, I think it was a 10 or 20nm bandwidth, but I'll check.

I guess the proof of the pudding will be in using it. So if it's ever clear again, I'll attempt the Dumbell and Ring nebulas, which I imaged before with the CLS filter, to see what the difference is. I'll keep the CLS clip filter in place as I don't want to remove it

......and start saving for a Ha filter!