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Andyb90

ASI1600mm cool

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wimvb    1,901

Unfortunately not a match to my bank account, $ 475 vs £ 125 . But just comparing the curves, they seem to have much better Oiii coverage and also much better sodium rejection. I would also expect the astrodon filters to be more uniform from set to set. The sodium rejection gap of zwo filters is very narrow and on the edge of the red and green curves. This makes it very sensitive to production fluctuations.

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Gina    8,255

Maybe the ZWO RGB matched filter set would be better than the Baader set I have ATM for the ASI1600MM-Cool.  I might think about that for when the galaxy season comes round.

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Gina    8,255

I see FLO are selling a NEW Baader LRGB filter set with a narrower green band than my earlier set, at least as far as I remember.  I feel sure the older Baader set have pretty much equal bands for the three colours.  I have not really tried my Baader RGB filters with the ASI1600MM-Cool - the weather didn't let me last galaxy season.  At £125 the ZWO filters look affordable and the spec looks good.  From the excellent impression I have had with ZWO kit I reckon their LRGB filter set could be a good buy.  I see they also do an IR pass filter which is interesting.

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wimvb    1,901
1 hour ago, Gina said:

Maybe the ZWO RGB matched filter set would be better than the Baader set I have ATM for the ASI1600MM-Cool.  I might think about that for when the galaxy season comes round.

When I bought the zwo asi 174mm, I also got the standard lrgb filters. Since then I've done the math and calculated the best exposure ratios between r, g, and b. In retrospect, I should have also done that for the asi1600 optimised filters, to compare.

Anyway, I found the ratios to be 145:100:107, for r:g:b. I.e. red needs 45% longer single frame exposures than green to get a proper colour balance from a white light source. The problem is that if I use this and shoot different exposures, I will also need to do different darks. That's the whole reason for getting optimised filters in the first place.

The Astrodon filter sets e-series and i-series are designed for red and green sensitive chips, respectively. You'd have to do the math to match the filters to any camera.

On casual inspection, the (new?) Baader set seems to be similar to the ZWO optimised, with two exceptions:

1. The green and blue filters overlap at Oiii, while H-b signal ends up in the blue channel only. (Good thing)

2. The red and green have a larger overlap at the sodium line. (Bad thing)

Based on filter curves alone, the Baader set may actually be poorer than ZWO in handling light pollution, and the Astrodon should outperform both (it better, at that price).

But beware, this comparison is solely based on published filter curves, NOT on actual experience, mechanical stability, reflection properties, or other optical characteristics.

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Gina    8,255

I have negligible light pollution here so that is not a problem.  From a practical point of view having equal exposures for all three colours would be nice but another thought comes to mind, how does the bandwidth of each colour affect the colour result?  Empirically one would think equal bandwidths might be best but I guess it depends on what we are comparing with.  Does the colour balance really matter assuming that exposures are adjusted to make white light appear white?  In view of what we do with NB imaging I would think not.  The general idea seems to be to make the prettiest picture :D  And to bring out the dark banding and other details.  I guess the only way to find out would be to compare results from both filter sets.  Oh, and I plan to add in Ha to the RGB (if that makes any difference to the RGB wavebands used).

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wimvb    1,901

The "compare-the-curves" exercise is strictly only valid for a single frame (= 3 exposures) white light source, without any weight factors in creating the rgb image. DSO imaging is an entirely different beast.

The Astrodon I-series red filter looks much more orange than the E-filter, but all that light is pressed into one red channel anyway. In principle you let orange light count as red. I think that someone imaging from a light polluted site should more carefully examine the filters. But in that case equalising fluxes is of less concern. I can imagine that if  comparing the various filters, you'd say that one set gives "cleaner" or "crisper" or "more saturated" results, but that may depend more on other characteristics than bandwidth. E.g. reflections or glass quality.

Adding Ha to the mix, offsets the balance, as you noted.

Edited by wimvb
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John78    147

So I still haven't actually ordered the camera - its frustrating that ZWO have put the camera on sale, every US vendor has mirrored that sale price of $1180 and the UK vendors are resolute in demanding £1309 in unison - with the new camera arriving to replace it next month and the new Atik Horizon to begin shipping when is the price coming down??  :dontknow:

Edit : to add you can buy one from a US vendor next day delivered, with import duty paid for £1116 - its not right.

 

Edited by John78

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Lee_P    59

To say the learning curve is steep is an understatement, but I've finally produced a photo not destined for the recycle bin. This and other SGL threads were invaluable in getting to this stage. Onward and upward!

The Elephant Trunk Nebula in Cepheus

 

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alcol620    59

Hi Lee

 

Nice image. Not sure what your camera Gain setting was but the following link is a good read on the capability and benefits of taking short exposures with the ASI1600 camera. Keep up the good work

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Lee_P    59
5 minutes ago, alcol620 said:

Hi Lee

 

Nice image. Not sure what your camera Gain setting was but the following link is a good read on the capability and benefits of taking short exposures with the ASI1600 camera. Keep up the good work

Thanks! I've been shooting Gain 300, five-minute exposures. Do you think that I should change this? (I can't see the link you refer to..?)

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alcol620    59
10 minutes ago, alcol620 said:

Hi Lee

 

Nice image. Not sure what your camera Gain setting was but the following link is a good read on the capability and benefits of taking short exposures with the ASI1600 camera. Keep up the good work

OOOPs forgot to put the link in  https://www.cloudynights.com/topic/570020-gain-settings-for-asi1600mm-cool/page-2

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