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Old 11-10-2013, 05:25 PM
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KAF6303E or KAF8300?

I have an option to switch sensors on my FLI Microline camera. Its at FLI being serviced. I can swap out the KAF8300 for a KAF6303E for US$3750.

What do you think? I'd use it mainly on my CDK17 I suppose for galaxies.

The KAF8300 chip does quite well on my refractors (but not as well as my Proline 16803) but not so good on the CDK17 as the small pixels are mismatched to the seeing and focal length and I get lesser results over my 16803.

Comments?

How much of a problem is blooming with these chips?

Greg.
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Old 11-10-2013, 07:24 PM
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Bassnut (Fred)
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Gee I don't think you can even compare these chips to each other.

The 6303e has much deeper wells and much higher QE, but the QE peaks at Ha.

So It's great for NB and I can do 40min subs at 3nm NB without blooming (usually) but it blooms to hell quickly in LRGB.

I wouldn't pick the 6303 for mainly LRGB galaxy's at all IMO.
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Old 11-10-2013, 07:47 PM
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Thanks Fred. Because of the blooming?

It seems to be the chip of choice for narrowband.

Still that's a pretty large segment of available imaging plus you can do narrowband at any time not just in the moon periods as opposed to LRGB which really limits you to the no moon nights.

Greg.
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Old 12-10-2013, 07:59 AM
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Fred's wrong, the 6303 is great for rgb galaxies. It is also great for nb.

I could not wait to be rid of an 8300 that I had for a while. Swap it out.

My 2c
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Old 12-10-2013, 08:42 AM
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Yes, Im probably wrong there, I must say ive seen some excellent galaxy pics with it. I hardly do any LRGB actually, so im the wrong guy to comment on that.

The sensitivity at Ha is pretty amazing (going by results) and with 40min subs it goes very deep indeed on a 10". On a 17" it would be nuts. Youd be hard pressed to get close on any other front illuminated chip.

If you can swap for that price, do it, the 16803 will cover anything else.
The blooming I do get is easily fixed, but it is an extra processing step.

The only good thing ive heard about the 8300 is the price.
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Old 12-10-2013, 09:43 AM
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Quote:
Originally Posted by bert View Post
Fred's wrong, the 6303 is great for rgb galaxies. It is also great for nb.

I could not wait to be rid of an 8300 that I had for a while. Swap it out.

My 2c
I did check through quite few images last night of 6303 galaxy images and there were a lot that were very good. They seemed quite luminous and clear. I guess that is a reflection of the high QE.


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Originally Posted by Bassnut View Post
Yes, Im probably wrong there, I must say ive seen some excellent galaxy pics with it. I hardly do any LRGB actually, so im the wrong guy to comment on that.

The sensitivity at Ha is pretty amazing (going by results) and with 40min subs it goes very deep indeed on a 10". On a 17" it would be nuts. Youd be hard pressed to get close on any other front illuminated chip.

If you can swap for that price, do it, the 16803 will cover anything else.
The blooming I do get is easily fixed, but it is an extra processing step.

The only good thing ive heard about the 8300 is the price.
Thanks Fred. Blooming is the main issue. The Sony 694 chip is also 6mp and has the same QE in Ha (66%). But its a smaller chip, antiblooming.

Both would be good for different purposes. The 6303 for NB and the 694 if it works on a 17 inch (long focal length and small pixels don't work well) could be great.

Greg.
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Old 12-10-2013, 04:45 PM
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just had a squiz at the 694 spec. Yes the pixels are tiny, but the QE is very good.

Then I saw the dynamic range, not good. Its well depth is only 20k (vs 100k for 6303) thats as bad as the 8300 !.Sounds like trouble to me.
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Old 12-10-2013, 07:39 PM
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The 6303 would be a really good match for your big scope - would seem to be a good value swap for galaxy/NB imaging if you can deal with the blooming. Not sure it would be any better than your 16803 though, except for Ha imaging.

the 694 is not very well matched to your CDK, being better suited to ~1m fl scopes. You need not be concerned about the well depth though, since the 694 actually has more dynamic range than the 6303 when multiple subs are allowed. For example, adding 9x5 minute subs with the 694 will produce the same read noise power and signal as 1x45 minute sub with the 6303. The 9 subs with the 694 will allow 180,000 electrons before saturation, which is much higher than the 100,000 allowed in the 6303, so the 694 is the better chip for dynamic range. You just need to forget the old way of thinking and accept that short subs can be effective when you have low read noise. And of course don't forget that the 694 will be twice as fast as a 6303 with O3 NB data - it has way better QE at short wavelengths. It would be a very effective chip for your shorter focal length scopes.

regards ray

Last edited by Shiraz; 12-10-2013 at 08:01 PM.
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Old 13-10-2013, 01:33 AM
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Quote:
Originally Posted by Shiraz View Post
The 6303 would be a really good match for your big scope - would seem to be a good value swap for galaxy/NB imaging if you can deal with the blooming. Not sure it would be any better than your 16803 though, except for Ha imaging.

the 694 is not very well matched to your CDK, being better suited to ~1m fl scopes. You need not be concerned about the well depth though, since the 694 actually has more dynamic range than the 6303 when multiple subs are allowed. For example, adding 9x5 minute subs with the 694 will produce the same read noise power and signal as 1x45 minute sub with the 6303. The 9 subs with the 694 will allow 180,000 electrons before saturation, which is much higher than the 100,000 allowed in the 6303, so the 694 is the better chip for dynamic range. You just need to forget the old way of thinking and accept that short subs can be effective when you have low read noise. And of course don't forget that the 694 will be twice as fast as a 6303 with O3 NB data - it has way better QE at short wavelengths. It would be a very effective chip for your shorter focal length scopes.

regards ray
In theory that is correct Ray but mated with an AO unit plus its high QE I think it still might be very nice on the CDK. Oversampled just means less sensitivity so you are not at risk of anything really except losing some of the sensitivity.

I kind of like the idea of a 6303 chip as well but it seems too similar to the 16803 except QE is slightly higher in visible and substantially higher QE for the 6303 in Ha.

Quote:
Originally Posted by Bassnut View Post
just had a squiz at the 694 spec. Yes the pixels are tiny, but the QE is very good.

Then I saw the dynamic range, not good. Its well depth is only 20k (vs 100k for 6303) thats as bad as the 8300 !.Sounds like trouble to me.
Small wells can sometimes interfere when there are bright stars in the field. But there are hundreds of excellent images using the KAF8300 around. I think its more a matter of shorter subs if you start getting bright star bloat.

I agree though the 6303 with AO would be an even better match for the CDK although less FOV which isn't really an issue for galaxies but would be for nebulas etc.

Greg.
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