Help - Stars with red haloes - why?

[Dennis]

Hi

This is my first image through my new William Optics 80mm f7 triplet ED refractor. It was taken from light polluted Brisbane. Exposure details are:

5 images
30 secs exp (auto-dark subtracted in-camera)
Pentax *istDS DSLR

The original image has been cropped in the centre (appox ½ size) and resampled down to 800x600

Can anyone explain why there are red haloes around some of the field stars? If this was chromatic aberration, I would have expected blue haloes? Or, have I got a duff objective? The inside and outside of focus images look textbook.

Thanks!

Dennis

[h0ughy]

denis have a look at the images I took from Lostock in this thread http://www.iceinspace.com.au/forum/showthread.php?t=7315 I think it is the Pentax camera.

[asimov]

I can't answer your question, but that is a very nice image!

[Striker]

It cant be the refractor....Only explanation is like Houghy said...the camera....but I am a bit surprised at this either way.

[h0ughy]

look at my shot in the link tony, the red is accentuated by the orion express, but the feature is still there. so comparing to Dennis's shot it must also be the camera

[Dennis]

Hi Guys

Thanks for the feedback. The Pentax you reckon H0ughy, hmm, looks that way doesn't it? Especially after looking at your (excellent) images from Lostock. I have a little less blue around the stars in my image, so maybe the WO 80mm ED triplet is better colour corrected that the Orion Express?

I'll try to get out again and experiment more to see if I can chase this down, as I understood that unmodified DSLR's block some of the red wavelengths.

Cheers

Dennis

[h0ughy]

I think different camras are sensitive to different light depending on the setup of the camera. Canons are different to the Pentax's difference sensors. if you noticed the 20Da shot it showed white stars. Maybe that star has a predominant red colour and the pentax picks it up differently to the canon. Speculation really :nerd:

[tornado33]

I wonder if its the type of Infra red cut filter pentax uses. If someone is game enough they could risk "modding" a pentax the same way as a canon :)

[Dennis]

Go on H0ughy - you know you want to :wink2: ....be a pioneer and mod yours. :scared: You'll be the first - what an accolade.

Cheers

Dennis

[h0ughy]

The thought had crossed my mind :nerd:

[Dennis]

Just one word Mr h0ughy - TRAITOR. :sad:

I saw on another IIS thread that you just purchased Robby's modified Canon.

Bah humbug. :mad2:

Dennis

[h0ughy]

No way, its not a true Canon its been modified :lol: :wink2: