Optical quality of the Televue NP127is

[MLParkinson (Murray)]

This sequence of narrow band images of the Great Carina Nebula illustrates the optical capability of the Televue Nagler-Petzval (NP) 127is combined with a QSI683wsg camera. The raw data were recorded with the discontinued Televue 1.5x focal extender achieving an f-ratio of f/7.8 and focal length of 990 mm. Focusing the NP127is is challenging and I am never completely satisfied with the shape of the stars. The electronic Focus Master is an essential accessory to exploit the full optical capability. When focusing, one attempts to find the focal "sweet spot" (only 20-30 micrometers), a magic position where stars “snap” into roundish shapes across most of the frame. The first two images are crops of the corners of the full QSI683 frames. The stars aren’t perfect round dots in the corners, but to be fair, the light has passed through a 4-element objective (2 at the front of the tube and 2 at the rear), the compound lenses of the focal extender, and then finally the Astronomic H-alpha filter before reaching the CCD. When the focal sweet spot is achieved, the stars are reasonably pleasing in the corners.

Higher resolution versions are located here:

https://www.flickr.com/photos/mlparkinson/14891220757/

[multiweb (Marc)]

Love the palettes. Impressive little refractors. High res, although a bit over sharpened still shows some very cool details. Fantastic scope for widefields.

[MLParkinson (Murray)]

Yes Marc, I often worry about whether I should sharpen the image further to highlight more of the detail or leave it looking "softer". Showing good judgement is a constant challenge. I keep on telling my self to "back off" but fail to control my desire to see more detail. Ditto for the really faint stuff just above the noise threshold.

[FlashDrive (Poppy)]

Fantastic Shots....I like the ' sharper ' shots ... softer photos tend to ' mellow ' the detail and as such aren't as ' crisp and clear ' ...IMHO ...but that could be just my ' eyes ' .

Col......

[MLParkinson (Murray)]

I have reprocessed all of the full frames to improve the star shapes by using a more thorough selection of the most precisely focused frames. I have also added LRGB=HaSIIHaOIII and LRGB=HaHaHaOIII composites.

Higher resolution versions are located here:

https://www.flickr.com/photos/mlparkinson/15089680312/

[LightningNZ (Cam)]

Really impressive detail - crazy impressive for such a small scope.

My favourite colour blend is definitely the LRGB_HaHaGOIII, looks like it's carved out of Aussie sandstone. It's majestic.

I'd love to hear what people think of these scopes relative to the much vaunted Taks.

Cheers,
Cam

[multiweb (Marc)]

Originally Posted by MLParkinson

Yes Marc, I often worry about whether I should sharpen the image further to highlight more of the detail or leave it looking "softer". Showing good judgement is a constant challenge. I keep on telling my self to "back off" but fail to control my desire to see more detail. Ditto for the really faint stuff just above the noise threshold.

I know exactly how you feel. I tend to over sharpen too. Depending on the mood of the day. If it starts destroying very fine details and merge them into blobs then I try to back up a little.

[RickS (Rick)]

Some interesting colour schemes there, Murray, and it looks like a really nice scope.

Cheers,
Rick.

[dvj (John)]

The nebula details are delicious. This image in particular is the best color of the lot IMO. https://www.flickr.com/photos/mlpark...ream/lightbox/

[MLParkinson (Murray)]

Thanks a lot for your feedback on the colours. I produce a broad range of colour combinations when narrow band imaging because I see beauty in all of them. The optimum colour palette seems to change for every object and imaging run, as well as the optics used. No two images of the same object are identical. That's why we will still be fascinated when we all image and post the same objects next year.

Cam, I appreciate your comment about the HaHaGOIII image reminding you of Australian colours. I never quiet thought of deep southern objects imaged from Australia in that way, but you are right. The colours are reminiscent of the sunburnt country we live in.

Why on Earth does our Olympic team sport “Green and Gold.” That just doesn’t make sense to me. I think the Australian colour selection committee got it wrong. They should have gone walk-about in the outback before meeting.

[AG Hybrid (Adrian)]

I like it. Sharp and flat indeed.